[Measuring linezolid in biological fluids using high-efficiency liquid chromatography]

Objective: Evaluation of an analytic method for determining linezolid concentrations in biological fluids including plasma, vitreous humour and cerebrospinal fluid using high-efficiency liquid chromatography and subsequent ultraviolet detection.

Method: The method was validated by studying the following parameters: accuracy, precision, sensitivity, linearity and recovery. The drug was extracted from the biological matrix by means of a protein precipitation with perchloric acid. Chromatographic separation was performed by eluting linezolid with a mobile phase consisting of 80% K2HPO4 buffer solution (15 mM; pH=5) and 20% acetonitrile, and a stationary phase, NOVAPAK C18 150x3.9 mm with precolumn. The wavelength reading was 254 nm and the working flow rate was 1 ml/min.

Results: We obtained values with accuracies between 94.4 and 106.1%, and precisions between 0.88-6% and 3.7-5.6% for intra-and inter-day variability, respectively. Recovery obtained after analysing the plasma samples was at 93%. The method showed itself to be linear for the concentration levels under study.

Discussion: The method's behaviour can be described as linear, precise and accurate. Furthermore, the method is fast, sensitive, and inexpensive. It is useful for determining linezolid concentrations in multiple biological matrices. It can also be used as a basis for further clinical pharmacokinetic studies.