Quantitation of Benzodiazepine and Z-drug Hypnotics Using High Resolution, Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry

Transcription

1 Application Note LCMS-107 Quantitation of Benzodiazepine and Z-drug Hypnotics Using High Resolution, Liquid Chromatography-Quadrupole Time of Flight Mass Spectrometry Introduction Benzodiazepines and Z-drug hypnotics are psychoactive drugs that are used for a wide range of clinical therapies including anticonvulsant, sedative, hypnotic, anxiolytic and anti-insomnia treatments. However, due to their highly addictive nature, they are frequently misused or deliberately abused, resulting in sensory impairment, accidental injury and increased vulnerability to drug facilitated crimes. Consequently, they are classified as controlled substances by regulatory and law enforcement bodies, thus necessitating the requirement for their rapid detection and quantification in the forensic context. Traditionally due to their high specificity, sensitivity and wide scope of application, liquid chromatography - tandem mass spectrometry (LC-MS/MS) systems using multiple reaction monitoring (MRM) have generally been used for this purpose. The goal of this study is to evaluate the suitability of high resolution, accurate mass Quadrupole Time of Flight (QTOF) technology as an additional approach for the simultaneous detection, confirmation and quantification of benzodiazepine and non-benzodiazepine hypnotics in human serum. Authors Karin Wendt, Tony Drury, Sebastian Götz, Carsten Baessmann, Bruker Daltonics, Bremen, Germany Keywords Forensic Toxicology Accurate Mass Quantitation QTOF Benzodiazepine Instrumentation and Software impact II QTOF mass spectrometer TASQ ver1.0 software RSLC U3000 UHPLC

2 Origin of samples Two spiked human serum samples (A & B) were provided by Arvecon GmbH, Walldorf, Germany, organizing and realizing international proficiency testing (round robin test) on behalf of the Society of Toxicology and Forensic Chemistry (GTFCh). In total 77 independent laboratories participated in this round robin test, submitting results (or at least partial results) using a wide range of analytical technologies to perform the analysis. Methods Sample Preparation Serum samples were prepared using liquid-liquid extraction as described below. 500 µl of each sample were mixed with 1,500µL extraction solution (5% propan-2-ol in chloroform) and incubated for 15 minutes at 20 C using a rotary mixer. The samples were then centrifuged for 10 minutes at 13,000 g. The lower layer was then transferred to a glass vial containing 50 µl of 0.2M hydrochloric acid in methanol and evaporated to dryness at 40 C. The dry residue was then reconstituted in 500µL of a methanol/ water mixture (1:9), vortexed and then centrifuged for 5 minutes at 3,000 g. The clear supernatant was then transferred to a sample vial for analysis. Calibration Standards and deuterated standards (see table 1) purchased from Sigma-Aldrich (Germany) were spiked into drug-free serum (Biorad, Germany). The matrix matched calibrants were prepared using the same liquid-liquid extraction method as described for the samples. Depending on the covered concentration range, 9-10 calibration levels were used to generate the calibration curves using selected internal standards for multiple analytes (see Table 1). Instrumentation Chromatography: Instrument: Dionex U3000 Rapid Separations UHPLC Column: Perkin Elmer Brownlee SPP 2.7µm C18 2.1x100mm Injection volume: 1µL Eluents: A: H2O % formic acid; B: ACN % formic acid Flow: 0.4 ml/min Mass Spectrometry: Instrument: Scan mode: Scan range: ESI HV: Time [min] %A %B Total run time: 12 minutes Bruker impact II UHR-QTOF TOF-MS full scan m/z V Table 2: UHPLC binary gradient profile: Table 1: Calibrated concentration ranges and applied internal standards for all analytes Analyte m/z (M+H) Calibrated Linear Range [µg/l] Internal Standard Diazepam Diazepam D5 Nordiazepam Nordiazepam D5 Bromazepam alpha-hydroxyalprazolam D5 Clonazepam Alprazolam D5 Temazepam Nordiazepam D5 Alprazolam Alprazolam D5 Zolpidem Zolpidem D6 Flunitrazepam Flunitrazepam D7 7-Aminoflunitrazepam Aminoflunitrazepam D7 Oxazepam Oxazepam D5 Midazolam Zolpidem D6 Lorazepam Oxazepam D5 Zopiclone Zopiclone D4

3 Results All compounds eluted before 8 minutes, showing good separation with adequate chromatographic peak shape. High resolution extracted ion chromatograms (hrxic s) were processed using an extraction window of 3 mda throughout. The use of narrow hrxic windows provides additional selectivity by removing interferences in the processing step. The hrxic elution profile for the 13 compounds analyzed is shown in Figure 1. Figure 3 shows the overlaid hrxic s traces for the 2.5 ng/ml nordiazepam (C 15 H 11 ClN 2 O) calibrant. Note that the intensity of the M+2 trace ( 37 Cl) is within the expected tolerances for a mono-chlorinated molecule, providing an additional degree of confidence for quantitation using the more intense M+H trace. An example calibration curve in the TASQ quantitation view for nordiazepam extending for more than three orders of linear dynamic range (R 2 =0.9985) is shown in Figure 4. Data processing and reviewing of quantitative and confirmatory qualitative data was undertaken using Bruker TASQ ver1.0 (Target Analysis for Screening and Quantitation) software. Figure 2 shows an extract of the analytes found using accurate mass, isotopic pattern fit, ion ratio and retention time matching. User defined tolerances for all the above parameters can be adjusted according to individual requirements and the results are clearly visualized by color and ++ coding. Elution profile for suite of drugs analysed Intens. x Diazepam Zopiclone 7-Aminoflunitrazepam Zolpidem Midazolam Bromazepam Oxazepam Nordiazepam Lorazepam Alprazolam Clonazepam Flunitrazepam Temazepam Time [min] Intens Oxazepam Lorazepam Alprazolam Nordiazepam Clonazepam Time [min] Figure 1: Upper trace: hrxic traces of all 13 analytes at lowest calibrated level Lower Trace: Expanded chromatographic region from minutes

4 TASQ multi-pane viewer detailing confirmatory analyte information TASQ Batch at a glance multi-pane view, detailing mass accuracy, retention time and ion score for all analytes Oxazepam quantifier ion trace Confirmatory, qualifier ion trace (Intensity approximately 1% outside of user defined tolerance limits) Figure 2: The oxazepam ( 37 C) qualifier ion is marginally outside of user specified range, allowing the analyst to reconsider the validity of the result. The bottom right hand pane details isotopic pattern fit information for additional isotopes.

5 Visualization of ion ratio limits for quantitative ion and qualifier ion Monoisotopic ion and confirmatory 37 Cl isotope trace for nordiazepam at 2.5 ng/ml. The analyst can inspect each analyte to check that the ion ratio is within the user defined tolerances (shown by the horizontal lines) Figure 3: Nordiazepam qualifier ion view with 37 Cl qualifier ion intensity within the specified limits for the ion ratio TASQ quantitation view pane The TASQ quantitation pane enables selecting / changing the regression function, weighting and other curve fitting parameters as required. Calibrants, samples, blanks and quality controls are easily distinguished by color and shape coding on the regression curve. Figure 4: Example of TASQ linear calibration curve for nordiazepam >3 orders of magnitude R 2 = )

6 Table 3: Summary of quantitative results Sample Analyte Retention Time Target concentration measured concentration z-score Correlation Coefficient R 2 A Diazepam A Nordiazepam A Bromazepam A Clonazepam A Temazepam A Alprazolam A Zolpidem B Flunitrazepam B 7-aminoflunitrazepam B Oxazepam B Midazolam B Lorazepam B Zopiclone Quantitative reporting in TASQ 1.0 software Figure 5: Examples of TASQ quantitation report for bromazepam and alprazolam

7 Discussion Target values from the GTFCh round robin test were calculated by Arvecon GmbH using International Harmonized Protocols for Proficiency Testing [1] and outliers were removed according to Grubbs [2], α=5%. Calculated concentration values were accepted within a range of +/- 2 standard deviations of the target value. The standard deviation was calculated according to Horwitz [3]. With the exception of clonazepam (z = 1.57), all measured analytes were determined within one standard deviation of the target value. Good sensitivity and linearity was observed throughout allowing quantification down to the 2.5 ng/ ml level for all analytes except temazepam (5 ng/ml). By including an additional confirmatory diagnostic ion in the acceptance criteria for the calculated quantitative result, a higher degree of confidence is achieved (see Figure 2). Additionally, it is anticipated that further improvements in the quantitative result could be gained by using individual isotopically labeled internal standards for each analyte. Conclusion The application of LC-QTOF full scan, accurate mass analysis has been shown to deliver accurate quantitative results for the analysis of 13 benzodiazepine and z-drug hypnotics in serum. The ability of TASQ software to simultaneously display both quantitative and qualitative information in the same view provides additional confidence in the end result by providing a complete picture of the experiment at hand. Furthermore, the adoption of this quantitative high resolution workflow delivers additional analytical flexibility, as it also allows the possibility of retrospective quan/qual investigations to be undertaken without the requirement for further sample analysis. Acknowledgments Society of Toxicological and Forensic Chemistry (GTFCh) President Prof. Dr. Stefan Toennes Scientific Advisory Board Dr. Georg Schmitt, Prof. Dr. Gisela Skopp Organization and Realization of Proficiency Testing Arvecon GmbH Dr. Michael Herbold References [1] IUPAC Thompson & Wood (1993): International Harmonized Protocol for Proficiency Testing of Analytical Laboratories, Journal Of AOAC: International 76(4) [2] Grubbs, Frank E. (1950), Sample criteria for testing outlying observations, The Annals of Mathematical Statistics 21(1):27-58 [3] Horwitz, W. (1982): Evaluation of analytical methods used for regulation of foods and drugs. Anal Chem 54 (1):67A-76A

8 Bruker Daltonics is continually improving its products and reserves the right to change specifications without notice. Bruker Daltonics , LCMS-107, For research use only. Not for use in diagnostic procedures. Bruker Daltonik GmbH Bruker Daltonics Inc. Bremen Germany Phone +49 (0) Fax +49 (0) Billerica, MA USA Phone +1 (978) Fax +1 (978)