Matrix Effect on a New Dispersive Liquid–Liquid Microextraction‐High‐Performance Liquid Chromatography–Diode Array Detection Method for the Determination of Efavirenz in Human Plasma

Abstract

ABSTRACTA high‐performance liquid chromatography–diode array detection (HPLC‐DAD) method was developed and validated for the determination of efavirenz in human blood plasma samples from patients taking the antiretroviral drug. Results were compared with those previously obtained using gas chromatography/mass spectrometry (GC/MS) on the same sample extracts using dispersive liquid‐liquid microextraction. Validation of the HPLC‐DAD method yielded the United States Food and Drug Administration guidelines acceptable values. However, when validated, the accuracy using the HPLC‐DAD method was poor in contrast to GC/MS at the lower limit of quantification (LLOQ) level. The linearity of the HPLC‐DAD method was good with a coefficient of determination (R2) of 0.9922. The linear range of the calibration curve was 0.05–0.5 µg/mL. The LLOQ was 0.03 µg/mL at which spike level the accuracy was 8.9% (n = 3) and the precision was 8.3% (n = 3). Statistical analysis of the data showed that there were no systematic errors introduced in the HPLC‐DAD method but that there was a matrix effect that suppressed the signals and led to random error and subsequently impacted the accuracy of the results.