1. INTRODUCTION:

The formation of fixed-dose combinations (FDCs) and multi-drug preparations in the modern pharmaceutical industry has grown in number with the aim of ensuring patient compliance, therapeutic response, and treatment outcomes. Such recipes demand a high level of accuracy and consistency of analytical processes in simultaneous adjustment of a variety of active ingredients to secure the quality and safety of the product. High-Performance Liquid Chromatography (HPLC) is the ideal method to conduct such analysis because it is a highly selective, reproducible, and capable method of dealing with complex mixtures. In addition, the present regulatory requirements by ICH (Q14, Q2(R2)), WHO, and FDA focus on scientifically-grounded, sound, and validated analytical tools, which can be used to guarantee uniform product performance across the product lifecycle. Hence, it can be stated that the creation and confirmation of the HPLC techniques of multiple components estimation is even more pertinent today in the context of quality-by-design and international regulatory conformity of analytical chemistry and its significance in drug analysis.^1,2

Analytical chemistry involves separation, quantification and identification of chemical substances with natural and synthetic materials. Analytical chemistry can be divided into the two classes: Qualitative evaluation, that includes identification of the chemical compounds into the sample mixture and the second is Quantitative evaluation, it includes estimation of the amount of the chemical compound present into the sample mixture³.

1.1 History and evolution of chromatography:

The Chromatographic technique was originally developed by Russian botanist Tswett in 1903¹. HPLC is a highly precise analytical method for both Qualitative and Quantitative evaluation of the pharmaceutical products as well as evaluating the Drug’s stability.^1.

Chromatography is a process or procedure in which we separate solutions into different element using the stationary phase and mobile phase. The Components of the solutions travels at different speed, causing separations. Analytical chromatography is frequently carried out with lesser amount of material to figure out exact proportion of analyte into the solution.³

1.2 Instrumentation of HPLC:

The HPLC equipment comprises of eight primary components: A Mobile phase storage container(reservoir), A system for solvent delivery, A sample introduction system, A column, A detection system, A waste reservoir, tubbing for the connection and An integrating device or a recorder⁴.

1.3 Objective:

To gather and critically evaluate previously described HPLC techniques mentioned in different articles and used for simultaneous estimation for different pharmaceutical product with a special emphasis on the validation characteristics such as Accuracy, Precision, Linearity, etc ⁵ and to evaluate the regulatory frame work (ICH, FDA and WHO) and study its consequences for acceptance of HPLC procedures in pharmaceutical quality control.²

2. BASICS OF HPLC:

2.1 Principle and modes:

HPLC separates components based on differential interactions between analytes, a stationary phase (column packing) and a flowing mobile phase. Reversed-phase (RP-HPLC) is the common choice for pharmaceuticals; normal-phase, HILIC and ion-exchange are used when polarity/ionicity require them^4,5.

2.2 Stationary and Mobile Phase Selection:

Stationary phases (common options and when to choose).

1. C18 (ODS): default for nonpolar–moderately polar small molecules (high retention of hydrophobic analytes).

2. C8, phenyl, cyano, amino: used to tune selectivity (e.g., π–π interactions on phenyl, different silanol interactions on cyano).

3. HILIC phases (polar stationary phases) for highly polar compounds and where retention by aqueous mobile phases is difficult.

4. Choice depends on analyte polarity, pKa, and the separation goal (resolution vs speed)^5,6

2.3 Mobile phase (solvents, pH, buffers, gradient vs isocratic).

1. Common organic modifiers: acetonitrile and methanol. Water + buffer (phosphate, acetate, formate depending on pH needs) is the aqueous portion.

2. pH control is critical for ionizable drugs (pKa vs mobile-phase pH dictates ionization state→ retention and selectivity).

3. Isocratic for simple mixtures or similar retention; gradient for complex/multicomponent mixtures to improve peak shape and reduce run time.^8,7

2.4 Detection systems (UV, PDA, Fluorescence, MS)

Detection systems (UV, PDA/DAD, fluorescence (FLD), MS)^9.

1. UV / PDA (DAD): The most prevalent drugs that absorb in UV region are Analysed using the PDA detector, which help to validate peak purity through spectral matching.

2. Fluorescence (FLD): It is significantly more sensitive and selective for the analyte that exhibit fluorescence, which is beneficial when UV sensitivity is less.

3. MS (LC-MS/MS): This approach provides highest level of selectivity and sensitivity, establishing it as the method of choice for complex matrices and trace level analysis.

2.5 Advantages of HPLC over other analytical techniques^10,11.

1. It used in detection of APIs and impurities present Trace levels (µg/mL or lower), which is typically beyond the capabilities of basic spectrophotometric techniques.

2. HPLC ensures superior resolution in separation structurally similar or co-eluting compounds — a commonly faced difficulties during simultaneous estimation.

3. Unlike TLC or UV, HPLC it enables precise separation even in complex formulations or FDCs that have overlapping spectra.

3. ANALYTICAL METHOD DEVELOPMENT:

New techniques are developed to evaluate the new product that doesn’t have any reported method. New methodologies are establishing to analyse both pharmacopeial and non-pharmacopeial compounds, which helps in reducing the cost and time simultaneously with improving accuracy and durability. Alternative strategies are introduced and implemented to replace the current procedure in comparative laboratory data, considering all significant advantages and disadvantages.^12,13

3.1 Purpose of Method Development⁸

The demand for the New analytical techniques within the pharmaceutical sectors has significantly increased due to the rapid growth of industries and the ongoing production of drugs globally. Consequently, the establishment of the analytical techniques has become an essential part of analysis in Quality control laboratories.

These are the following factors that led to the development of novel drug analysis technique:

1. when the drug substances lack the sufficient analysis techniques due to the inferences caused by the excipients present in the formulation.

2. The existing analytical procedure requires expensive solvent and reagent.

3. If there is no analytical technique available for the quantification and qualification of the analytes⁸.

3.2 Need for Method Development^14,15

The process of Drug evaluation is based on identifying, characterizing, and resolving drugs in various dosage and biological fluids. Analyte methodologies are very crucial in process of drug development and production for generation of the data on:

1. Efficiency (ensuring correct dosage),

2. Impurity (safety concerns),

3. Bioavailability (drug properties such as crystal form, uniformity, and release),

4. Stability (monitoring degradation products).

3.3 Key Parameters in HPLC Method Development^16,17

Fig no 1: Key Parameters in HPLC Method Development^16,17

3.3 Steps for Analytical Method Development^.4,5,16,18

1. Understanding analyte properties:

Study solubility, pKa, logP, UV absorption (λmax), and stability to guide selection of mobile phase, buffer pH, diluent, and to predict retention and peak shape.

2. Preliminary (scouting) conditions:

Select an initial column (commonly RP-C18), tentative mobile phase, suitable detector, and preliminary flow rate and temperature to obtain initial separation and approximate retention times.

3. Sample and diluent preparation:

Prepare standard and sample solutions using compatible diluents, filter to remove particulates, and confirm analyte stability to avoid peak distortion and irreproducibility.

4. Method optimization:

Systematically adjust chromatographic parameters such as mobile phase composition, pH, gradient profile, flow rate, temperature, and modifiers to improve resolution, peak symmetry, and run time.

5. Robustness and reproducibility testing:

Evaluate the effect of small deliberate variations in method parameters (pH, flow, temperature, buffer strength, column lot) to ensure consistent performance under routine conditions.

6. Method validation:

Validate the method for specificity, linearity, accuracy, precision, range, LOD/LOQ, recovery, and stability-indicating capability as per regulatory guidelines.

7. Application to real samples:

Apply the validated method to actual pharmaceutical formulations or biological samples to confirm absence of matrix interference and reliable quantification in routine quality control.

4.Experimental Design Approaches in HPLC Development ⁽^19,20,22)

Fig no 2: Experimental design approach^19,20,22

5. Criteria for Selection of Drug Candidates for Multicomponent HPLC Analysis.^21,22

5.1 Analytical Target Profile (ATP):

Defines required method performance (specificity, accuracy, precision, LOD/LOQ, robustness) and ensures the method is fit for purpose.

5.2 Critical Quality Attributes (CQAs):

Identify essential components—APIs, impurities, degradation products—that must be separated and quantified.

5.3 Physicochemical Properties:

Polarity, pKa, solubility, UV absorbance, stability, and molecular size affect retention, separation, and detection.

5.4 Selectivity / Specificity:

Analytes must be completely separated without interference from excipients or degradation products.

5.5 Detection and Quantification Limits:

Method must detect and quantify analytes at expected levels, including trace impurities.

5.6 Method Robustness:

Evaluate effects of small changes (pH, mobile phase, flow rate) to ensure consistent performance.

5.7 Regulatory Lifecycle:

Method should remain valid throughout product shelf life and comply with regulatory requirements.

6. Sample Preparation Techniques.

Fig no 3: Sample preparation Technique.^23-26

7. HPLC Method Validation:

7.1 Scope of Validation ^27,28

The scope of validation defines the intended purpose and applicability of the HPLC method as per ICH Q2(R2). It specifies the type of method, sample matrix, analyte(s), working concentration range, and its regulatory use such as QC testing or stability studies.

7.2 Parameters of Validation

Table no 1: Parameters of validation^27,29

Parameter	What	How (Brief)	Typical Acceptance
Specificity	Ability to measure analyte without interference	Blank, placebo, spiked samples, forced degradation, peak purity	Rs > 1.5, no co-elution
Linearity	Response proportional to concentration	≥5 levels, regression equation, r²	r² ≥ 0.99 (typical), justified criteria
Accuracy	Closeness to true value (% recovery)	Spike at 80, 100, 120% (n≥3)	98–102% (assay), as justified for impurities
Precision	Agreement between results	Repeatability (n≥6), intermediate precision	%RSD ≤ 2% (assay)
Range	Working concentration interval	Based on linearity, accuracy, precision data	Assay: 80–120%; Impurities: LOQ–120%
LOQ	Lowest quantifiable level	S/N ≈10:1 or SD/slope	%RSD ≤ 20% at LOQ
LOD	Lowest detectable level	S/N ≈3:1 or SD/slope	Detectable, not necessarily precise
System Suitability	System performance check	n≥5 injections; check N, T, Rs, %RSD	%RSD ≤2%, Rs >1.5
Robustness / Ruggedness	Effect of small variations / different conditions	Deliberate parameter changes	No significant impact on results

11. CONCLUSION:

Simultaneous estimation of multicomponent drugs by HPLC is a vital analytical approach in pharmaceutical quality control due to the increasing use of fixed-dose combinations. HPLC offers high selectivity, sensitivity, and reproducibility, making it suitable for accurate separation and quantification of multiple active ingredients and their degradation products. Systematic method development based on analyte physicochemical properties, appropriate column and mobile phase selection, and optimized detection ensures reliable performance.

Incorporation of forced degradation studies is essential for establishing stability-indicating methods and meeting regulatory expectations outlined by ICH, FDA, and WHO guidelines. Proper validation of parameters such as specificity, accuracy, precision, linearity, robustness, and detection limits confirms the method’s suitability for routine analysis and lifecycle management.

The extensive literature review of antihypertensive and antihyperlipidemic drug combinations clearly indicates that reversed-phase HPLC remains the most widely adopted and versatile technique for simultaneous estimation, offering high resolution, sensitivity, and applicability to routine quality control.

Overall, well-designed and validated HPLC methods play a critical role in ensuring the quality, safety, and efficacy of multicomponent pharmaceutical products, while emerging trends such as AQbD, UHPLC, green chromatography, and hyphenated techniques continue to enhance method efficiency and regulatory compliance.

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Received on 16.01.2026 Revised on 05.03.2026

Accepted on 11.04.2026 Published on 16.04.2026

Available online from April 18, 2026

Asian Journal of Pharmaceutical Analysis. 2026; 16(2):153-159.

DOI: 10.52711/2231-5675.2026.00023

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Creative Commons License.

Sr No.	Name of Drug	Mobile phase, Detection wavelength, flow rate	Flow rate	Rt (Retention time)	References
1	Olmesartan Medoxomil+ Amlodipine Besylate	Acetonitrile: Methanol: water (60: 28: 12 v/v/v), 238nm, 10min	0.6ml/min	4.1 minutes and 3.5 minutes, respectively.	37
2	Olmesartan+ Amlodipine	TEA Buffer of pH 3.0: Acetonitrile (25:75), 258nm, 6min.	1ml/min	2.39 min and 3.33 min respectively.	38
3	Olmesartan Medoxomil+ Amlodipine Besylate	Acetonitrile:0.05 M ammonium acetate buffer: 0.1 mL triethylamine at pH 6.8, 239nm, 10min.	1ml/min	3.1 and 5.0 min, respectively	39

Sr No	Name of drug	Mobile phase, Detection wavelength, Run time	Flow rate	Rt (retention time)	References
1	Perindopril+ Indapamide	Acetonitrile: Phosphate Buffer 0.05 Molar (pH 3.5) (ration: 60:40), 215nm, 10min.	1ml/min	3.5 and 7.3 min, respectively.	42
2	Perindopril+ Indapamide	phosphate buffer pH 3.5±0.05 and methanol in the ratio of 65:35 v/v,215nm, 10min.	1.0mL/min	3.53 min and 4.09 min respectively.	43

Sr No	Name of drug	Mobile phase, Detection wavelength, Run time	Flow rate	Rt (retention time)	References
1	Atorvastatin + Ezetimibe	Phosphate buffer (pH 4.5): Acetonitrile [35:65, v/v], 228nm, 6min.	1 ml/min	2.36 and 3.43 min, respectively	44
2	Atorvastatin + Ezetimibe	Phosphate buffer [pH 3.5 with Ortho Phosphoric Acid] – acetonitrile 40:60 (v/v),235nm,8min.	1.2 ml/min	3.54 min and 4.47 min, respectively	45
3	Atorvastatin + Ezetimibe	acetonitrile: ammonium acetate buffer pH 3.0 (50:50, v/v), 247nm, 12min.	1.2 ml/min	3.0 and 5.2 minutes respectively.	46

Sr No	Name of drug	Mobile phase, Detection wavelength, Run time	Flow rate	Rt (retention time)	References
1	Simvastatin + Niacin	Methanol: water in ratio 85:15 water consisting of Triethylamine (TEA) (0.05%v/v),250nm, 10min.	1 ml/min	8.5 min and 1.8min, respectively	47
2	Simvastatin + Niacin	Phosphate buffer pH 2.5, Methanol and Acetonitrile in the ratio of 45:20:35,220nm,6min.	1.0 ml/min	2.970min and 4.747 min, respectively	48

Sr No	Name of drug	Mobile phase, Detection wavelength, Run time	Flow rate	Rt (retention time)	References
1	Olanzapine and Samidorphan	Acetonitrile and Mono basic potassium phosphate in a ratio of 50:50% v/v, 280nm.	1.0 mL/min	2.223 min and 3.257min, respectively	49
2	Olanzapine and Samidorphan	Buffer 0.01N Potassium dihydrogen phosphate: Methanol taken in the ratio 80:20 %v/v, 278nm.	0.9 ml/min	3.108 min and 2.365 min, respectively	50
3	Olanzapine and Samidorphan	buffer and acetonitrile within the ratio of 60:40, 261nm, 15min.	1.0 ml/min	4.636min and 7.732 min, respectively	51