Solid-phase microextraction of human plasma samples for determination of sufentanil by gas chromatography-mass spectrometry

Rapid Determination of Sufentanil in Human Plasma by UHPLC-QqQ-MS-MS

This paper presents a rapid, sensitive and precise method developed and validated for the quantification of sufentanil in biological samples using ultra-performance liquid chromatography coupled with QqQ-MS-MS. Plasma samples were extracted with simple and fast liquid-liquid extraction (ethyl acetate, pH 9). Calibration curve showed linearity in the concentration range of 0.005-30 µg/L. The lower limit of quantification was 0.010 µg/L. The most important method features are low lower limit of quantification value, simple plasma extraction and small sample volume. This method is suitable not only for evaluation of the pharmacokinetics, toxicology, bioavailability and clinical pharmacology of sufentanil but also for the detection and identification of this compound in human plasma samples for forensic purposes.

Simultaneous detection of ketamine, lorazepam, midazolam and sufentanil in human serum with liquid chromatography-tandem mass spectrometry for monitoring of analgosedation in critically ill patients

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the determination and quantification of four predominantly used analgosedatives in the intensive care unit: ketamine, lorazepam, midazolam and sufentanil in human serum. The extraction procedure consisted of protein precipitation of serum samples with acetonitrile and subsequent centrifugation. D₅-fentanyl and D₄-midazolam served as internal standards (ISTD). Separation of analytes was performed with a Hypersil C18 column and a mobile phase with acetonitrile and 0.1% formic acid (60/40, v/v) under isocratic conditions at a flow rate of 280μl/min. Analytes were simultaneously detected with a triple-stage quadrupole mass spectrometer (LC-MS/MS) in a selected reaction monitoring (SRM) mode with positive heated electrospray ionization (HESI) within a single 2-min run. Calibration curves were linear over a range of 50-2000 for ketamine, 10-1000 for lorazepam, 5-500 for midazolam and 1-100 for sufentanil (ng/ml). The limit of detection and the lower limit of quantification were 0.01 and 10.00 for ketamine, 0.005 and 10.00 for lorazepam, 0.018 and 5.00 for midazolam and 0.068 and 0.25 for sufentanil (ng/ml). Intra- and inter-day accuracies and precisions of all analytes were less than 15%. Bench stability with spiked serum samples was ensured after 12, 24 and 48h at room temperature, freeze- and thaw-stability after 3 cycles of thawing and freezing. The method was successfully established according to International Conference on Harmonization (ICH) guideline Q2 (R1) "Validation of Analytical Procedures" and applied in critically ill adult patients in the intensive care unit. We suggest its suitability for parallel quantification of the sedative analgesics ketamine, lorazepam, midazolam and sufentanil. The method serves as an instrumental tool for therapeutic drug monitoring (TDM) and pharmacokinetic studies [1].

Role of microextraction sampling procedures in forensic toxicology

The last two decades have provided analysts with more sensitive technology, enabling scientists from all analytical fields to see what they were not able to see just a few years ago. This increased sensitivity has allowed drug detection at very low concentrations and testing in unconventional samples (e.g., hair, oral fluid and sweat), where despite having low analyte concentrations has also led to a reduction in sample size. Along with this reduction, and as a result of the use of excessive amounts of potentially toxic organic solvents (with the subsequent environmental pollution and costs associated with their proper disposal), there has been a growing tendency to use miniaturized sampling techniques. Those sampling procedures allow reducing organic solvent consumption to a minimum and at the same time provide a rapid, simple and cost-effective approach. In addition, it is possible to get at least some degree of automation when using these techniques, which will enhance sample throughput. Those miniaturized sample preparation techniques may be roughly categorized in solid-phase and liquid-phase microextraction, depending on the nature of the analyte. This paper reviews recently published literature on the use of microextraction sampling procedures, with a special focus on the field of forensic toxicology.

A comprehensive LC-MS-based quantitative analysis of fentanyl-like drugs in plasma and urine

Fentanyl, norfentanyl, alfentanil, sufentanil, remifentanil and 3-methylfentanyl are potent, short-acting, synthetic narcotic analgesics that are not revealed in standard opiate immunoassays. In this article, a fully validated analytical method for the determination of these fentanyl-type compounds in plasma and urine is presented, consisting of a liquid-liquid extraction followed by a LC-MS/MS analysis using electrospray ionisation in the positive ionisation mode. Fentanyl-d(5) and norfentanyl-d(5) were used as internal standards. The lower LOQ in plasma and urine was 0.1 ng/mL for fentanyl, norfentanyl, alfentanil, remifentanil and 3-methylfentanyl, and 0.2 ng/mL for sufentanil. The method proved linear over a concentration range of 0.2-50 ng/mL for sufentanil and 0.1-50 ng/mL for all other analytes, with correlation coefficients of 0.998 or better. The analytical procedure showed excellent selectivity and precision (all CVs below 15%) for all analytes. Accuracy was good, except for sufentanil, where deviations of more than 15% from nominal concentrations were observed. No matrix effects were observed, and stability of stock and internal standard solutions was within acceptability limits.

Determination of fentanyl, metabolite and analogs in urine by GC/MS

A rapid and sensitive method for the simultaneous determination of alfentanyl, sufentanyl and fentanyl (and its major metabolite norfentanyl) in urine was developed and validated. The method involved a liquid-liquid extraction in alkaline conditions, derivatization with pentafluoropropionic anhydride to improve the sensitivity for norfentanyl and subsequent analysis in GC/MS. The LODs are 0.08 ng ml(-1) for all substances (0.04 ng ml(-1) for alfentanyl). Intra- and inter-day precision coefficient of variation was always below 15%; mean relative error (accuracy) was always below 15%. The method was linear for all analytes, with quadratic regression of calibration curves always higher than 0.99. The method was applied to real samples of subjects who had received therapeutic doses of fentanyl, showing its suitability for the determination of low levels of these substances. The method was also applied to a subject whose death was attributed to fentanyl overdose.

Intravenous fentanyl is exhaled and the concentration fluctuates with time

Previous studies have reported that fentanyl is eliminated predominantly by hepatic biotransformation, and that some is eliminated unchanged in urine and stools. No reports have described the elimination of fentanyl via the lungs. In this study, exhaled gas samples from eight anaesthetized patients undergoing cardiac surgery were analysed using solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Results confirmed that fentanyl was exhaled by patients after intravenous administration, that the concentration of exhaled fentanyl fluctuated with time and peak concentrations were reached approximately 15 - 20 min after intravenous fentanyl administration. Thus, in addition to hepatic biotrans formation and elimination via urine and faeces, fentanyl is also eliminated unchanged by the lungs. The potential risk to operating theatre personnel from long-term exposure to low levels of exhaled anaesthetic agents following intravenous administration to patients during surgery warrants further research.

Investigation of the effect of the extraction phase geometry on the performance of automated solid-phase microextraction

A new configuration of C(18) thin film extraction phase designed for high sample throughput has been developed and applied to the analysis of benzodiazepines in spiked urine samples using high performance liquid chromatography coupled with tandem mass spectrometry. The high throughput analysis was achieved with the use of a robotic autosampler which enabled parallel analyte extraction in a 96-well plate format. Factors affecting data reproducibility, extraction kinetics, sample throughput, and reliability of the system were investigated and optimized. The intrawell reproducibility was 4.5-7.3%, while interwell reproducibility was 7.0-11% in urine and PBS samples. The limits of detection and quantitation were 0.05-0.15 ng/mL and 0.2-2.0 ng/mL for all analytes, respectively. By comparison with optimized automated multifiber SPME relying on rod geometry, the C(18) thin films showed higher extraction rates (approximate 2-fold increase) and hence higher sample throughput because of the improved configuration and more effective agitation/mass transfer. In addition, this new configuration provided an extraction phase with greater surface area to volume ratio and greater extraction phase volume, which resulted in approximately 2-fold increase in the extraction capacity for diazepam compared with the extractions with automated multifiber SPME rod geometry. The results of this investigation demonstrated the advantages of using thin films to improve extraction kinetics and sensitivity of automated SPME methods for high performance liquid chromatography.

Rapid and sensitive determination of fentanyl in dog plasma by on-line solid-phase extraction integrated with a hydrophilic column coupled to tandem mass spectrometry

We have developed and validated a method for the quantification of fentanyl, a synthetic opioid, in dog plasma by on-line SPE with a hydrophilic column coupled to tandem mass spectrometry in positive electrospray mode. A column-switching instrument with 10-port valve and two HPLC pumping systems were employed. Deuterated fentanyl served as the internal standard. A Waters Oasis HLB extraction column and a Waters Atlantis HILIC Silica analytical column in a column-switching set-up with gradient elution were utilized. Both fentanyl (analyte) and the internal standard (fentanyl-d5) were determined via multiple reaction monitoring (MRM) and the MS/MS ion transitions monitored were m/z 337.0/188.0 and 342.0/188.0, respectively. Each plasma sample was chromatographed within 5 min. The calibration curves were linear over a widely range of 0.01-50 ng/mL using weighted linear regression analysis (1/x). The low limit of quantitation was 0.01 ng/mL. The intra- and inter-day accuracy ranged from 102 to 112% and the overall precision was less than 3%. The recoveries ranged from 90 to 105% in plasma at the concentrations of 0.04, 0.4, 4 and 40 ng/mL. No influence of freeze/thaw and long-term stability were observed. This validated method has been successfully applied to analyze the dog plasma samples of a pharmacokinetics study.

Application of solid-phase microextraction in analytical toxicology

Solid-phase microextraction (SPME) is a miniaturized and solvent-free sample preparation technique for chromatographic-spectrometric analysis by which the analytes are extracted from a gaseous or liquid sample by absorption in, or adsorption on, a thin polymer coating fixed to the solid surface of a fiber, inside an injection needle or inside a capillary. In this paper, the present state of practical performance and of applications of SPME to the analysis of blood, urine, oral fluid and hair in clinical and forensic toxicology is reviewed. The commercial coatings for fibers or needles have not essentially changed for many years, but there are interesting laboratory developments, such as conductive polypyrrole coatings for electrochemically controlled SPME of anions or cations and coatings with restricted-access properties for direct extraction from whole blood or immunoaffinity SPME. In-tube SPME uses segments of commercial gas chromatography (GC) capillaries for highly efficient extraction by repeated aspiration-ejection cycles of the liquid sample. It can be easily automated in combination with liquid chromatography but, as it is very sensitive to capillary plugging, it requires completely homogeneous liquid samples. In contrast, fiber-based SPME has not yet been performed automatically in combination with high-performance liquid chromatography. The headspace extractions on fibers or needles (solid-phase dynamic extraction) combined with GC methods are the most advantageous versions of SPME because of very pure extracts and the availability of automatic samplers. Surprisingly, substances with quite high boiling points, such as tricyclic antidepressants or phenothiazines, can be measured by headspace SPME from aqueous samples. The applicability and sensitivity of SPME was essentially extended by in-sample or on-fiber derivatization. The different modes of SPME were applied to analysis of solvents and inhalation narcotics, amphetamines, cocaine and metabolites, cannabinoids, methadone and other opioids, fatty acid ethyl esters as alcohol markers, gamma-hydroxybutyric acid, benzodiazepines, various other therapeutic drugs, pesticides, chemical warfare agents, cyanide, sulfide and metal ions. In general, SPME is routinely used in optimized methods for specific analytes. However, it was shown that it also has some capacity for a general screening by direct immersion into urine samples and for pesticides and other semivolatile substance in the headspace mode.

Simultaneous determination of selegiline and desmethylselegiline in human body fluids by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method for the simultaneous determination of selegiline and its metabolite, desmethylselegiline, in human whole blood and urine is presented. The method, which combines a fiber-based headspace solid-phase microextraction (SPME) technique with gas chromatography-mass spectrometry (GC-MS), required optimization of various parameters (e.g., salt additives, extraction temperatures, extraction times and the extraction properties of the SPME fiber coatings). Pargyline was used as the internal standard. Extraction efficiencies for both selegiline and desmethylselegiline were 2.0-3.4% for whole blood, and 8.0-13.2% for urine. The regression equations for selegiline and desmethylselegiline extracted from whole blood were linear (r(2)=0.996 and 0.995) within the concentration ranges 0.1-10 and 0.2-20 ng/ml, respectively. For urine, the regression equations for selegiline and desmethylselegiline were linear (r(2)=0.999 and 0.998) within the concentration ranges 0.05-5.0 and 0.1-10 ng/ml, respectively. The limit of detection for selegiline and desmethylselegiline was 0.01-0.05 ng/ml for both samples. The lower and upper limits of quantification for each compound were 0.05-0.2 and 5-20 ng/ml, respectively. Intra- and inter-day coefficients of variation for selegiline and desmethylselegiline in both samples were not greater than 8.7 and 11.7%, respectively. The determination of selegiline and desmethylselegiline concentrations in Parkinson's disease patients undergoing continuous selegiline treatment is presented and is shown to validate the present methodology.

Development of an enzyme-linked immunosorbent assay for fentanyl and applications of fentanyl antibody-coated nanoparticles for sample preparation

A sensitive enzyme-linked immunosorbent assay (ELISA) was developed for the detection of fentanyl in serum and urine. The ELISA used an indirect competitive method produced by coating the plate with thyroglobulin conjugated with fentanyl hapten. Antibodies against fentanyl-hemocyanin were detected by a goat-anti-rabbit antibody conjugated with alkaline phosphatase. Calibration standard curves ranged from 0.5ng/ml to 50mug/ml (IC(50)=10ng/ml), and the limits of detection were 0.5 and 1.0ng/ml for serum and urine, respectively. The intra- and inter-assay variations were less than 8% and 10%, respectively. The antibody produced against fentanyl completely cross-reacted with p-fluorofentanyl, thienylfentanyl and 3-methylthienylfentanyl, cross-reacted highly with carfentanil (85%), but was considered non-cross-reactive with alpha-methylfentanyl (5%), sufentanil (<1%), alfentanil (<1%) and lofentanil (<1%). Nano-sized iron oxide magnetic particles coated with the developed fentanyl antibody were capable of specific binding and releasing of fentanyl from urine samples. This enabled the drug to be effectively pre-concentrated and decreased the limit of detection by approximately one order of magnitude. The analytical background noise was significantly reduced to enable fentanyl detection at concentrations originally below chromatographic limit of detection. The change of platform for antibody binding with nanoparticles demonstrated a novel use of antibodies for sample preparation and should facilitate drug screening by traditional ELISA.

Position of chromatographic techniques in screening for detection of drugs or poisons in clinical and forensic toxicology and/or doping control

This paper reviews chromatographic screening procedures for simultaneous detection of several drug classes relevant to clinical and forensic toxicology or doping control in urine or blood using gas chromatography-mass spectrometry (GC-MS), liquid chromatography coupled with a diode-array detector (LC-DAD) or a mass spectrometer (LC-MS). The pros and cons of the different techniques and procedures are discussed leading to the following conclusions and perspectives. GC-MS, especially in the electron ionization full-scan mode, is still the method of choice for comprehensive screening providing best separation power, specificity and universality, although requiring derivatization. LC-DAD is also often used for screening, but its separation power and its specificity are still inferior to those of GC-MS. Finally, LC-MS has shown to be an ideal supplement, especially for the detection of more polar, thermolabile and/or low-dose drugs, especially in blood plasma. It may become the gold standard in clinical and forensic toxicology and doping control if, at a later date, the costs of the apparatus will be markedly reduced, the current disadvantages like irreproducibility of fragmentation, reduction of ionization by matrix, etc. will be overcome, and finally if one of the increasing number of quite different techniques will become the apparatus standard.