Micro-solid-phase extraction of diazepam and oxazepam from wastewater and biological fluids based on miniaturized pipette-tip method and electrospun nanofibers as an efficient sorbent

Nitrazepam and oxazepam belong to a major class of pharmaceuticals named benzodiazepines. Benzodiazepines are widely consumed as anticonvulsants, central muscle relaxants, minor tranquillizers, sedative hypnotics, and anxiolytic agents, however, they induce many unwanted side effects, including drug dependency, impaired memory and concentration, depression, and loss of balance. Overdoses of these drugs can cause acute symptoms; therefore, it is desirable to monitor their concentrations in the biological fluids [1]. Pipette tip solid-phase extraction (PT-SPE) method is a miniaturized form of SPE. In this method, the pipette tip with a small outlet diameter requires tiny amount of sorbent to be used and the PT-SPE setup has low solution consumption. By using this approach, a large number of reusable SPE tips can be prepared simultaneously [2]. Electrospinning is a technology that can produce ultrathin nanofibers economically, and has features such as extremely long lengths, a high surface area to volume ratio, a small pore size, and high porosity. The use of electrospun nanofibers with mentioned properties allows for a reduction in sorbent mass in sorption studies [3]. In this work, a self-assembly of miniaturized pipette-tip-based solid-phase extraction for the coextraction of diazepam and oxazepam was developed with electrospun nanofibers used as sorbents. The electrospun nanofibers were characterized by SEM, TEM, XRD and FTIR analysis. The results showed that the pipette-tip-based solid-phase extraction was effective in extracting of target analytes in the pH (≈ 8). The investigation also revealed that the optimum mass of electrospun nanofibers sorbent was 10 mg and 4 aspirating/dispensing cycles gave the maximum recovery of target analytes with 250 µL propanol/methanol as the best eluting solvent. Under the optimum conditions linear dynamic ranges were achieved in the range of 1.0–1000µg L−1 with coefficients of determination 0.999. Relative standard deviations (n = 5) of 11% were obtained. Moreover, the performance of the present method was studied for the extraction and determination of diazepam and oxazepam in wastewater and biological fluids and satisfactory results were obtained.