Development of Analytical Method for Simultaneous Estimation of Cefixime and Linezolid in Tablet Dosage Form


Jawed Akhtar, Madhuri Baghel, Dharti Patel*

Parul Institute of Pharmacy and Research, Limda, Vadodara, Gujarat, India.

*Corresponding Author E-mail:




A simple, accurate, precise and sensitive UV spectrophotometric method is developed for simultaneous estimation of Cefixime and Linezolid in tablet dosage form. The method is based on the absorption ratio and wavelengths selected for analysis were 236.80 nm (λmax of Cefixime) and 242.80 nm (iso-absorptive point) respectively. The linearity was obtained in the concentration range of 2-30 μg/ml for Cefixime and 2-30 μg/ml for Linezolid. The correlation coefficient of Cefixime and Linezolid were found to be 0.9992 and 0.9991 respectively. The proposed method was successfully applied for the simultaneous determination of both drugs in commercial tablet formulation.  The method was validated for linearity, accuracy and precision as per ICH guidelines and hence can be used for the quantitative analysis of commercially available solid dosage form.


KEYWORDS: Absorption ratio method, Cefixime, Linezolid, UV spectrophotometer, Q2 (R1) guideline




Cefixime (CEF) is an oral third generation cephalosporin antibiotic. Chemically, it is (6R,7R)-7-{[2-(2-amino-1,3-thiazol-4-yl)-2-(carboxymethoxyimino)acetyl]amino}-3-ethenyl-8-oxo-5-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylic acid, clinically used in the treatment of susceptible infections including gonorrhoea, otitis media, pharyngitis, lower respiratory-tract infections such as bronchitis, and urinary-tract infections[1-4]


Linezolid (LIN) is synthetic antibiotic of the oxazolidinone class. Chemically it is N-[[(5S)-3-[3-fluoro-4-(4-morpholinyl) phenyl]-2oxo-5-oxazolidinyl] methyl] acetamide, mainly used for the treatment of infections caused by multi-resistant bacteria including streptococcus and methicillin-resistant Staphylococcus aureus (MSRA).


The review of literature revealed that various analytical methods involving spectrophotometry, HPLC, have been reported for CEF in single form and in combination with other drugs [5-8]. According to literature survey LIN can be estimated by analytical methods like UV, HPLC, HPTLC methods [9, 10]. The present work describes simple, precise, accurate and reproducible spectrophotometric method for the simultaneous estimation of CEF and LIN.


Reagents and chemicals

Standard gift sample of cefixime was provided by Vapi Healthcare Ltd. And linezolid was provided by Alembic Pharmaceuticals Ltd. Combined dosage form of Cefixime and Linezolid tablets were purchased from local market. Other chemicals were purchased from Merck Pvt. Ltd., India.


Instrument and apparatus

Shimadzu-1800 UVVisible Spectrophotometer was used for spectral measurements with spectral band width 1 nm; wavelength accuracy is 0.5 nm and 1 cm matched quartz cells. Software used was UV Probe (version 2.34). An Electronic analytical balance (Shimadzu) was used for weighing. Glassware used in each method were soaked overnight in a mixture of chromic acid and sulphuric acid rinsed thoroughly with double distilled water and dried in hot air oven.


Preparation of Stock Solution

Standard stock solution of CEF and LIN were prepared by dissolving  accurately 100 mg CEF and 100 mg LIN separately in 100 ml of 0.1 N NaOH in two separate 100 ml volumetric flask.(1000 µg/ml)


Preparation of working standard solution

10 ml of stock solution is diluted upto 100 ml with distilled water (100 µg/ml). From that further dilutions were prepared with water for both drugs.


Selection of wavelength

By appropriate dilution of two standard drug solutions, solutions containing 10 µg/ml of CEF and       10 µg/ml of LIN were scanned separately in the range of 200-400 nm to determine the wavelength of maximum absorption for both the drugs.CEF and LIN showed absorbance maxima at 236.8nm and 247.6 nm respectively.


Preparation of Calibration Curve

Appropriate dilutions of the working standard solution were done separately to get 2, 4, 6, 8, 10 upto 30 μg/ml of CEF and LIN, respectively. The absorption spectra of all solutions were recorded between 200-400 nm. The absorbances were measured at 236.80 nm (λmax of CEF), 242.80 nm (iso-absorptive point). Beer’s lamberds range for CEF and LIN were selected and working calibration curves of both the drugs were plotted separately. Straight line equations were obtained from these calibration curves (graph 1-3).


Figure 1- Overlay Spectra


Absorption Ratio Method [11-14]

It uses the ratio of absorbances at two selected wavelengths, one which is anis absorptive point and other being the λ- max of one of the two components. From the overlay spectra, CEF and LIN show iso absorptive point at 242.8 nm. The second wavelength used is 236.8 nm, which is the λ-max of CEF. The concentration of two drugs in the mixture can be calculated using following equations.


CX = [(QM – QY) / (QX -QY)] × A1/aX1 (1)

 CY = [(Qx-Qm)/ (Qx-Qy) × A1/ay1 (2)


Where, A1 and A2 are absorbances of mixture at 236.8 nm and 242.8 nm;

ax1 and ay1 are absorptivities of CEF and LIN at 236.8 nm;

ax2 and ay2 are absorptivities of CEF and LIN respectively at 242.8 nm;

QM = A2 / A1, QX = ax2 / ax1 and QY = ay2 / ay1.


Validation [15]

The method was validated with respect to linearity, LOD, LOQ, Accuracy and Precision, Robustness and Specificity as per ICH guideline Q2 (R1).



The method for simultaneous analysis of CEF and LIN was validated as per ICH guidelines. In absorption ratio method, wavelengths selected for analysis were 236.8 nm (λmax of Cefixime) and 242.8 nm (iso-absorptive point) (figure 1).


In this method linearity for detector response was observed in the concentration range of 2-30μg/ml for CEF and 2-30μg/ml for LIN as shown in graphs 1-3 & table-2. Absorptivities were calculated for both the drugs at selected wavelengths and substituted in equations for determining concentration of CEF and LIN in tablet sample solution. Percent label claim for CEF and LIN in tablet analysis, by this method was found 99.03% for CEF and 99.1% for LIN.


Lower values of LOD and LOQ indicated good sensitivity of proposed method. Accuracy of proposed methods was ascertained by recovery studies shown in Table 1 and the results are expressed as 100.19 % recovery. The method was also found to be specific, as there was no interference observed when the drugs were estimated in presence of excipients and robust, as there was no significant change in absorbance up to 24 hours of preparation of stock solution in 0.1 N NaOH.


Figure 2 calibration curve of cefixime at 236.8 nm


Figure 3 calibration curve of cefixime at 242.8 nm

Table 1- Recovery study

Mixture (µg/ml)


Conc before spiking

Conc after spiking

Actual Conc added

% Recovery





(2 CEF +

6 LIN)

236.8 nm







242.6 nm





236.8 nm





242.6 nm







236.8 nm





242.6 nm







Figure 4 calibration curve of linezolid at 236.8 nm and 242.8 nm


Table 2- Result Summary

Sr. No.






236.8 nm

247.6 nm


Range (µg/ml)





R2 = 0.9992

R2= 0.9991


Precision (%RSD)





































The proposed Absorption ratio method provides simple, specific, precise, accurate and reproducible quantitative analysis for simultaneous determination of CEF and LIN in combined dosage form. The method was validated as per ICH guidelines in terms of specificity, linearity, accuracy, precision, limits of detection (LOD) and quantification (LOQ), robustness and reproducibility and can be used for routine analysis and quality control assay of CEF and LIN in combined dosage form.



Authors are thankful to Vapi Healthcare Ltd. and Alembic Pharmaceuticals Ltd. for providing gift samples.



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Received on 28.03.2013       Modified on 15.04.2013

Accepted on 10.05.2013      © RJPT All right reserved

Research J. Pharm. and Tech. 6(5): May 2013; Page 592-594