The use of microchip capillary electrophoresis/tandem mass spectrometry for the detection and quantification of opioids
Silver, Brianna Danielle
MetadataShow full item record
Forensic toxicology is a critical field in which scientific techniques are employed in order to establish the presence or absence of pharmacological substances and/or their metabolites within an individual. The results of such analyses can have legal implications, and toxicology has a number of important applications, including post-mortem investigations, workplace drug testing, therapeutic drug monitoring, and impaired driving studies. The focus of this specific body of work is on the use of toxicology in the detection and quantification of drugs of abuse –specifically opioids - in biological samples. In recent years, there has been a surge in opioid abuse and the need for forensic toxicology labs to process samples from such cases quickly and accurately continues to increase. As a result, it is imperative to research different techniques and technologies that can be applied in toxicology to improve efficiency of sample processing while still remaining sensitive and specific. Many toxicology laboratories today use immunoassay techniques for screening, and utilize a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantification. While these methods are established and reliable, the need to analyze an increasing number of samples in a more efficient time frame is essential, and with that, the need to develop and validate new analytical methods. This study sought to validate the use of Microchip Capillary Electrophoresis-Tandem Mass Spectrometry (CE-MS/MS) as a method for detecting and quantifying a panel of fourteen opioids. The experiments were run using a ZipChip (908 Devices, Boston, MA) as the separation scheme, which contains a small capillary where analytes are separated out by electrophoretic mobility - dictated largely by size and charge. These analytes were then ionized by electron spray ionization (ESI) at the end of the chip, and then detected, fragmented, and analyzed in a SCIEX 4500 Triple Quadrupole Mass Spectrometer (Framingham, MA). The analytical run time of the method evaluated was two and half minutes per sample. Calibration curves were run and the method was assessed for a number of validation parameters, including bias, precision, limit of detection, common analyte interferences, matrix interferences, and carryover, as recommended by the American Academy of Forensic Sciences Standards Board. The fourteen drugs and metabolites looked at in this study were 6-monoacetylmorphine, buprenorphine, codeine, dihydrocodeine, 2-ethylidene-1, 5-dimethyl-3, 3-diphenylpyrrolidine (EDDP), fentanyl, heroin, methadone, morphine, naloxone, norfentanyl, oxycodone, oxymorphone, and tramadol. All standards were ordered from Cerilliant (Round Rock, TX), as well as deuterated internal standards used for quantification purposes. This study showed that as the method currently stands, it can reliably detect this panel of opioids at limits of detection between 1 and 15 ng/mL, with the exception of buprenorphine and morphine, for which the method appeared less sensitive. While some applications desire higher sensitivity than this, this level of detection could be very useful as a screening technique that is quick and also far more specific than current immunoassay screening techniques, and provide the additional advantage of quantification for samples at slightly higher concentrations. Quality control samples at 100 ng/mL and 150 ng/mL generally showed consistent results and acceptable levels of bias and precision, indicating that the method can be used to reliably quantify this panel of opioids at those concentrations. In addition, interference signals detected during analysis of other common analytes often encountered with opioids were negligible, with the exception of heroin and norfentanyl. Analysis of ten lots of urine for blank matrix interferences also demonstrated low potential for interference, with the exception of heroin. Finally, there was no evidence of significant carryover between samples, or interference from the deuterated internal standards. While some potential instrumentation issues such as mass spectrometer calibration prompt further study, the method shows promise for future use as a high throughput analysis tool in forensic toxicology labs. CE-MS/MS has the added benefit of not only faster run times, but significantly less sample consumption per run, and additionally, less sample preparation. CE is a viable separation scheme for metabolites and forensic applications, and could make large impacts as an effective way to analyze toxicological samples.