Direct Determination of Benzodiazepines in Biological Fluids by Restricted-Access Solid-Phase Microextraction

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Abstract
A biocompatible solid-phase microextraction (SPME) fiber was prepared using an alkyl−diol−silica (ADS) restricted-access material as the SPME coating. The ADS-SPME fiber was able to simultaneously fractionate the protein component from a biological sample, while directly extracting several benzodiazepines, overcoming the present disadvantages of direct sampling in biological matrixes by SPME. The fiber was interfaced with an HPLC−UV system, and an isocratic mobile phase was used to desorb, separate, and quantify the extracted compounds. The calculated clonazepam, oxazepam, temazepam, nordazepam, and diazepam detection limits were 600, 750, 333, 100, and 46 ng/mL in urine, respectively. The method was confirmed to be linear over the range of 500−50 000 ng/mL with an average linear coefficient (R2) value of 0.9918. The injection repeatability and intra-assay precision of the method were evaluated over 10 injections, resulting in a RSD of ∼6%. The ADS-SPME fiber was robust and simple to use, providing many direct extractions and subsequent determination of benzodiazepines in biological fluids.