Flow-injection determination of zidovudine in plasma samples using multivariate curve resolution

This paper describes a spectrophotometric flow-injection method for the determination of an antiretroviral drug (zidovudine) in plasma samples. The main goal of this study is the development of feasible analytical method to monitor the plasmatic drug levels in a rapid and simple way as an alternative to chromatographic procedures. The flow-injection system proposed consists of a two-channel manifold with the injection of the sample into an acid carrier and on-line generation of a pH-gradient. The corresponding data are monitored over time using a diode array spectrophotometer. The discrimination of zidovudine species from plasma components is accomplished through chemometric data analysis based on the zidovudine features on both spectral and time domains. A pretreatment procedure consisting of liquid-liquid extraction is used for sample clean-up. However, despite the pretreatment, noticeable amounts of unknown substances acting as interferences are still present in the extracts. As relevant analytical parameters, the analyte recovery in the extraction process is 101% at 5.3 μg mL−1 and the detection limit is 0.013 μg mL−1. Multivariate curve resolution with alternating least squares is used to recover the analyte profiles for its further determination. As a result, the quantification of zidovudine in plasma can be accomplished even in the presence of plasma components with overall prediction error below 3%.