Rationale The workload of clinical laboratories has been steadily increasing over the last few years. High‐throughput (HT) sample processing allows scientists to spend more time undertaking matters of critical thinking rather than laborious sample processing. Herein we introduce a HT 96‐solid‐phase microextraction (SPME) transmission mode (TM) system coupled to direct analysis in real time (DART) mass spectrometry (MS). Methods Model compounds (opioids) were extracted from urine and plasma samples using a 96‐SPME‐TM device. A standard voltage and pressure (SVP) DART source was used for all experiments. Examination of SPME‐TM performance was done using high‐resolution mass spectrometry (HRMS) in full scan mode (100–500 m/z), whereas quantitation of opioids was performed using triple quadrupole MS in multiple reaction monitoring mode and by using a matrix‐matched internal standard correction method. Results Thirteen points (0.5 to 200 ng mL−1) were used to establish a calibration curve. Low limits of quantitation (LOQ) were obtained (0.5 to 25 ng mL−1) for matrices used. Acceptable accuracy (71.4–129.4%) and repeatability (1.1–24%) were obtained for validation levels tested (0.5, 30 and 90 ng mL−1). In less than 1.5 hours, 96 samples were extracted, desorbed and processed using the 96‐SPME‐TM system coupled to DART‐MS. Conclusions A rapid HT method for detection of opioids in urine and plasma samples was developed. This study demonstrated that ambient ionization mass spectrometry coupled to robust sample preparation methods such as SPME‐TM can rapidly and efficiently screen/quantify target analytes in a HT context.
Rationale Matrix interference attributed to urea and other nitrogenous substances in unprocessed urine is significant. In this study desorption ionization of sub‐microliter volume samples is performed in an effort to improve the detection of drugs in unprocessed urine using transmission mode‐direct analysis in real time mass spectrometry (TM‐DART‐MS). Methods Urine samples were spiked with analytical standards of two drugs of abuse, codeine and methadone. Various sub‐microliter volumes of unprocessed urine were deposited onto wire mesh screen consumables and analyzed using TM‐DART for desorption ionization and a high‐resolution mass spectrometer operated in full scan mode for mass analysis. A 22 factorial design of experiment (DOE) was employed to examine the effects of sample volume and sample introduction speed to the DART source. Results Results from analysis of one microliter and sub‐microliter sample volumes were compared by measuring the signal produced by TM‐DART‐MS. Based on an α of 0.05, the lower‐volume samples yielded spectra where the abundance of urea and creatinine ions was reduced, thus significantly improving the TM‐DART‐MS signal for drugs of abuse. Using slower sample introduction speeds increased the time during which the sample was exposed to the heated ionization gas, resulting in a significant increase in the TM‐DART‐MS signal. Conclusions Reducing the sample volume to sub‐microliter levels improved the detection of drugs of abuse present as either individual or multiple components of the untreated urine. The improved signal demonstrates the potential for using sub‐microliter volumes for screening drugs in urine without the need for chromatography or sample pretreatment.
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