Spectrophotometric Determination of Etravirine in Bulk and Pharmaceutical Formulations ()
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Received December 3, 2013; revised December 30, 2013; accepted January 9, 2014
Figure 2. Absorbance spectrum of ETR with NQS.
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Figure 3. Absorbance spectrum of ETR with MBTH.
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Figure 4. Beer’s Lambert plot of ETR with NQS.
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Figure 5. Beer’s Lambert plot of ETR with MBTH.
the Beer’s law plots at λmax reveals a good correlation. The graphs shows negligible intercept and were de- scribed by the regression equation, Y = bC + a (where Y
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Table 1. Optical characteristics and linear least square re- gression analysis of proposed methods for Etravirine.
is the absorbance of 1 cm layer, b is the slope, a is the intercept and C is the concentration of the measured so- lution in µg/ml). The molar absorptivities of the resulting colored complexes indicate the high sensitivity of the methods. Linear regression parameters are also given in Table 1.
5.2. Precision and Accuracy
Precision of the developed methods was ascertained from the absorbance values obtained by actual determination of six replicates of a fixed amount of the test solution. The percent of relative standard deviation and percent range of errors were calculated and presented in Table 2 for the developed methods. To determine the accuracy of these methods, three different amounts of bulk samples within the Beer’s law limits were prepared and analyzed by the developed methods. The results are presented in Table 3. Percent of relative standard deviation (% RSD) were found to be less than 2, which indicate that the de- veloped methods were precise. The percentage recoveries of the drug by these methods were found to be within the range of 100.03 - 100.24 and 100.09 - 100.32 for method A and method B, respectively, indicating that the devel- oped methods are accurate. Studies also revealed that the common excipients and other additives usually present in tablets did not interfere in the proposed methods.
6. Application to the Pharmaceutical Dosage Forms
It is evident from the above mentioned results that the proposed methods gave satisfactory results with Etravi- rine in bulk. Thus its pharmaceutical dosage forms (Inte- lence) were subjected to analysis of their Etravirine con- tents by proposed and reference methods. An ICH vali- dated spectrophotometric method with UV-Visible de- tection for determination of Etravirine in tablets was car- ried out. The label claims of Etravirine in tablet dosage forms are 100 mg and 200 mg whose percentages were 100.38, 100.35 and 199.95, 199.92 for Method A and Method B respectively. The statistical data was presented in Table 4. This result was compared with the reference method obtained statistical analysis with respect to the accuracy (by t-test) and precision (by F-test). No signifi- cant differences were found between the calculated and theoretical values of t-test and F-tests at 0.05% confi- dence level proving similar accuracy and precision in the determination of Etravirine by both methods.
7. Scheme of the Colored Products
7.1. Method-A
The results obtained in Method A were based on the nucleophilic substitution reaction of ETR with NQS in the presence of NaOH at 50˚C, yields a cherry colored
product having maximum absorption at a wavelength of 414 nm against the corresponding reagent blank. The colored species is represented as given in the Scheme 1 [14].
7.2. Method-B
The results obtained in Method B were based on the oxidative coupling reaction of ETR with MBTH in the presence of NaIO4 in acidic medium, yields a green co- lored product having maximum absorption at a wave- length of 635 nm against the corresponding reagent blank. Actually, this is sodium metaperiodate catalyzed oxida- tive coupling reaction of MBTH with the primary amino group of the drug. Under the reaction conditions, on oxi- dation, MBTH loses two electrons and accept one proton forming an electrophilic intermediate, which is the active coupling species. This intermediate undergoes electro- philic substitution with the ETR to form the colored pro- duct. The proposed reaction mechanism is presented in Scheme 2 [15].
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Table 2. Precision of the test method.
*Mean of six determinations.
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Table 3. Accuracy of the proposed methods.
*Mean of five determinations.
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Table 4. Assay of formulations of Etravirine.
*Mean of six determinations. Theoretical values at 0.05 level of confidence limit F = 5.19, t = 1.833. 100 mg/tablet and 200 mg/tablet formulations are analyzed (average of six determinations). M-A: Method-A, M-B: Method-B.
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Scheme 1. Nucleophilic substitution reaction of Etravirine with NQS.
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Scheme 2. Oxidative coupling reaction of Etravirine with MBTH.
8. Conclusion
The proposed methods were simple, selective, and re- producible and can be used in the routine analysis of Etravirine in bulk drug and pharmaceutical formulations with reasonable accuracy and precision.
Acknowledgements
The authors thank the authorities of University and NRI Institute of Technology for providing facilities to carry out the present work and greatly acknowledge to Ara- bindo Labs Ltd., Hyderabad for providing a gift sample of the drug.
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