INTRODUCTION:

Spectroscopy can be defined as the interaction between matter and light. Infrared (IR) spectroscopy is one of the oldest and well-established experimental technique for the analysis of proteins, food stuffs, dyes, pharmaceutical formulations, etc. The use of stable and powerful laser has led to the development of the Fourier transform (FT) method for IR data acquisition and reliable digital subtraction. The availability of modern computers has enabled the rapid and powerful FTIR data processing and conversion.^[1]

Infrared spectroscopy is a very powerful technique which uses electromagnetic radiation in the infrared region for the determination and identification of molecular structure.^[2] For a molecule to show IR absorptions, it must possess a specific feature: an electric dipole moment of the molecule must change during the movement which is associated with vibrations and rotations. Vibrations can involve either stretching (change in bond length) or bending (bond angle).^[3] The infrared region of the electromagnetic spectrum extends from 14000 to 50 cm^-1 and is divided into three areas: the far-infrared from 400 to 50 cm^-1; the mid-infrared region from 4000 to 400 cm^-1, which is a very interesting region of the spectrum for the study of organic compounds and the near-infrared (NIR) from 14000 to 4000 cm^-1.^[4]

We have two types of IR spectrophotometers: the classical (Figure 1) and the Fourier Transform spectrophotometers (Figure 2) with the interferometer, which allows all the frequencies to reach the detector at once and not one at the time. The classical IR consists of four main elements: a light source of irradiation, a dispersing element/diffraction grating/prism, a detector and an optical system of mirrors whereas FT-IR spectrometers has the following main parts: light source, beam splitter (half silvered mirror), translating mirror, detector and optical System (fixed mirror).^[5]

Fig. 1. Schematic diagram of classic IR spectrophotometer

Fig. 2: Schematic diagram of classic FT-IR spectrophotometer

Recent advances have revealed the development of 2D IR techniques which are being applied to variety of quantitative applications in different fields. IR spectroscopy is used in both research and industry for measurement and quality control. The infrared absorption spectrum of a nucleic acid (RNA and DNA) shows a great amount of information about its molecular structure.^[6] Near Infrared Spectroscopy (NIRS) is a useful method for accurately determining low quantities of the crystalline lactose in a physical mixture,^[7] for determination of amoxicillin in pharmaceutical suspension formulations,^[8]therefore helpful in pharmaceutical area. The study of conversion degree in dental composites by FTIR technique provides a better understanding of these materials, which will result in improved dental restorations with aggregated higher quality and durability.^[9] The determination of lipids and evaluation of fatty acids composition in foods (Salmon oil, soyabean oil, extra virgin olive oil, refined olive oil, sunflower oil, rapeseed oil) can be done by IR.^[10]The applications of FTIR to the secondary structure analysis, conformational changes, structural dynamics and stability studies of proteins are also explored.^[1]Other areas of note where IR spectroscopy is being utilized are in stem cell studies, materials science, catalysis, and reaction kinetics, which demonstrate the applicability and flexibility of this analytical technique.^[2] Various applications of IR techniques (Table 1) have been depicted in the following sections of this review:

1. Determination of soyabean routine quality parameters using near-infrared spectroscopy:

China is a high expenditure country of soybean which is highly consumed as significant health food.^[11] In China, soybean is one of the main agricultural product and various other diversities are grown, with a piece of huge difference information that turns up from rich genetic diversity and as well as regional planting.^[12] Big difference in quality existed between soybean sample in sequence to promptly recognize soybean quality between a sample from contrasting zones. Zhu et al. progressed near-infrared spectroscopy (NIRS) replicas for the moisture, crude fat, and protein content of soybeans, based on 360 soybean samples collected from different zones. To enlarge the prediction model, a consistent particle size of soybean was prepared by granulating and straining soybean with various sizes and colours. In this work it was concluded that attaining a constant particle size by grinding and sieving furnish a superior solution to the issue of poor reproducibility of prediction models for soybean quality indices originated by individual differences in sample among various varieties. Zhu et al have studied the optimal particle size of NIR models of moisture, crude fat, and protein content of soybeans, using the technology that is FT-NIRS. For the selected samples moisture, crude fat, and protein contents were found to be 8.47-10.67%, 17.71-25.14%, 37.37%-43.20% respectively. For 216 samples these values were found to be 7.42-13.71%, 15.78-25.97% and 37.37-43.21%. For the remaining 54 samples these values were recorded as 6.92-11.24%, 17.75-25.39% and 37.04-43.56% respectively. In this study, modelling analysis shows that the internal cross-validation correlation coefficients (Rcv) for the moisture, crude fat, and protein content of soybeans were .965, .941, and .949, respectively, and the determination coefficient (R²) were .966, .958, and .958. the predictive presentations of the models, accepted using soybean calibration set on samples of the external validation set, was formed to be credible, specifying that the NIRS detection models for determination of the important soybean component are more convenient and can also be used for rapid determination of the constituents of soyabean.^[13]

2. Application of visible and near-infrared spectroscopy to classification of Miscanthus species:

The huge grasses and some species in Miscanthus have a very high potential of biomass efficiency and also be used as a feedstock sustainable energy. Nowadays, M. sacchariflorus, M. sinensis, and M. fIoridulu were manifest to the most potential biomass grass species. Xi and Jeźowski furnish orderly positions of all the species, M. sacchariflorus, M. sinensis and M. fIoridulus which belongs to Subtrib. Saccharinae.^[14]The species that are mentioned generally used to grow in a similar environmental condition, and they also grow together. ^[14,15] Meantime, they show resemblance in the morphological examination, so the recognization of Miscanthus diversity has to been attained by morphological examination, field inspection, exploration of cultivated accessions and statistical analysis.^[16]

As we classify the species, the detailed morphological attributes like height of the plant, the diameter of the stem near base; column number, auricles, panicle, glumes, types of roots etc, in this growth period have to be recorded and observed time to time.^[14]

Up to date, various other methods have been tried to differentiate the Miscanthus species like DNA constituents of diploid M. sacchariflorus, M. sinensis, and M. fIoridulus cannot be very well differentiated. Miscanthus species shows a high quantity or amount of genetic variation within and inside species.^[17]Comprehensive, these all methods are very much time consuming, arduous, and costly or it also requires a highly skilled person in taxonomy. So, till now, there is no method which is effective or to differentiate between M. sacchariflorus, M. sinensis, and M. fIoridulus. Taking this into report Near-infrared (NIR) spectroscopy is a very systematic and well-organized method for high-throughput screening of plant substances for their chemical attributes. It gives rapidly non-destructive, less cost and environment-friendly quantification. In this paper, the author Xiaoli Jin et.al has analyzed three various types of Miscanthus plant that names, M. sinensis, M. sacchariflorus, and M. fIoridulus, using a NIR spectrophotometer therefore in this five calibration models based on the NIR spectra data evolved, namely; namely LDA, PLS, Lin_LSSVR, RBF_LSSVR and RBF_NN arithmetics. Due to the incomplete overlaps between the species, LDA could not be clearly differentiated the experimental sample. 88.24, 86.67 and 87.10% of the samples were allocated accurately to the M. sinensis, M. sacchariflorus and M. fIoridulus group respectively. In the PLS model, the rate of accurate classification was amplified to 94.12, 98.33 and 93.55%, respectively, for the three species, but incorrectly assigned accessions. To upgrade the grouping accuracy some other three methods were involved that are as follows Lin_LSSVR, RBF_LSSVR, and RBF_NN. These models indicate fine correlation among the expected and actual values. Among these only one sample is incorrectly grouped. The entire correct classification rates of 87.79 and 96.51% were perceived based on LDA and PLS model in the testing set, respectively. While the line LSSVR showed 99.42% of entire accurate classification rate of 100, 100 and 96.77% for M. sinensis, M. sacchariflorus and M. fIoridulus, respectively. As the line_ LSSVR model allocate 99.42% of samples to the correct groups, excluding one M. fIoridulus sample. The outcome indicates that NRI spectra merged with a preliminary morphological classification could be a successful and dependable procedure for the classification of Miscanthus species.^[18]

3. Quantitative determination of crystallinity of alpha-lactose monohydrate by Near Infrared Spectroscopy (NIRS):

Most organic and inorganic solid-state substances in nature, as well as the majority of the synthetically manufactured materials, have a crystalline structure. They carry physically and thermodynamically stable state, but some technological operations convert crystalline materials to amorphous form, for eg: freeze-drying, rapidly cooling of the melted substance .but, amorphous state is thermodynamically unstable state with higher energy level, so these materials contains issues regarding stability and hygroscopicity, resulting in that transformation to the more stable crystalline form during storage.^[19]The particle properties may govern the processibility of materials and also the bioavailability of dosage forms.^[20] The amorphous state of a solid powder may change the bioavailability of moderately water-soluble drug due to changes in solubility and consequently absorption of the drug within the gastrointestinal tract. So, it is very important to know the crystallinity of materials. In order to qualify raw materials, intermediates and end products, it is highly important to determine the crystallinity. There are various other methods to study crystallinity such as X-ray powder diffraction (XRPD), density determination, solid-state NMR, and also water vapour absorption.^[21] By using isothermal microcalorimetry and DSC changes in crystallinity can also be detected.^[22] Nowadays, an alternative method is used that is NIRS for the quantification of amorphous and crystalline forms of materials.^[23] Ágota Gombás et al. evaluated the quantitative capability of NIRS for governing crystallinity in a crystalline/amorphous powder mixture of lactose and to differentiate precision of the NIRS method with that of conventional XRPD. As an auxiliary material; Alpha-lactose monohydrate was investigated because it is very well known that its crystalline and amorphous forms impact the production and suitability of solid state dosage forms.^[24] By spray drying, amorphous lactose was prepared. And the sample containing different crystallinity was prepared by physical mixing of 100% amorphous and 100% crystalline materials. The samples were distinguished by XRPD and NIRS. also the analysis was performed on the data sets by multiple linear regression (MLR). There is a very close correlation between the predicted and the actual crystallinity of a physical mixture of crystalline and also amorphous lactose, determined by NIRS (R2 = 0.9994). NIRS results were compared to the XRPD by using the sample sets. The correlation coefficient was 0.9981. The outcomes showed that NIRS is a useful method for correctly determining low quantities of the crystalline lactose in a physical mixture. Therefore, it concludes that NIRS can be used for the quantitative determining of crystallinity of material during pharmaceutical procedures.^[25]

4. Quantitative screening of the pharmaceutical ingredient for the rapid identification of substandard and falsified medicines using reflectance infrared spectroscopy:

The world health organization recommended that approximately 10% of medicines around the world are either fake counterfeit or substandard with higher figures in low and middle-income countries and this poor quality of medicines which are supplied can cause a big issue or a threat to the economy, and they can also harm the patients. The increasing problem of substandard and fake medicines or pharmaceuticals presents a serious and big threat to international public health and safety of the patients.^[26-28] Substandard medicines result from poor manufacturing and assurance of quality processes and attain the public due to lax control measures whereas false medicines or counterfeit pharmaceuticals are intentionally and fraudulently labelled.^[29] The world health organization (WHO) has nowdays, introduced the term ‘substandard and falsified (SF) medical products’.^[30] In a seek to alter the situation where there is no globally accepted definition for such pharmaceuticals and poorly coordinated legal controls that seem to uplift the production of poor quality medicines.^[31] falsification medicine involves as follows: paracetamol, also known to be acetaminophen (4-acetaminophen, N-acetyl-p-phenacetin), has been identified as the most frequently used active pharmaceutical ingredient (API) after acetylsalicylic acid and paracetamol involving OTC medicines have been targeted by counterfeiters. Paracetamol has also been used, instead of a particular API in falsified medicines. Accounts of a situation in the USA where 500mg paracetamol tablets were literally labeled as 325mg recommended that the people in both industrialized and LMICs are exposed to miss-labeled medication. There are many other analytical techniques for determining the content of API the techniques used for determining API as high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection, liquid chromatography coupled with mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy and have been used in the authentication of various other tablet formulations. A large volume of expensive solvents is required in the techniques that are chromatographically based and have long analysis times due to complicated sample preparation steps which make them inappropriate for rapid, simple and cheap analysis. These types of techniques also require well-trained experts and well-maintained laboratories which are not willingly available LMICs. Vibrational spectroscopic techniques are broadly recorded as being suitable analytical methods for the authentication of pharmaceutical products. In this paper the author Graham Lawson et.al investigated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy as an easier and rapid method for determining the drug content in tablet dosage forms paracetamol was used as the model pharmaceutical constituent. Spectra of standard mixtures of paracetamol with different other excipients formed the basis for multivariate PLS based quantitative analysis of simulated or duplicate tablet content using different selected infrared absorbance bands. Calibration methods with the help of ATR-FTIR were differentiated with the ATR-FTIR and conventional ultraviolet spectroscopic analysis of real tablet samples and showed that the paracetamol/ microcrystalline cellulose mixtures furnish favorable results for all spectral bands tested. The quantitative data for band 1524±1493cm-1 was linear (R2 >0.98; LOQ 10%w/w tablet). Worldwide example of paracetamol tablets was tested using protocol and 12% of the tablet samples examined was recognized as substandard. Each sample analysis was done in just a few minutes. Therefore, in rapid screening of tablet formulations, ATR-FTIR can be used. The clarity of the suggested method makes it appropriate for use in low and middle-income countries. Where analytical facilities are not accessible. This study concludes that the simple ATR-FTIR approach employed has the capacity to rapidly identify and also quantify paracetamol in the presence of excipients. The whole procedure of grinding, identifying and quantifying a tablet would take almost about 5 minutes per tablet sample after the method has been optimized. The multivariate PLS calibration model used in this study is an automated process further fasting up the time for data processing. This automated method further reduces variation in data due to errors in manual integration of attribute peaks for paracetamol identified. As the elimination of solvent extraction of APIs reduces the amounts of toxic chemicals used thus, reducing chemical waste; so, it is also known as green technique. Furthermore, the technique will enable quick withdrawal of substandard and falsified medicines from the market so that, to decrease the threat to public health and safety purposes.^[32]

5. Application of near (NIR) infrared and mid (MIR) infrared spectroscopy as a rapid tool to classify extra virgin olive oil on the basis of fruity attribute intensity.:

Olive oil legislation is in a constant upgrading phase with the aim both to guarantee the quality of the product to different commercial categories (extra virgin, virgin, and lampante) and to identify possible sophistication and illegally treatments. To protect the quality of the virgin olive oil, the sensory analysis is one of the most important tools. This approach has been suggested in June 1987 by the International Olive Council (International Olive Council, 1987) and recognized by the European Community in July 1991 (EEC Reg., 2568/1991). This method was then replaced by the other new method (COI/T.20/Doc. No. 15) for the organoleptic assessment of virgin olive oils (International Olive Council, 1996), and identified by the European Community (EC Reg., 796/2002) more genuine and simpler. Afterward, the modification of the last method was done in September 2007 (international olive council, 2007) allowing the use of optional terminology of labeling purposes (EC Res., 1019/2002).^[33] This approach also saves the time and it is not always practical for large-scale commercial purposes as including the use of trained sensory panelist or individual, and therefore, use of molecular spectroscopic techniques, like near-infrared spectroscopy (NIR) and mid-infrared spectroscopy (MIR), related with the chemometric methods has been recognized in various other analytical application for evaluating the olive oil constitution. For adulteration and detection of virgin oil by different vegetable oil oils,^[34-35] The given techniques are successfully deployed. Nicoletta Sinelli et.al has done a sensory analysis of 112 virgin olive oils was composed by a fully trained taste panel. On the bases of the olfactory attributes the samples were divided into two categories that “defective” and “not defective”. Then, further, the “not defective” samples were subcategorized into “low”, “medium”, and “high” according to the fruity aroma intensity recognized by assessors. By FT-NIR and FT-IR spectroscopy and processed by classification methods (LDA and SIMCA), all the samples are analyzed. the prediction rate assorted between 71.6% and 100% as an average value. This study concludes that the potential of NIR and MIR spectroscopy, coupled with chemometric analysis, to classify extra virgin olive oil on the basis of their fruity aroma intensity. Good classification models were attained after feature selection, compulsory to delete wavenumbers which are associated with non-useful information. The best outcome was obtained using only the “not defective oils”, which were categorized into three classes; ‘low fruity’ (class1), ‘medium fruity’ (class2), ‘high fruity’ (class 3). The results showed that the IR spectroscopy is a good, dependable, cheap, as fast classification tool able to draw a complete fingerprint of a food product, describing its intrinsic quality characteristics that also includes its sensory attributes.^[33]

6. Monitoring of fatty acid composition in virgin olive oil by Fourier transformed infrared spectroscopy coupled with partial least squares:

Virgin olive oil (VOO) is one of the widely used oil, it is generally used in dressing and cooking fats in Mediterranean countries, and it is also the central constituents of the diet in this region.^[36] Virgin olive oil (VOO)contains many qualities such as it is low in PUFA, particularly in linolenic acid, and in addition it is free of trans fatty acids, thus fulfilling all major criteria of the stable frying fats^[37] and this oil is an excellent oil for high-temperature cooking being rich in MUFA. For the identification of MUFA PUFA and SFA usually carried out by the methods as follows by capillary gas chromatography with flame ionisation detection (cGC-FID), this method is a time consuming method, and also involves sample pretreatment; peroxide value determination also relies on a titration involving large amounts of solvents and reagents (EEC Reg. No. 2568/91). But the (FTIR) Fourier transformed infrared spectroscopy do not require any pre-treatment sample and is simple to perform also a fast process. In the last 15 years FTIR has been successfully used to quantitate a number of olive oil parameters like acidity, peroxide and iodine values. In this paper the author, Rubén M. Maggio has developed and validate an analytical method which is based on ATR-FTIR spectroscopy, in combination with multivariate calibration methodologies, for the concurrent evaluation of main quality parameter of virgin olive oil, involving the composition of total fatty acids and peroxide value. A sequence of virgin olive oil samples coming from dissimilar Italian region and manufactured during two harvest seasons were analyzed by official methods, taken as allusions, and by proposed ATR-FTIR method. calibration method was established in the spectral range from 3033 to 700cm. Oleic acid (62.0–80.0%), linoleic acid (5.3–15.0%), saturated fatty acids (SFA, 12.6–19.7%), mono-unsaturated fatty acids (MUFA, 64.4–81.0%) and poly-unsaturated fatty acids (PUFA, 6.0–15.9%) were contemplated for chemometric analysis. PV (5.7–15.7 meq O₂ kg1) was calibrated with the help of signal of the full spectral range 4000–700 cm1 with first derivative pre-treatment. The LODs of the FTIR-chemometric methods were: 3.0% for oleic acid, 0.5% for linoleic acid, 1.3% for SFA, 3.0% for MUFA, 0.3% for PUFA and 1.0 meq O2 kg1 for PV. Analytical methods were evaluated by use of validation samples (n = 25 for all the FA-associated parameters and n = 10 for PV) with nearly quantitative recovery rates (98–103%). the suggested chemometrically-assisted FTIR analysis provided outcomes statistically alike to official procedures of traditional use in terms of analytical performances. Therefore, the proposed spectroscopic method appoints a highly suitable alternative in terms of time and solvent savings for routine analysis of a large number of virgin olive oil samples, especially for high throughput determination throughout the industrial process without sacrificing reproducibility and accuracy. this procedure is environmental friendly and also permits high sample throughput than previously accounted alternatives, as no sample pre-treatment was required and virtually no waste of solvent is produced.^[38]

7. Determination of chemical properties in ‘calçot’ (Allium cepa L.) by near infrared spectroscopy and multivariate calibration:

‘Calçots’, is the immature floral stem of second-year onion resprouts, It is economically important for agriculture and restaurants in Catalonia (Spain), where popular celebrations called ‘calçotades’ which bring people to eat cooked ‘calçots’. As ‘calçots’ grow they are generally covered with soil so that the edible lower part remains white. The European Union has designated the Protected Indication ‘Calçot de Valls’ (EC No 905/2002) for ‘calçots’ from the ‘Cuba Blanca Geographical Tardana de Lleida’ landrace of onions that is cultivated in four countries. Despite, the economic importance of ‘calçots’ research on this crop is comparatively recent. Till date, only their agronomic performance has been studied, and some of the tools for yield breeding have been developed. As an outcome two other new varieties with significantly increased yields have been attained; in a parallel, a sensory ideotype has been amplified, identifying that the ideal ‘calçots’ contains a high level of sweetening property, low fiber perception, and do not contains any off flavors. As this is known about the chemical constituents related to the sensory and nutritional characteristics of ‘calçots’, the fact is that some studies have just focused on total and antioxidant properties. Breeding programs need to assess many accessions or individuals. On the other side breeding for organoleptic traits consist of sensory analysis with highly trained panelists who can only evaluate a restricted number of samples per tasting season, thus making it impracticable to deal with a large number of samples. Consequently, initiating relationships between chemical composition and sensory traits would facilitate sensory analysis. In other crops like rice, peaches, onions, melons, and apples these relationships have been already established. For example; soluble solid constituents has been broadly used to indicate sweetness of fresh and processed horticultural products; titratable acidity correlates with acid taste perception; and ash is a rough measure of the number of mineral cations, which interact with carboxylic acids and facilitate the cross-linking of uronic acid polymers that can increase the perception of fiber. Nevertheless, standard chemical analysis is costly in nature, they are laborious, time-saving, and sometimes also consist of considerably large samples. Therefore, breeding programs including sensory or chemical, measurements face several impediments. Near-infrared spectroscopy (NIRS) is a very well established technique for identifying or determining the chemical components of foods. The other extensive reviews about its use in meat, dairy products, fruits, and vegetables have already been published. NIRS contains many advantages like speed and ease of analysis, having a low cost per test, and the possibility of simultaneous estimation several more properties from a single spectrum. and they also don't produce waster of chemicals. these all advantages make this technique more suitable. For breeding, research, and quality evaluation when many other samples need to be analyzed. Although NIRS or other rapid techniques have not been used to predict chemical characteristics of ‘calçots’, they have been employed in related to crops like onions and garlic. An early application of NIRS in horticulture is that the identification of dry matter content of onion. NIRS has also been used for identifying solid soluble content ^[39] has recently used NIRS to predict dry matter and solid soluble content in intact dehydrator onions and garlic cloves. In these studies, spectra were recorded from the intact bulb. Another rapid technique, Fourier-transform infrared spectroscopy, has been used to identify some nutritional attributes in onions: total phenolic content, total antioxidant property, and quercetin content. Foods undergo chemical changes during cooking, so the chemical constituents of cooked foods should correlate better both with nutritive value and with organoleptic characteristics than those of the raw samples. Although not generally used on cooked vegetables, NIRS has been used to identify chemical or sensory parameters in cooked rice, potatoes, and carrots. The aim of the study was to investigate the ability of NIRS to predict chemical parameters in cooked ‘calçots’ that can affect their sensory and nutritive properties. We developed models to predict dry matter, soluble solid content, titratable acidity, and ash content. And to guarantee the robustness of the models, In the first season and validation samples in a second season were grown and analyzed in the calibration sample. ‘calçots’ that is the immature floral stem of second-year onion resprouts, is an economically important traditional crop in Catalonia (Spain). Approaches to evaluating the chemical properties of our time-saving and costly; near-infrared spectroscopy (NIRS) may be cheaper and faster. we generally used NIRS to develop partial least square (PLS) models to predict dry matter, soluble solid content, titratable acidity, and ash content in cooked ‘calçots’. And To guarantee the robustness of the models, calibration samples were grown and analyzed in the first season (2014–15) and validation samples in a second season (2015–16). NIRS on puree spectra estimated dry matter and soluble solid content with high accuracy (R2 pred=0.953, 0.985 and RPD=4.571, 8.068, respectively). However, the correct estimation of titratable acidity and ash content needed using ground dried puree spectra (R2 pred=0.852, 0.820 and RPD=2.590, 1.987, respectively). NIRS can be a helpful tool for ‘calçots’ breeding and quality control. ^[40]

8. Discriminant analysis of edible oils and fats by FTIR, FT-NIR and FT-Raman spectroscopy:

The most important criterion for edible oils and fats is Authenticity because there is a huge difference in prices of various types of oils and fats is traditionally a time saving and laborious process, typically using a chromatographical method. Combined with chemometric methods, vibrational spectroscopy, involving infrared (IR) and Raman techniques, it is an emerging analytical technique to verify the authenticity of edible oils and fats, due to its simplicity, rapidity, and ease of sample preparation. IR and Raman techniques both have been used for quantitative and qualitative measurement of edible oils and fats. The peaks in the IR and Raman spectra at a specific frequency/wavenumber are attributes of functional groups that constitute the constituents in the samples. The change in the molecular dipole moment during vibration is obtained by IR spectrum, while the Raman spectrum is obtained by a change in polarizability during the vibration. To qualitatively classify oil and fat products NIR spectroscopy is applied. Thus, the peaks in the NIR region (1100–2500 nm or 9091–4000 cm_1) are broad and weak, as per they are overtones and combination of the sample functional groups. Fourier transforms infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) or transmission cell accessories has been used to authenticate, determine or classify fats and oils. Generally, an ATR accessory is used with the FTIR spectrometer for oil and fat study, due to its ability to hold the liquid samples easily. Fourier transforms (FT)-Raman spectroscopy can be involved as a complementary method to the IR technique for analysis. Same as FTIR spectroscopy, FT-Raman spectroscopy can also give qualitative and quantitative information of the functional groups in samples. FT-Raman spectroscopy was generally used to discriminate and classify oils and fats. Two techniques, namely FTIR and FT-Raman techniques were compared to determine the authentication of edible oil.^[41] Therefore, with linear discriminant analysis and ANNs, FTIR spectroscopy shows the precision of 100% for the authentication of olive oil, while FT-Raman spectroscopy gave 93.1%. Yang and Irudayaraj (2001) have used two spectroscopies that are; Fourier transform mid-infrared (FTIR), near-infrared (FT-NIR) and Raman (FT-Raman) spectroscopy for discrimination along with 10 different edible oils and fats, and to differentiate the presentation of these spectroscopic methods. for edible oil/fat study compared NIR, FTIR-ATR, FTIR-PAS, and FT-Raman techniques to determine olive oil adulteration in extra virgin olive oil with PLS regression. FT-Raman spectroscopy gave the highest correlation (R² = 0.997) with the lowest prediction error (SEP = 1.72%). Other techniques that are NIR and MIR techniques, they also provide good predictions with an R² value that is greater than 0.99. Past literature indicates that NIR, FTIR, and FT-Raman techniques have been used for discriminant analysis of edible oils and fats, respectively. However, a comparative study of discriminant analysis for a different type of oil and fat samples using various vibrational spectroscopic methods could not be found in the literature. In this study, Types of fats and edible oils were analyzed by spectroscopic methods and chemometrics, As a more visual examination of spectra may not be sufficient and hence the need for spectral enhancement or analysis methods. The aim of this study was to compare FTIR, FT-NIR, and FT-Raman spectroscopic methods for rapid discrimination of edible oils and fats. Many Efforts were also done to correlate the degree of saturation with the classification of oils/fats with the help of spectroscopic methods. The spectral features of edible oils and fats were studied and the unsaturation bond (C@C) in IR and Raman spectra was determined and used for discriminant analysis. these two analytical methods that are; Linear discriminant analysis (LDA) and canonical variate analysis (CVA) were utilized for the discrimination and classification of various other edible oils and fats which are based on spectral data. The FTIR spectroscopy attained was found to be highly efficient in the classification of various oils and fats when applied with CVA and yielded about 98% classification accuracy, followed by FT-Raman (94%) and FT-NIR (93%) methods; Nevertheless, the number of factors were much higher for FT-Raman and FT-NIR methods. Overall outcomes elaborated and demonstrated that FTIR, FT-NIR, and FT Raman techniques can be used to rapidly and simply determine the authenticity of edible oils and fats with chemometric analysis.^[42]

9. Development and analytical validation of a multivariate calibration method for determination of amoxicillin in suspension formulations by near infrared spectroscopy:

Nowadays, the quality control of active principles in formulations from the pharmaceutical industry has been largely based on well accepted and officially recognized high-performance liquid chromatography (HPLC) method. In recent years, the alternative for quantitative determination of active pharmaceutical ingredients (API) the use of near-infrared spectroscopy (NIRS) combined with multivariate calibration method has gained much popularity. The method that are based on NIRS are a simple, fast, present relative of less cost and wide application, it also does not require any solvents or generates any waste of chemical products. They permit the analysis of solid and liquid forms with less or no sample pre-treatment and furnish accuracy and precision with less human intervention. Although US and Brazilian Pharmacopoeias present a bit of general advice about the use of NIRS, a disadvantage for its additional widespread use in the pharmaceutical industry is the absence of monographs that prescribe multivariate methods for the quantification of specific pharmaceuticals. Traditional regulation has been conceived in a univariate method and the acceptance of the multivariate thinking has endured a challenge. In Brazil, this feature is regulated by ANVISA (National Agency of Sanitary Vigilance), which has published specific guidelines which are based on ICH (International Conference on Harmonisation) ones. Furthermore, the certification of specific NIRS methods by pharmacopeias has been limited to qualitative identification of pharmaceuticals or quantitative univariate resolution in raw materials, in situations where a selective wavelength do exist. The requirement for regulation improvement stems from the identification that ICH guidelines (and ANVISA in Brazil) for analytical validation may not always be applied to new methods based on NIRS. As mentioned above, they very important challenge is that, the harmonization of the univariately conceived regulation with the peculiarities of the multivariate methods. For example; the principal parameter used for the evaluation average accuracy of multivariate methods is the root mean square error of prediction (RMSEP), which is not identified by ICH guidelines. Total selectivity or 100% of specificity used to be needed, which is usually not used with multivariate methods, thus they are indicated only when there is signal overlapping. Linearity is used to be evaluated through traditional calibration curves (signal as a function of analyte concentration), which are further not possible to be constructed for a multivariate case. Net analyte signal (NAS), is the most important concept for multivariate validation, which is used for estimating figures of merit (FOM), like sensitivity and limits of detection and quantitation, as well as it is used to construct pseudo – univariate calibration curves, the simplest manner to present multivariate models as univariates ones. since taking into the reports the state of the art of FOM in multivariate calibration, the objective of this work was just to develop and validate an analytical method for determining the drug; amoxicillin (AMX) in pharmaceutical formulation (powder of suspension) with the help of transflectance NIRS measurements in aqueous suspensions and partial least squares (PLS). Besides the validation, there is a procedure a robust that was implemented for the method development, including experimental design, data preprocessing, sample selection and outlier detection. Additional to this specific application, the purpose is also to divulge the potential of this analytical strategy for the quality control of other such pharmaceutical formulations. Some of the broad-spectrum antibiotics are present in the WHO (World Health Organization) list of essential medicines that are AMX, d-(−)-alfa-amino-p-hydroxy benzylpenicillin. it contains the activity against both gram-positive and gram-negative bacteria. Many such methods are introduced for AMX determination in pharmaceutical formulations. Most of them are based on the chromatography, but also on the techniques such as titrimetry, microbiological assays, UV/Vis absorbance spectrophotometry, molecular luminescence spectroscopy, electrophoresis and electroanalytical. Although, the great majority of these methods are not able to directly recognize AMX in the presence of interferences, like excipients, impurities and other active principles, demanding steps of derivatization or chemical/physical separation. In the recent paper, it has applied NIRS for the identification and for the particle size determination of AMX in raw materials. However, there is only one paper that has been published for AMX determination in a pharmaceutical formulation (powder) by diffuse reflectance NIRS. The best outcome of this work has been attained with principal component analysis (PCA) –radial basis function neutral networks, commonly, a complex method is used for modeling non-linearities. It is important to notice that this paper does not perform a full analytical validation and has been analyzed as a simple formulation. At which it consists of only one excipient that is starch. By doing the comparison, the method that is proposed in this paper aims at analyzing a much-complicated formulation, which contains seven excipient substances, in a more realistic situation. Another very important aspect to mention is that the initial purpose of the present work was to determine AMX by diffuse reflectance spectra that are directly recorded on the powder. However, unacceptable predictions were, attained for reason that will be discussed in section 4.1. since the original planning was improved for determining AMX in aqueous suspension by transflectance measurements. This work proposes one new method for the determination of amoxicillin in pharmaceutical suspension, which is based on transflectance near infrared (NIR) measurements and also partial least squares (PLS)multivariate calibration. Therefore, implemented a complete methodology was for developing the proposed method, involving an experimental design, data pre-processing with the help of multiple scatter correction (MSC) and outlier detection which is based on high values of leverage, and X and Y residuals. The best PLS model was attained with seven latent variables in the range from 40.0 to 65.0 mg mL−1 of amoxicillin, providing a root mean square error of prediction (RMSEP) of 1.6 mg mL−1. In accordance with Brazilian and international guidelines, the method is validated, through the estimate of figures of merit, such as linearity, precision, accuracy, robustness, selectivity, analytical sensitivity, limits of detection and quantitation, and bias. The outcome for determinations in four commercial pharmaceutical formulations was in agreement with the official high performance liquid chromatographic (HPLC) method at the 99% confidence level. A pseudo-univariate calibration curve was also attained, which is based on the net analyte signal (NAS). The proposed chemometric method presented the advantages of fast, simplified, less cost, and with no use of solvents, as compared to the principal alternative method based on HPLC.^[43]

10. Application of FT-MIR Spectroscopy for Fast Control of Red Grape Phenolic Ripening:

In recent years, the study of phenolic compounds has taken on a very special significance due to their contribution to the organoleptic properties of red wine. Tannins and anthocyanins are the two most important classes of phenolic compounds found in grapes.^[44] During the grape ripening the concentration of the phenolic compound changes, although it is affected by many other such factors which include grape variety,^[45] climatic conditions, and soil conditions (“terror”), and viticulture techniques and also involves enological treatments. There fore the determination of this concentration which has a direct relationship with the phenolic ripening state, it is the key criterion in setting up the harvest data to produce good quality red wines. Recently, the technique such as-as Fourier transform mid-infrared (FT-MIR) spectroscopy, has emerged as emerged as a powerful analytical tool that allows the rapid and simultaneous analysis of various other parameters in a large number of samples. as knowing the great amount of information about the composition of sample that each FTMIR spectrum provides, it is compulsory to use of chemometrics tools to make the most of its potential both for quantitative and qualitative analysis. Therefore, in this study, the author Sandra Fragoso et.al has done the study to evaluate the potential level of FT-MIR, combined with PLS multivariate calibration, for quantifying phenolic compound in a red grape. With this aim, the phenolic constituents evaluated as the total (phenolic compounds, total anthocyanins, and condensed tannins) of various fresh red grapes at different degree of maturity were spectrophotometrically determined according to the methods usually employed in cellars, and the outcomes attained were correlated with FT-MIR response.the reference method which was used for quantifying these compounds (which were evaluated as total phenolic compounds, total anthocyanins, and condensed tannins) were the usual ones that are in cellars that employed UV-vis spectroscopy . To take into a report the high natural variability of grapes when building up the calibration models, fresh grapes from six different varieties, at different phenolic ripening states were harvested during three vintages. Crushed and destemmed grapes were subjected to an accelerated extraction process and it is used as calibration standards. Total 192 extracts (objects) were attained, and these were further divided into a training set (106 objects) and a test set (86 objects) for evaluating the predictive ability of the models. Along with the different MIR regions of the extract raw spectra, those that provided the highest variability on the absorption were chosen. The outcomes showed that the best PLS regression model was the one attained when working in the region of 1168-1457 cm^-1 because it gave the more accurate and robust prediction for total phenolic compounds (RMSEP % = 4.3 and RPD = 4.5), total anthocyanins (RMSEP % = 5.9 and RPD = 3.5), and condensed tannins (RMSEP % = 5.8 and RPD = 3.8). And at last, it can be concluded that FT-MIR spectroscopy can be a rapid and reliable technique for monitoring the phenolic ripening in red grapes during the harvest period.^[46]

11. Application of Visible and Near-Infrared Reflectance Spectroscopy (Vis/NIRS) to Determine Carotenoid Contents in Banana (Musa spp.) Fruit Pulp:

The world’s fourth most important food crop is Banana and plantains (Musa spp.), with an annual production of about 100 Mt. Some of the poorest parts of the world, including Africa, Latin America, and southeast Asia they are the staple part of the diet, where the fruits are not only consumed raw but are also processed in a broad variety of methods. Musa fruits and fruit products represent a very important source of essential dietary micronutrients,^[47] Most dietary like Vit A is usually obtained from plants, and there are about 50 naturally occurring carotenoid components having vit A biological activity.^[48] These are generally called as a provitamin. A carotenoid (pVACs), which are broken down in the body to yield retinol, the active constituent form of Vit A.^[48,49] The broadly perceived health benefits of carotenoids have stimulated more interest in the development of food crops with increased carotenoid contents. In this study, the author MARK W. DAVEY et.al were interested in developing methodologies for the high-throughput analysis of fruit PVAc content and vit A nutritional content as encountered in breeding and germplasm-screening programs. For this, the author in his study has carried out a relatively small-scale trial to evaluate the potential of visible and near-infrared reflectance spectroscopy (Vis/NIRS) to generally screen for the carotenoid contents in fruits from a wide variety of Musa genotypes. The author in his study evaluated that with the help of visible and near-infrared reflectance spectroscopy (Vis/NIRS) to measure carotenoid contents in fruit from 28 Musa (banana and plantain) various varieties. Using standardized RP-HPLC protocols the carotenoid content was first quantified, and these outcomes were then used to develop algorithms to just predict carotenoid content from Vis /NIR spectra of the same samples. Cross-validation is proceeded for predictive algorithms across a genetically different group of several varieties demonstrated that correlation coefficients between the HPLC measurements and the Vis/NIRS predictions distinguished from good for the total carotenoids and -carotene fractions (r2cv, 0.84, 0.89) to reasonable for R-carotene and cis-carotenes (r2cv, 0.61, 0.66), but there was only a poor correlation (r2cv, 0.30) for the lesser lutein component. However, since ∼90% of the Musa carotenoids consist of only R- and -carotene. The outcomes from this trial study demonstrated that VIS/NIR has very good potential for high- throughput screening of carotenoid contents and individual for the total carotenoid content of lyophilized Musa fruit sample. Despite the comparatively small sample group used to develop the predictive models, the composition shows good precision for total carotenoids and carotene content but it endures to be seen whether larger sample sets will modify models sufficiently to enable the reasonable prediction of the concentration of other carotenoid compounds that are present.^[47]

12. Simultaneous Quantification of Ibuprofen and Paracetamol in Tablet Formulations Using Transmission Fourier Transform Infrared Spectroscopy:

Non-steroidal anti-inflammatory drugs (NSAIDs) are highly recommended for curing severe and mild inflammatory diseases like rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, and bartter’s syndrome. Paracetamol and ibuprofen are mostly prescribed because these drugs carry many properties such as they are antipyretic, anti-inflammatory analgesic medicine which further contains very less gastrointestinal adverse effect as compared to other NSAIDs.^[50-52] For the relief of fever headache and other minor aches and pain, paracetamol is highly preferred because of common analgesic and anti-pyretic drugs .ibuprofen has excellently shown the efficacy against gout arthritis, prostatic arthritis, and ankylosing spondylitis. Either in individual form or in the binary mixture has been usually and constantly carried out by many techniques for the analysis of Paracetamol and ibuprofen but all these generally consist lengthy procedures and a number of organic solvents contributing towards the very high cost of the analysis and generating waste. FTIR is a very simple and fast process and also a non-destructive technique which is probably playing a very efficient role for the rapid determination of several components that are present in the complex as well as simple matrices.^[53-55] In this study the author Muhammad Ali et.al has elaborated the simultaneous determination of paracetamol and ibuprofen using FTIR in multicomponent pharmaceutical preparations for routine quality control. This method is generally carried off for the assessment of paracetamol and ibuprofen in pharmaceutical samples is an analytical method which is of low cost and also eco-friendly. it removes the complexity of usually extracted method allowing rapid analysis excluding the use of hazardous organic chemicals. KBr pellet consisting given amount of standards and samples were required for acquisition of FTIR spectra for determining the active pharmaceutical ingredient (API). by using the spectral region from 1781 - 1683 cm⁻¹for IBP and 1630 - 1530 cm⁻¹ for PC the partial least squares (PLS) calibration model was developed. The efficient coefficient of determination (R²), 0.9999 and 0.9998 were attained for Ibuprofen and Paracetamol, respectively. through root mean square error of cross-validation (RMSECV), the accuracy of the calibrated model was verified which was initiated to be 0.064. this study clearly shows that the capability of transmission FTIR spectroscopy for assessment of the accurate quantity of API to control the quality of finishing product and also during processing in pharmaceutical industries excluding the involvement of any other solvent. ^[56]

13. Quantitative analysis of synthetic calcium carbonate polymorphs using FT-IR spectroscopy:

Calcium carbonate is frequently present as preserving insoluble hard scale formations in boilers, cooling towers, heat exchangers, geothermal processing apparatus as well as in various cases (stone formation, pancreatic calcification) and also in mineral (marble, limestones). The several calcium carbonates polymorphs experienced at polymorphs which are generally present numerous cases because it consists of different crystal structure the three phases can be differentiated by using by a vibrational technique that are infrared spectroscopy and Raman spectroscopy. Although for the capability of XRD for quantitative analysis is limited to the minerals having efficient crystal structure X-ray powder diffraction (XRD) can be also used. IR methodologies developed were restricted only to a binary mixture of the calcium carbonate phases likely due to strong overlapping of the bands. therefore no detection limit was reported in this study the effective range of individual calibration line made obvious that the proposed methodologies can be used in the cases where the single component in the mixture was less than 5mol % while calibration line that initiated at 30 mol% were generally used. But in this N.V. Vegenas has used FTIR for recognization of the absorptivities of all the three calcium carbonate crystals crystal phases which in turn used in the order to quantitatively discriminate among all the three calcium carbonate experienced in the aqueous media which involve vaterite, aragonite, and calcite, in the order of decreasing solubility. such as methodology can be applied also for the quantitative determination of the calcium carbonate polymorphs in a ternary mixture. the observational limits were also determined with the help of FTIR spectra of pure calcite, aragonite and vaterite powders with KBr powder, the absorptivities of the absorption bands at 713 cm _1 for calcite, 713 and 700 cm _1 for aragonite and 745 for vaterite were determined. in the order to overcome the absorption band overlapping a set of equation which is further based on Beer s law was developed. The detection limits were also developed and found which is 1.1 _10_4 mg calcite per mm2 of the pellet at 713 cm_1, 3.6_10_4 mg aragonite per mm2 of the pellet at 700cm _1 1.8 _10_4 mg aragonite permm2 of the pellet at 713 cm _1 and 3.1_10_4 mg vaterite per mm2 of the pellet at 745 cm _1. so finally, therefore, the proposed methodology allows the direct simultaneous quantitative determination of calcium carbonates phases opposing the Raman spectroscopy where further only relative ratios can be determined.^[57]

14. Quantitative analysis of ibuprofen in pharmaceutical formulations through ftir spectroscopy:

Ibuprofen [(+/-) 2-(p-isobutyl phenyl propanoic acid, (CH3)2CHCH2C6H4CH3CHCO2H] is generally known as a non-steroidal anti-inflammatory (NSAID), analgesic as well as antipyretic agent.^[58] Therefore, the literature shows several varieties of methods (approved and non-approved by health government agencies) generally to analyze raw ibuprofen (IBU for brevity) and pharmaceutical formulations, such as direct titration including sodium hydroxide in methanol, potentiometric titration, high-performance liquid chromatography, UV spectroscopy and flow injections, infrared analysis. However infrared spectroscopy is the method that is prescribed by the pharmacopeias to identify IBU. In this study the author Garrigues et al. developed the quantification of IBU measuring the infrared absorption of the carbonyl species of the acid through an FTIR spectrometer on-line with a flow injection device^[59] And the authors also pointed out that the device is no commercially available and was specially built for the application which is a disadvantage of the method. moreover, the flow rate fluctuation of the mobile phase and the volume of the sample might be very less the reproducibility of the assays. Nowdays the investigation shows that the development and the validation, according to the US Pharmacopeia recommendation of the quantitative analysis of IBU in tables through infrared spectroscopy. In this study, S.R. MATKOVIC has completed the quantification of ibuprofen through infrared spectroscopy and validated it for further pharmaceuticals in tablet form. The method also includes the extraction of the active ingredient with chloroform and the measurement of the area of the infrared band which is corresponding to the carbonyl group centered at 1721.5 cm_1. the statistical outcome was compared with the quantification of ibuprofen through UV detection. the recovery values attained in the analysis of pharmaceuticals are within the 98-110% range. The quantification of IBU through infrared spectroscopy accomplishes with the requirement of specificity, precision, and also accuracy in order to be used as a method for the quality control of pharmaceutical.^[60]

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Received on 31.05.2020 Modified on 25.06.2020

Asian J. Pharm. Ana. 2020; 10(4):218-230.

DOI: 10.5958/2231-5675.2020.00040.X

S. No.	IR Technique Involved	Analytes	Parameters Determined	Reference
1.	Near IR	Chinese Soyabean from different zones	Moisture, crude fat and protein content	13
2.	Near IR	Miscanthus species	Genetic variation between M. sacchariflorus, M. sinensis, and M. fIoridulu	18
3.	Near IR	Alpha reductase monohydrate	Determination of crystallinity	25
4.	Reflactance IR	Various pharmaceutical ingredients including API	Identification of substandard and falsified medicines	32
5.	Near and Mid IR	Extra virgin olive oil	Identification of 112 virgin oils on olfactory basis	33
6.	FTIR coupled with Partial Least Squares	Virgin olive oil	Monitoring of fatty acid composition	38
7.	Near IR and multivariate calibration	Calcot (Alium cepa)	Determination of chemical properties and composition	40
8.	FTIR, FT-NIR	Edible oils and fats	Determination of authenticity	42
9.	Near IR	Amoxicillin in suspension	Development and validation of multivariate calibration method	43
10.	FT-MIR	Red grape	Analysis of phenolic compounds involved in grape ripening	46
11.	Near-Infrared Reflectance Spectroscopy	Banana fruit pulp	Determination of carotenoid content	47
12.	Transmission-FTIR	Ibuprofen and paracetamol	Simultaneous estimation in formulation	56
13.	FTIR	Calcium carbonate polymorphs	Quantitative analysis in formulations	57
14	FTIR	Ibuprofen	Quantitative analysis in formulations	60