Simultaneous Determination of Paracetamol , Acetyl Salicylic Acid , Mefenamic Acid and Cetirizine Dihydrochloride in the Pharmaceutical Dosage Form

A simple, specific, accurate and economical isocratic reversed phase liquid chromatographic (RP-HPLC) method was developed and subsequently validated for the determination of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride. Separation was achieved with a Nucleodur 100 C–18 column having 250 x 4.6 mm i.d. with 5 μm particle size and disodium hydrogen phosphate buffer adjusted to pH 6.5 using diluted orthophosphoric acid and acetonitrile (60:40 v⁄v) as eluent at a constant flow rate of 1.0 mL per min. UV detection was performed at 220 nm. The retention time of acetyl salicylic acid, paracetamol, mefenamic acid and cetirizine dihydrochloride were 2.01 min, 2.92 min, 4.91 min and 10.2 min respectively. This method is simple, rapid and selective and can be used for routine analysis of analgesic and antipyretic drugs in pharmaceutical formulations. The proposed method was validated and successfully used for estimation of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride in the pharmaceutical dosage form.


Introduction
Analysis is an integral component of preformulation, formulation and active ingredient drug development research.It is essential to have a validated, stability indicated or specific analytical method of analysis for the drug for which the drug delivery system is to be designed.If a suitable analytical method is not available then it is essential to develop an appropriate simple, specific, accurate and economical analytical method for the selected drug to aid during various steps of formulation design.Reversed phase liquid chromatographic (RP-HPLC) technique is one of the latest and most widely applied techniques for drug estimation.Reversed phase liquid chromatographic method is preferred over other techniques for routine analysis of drug as it is less time consuming and also economical.A literature survey regarding quantitative analysis of these drugs revealed that attempts were made to develop analytical methods for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride using spectrophotometry [1][2][3][4][5][6][7][8][9][10][11][12][13] , titration 14 , HPTLC 15 , disintegration test 16 , dissolution test 17 , FTIR, DSC and XRD 18 , IR and NMR 19 , HPLC [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] , LC -eletrospray ionization MS 38 , LC -MS/MS 39 and micellar electrokinetics capillary chromatography 40 .Paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride is official in pharmacopoeias and HPLC method had been reported for its estimation.This paper describes a new RP-HPLC method for the estimation of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride combination in mixture using simple mobile phase.In the present study simple, rapid and selective RP-HPLC method was developed for estimation of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride in the pharmaceutical dosage form.Linearity, accuracy, precision, detection limit, quantitation limit and recovery studies were carried out to establish precision.This paper describes the development and validation of the proposed methods.

Preparation of reagent and solution
A 200 µg/mL stock solution of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were prepared as per the following procedure.Stock solution of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were prepared in water and acetonitrile (1:1) by first dissolving 50 mg each of the standard sample in 50 mL water: acetonitrile (1:1) .10 mL of the above solution was pipetted out into 50 mL volumetric flask and then, making up the final volume with diluent.From the above stock solution, various standard solutions were made to obtain solutions of 100, 150, 200, 250 and 300 µg/mL and their respective absorbance values were measured at fixed wavelength.Average absorbance values, standard deviation and percentage correlation coefficients at each concentration were calculated for each drugs.

Optimization of experimental condition
Disodium hydrogen phosphate (Na 2 HPO 4 ) was weighed (2.84 g) and dissolved in 1000 mL water.Finally the pH 6.5 was adjusted with diluted ortho phosphoric acid.The buffer solution was sonicated for about 5 to 10 minutes and filtered using Whatman filter paper (No.1).An isocratic reversed phase C-18 column equilibrated with mobile phase 0.02 mmol disodium hydrogen phosphate-acetonitrile (60:40) was used.Mobile phase composition: 60 volume of buffer and 40 volume of acetonitrile were mixed.Mobile phase flow rate was maintained at 1.0 mL per min.and effluents were monitored at 220 nm.The sample was injected using a 10 µL fixed loop and the total run time was 15 min.

Limit of detection and limit of quantification
A calibration curve was prepared using concentrations in the range of 0.1-0.3mg/mL for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride.The standard deviations of y-intercepts of regression lines were determined and kept in the following equation for the determination of detection limit and quantitation limit.Detection limit = 3.3σ /s; quantitation limit = 10σ /s; where in σ is standard deviation of y-intercepts of regression lines and s is the slope of the calibration curve.Detection limit and quantitation limit can also be estimated using signal to noise and relative standard deviation method.

Linearity studies
The content of twenty tablets were taken and weighed.Powder equivalent to 100 mg of paracetamol (PARA), acetyl salicylic acid (ECO), mefenamic acid (MEF) and cetirizine dihydrochloride (CET) respectively were accurately weighed and transferred to four separate 100 mL volumetric flasks and 50 mL of diluent was added to the same and the flasks were sonicated for 15.0 min.The flasks were shaken and the volume was diluted up to the mark with the same mixture.The above solutions were filtered using Whatman filter paper (No.1).Appropriate volume of the aliquots of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride stock solutions were taken in different 20 mL volumetric flasks and the volume was made up to the mark with diluent to obtain final concentration of 100, 150, 200, 250 and 300 µg/mL of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride respectively.The solutions were sonicated for 5.0 min.The solutions were injected at above chromatographic conditions and peak areas were measured.Calibration curves were constructed by plotting the average peak areas versus concentrations.

Paracetamol and Mefenamic acid
The content of twenty tablets of meftal forte were taken and weighed.Powder equivalent to 100 mg of paracetamol and mefenamic acid were accurately weighed and transferred to 100 mL volumetric flask and 50 mL of diluent was added to the same and the flask was sonicated for 15.0 min.The flask was shaken and the volume was diluted up to the mark with the same mixture.The above solution was filtered using Whatman filter paper (No.1).Appropriate volume of the aliquot of solution was taken to obtain 250, 200 and 100 µg/mL of paracetamol and mefenamic acid.The drug content per tablet of the above brand of paracetamol and mefenamic acid were calculated from the absorbance values obtained (by taking average of three determinations).

Acetyl salicylic acid
The contents of twenty tablets of ecosprin were taken and weighed.Powder equivalent to 100 mg of acetyl salicylic acid was accurately weighed and transferred 100 mL volumetric flask and 50 mL of diluent was added to the same and the flask was sonicated for 15.0 min.
The flask was shaken and the volume was diluted up to the mark with the same mixture.The above solution was filtered using Whatman filter paper (No.1).Appropriate volume of the aliquot of solution was taken to obtain 250, 200 and 100 µg/mL of acetyl salicylic acid.The drug content per tablet of the above brand of acetyl salicylic acid was calculated from the absorbance values obtained (taking average of three determinations).

Cetirizine dihydrochloride
The content of twenty tablets of alerid were taken and weighed.Powder equivalent to 100 mg of cetirizine dihydrochloride was accurately weighed and transferred 100 mL volumetric flask and 50 mL of diluent was added to the same and the flask was sonicated for 15.0 min.The flask was shaken and the volume was diluted up to the mark with the same mixture.The above solution was filtered using Whatman filter paper (No.1).Appropriate volume of the aliquot of solution was taken to obtain 250, 200 and 100 µg/mL of cetirizine dihydrochloride.The drug content per tablet of the above brand of cetirizine dihydrochloride was calculated from the absorbance values obtained (by taking average of three determinations).The accuracy of the method was determined by calculating recoveries of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride using standard solutions.

Results and Discussion
Optimization of mobile phase or chromatographic condition was performed based on resolution, tailing factor, symmetric factor and peak areas obtained for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride are shown in Table 1 The mobile phase 0.02 mmol disodium hydrogen phosphate adjusted to pH 6.5 using diluted orthophosphoric acid and acetonitrile in the composition (60:40) was found to be satisfactory.The retention time for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were about 2.92 min, 2.01 min, 4.91 and 10.2 min.respectively (Figure1).
These mobile phase composition gave symmetric and well resolved peaks for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride.Overlain UV spectra of paracetamol-acetyl salicylic acid and mefenamic acid-cetirizine dihydrochloride showed that these drugs absorbs appreciably at 220 nm.Hence 220 nm was selected as the detection wavelength in the liquid chromatography (Figures 2 & 3).   2. The resolution between the acetyl salicylic acid and paracetamol were found 4.68 and resolution between paracetamol and mefenamic acid were found 6.73, where as resolution between mefenamic acid and cetirizine dihydrochloride were found 9.45, which indicates good separation of these four compounds.The symmetric factors for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were 0.64, 0.77, 0.78 and 0.75 respectively.0.999 1.000 0.999 0.999 The detection limit for paracetamol was 0.39 µg/mL and the quantification limit was 1.2 µg/mL.The detection limit for acetyl salicylic acid and mefenamic acid were 0.39 µg/mL and the quantification limits were 1.2 µg/mL.Similarly the detection limit for cetirizine dihydrochloride was 0.37 µg/mL and the quantification limit was 1.1 µg/mL, which suggest that these compounds can be estimated accurately.The system suitability parameters are summarized in Table 3.The linearity or calibration curves for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were obtained by plotting the average peak areas of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride versus concentrations over a range of 100, 150, 200, 250 and 300 µg/mL of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride respectively shown in Table 4.
Table 3 Paracetamol was found to be linear with correlation coefficient (r) = 1.000.Similarly the calibration curves for acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were found to be linear with correlation coefficient (r) = 1.000, 0.999 and 0.999 respectively (Figures 4-7).The recovery study of paracetamol was found in the range of 99.3% to 99.5%.Acetyl salicylic acid was found in the range of 100.0% to 100.4%, mefenamic acid was found in the range of 99.7% to 102.2% and cetirizine dihydrochloride was found in the range of 100.5% to 102.5% respectively.The recovery of paracetamol was found in tablets in the range of 446.9 mg to 447.8 mg.The recovery of acetyl salicylic acid was found in the range of 325.0 mg to 326.3 mg.The recovery of mefenamic acid was found in the range of 498.5 mg to 511.0 mg and cetirizine dihydrochloride was found in the range of 10.05 mg to 10.25 mg.The chromatographic method was applied to the determination of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride in their pharmaceutical dosage form.The results for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were comparable with their corresponding labeled amounts are shown in Table 5.

Conclusion
We have successfully developed a new RP-HPLC method for the determination of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were found to be simple, economical and useful with high accuracy, precision and low detection limit and quantitation limit.Rapidity and capability of quantifying very low concentration of respective drugs, made them useful for variety of analyses, including pure drug analysis, assay of formulations and stability studies analysis.The proposed methods did not utilize any extraction step for recovering the drug from the formulation excipient matrixes and their by decreased the degree of error, time in estimation of drugs and the overall cost of the analysis.The solvent system used were simple mobile phase with low buffer concentration compared to the reported method.The method gives good resolution between paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride with a short analysis time (less than 15 minutes).The method was validated and found to be simple, sensitive, accurate, precise and economical.Percentage of assay recovery shows that the method is free from interference of the excipients used in the formulation.Therefore, the proposed method used for routine analysis of paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride in their pharmaceutical dosage form.

Figure 1 .
Figure 1.Typical chromatogram of PARA, ECO, MEF and CET (Chromatogram showing well resolved peaks of PARA, ECO, MEF and CET).

Figure 2 .
Figure 2. UV overlain spectra of PARA and ECO The data of regression analysis of the calibration curves are shown in Table2.The resolution between the acetyl salicylic acid and paracetamol were found 4.68 and resolution between paracetamol and mefenamic acid were found 6.73, where as resolution between mefenamic acid and cetirizine dihydrochloride were found 9.45, which indicates good separation of these four compounds.The symmetric factors for paracetamol, acetyl salicylic acid, mefenamic acid and cetirizine dihydrochloride were 0.64, 0.77, 0.78 and 0.75 respectively.

Figure 3 .
Figure 3. UV overlain spectra of MEF and CET Table2.Regression analysis of the calibration curves for the proposed method

Table 2 .
Regression analysis of the calibration curves for the proposed method

Table 4 .
Linearity or calibration curves

Table 5 .
Assay of combined dosage form and recovery studies