Restricted access carbon nanotube for microextraction by packed sorbent to determine antipsychotics in plasma samples by high-performance liquid chromatography-tandem mass spectrometry

This manuscript describes the development of the restricted access carbon nanotube (RACNT) as a selective stationary phase for microextraction by packed sorbent (MEPS) to determine antipsychotics (chlorpromazine, clozapine, olanzapine, and quetiapine) in untreated plasma samples from schizophrenic patients by ultra-high liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS). The synthesis was achieved by chemically covering commercial multi-walled carbon nanotubes with bovine serum albumin (BSA) to subsequently pack the material in a polyethylene conical tube (1000 μL). The RACNTs’ sorbents were able to exclude about 97% of the plasma proteins, maintaining the same performance for about 100 assays. The MEPS variables (sample pH, draw–eject cycles, desorption and phase cleanup) were evaluated to improve sensibility and selectivity. The MEPS/UHPLC–MS/MS method was linear at concentrations ranging from the lower limit of quantification (10.0 ng mL −1 ) to the upper limit of quantification (200–700 ng mL −1 ) with coefficients of determinations higher than 0.99. The precision assays presented relative standard deviation (RSD) values lower than 13%, and the accuracy assays presented relative error (RE) values that ranged from − 8.01 to 11.53%. Neither significant matrix effects nor carryover was observed. The developed method was successfully applied to determine antipsychotics drugs for therapeutic drug monitoring of schizophrenic patients.