HPLC-ESI-MS/MS validated method for simultaneous quantification of zopiclone and its metabolites, N-desmethyl zopiclone and zopiclone-N-oxide in human plasma

Department of Chemistry, School of Sciences, Gujarat University, Navrangpura, Ahmedabad 380009, India.
Journal of Chromatography B (Impact Factor: 2.69). 03/2008; 864(1-2):137-48. DOI: 10.1016/j.jchromb.2008.02.004
Source: PubMed

ABSTRACT A simple, selective and sensitive isocratic HPLC method with triple quadrupole mass spectrometry detection has been developed and validated for simultaneous quantification of zopiclone and its metabolites in human plasma. The analytes were extracted using solid phase extraction, separated on Symmetry shield RP8 column (150 mm x 4.6 mm i.d., 3.5 microm particle size) and detected by tandem mass spectrometry with a turbo ion spray interface. Metaxalone was used as an internal standard. The method had a chromatographic run time of 4.5 min and linear calibration curves over the concentration range of 0.5-150 ng/mL for both zopiclone and N-desmethyl zopiclone and 1-150 ng/mL for zopiclone-N-oxide. The intra-batch and inter-batch accuracy and precision evaluated at lower limit of quantification and quality control levels were within 89.5-109.1% and 3.0-14.7%, respectively, for all the analytes. The recoveries calculated for the analytes and internal standard were > or = 90% from spiked plasma samples. The validated method was successfully employed for a comparative bioavailability study after oral administration of 7.5 mg zopiclone (test and reference) to 16 healthy volunteers under fasted condition.

  • [Show abstract] [Hide abstract]
    ABSTRACT: An ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for the determination of zopiclone and zolpidem in whole blood, for use in cases with suspected driving under influence of drugs (DUID) and autopsy cases. Sample preparation was performed with liquid-liquid extraction (LLE) using ethyl acetate/n-heptane (80:20, v/v) and 0.1mL whole blood. Deuterated analogues were used as internal standards (IS) for both compounds. The compounds were separated using a reversed phase C18-column (2.1mm×100mm, 1.7μm), with a flow rate of 0.5mL/min, 1μL injected and gradient elution with 5mM ammonium formate pH 10.2 and acetonitrile. Quantification was done by MS/MS using multiple reaction monitoring (MRM) in positive mode. The run time of the method was 4.5min including equilibration time. The calibration curves of extracted whole blood standards were fitted by linear-order calibration curves weighted 1/x, with R(2) values above 0.999 for both compounds. Intermediate precision and accuracies (bias) were 2.4-12.9% RSD and from -5.9 to 6.8%, respectively. Recoveries of the compounds were ≥70%. The lower limit of quantification (LLOQ) for zopiclone was 0.50nmol/L (0.19ng/mL) or 0.05pg injected on column, and 3.5nmol/mL (1.10ng/mL) for zolpidem, or 0.27pg injected on column. The limit of detection (LOD) was 0.2nmol/L (0.08ng/mL) for zopiclone and 0.3nmol/L (0.09ng/mL) for zolpidem. Matrix effects (ME) were between 108 and 115% when calculated against IS. A comparison with former confirmation LC-MS method at the Norwegian Institute of Public Health, Division of Forensic Medicine (NIPH) was performed during method validation. Good correlation was seen for both compounds. The method has been running on a routine basis for two years, and has proven to be very robust and reliable with satisfactory long term precision and bias and with results for external quality samples corresponding well to consensus mean or median. Zopiclone and zolpidem concentrations in post mortem and ante mortem cases were reported. The method also meets the requirements of the legislative limits for driving under the influence of non-alcohol drugs introduced in the Norwegian Road Traffic Act Law from 2012.
    Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 09/2014; 971C:72-80. DOI:10.1016/j.jchromb.2014.09.018 · 2.69 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (-1, 1) ring satisfying the Weak Novikov identity (w, x, yz) = y(w, x, z) is studied in this paper. The ring is associative under the following assumption that (i) it has finite number of generators, (ii) it is a 2-torsion free prime ring and has minimum condition on either right ideals or on trivial left ideals,(iii) is a 2-torsion free simple and (iv)is a semiprime ring which is both (-1, 1) and (1, 0).
    International symposium on engineering and natural science, Macau China; 08/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: 2-Amino-5-chloropyridine (ACP) is a degradation product of zopiclone (ZOP) and its two main metabolites N-desmethylzopiclone (NDZOP) and zopiclone N-oxide (ZOPNO). ACP may be formed when specimens are stored. ZOP instability in blood makes interpretation of concentrations difficult especially in cases of prolonged sample storage. This study investigated how ACP could be used to estimate the original concentration of ZOP in authentic samples. For that purpose, an analytical liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the quantitation of ACP, ZOP, and NDZOP in blood was developed and validated. Due to poor extraction recovery, ZOPNO was not included in the analytical method. The method was then applied to investigate ACP formation, ZOP and NDZOP degradation in stored ZOP post-dosed authentic whole blood and two mathematical models were used to calculate the original concentration of ZOP. During storage, ACP was formed in amounts equimolar to the ZOP and NDZOP degradation. Results from samples in which ACP had been formed were used to test two models to estimate the original ZOP concentration. The correlation tests of the models showed strong correlations to the original ZOP concentration (r = 0.960 and r = 0.955) with p < 0.01 and explained more than 90 % of the ZOP concentration. This study showed that the equimolar degradation of ZOP and NDZOP to ACP could be used to estimate the original concentration of ZOP.
    Deutsche Zeitschrift für die Gesamte Gerichtliche Medizin 07/2014; 129(2). DOI:10.1007/s00414-014-1049-2 · 2.60 Impact Factor