INTRODUCTION:

Pharmaceutical analysis cab be defined as a group of procedures used for identification, determination, separation, purification, and structural elucidation of a pharmaceutical substances used in the development of pharmaceutical products. Based on the goal (identification and/or determination) of the analysis, pharmaceutical analysis may be divided into two broad types: Qualitative and Quantitative analysis.¹

The most precise analytical technique for both quantitative and qualitative pharmaceutical analysis is high performance liquid chromatography (HPLC).² Pharmacopeial tests still mainly rely on direct UV spectroscopy, however in the industry, UV spectrophotometry detection is typically paired with an initial HPLC separation.³ Particularly reversed phase HPLC (RP-HPLC), is the most prevalent method of analysis.⁴ Developing these methods can be a time-consuming that takes up more research time. It is common practice to create methods employing the one factor at a time (OFAT) approach, which involves changing one variable at a time until an appropriate chromatographic condition is found.⁵ Another science based and less time consuming approach is the QbD approach. The literature survey revealed that there is no QbD approach implemented for estimation of TBF HCl and ITZ by RP-HPLC in combined pharmaceutical dosage form. So, the purpose of this study is to develope a quick, sensitive, precise and robust analytical technique employing the QbD strategy and to allow the use of the method for estimating ITZ and TBF HCl together in tablet dosage form and for separating the peaks of degradation products.^6,7,8

The Food and Drug Administration (FDA) has taken a leading role in advancing the concept of (QbD), which encourages integrating quality into the process developement and the end product rather than attempting to do it retroactively. The International Conference on Harmonization (ICH) has released a number of guidelines to standardize and streamline the application of the QbD framework.⁹

According to ICH Q8 QbD is defined as “A systematic approach to the development that begins with predefined objectives and emphasizes product and process understanding and process control, based on sound science and quality risk management.”10 To detect and quantify several drugs in a single dosage form, methods developed by the QbD approach involve fewer tests and are faster which leads to less expense.¹⁰

Table 1: Difference between current approach and QbD approach

Current approach	QbD approach
Testing and inspections are used to ensure quality.	Quality is built into the product and process, supported by scientific knowledge.
It only accepts submissions with a significant amount of data with disconnected information and no "big picture" perspective.	It contains a Knowledge-rich proposal that demonstrates product and process knowledge.
Any parameters are dependent on batch history in this case.	Any specifications based on product performance criteria can be found here.
There is a "frozen process" here, which is constantly opposed to change.	Within the design space, there is a flexible approach that allows for ongoing improvement.
It emphasizes repeatability while ignoring variance.	It focuses on robustness, or the ability to recognize and control variance.

As a result, the suggested study employs QbD with a lower cost of analysis to provide sensitivity and accuracy to the developed technique.^11,12,13

Crucial steps for effective QbD implementation in HPLC

· Establish the experiment’s goal - According to the conventional way of thinking, you may infer any pertinent information after you get the findings from the experiment. This strategy also adheres to the notion that in order to gather accurate data, the number of experiments should be as high as possible. Rather, in QbD-supported studies, the aim (analysis of the analyte's chromatographic behaviour, separation of closely eluted analytes) should be defined before experiments are conducted. As a result, HPLC research becomes more rational and of higher quality.¹⁴

· Perform preliminary studies - During the initial trials, the standard methodology for the development and validation of the HPLC technique should be followed. The goal of this stage is to choose the basic HPLC conditions, such as type of column and composition of mobile phase. Nevertheless, a rising number of research are adopting the QbD to address the problem of choosing the mobile phase.^15,16

· Choose the experimental variables and their levels - The accurate identification of all the crucial factors is essential to the success of QbD-supported HPLC research. It is possible to see unusual behaviour of the analytical system if a crucial variable isn’t recognized as an input factor. On the other hand, sequential phases of research may become excessively difficult if an unimportant variable is found as a factor.¹⁷

· Select the response – Response is the quality or quantity value that has been observed or measured and that we use to determine the importance of a factor or that we wish to optimize. Defining several responses that must be observed during the experiment is general practice. Most frequently, responses like selectivity and retention factors are assessed during the stage of screening stage for development of method. Resolution and retention factor, all be observed during the optimization phase.¹⁸

· Plan the experiment - A convenient design for experimental work must be selected in this step. The designs can be divided into two distinct groups based on the ultimate objective of HPLC experiments: screening designs and response surface designs. To determine how the factors affect the desired result, screening designs are tested. Screening designs identify components and their interactions with the greatest effects because there are many variables that may have an impact on the HPLC retention. Only the remaining factors are thoroughly analysed using a response surface design, and factors that do not have a major impact are not taken into account. Since they are intended to set up experimental conditions under which the best desirable response and/or criteria (maximum, minimum or range) are obtained, response surface designs are referred to as optimization designs.¹⁹

· Perform the experiment - The QbD methodology downplays experimental work, yet it is still important to conduct and produce results. To lower the influence of uncontrollable factors, the trials must be run in a random order. Performing experiments in duplicates, which are used to evaluate the experimental error, is also recommended.²⁰

· Analyze the data - There are two different kinds of statistical data analysis: regression analysis and analysis of variance (ANOVA). To evaluate the link between factors and response, regression analysis is performed. The multiple-linear regression (MLR) approach is the most often used regression method because a substantial number of variables must be fitted into the mathematical model. The F-test in an ANOVA is used to determine if one or more factors are significant. The resulting model can be validated with the help of ANOVA.²¹

Validation of analytical method is the process of demonstrating that an analytical approach is suitable for its intended application. Validation data must be produced in accordance with a protocol endorsed by the sponsor, using qualified instrumentation, and adhering to current good manufacturing practices. The protocol must include a methodology description for each validation characteristic as well as predetermined and justified acceptance criteria. The USP, ICH Q2(R1), FDA etc. guidelines can provide a basis for the validation of pharmaceutical techniques. Results of method validation dictates the reliability, quality and consistency of the developed method.^22,23

Stress testing helps to achieve a number of objectives, including the identification of degradation products, design of degradation routes, assessment of the inherent stability of therapeutic molecules, and validation of the analytical process. Stability tests are used to indicate how a drug substance's or product's quality might alter over time as a result of a variety of environmental conditions, including light, humidity and temperature. This information is used to recommend storage conditions, retest intervals, and shelf lives. Various scenarios recommended for forced degradation studies include acidic, alkaline, thermal, oxidative, neutral hydrolysis and light stress conditions.^24,25,26,27

MATERIALS AND METHODS:

Materials:

R.S.I.T.C Jalgaon supplied the bulk ITZ and TBF HCl. HPLC quality orthophosphoric acid provided by Avantor performance material India Ltd., Thane. HPLC quality methanol and water supplied by Merck Speciality Ltd., Mumbai. Analytical grade chemicals were employed for the rest of the experiment. The antifungal formulation in tablet dosage form, Duofaze (Itraconazole 100 mg + Terbinafine HCl 250mg) was purchased from a local pharmacy.

Equipments:

Younglin (S.K) gradient system equipped with reversed phase C18 (Agilent) column (4.6 x 250mm), SP930 D pump, 20µl injection loop and UV730D (DAD) absorbance detector was used for the whole analysis. Autochro-3000 software was used to collect and analyze the data from the operation. Ultrasonicator was used to degas the mobile phase.

Selection of analytical wavelength (Isoabsorptive point):

ITZ and TBF HCl standard solutions (10ppm each) were prepared and scanned individually by UV spectrophotometer in the 200-400nm wavelength range. From their combined UV spectra, isoabsorptive point was obtained at wavelength of 270nm which is used as detection wavelength for the separation of ITZ and TBF HCl.

Figure 1: Merged ultraviolet spectrum Itraconazole & Terbinafine HCl.

Mobile phase preparation:

HPLC grade methanol and 0.05% orthophosphoric acid in 84:16 volume mixed and degassed in ultrasonicator for 10-15min.

Standard preparation:

Ratio of label claim of both APIs were taken which was 10:25. Hence 10mg of bulk ITZ and 25mg of bulk TBF HCl weighed accurately and then transferred into two separate volumetric flask of 10mL, dissolved in mobile phase and sonicated (Stock I and II). By using stock solution prepared freshly, 5 to 25 and 12.5 to 62.5 µg/mL dilutions were prepared for ITZ and TBF HCl respectively.

Sample preparation:

When 20 tablets were individually weighed, the average tablet weight was found to be 630mg. Single tablet was finely grounded in dry and clean, mortar and pestle. Equivalent weight of tablet was calculated as 63mg. Then 63mg grounded tablet was transferred in volumetric flask of 10mL. (1000 and 2500µg/mL ITZ and TBF HCl respectively)

RESULT AND DISCUSSION:

Authentication of bulk API:

Bulk ITZ and TBF HCl was authenticated with the help of melting point determination and UV spectrophotometer. Melting point for ITZ and TBF HCl was found to be 170°C and 197°C respectively. Whereas maximum absorption wavelength for ITZ and TBF HCl was detected at 268nm and 282nm respectively.

Design of experiment:

At first, tests were carried out to choose a mobile phase that provides a reasonable separation between the two analytes. Various mobile phases using water with 0.05% orthophosphoric acid buffer as the aqueous portion were tested. As organic modifiers, acetonitrile and methanol were investigated. The variables that affected significantly the measured responses, were identified using the Taguchi screening method. Mobile phase ratio and flow rate were found to be the significant. Because of great efficiency and ability to minimize the number of runs, CCD was frequently adopted. Version 9.0.02 of design Expert® software was used to fit the entire second order polynomial equations. The mathematical model associated with the design includes both main effects and possible interaction effects (2 FI). While building CCD, two factors having significant impact on the response were optimized using three levels of each (−α, 0, +α) providing 8 random runs. The evaluated responses were the retention time, peak area and resolution (R). To predict the optimized composition overlay plotting was done using brute force method and numeric approach of desirability function. The ideal composition was also determined using the Overlay Plot (i.e., combined contour plot) feature of the software. By balancing diverse responses inside this ideal region, an optimal chromatographic condition was discovered.

Table 2: Optimised chromatographic conditions for TBZ HCl and ITZ

Parameters	Optimised condition
Column	C18(Agilent) 4.6 x 250 mm, 5 µm
Mobile phase	Methanol: 0.05% O.P.A - pH 3.5, 84:16
Detection wavelength	270nm
Column temperature	250C
Flow rate	0.95mL/min
Injection volume	20µL
Run time	10min

Figure 2: Typical chromatogram of sample solution (62.5 mg TBF HCl and 25 mg ITZ) with optimized chromatographic condition.

Method validation:

The optimized method was validated for the following parameters in accordance with ICH guidelines:

a) System suitability (repeatability):

The test is based on the idea that the tools, electronics, analytical processes, and test samples form an integrated system (ICH Q2B).²⁸ Six replications of freshly made standard solutions were tested to determine the system suitability of the developed method. The observed RSD values fell well within the accepted limits (≤ 2%). TBF HCl and ITZ's theoretical plates, tailing factor, and resolution were calculated and found to be within the permitted limits.

b) Linearity and range:

Linearity is the ability of an analytical method to produce test results that are directly proportional to the concentration (amount) of analyte in the sample.²⁹ Five concentrations of ITZ and TBF HCl was made in the range of 5 to 25 and 12.5 to 62.5 µg/mL. Analysis were done in triplicate for each concentration. Average area from each concentration taken for the regression analysis. Calibration curve was obtained by taking average area vs concentration. Obtained R² values are reported below.

Figure 3: Calibration curve for TBF HCl and ITZ

c) Accuracy (recovery):

The accuracy of an analytical technique is defined as the degree of agreement between the value considered to be a conventional true value or a recognized reference value and the value obtained experimentally.³⁰ By using the usual addition method, the accuracy was tested at three distinct concentration levels of 80%, 100%, and 120%. The percentage recovery found within 98% to 102%. As a result, the suggested approach demonstrated great accuracy and good recoveries.

Table 3: Results of accuracy (recovery)

Drug	% level	Amount taken (µg/mL)	Amount added (µg/mL)	Amount recovered Mean±SD	% recovery Mean ± SD
TBF HCl	80%	25	20	20.38±0.11	101.94±0.59
	100%	25	25	24.78±0.11	99.11±0.42
	120%	25	30	30.23±0.28	100.77±0.94
ITZ	80%	10	8	7.85±0.02	98.09±0.23
	100%	10	10	10.25±0.03	102.55±0.34
	120%	10	12	11.94±0.10	99.50±0.79

d) Precision:

The precision of an analytical method is defined as the amount of variation between a series of measurements obtained from serial sampling of the same homogenous sample under the given conditions.³¹ Intraday and interday precisions were performed. The calculated percent RSD values were confirmed to be below the permissible limit (RSD <2%). It reveals that the analytical approach has a high precision percent amount ranging from 98% to 102%.

Table 4: Results of precision

Drug	Conc (µg/mL)	Intraday precision		Interday precision
Drug	Conc (µg/mL)	Mean±SD	% amount found	Mean±SD	% amount found
TBF HCl	25	310.31±0.74	100.88	302.31±0.66	98.32
	37.5	480.35±0.73	101.95	480.35±0.67	101.95
	50	623.22±1.65	100.68	624.22±1.65	100.84
ITZ	10	282.44±1.81	100.50	288.11±0.85	102.70
	15	412.95±0.71	100.00	416.45±1.42	101.20
	20	549.79±1.56	101.45	551.29±0.56	101.75

e) Robustness:

The suggested method's sensitivity to modest changes in the optimized conditions was further investigated. Changes were made in following parameters of optimized method: flow rate (±0.10mL), mobile phase volume (±1mL) and detection wavelength (±1nm).^32,33 % RSD were calculated to assure robustness of method and which should be < 2%.

Table 5: Results of robustness

Condition	Wavelength
Wavelength variation	269 nm	271 nm
Std (µg/mL)	15	15
Amount found (µg/mL)	15.19	15.44
% amount recovered	101.23	102.00
% RSD	0.1646	0.5181
Condition	Flow rate
Flow rate variation (mL/min)	0.85		1.5
Std (µg/mL)	15		15
Amount found (µg/mL)	15.33		14.83
% amount recovered	102.11		98.86
% RSD	0.2282		0.4045
Condition	Mobile phase ratio
Mobile phase ratio variation	83:17		85:15
Std (µg/mL)	15		15
Amount found (µg/mL)	15.32		14.74
% amount recovered	102.01		98.26
% RSD	0.4569		0.5427

f) LOD and LOQ:

The method's sensitivity was assessed with respect to LOD and LOQ. LOD is the lowest detectable concentration that cannot be measured.³⁴ On the other side, the lowest concentration that that can be measured is the LOQ.

Table 6: Results of LOD and LOQ

Drug	LOD (µg/mL)	LOQ (µg/mL)
TBF HCl	0.350	1.061
ITZ	0.131	0.398

Assay of marketed formulation:

The proposed methodology was successfully implemented on marketed tablets. The %RSD and the % label claim for ITZ and TBF HCl are in good agreement. Hence for routine analysis the proposed methodology could be used to determine ITZ and TBF HCl in tablet dosage forms.

Table 1: Results of assay

Marketed formulation (Duofaze)	Label claim (mg/tablet)	Conc. (µg/mL)	Amount found (µg/mL)	% amount found	% RSD
ITZ	100	20	19.79	98.96	0.71
TBF HCl	250	50	49.74	99.48	0.42

Degradation study:

Forced degradation studies on ITZ and TBF HCl marketed tablet formulation were conducted by subjecting the formulation to various stress conditions. Acidic, alkaline, neutral and oxidative stress was applied to determine the potential of the developed method to separate ITZ and TBF HCl from their degradation products. It will also show how quickly and how much it degrades under processing and storage circumstances.

Table 8: Results of degradation studies

Parameters	Drug	% degradation	% RSD
Acid	ITZ	9.32	0.34
Acid	TBF HCl	6.62	0.49
Base	ITZ	7.74	0.67
Base	TBF HCl	5.87	0.32
Oxidative	ITZ	4.8	0.18
Oxidative	TBF HCl	7.41	0.37
Neutral	ITZ	0.74	0.94
Neutral	TBF HCl	0.96	0.44

CONCLUSION:

For estimation of ITZ and TBF HCl in tablet dosage form, a novel, cost effective, accurate, sensitive and robust RP-HPLC method was developed utilizing QbD approach. Taguchi screening was applied to screen the critical factors having impact on selected responses and finally chromatographic conditions were optimized by utilizing central composite design (CCD). The suggested method met the highest levels of linearity, specificity, accuracy, system suitability, and robustness after being validated in accordance with ICH recommendations. The developed method's precision was determined to be good, as shown by low %RSD values below the permitted limit. From specificity and percentage recovery values it can be concluded that the excipients in the formulations do not cause any interference. Values for LOD and LOQ have been identified to be optimal. The sample was also subjected to forced degradative conditions like acid, base, H₂O₂ and neutral. Obtained results shows that the degraded peaks of compound from sample peaks was achievable with the developed method. Hence the method can be utilized in routine analysis of ITZ and TBF HCl in pharmaceutical formulations.

CONFLICT OF INTEREST:

The authors have no conflicts of interest regarding this investigation.

ACKNOWLEDGMENTS:

The authors would like to express their profound gratitude to all of those with whom they have had the pleasure to work.

REFERENCES:

1. Akash MS, Rehman K, Akash MS, Rehman K. Ultraviolet-visible (UV-VIS) spectroscopy. Essentials of Pharmaceutical Analysis. 2020; 29-56. doi.org/10.1007/978-981-15-1547-7_3

2. Vidushi Y, Meenakshi B, Bharkatiya MB. A review on HPLC method development and validation. Res J Life Sci, Bioinform, Pharm Chem Sci. 2017; 2(6): 178. doi.org/10.26479/2017.0206.12

3. Watson DG. Pharmaceutical analysis E-book: a textbook for pharmacy students and pharmaceutical chemists. Elsevier Health Sciences; 2020 Jun 10.

4. Bhatt DA, Rane SI. QbD approach to analytical RPHPLC method development and its validation. International Journal of Pharmacy and Pharmaceutical Sciences. 2011; 3(1): 179-87.

5. Costa GM, Gazola AC, Madóglio FA, Zucolotto SM, Reginatto FH, Castellanos L, Ramos FA, Duque C, Schenkel EP. Vitexin derivatives as chemical markers in the differentiation of the closely related species Passiflora alata Curtis and Passiflora quadrangularis Linn. Journal of Liquid Chromatography & Related Technologies. 2013 Apr 1; 36(12): 1697-707. doi.org/10.1080/10826076.2012.695316

6. Kathirvel S, Gayatri Ramya, Rajesh Akki, Prem Kumar. Newer RP-HPLC Method Development and Validation for the Simultaneous Estimation of Terbinafine and Itraconazole in Combined Dosage Form. IJPPR. 2019; 17(1): 233-244.

7. Rode DM, Rao DN. Stability-indicating method development and validation of itraconazole and terbinafine HCl in bulk and pharmacutical tablet dosage form. Asian J. Pharm. Clin. Res. 2019; 12: 51-5. doi.org/10.22159/ajpcr.2019.v12i9.33922

8. Vankayalapati Manjusha, P. Sreenivasa Prasanna, K. Thejomoorthy. Stability indicating method development and validation for the estimation of terbinafine and itraconazole in API and tablet dosage form by RP-HPLC. WJPMR. 2021; 7(6): 322-332.

9. Nistor I, Lebrun P, Ceccato A, Lecomte F, Slama I, Oprean R, Badarau E, Dufour F, Dossou KS, Fillet M, Liégeois JF. Implementation of a design space approach for enantiomeric separations in polar organic solvent chromatography. Journal of Pharmaceutical and Biomedical Analysis. 2013 Feb 23; 74: 273-83. doi.org/10.1016/j.jpba.2012.10.015

10. Patil AS, Pethe AM. Quality by Design (QbD): A new concept for development of quality pharmaceuticals. International journal of pharmaceutical quality assurance. 2013 Apr;4(2):13-9.

11. Thakur D, Kaur A, Sharma S. Application of QbD based approach in method development of RP-HPLC for simultaneous estimation of antidiabetic drugs in pharmaceutical dosage form. Journal of Pharmaceutical Investigation. 2017 May; 47(3): 229-39. doi.org/10.1007/s40005-016-0256-x

12. Jatte KP, Chakole RD, Charde MS. Degradation profiling of lisinopril and hydrochlorothiazide by RP-HPLC method with QBD approach. Asian Journal of Pharmaceutical Analysis. 2021; 11(4): 270-4. doi.org/10.52711/2231-5675.2021.00046

13. Ashok PK, Dinkar FS. Determination and Development of UV-Spectrophotometric method for the Amodiquine Hydrochloride by using quality by design (QBD) approach. Asian Journal of Pharmaceutical Analysis. 2019; 9(3): 113-7. doi.org/10.5958/2231-5675.2019.00021.8

14. Leardi R. Experimental design in chemistry: A tutorial. Analytica Chimica Acta. 2009 Oct 12; 652(1-2): 161-72. doi.org/10.1016/j.aca.2009.06.015

15. Hadjmohammadi MR, Ebrahimi P. Optimization of the separation of anticonvulsant agents in mixed micellar liquid chromatography by experimental design and regression models. Analytica Chimica Acta. 2004 Jul 19; 516(1-2): 141-8. doi.org/10.1016/j.aca.2004.04.019

16. Vemić A, Stojanović BJ, Stamenković I, Malenović A. Chaotropic agents in liquid chromatographic method development for the simultaneous analysis of levodopa, carbidopa, entacapone and their impurities. Journal of Pharmaceutical and Biomedical Analysis. 2013 Apr 15; 77: 9-15. doi.org/10.1016/j.jpba.2013.01.007

17. Stojanović BJ. Factorial-based designs in liquid chromatography. Chromatographia. 2013; 5(76): 227-40. doi.org/10.1007/s10337-012-2350-1

18. Ganorkar SB, Shirkhedkar AA. Design of experiments in liquid chromatography (HPLC) analysis of pharmaceuticals: Analytics, applications, implications and future prospects. Reviews in Analytical Chemistry. 2017 Sep 1; 36(3). doi.org/10.1515/revac-2016-0025

19. Vogt FG, Kord AS. Development of quality-by-design analytical methods. Journal of Pharmaceutical Sciences. 2011 Mar 1; 100(3): 797-812. doi.org/10.1002/jps.22325

20. Sahu PK, Ramisetti NR, Cecchi T, Swain S, Patro CS, Panda J. An overview of experimental designs in HPLC method development and validation. Journal of Pharmaceutical and Biomedical Analysis. 2018 Jan 5; 147: 590-611. doi.org/10.1016/j.jpba.2017.05.006

21. FDA Guidance Document Analytical Procedures and Methods Validation for Drugs and Biologics JULY 2015

22. Ravisankar P, Navya CN, Pravallika D, Sri DN. A review on step-by-step analytical method validation. IOSR J Pharm. 2015 Oct;5(10):7-19.

23. Sinha VR, Kumria R, Bhinge JR. Stress degradation studies on duloxetine hydrochloride and development of an RP-HPLC method for its determination in capsule formulation. Journal of Chromatographic Science. 2009 Aug 1; 47(7): 589-93. doi.org/10.1093/chromsci/47.7.589

24. Naidu KR, Kale UN, Shingare MS. Stability indicating RP-HPLC method for simultaneous determination of amlodipine and benazepril hydrochloride from their combination drug product. Journal of Pharmaceutical and Biomedical Analysis. 2005 Sep 1; 39(1-2): 147-55. doi.org/10.1016/j.jpba.2005.04.001

25. Leyden J. Pharmacokinetics and pharmacology of terbinafine and itraconazole. Journal of the American Academy of Dermatology. 1998 May 1; 38(5): 42-7. doi.org/10.1016/S0190-9622(98)70483-9

26. Patel RA, Patel MP, Raj HA, Shah N. Forced Degradation Studies of Olmesartan Medoxomil and Characterization of Its Major Degradation Products by LC-MS/MS, NMR, IR and TLC. Asian Journal of Pharmaceutical Analysis. 2015; 5(3): 119-25. doi.org/10.5958/2231-5675.2015.00019.8

27. Thangabalan B, Salomi M, Sunitha N, Babu SM. Development of validated RP-HPLC method for the estimation of Itraconazole in pure and pharmaceutical dosage form. Asian Journal of Pharmaceutical Analysis. 2013;3(4):119-23. doi.org/10.52711/2231-5675.2021.00031

28. Sri KV, Anusha M, Reddy SR. A rapid RP-HPLC method development and Validation for the Analysis of Linagliptinin Bulk and Pharmaceutical Dosage Form. Asian Journal of Pharmaceutical Analysis. 2015; 5(1):16-20. doi.org/10.5958/2231-5675.2015.00003.4

29. Konidala SK, Penumala A, Mugada VK, Kamala GR. Development and validation of RP-HPLC method for simultaneous estimation of Paracetamol and Flupirtine Maleate. Asian Journal of Pharmaceutical Analysis. 2015; 5(2): 105-11. doi.org/10.5958/2231-5675.2015.00017.4

30. Gandla K, Lalitha R, Bommakanti S, Suthakaran R, Pallavi K. Development and Validation of RP-HPLC Method for Simultaneous Estimation of Albendazole and Praziqantel in Tablet Dosage Form. Asian Journal of Pharmaceutical Analysis. 2015; 5(3): 115-8. doi.org/10.5958/2231-5675.2015.00018.6

31. Ganji S, Satyavati D. Development and validation of RP-HPLC method for the analysis of Cobicistat and related impurities in bulk and pharmaceutical dosage forms. Asian Journal of Pharmaceutical Analysis. 2015; 5(1): 1-8. doi.org/10.5958/2231-5675.2015.00001.0

32. Mangalagiri Y, Mamidala SS, Konidala SK. A simple and validated RP-HPLC method for the simultaneous determination of Ezetimibe and Fenofibrate in bulk and pharmaceutical dosage forms. Asian Journal of Pharmaceutical Analysis. 2015; 5(2): 93-9. doi.org/10.5958/2231-5675.2015.00015.0

33. Israel DS, Ganji S, Kumar BV. A Rapid RP HPLC Method Development and Validation for the Analysis of Divalproex in Bulk and Pharmaceutical Dosage Forms. Asian Journal of Pharmaceutical Analysis. 2016; 6(1): 15-22. doi.org/10.5958/2231-5675.2016.00003.X

34. Vanaja N, Preethi C, Manjunath SY, Pal K. Method development and validation for simultaneous estimation of telmisartan and chlorthalidone by RP-HPLC in pharmaceutical dosage form. Asian Journal of Pharmaceutical Analysis. 2015; 5(4): 171-7. doi.org/10.5958/2231-5675.2015.00027.7

Received on 27.04.2023 Modified on 17.11.2023

Asian J. Pharm. Ana. 2024; 14(2):69-75.

DOI: 10.52711/2231-5675.2024.00013