Development and validation of a liquid chromatography–atmospheric pressure photoionization–mass spectrometry method for the quantification of alprazolam, flunitrazepam, and their main metabolites in haemolysed blood

Recent developments in atmospheric pressure photoionization-mass spectrometry

Recent developments in atmospheric pressure photoionization (APPI), which is one of the three most important ionization techniques in liquid chromatography-mass spectrometry, are reviewed. The emphasis is on the practical aspects of APPI analysis, its combination with different separation techniques, novel instrumental developments - especially in gas chromatography and ambient mass spectrometry - and the applications that have appeared in 2009-2014. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:423-449, 2017.

Evaluation of Multiple Blood Matrices for Assessment of Human Exposure to Nerve Agents

Biomedical samples may be used to determine human exposure to nerve agents through the analysis of specific biomarkers. Samples received may include serum, plasma, whole blood, lysed blood and, due to the toxicity of these compounds, postmortem blood. To quantitate metabolites resulting from exposure to sarin (GB), soman (GD), cyclosarin (GF), VX and VR, these blood matrices were evaluated individually for precision, accuracy, sensitivity and specificity. Accuracies for these metabolites ranged from 100 to 113% with coefficients of variation ranging from 2.31 to 13.5% across a reportable range of 1-100 ng/mL meeting FDA recommended guidelines for bioanalytical methods in all five matrices. Limits of detection were calculated to be 0.09-0.043 ng/mL, and no interferences were detected in unexposed matrix samples. The use of serum calibrators was also determined to be a suitable alternative to matrix-matched calibrators. Finally, to provide a comparative value between whole blood and plasma, the ratio of the five nerve agent metabolites measured in whole blood versus plasma was determined. Analysis of individual whole blood samples (n = 40), fortified with nerve agent metabolites across the reportable range, resulted in average nerve agent metabolite blood to plasma ratios ranging from 0.53 to 0.56. This study demonstrates the accurate and precise quantitation of nerve agent metabolites in serum, plasma, whole blood, lysed blood and postmortem blood. It also provides a comparative value between whole blood and plasma samples, which can assist epidemiologists and physicians with interpretation of test results from blood specimens obtained under variable conditions.

Determination of the psychoactive drugs carbamazepine and diazepam in hospital effluent and identification of their metabolites

This study addresses the occurrence of carbamazepine and diazepam and their metabolites in the wastewater of the University Hospital (HUSM) of the Federal University of Santa Maria, RS-Brazil. Samples were collected from three sampling points of the sewage treatment system: point A ('emergency effluent'), point B ('general effluent') and point C ('water course-receptor'). Eight metabolites were identified: carbamazepine-10-11-epoxide, 10-dihydro-carbamazepine, 2-OH-carbamazepine, iminoquinone, acridone, nordiazepam, oxazepam and temazepam. The mean concentrations in the emergency, general effluent and water course-receptor were as follows: 433.0 ± 4.7, 349.0 ± 5.0 and 485.0 ± 5.6 ng L(-1), for carbamazepine and 550.0 ± 4.3, 441.0 ± 7.9 and 586.6 ± 9.3 ng L(-1), for diazepam, respectively. Liquid chromatography with electrospray ionization tandem mass spectrometry (LC-QqLIT-MS) proved to be a method fit-to-purpose. The determination of carbamazepine and diazepam, and the identification of active metabolites showing environmental persistence (carbamazepine-10-11-epoxide, nordiazepam and oxazepam) revealed the need for a more effective treatment of the HUSM effluent. As far as we know, no similar study has been carried out on the wastewater of Brazilian hospitals.

New approach to the determination of contaminants of emerging concern in natural water: study of alprazolam employing adsorptive cathodic stripping voltammetry

Contaminants of emerging concern (CECs) are chemicals, including pharmaceutical and personal care products, not commonly monitored in the aquatic environment. Pharmaceuticals are nowadays considered as an important environmental contaminant. Chromatography methods which require expensive equipment and complicated sample pretreatment are used for detection of CECs in natural water. Thus, in this study we proposed a simple, fast, and low-cost voltammetric method as a screening tool for the determination of CECs in natural water prior to chromatography. A case study was conducted with alprazolam (benzodiazepine). The method was optimized and validated in-house. The limit of quantification was 0.4 μg L(-1) for a 120 s preconcentration time. The recoveries ranged from 93 to 120 % for accuracy tests. A further proposal aim was to determine for the first time the occurrence of alprazolam in Brazilian river water and to evaluate its potential use as a marker of contamination by wastewater.

Simultaneous quantification of diazepam, flunitrazepam and metabolites in reinforced clostridial medium by liquid chromatography-tandem mass spectrometry

A novel liquid chromatography-tandem mass spectrometry method was validated for identification and quantification of diazepam, flunitrazepam and metabolites in reinforced clostridial medium (RCM), a complex matrix used to provide the nutrients required for bacterial growth. The method was designed for subsequent use in the investigation of gastrointestinal bacteria as a potential source of postmortem alteration of drugs of abuse and respective metabolite concentrations. A literature review yielded no experimental means or model for the extraction and analysis of samples from RCM or similar bacterial medium. Development and validation of a new experimental method were therefore critical. In future work, this method could be adapted and extended to similar organic compounds of interest. The calibration curves extended from 0.100 to 500 ng/mL. Analyte recoveries ranged from 95 to 119% and matrix effects from 97 to 119%. Bias was ≤±17.6%, within-run precision ≤12.2%, and between-run precision ≤11.7% across all concentration levels. The limits of detection and quantitation ranged from 0.100 to 1 ng/mL. Dilution integrity was maintained for 1:2 and 1:5 dilutions. Analytes were stable through two freeze-thaw cycles and processed samples for 48 h. Method robustness was evaluated by changes in buffer composition and column temperature as well as samples prepared by an alternate analyst.

Simplifying sample pretreatment: application of dried blood spot (DBS) method to blood samples, including postmortem, for UHPLC-MS/MS analysis of drugs of abuse

The complexity of biological matrices, such as blood, requires the development of suitably selective and reliable sample pretreatment procedures prior to their instrumental analysis. A method has been developed for the analysis of drugs of abuse and their metabolites from different chemical classes (opiates, methadone, fentanyl and analogues, cocaine, amphetamines and amphetamine-like substances, ketamine, LSD) in human blood using dried blood spot (DBS) and subsequent UHPLC-MS/MS analysis. DBS extraction required only 100μL of sample, added with the internal standards and then three droplets (30μL each) of this solution were spotted on the card, let dry for 1h, punched and extracted with methanol with 0.1% of formic acid. The supernatant was evaporated and the residue was then reconstituted in 100μL of water with 0.1% of formic acid and injected in the UHPLC-MS/MS system. The method was validated considering the following parameters: LOD and LOQ, linearity, precision, accuracy, matrix effect and dilution integrity. LODs were 0.05-1ng/mL and LOQs were 0.2-2ng/mL. The method showed satisfactory linearity for all substances, with determination coefficients always higher than 0.99. Intra and inter day precision, accuracy, matrix effect and dilution integrity were acceptable for all the studied substances. The addition of internal standards before DBS extraction and the deposition of a fixed volume of blood on the filter cards ensured the accurate quantification of the analytes. The validated method was then applied to authentic postmortem blood samples.

A rapid UPLC-MS/MS method for simultaneous determination of flunitrazepam, 7-aminoflunitrazepam, methadone and EDDP in human, rat and rabbit plasma

A simple, high-throughput, sensitive LC-ESI-MS/MS method is presented for the simultaneous determination of methadone (MET), flunitrazepam (FNZ) and their major metabolites, EDDP (2-ethilidene-1,5-dimethyl-3,3-diphenylpyrrolidone) and 7-aminoflunitrazepam (7-AFNZ), respectively, in human, rat and rabbit plasma. The isolation of the selected compounds involved a liquid-liquid extraction with ethyl acetate at a basic pH. Good chromatographic separation was achieved on a HSS T3 column (1.8 μm particle size), with a 3 min gradient elution using a mixture of acetonitrile with 0.1% formic acid (solvent A) and 5mM ammonium acetate (solvent B) as the mobile phase. The tandem mass spectrometric detection was performed in multiple reaction monitoring (MRM) mode with ionization of the analytes in positive mode. The assay was fully validated according to current acceptance criteria for bioanalytical methods validation. It was proved to be linear in the range of 0.5-250 ng/mL, with adequate accuracy and precision over this range. Based on accuracy and CV% values the LOQ and ULOQ values were set at 0.509 ng/mL and 2036 ng/mL for MET, 0.520 ng/mL and 2080 ng/mL for EDDP, 0.524 ng/mL and 2096 ng/mL for FNZ and 0.528 ng/mL and 2114 ng/mL for 7-AFNZ, respectively. The method was tested for potential matrix effects, without observing significant ion suppression. The investigated compounds stability was examined in plasma at room temperature and after three freeze-thaw cycles and in the final extract when maintained at 4 °C in the autosampler. Potential stability issues were observed only for FNZ at room temperature. The method was successfully applied to quantify the selected compounds in human, rat and rabbit plasma samples, after exposure to FNZ or simultaneous exposure to FNZ and MET.

Flexibility and applicability of β-expectation tolerance interval approach to assess the fitness of purpose of pharmaceutical analytical methods

An innovative versatile strategy using Total Error has been proposed to decide about the method's validity that controls the risk of accepting an unsuitable assay together with the ability to predict the reliability of future results. This strategy is based on the simultaneous combination of systematic (bias) and random (imprecision) error of analytical methods. Using validation standards, both types of error are combined through the use of a prediction interval or β-expectation tolerance interval. Finally, an accuracy profile is built by connecting, on one hand all the upper tolerance limits, and on the other hand all the lower tolerance limits. This profile combined with pre-specified acceptance limits allows the evaluation of the validity of any quantitative analytical method and thus their fitness for their intended purpose. In this work, the approach of accuracy profile was evaluated on several types of analytical methods encountered in the pharmaceutical industrial field and also covering different pharmaceutical matrices. The four studied examples depicted the flexibility and applicability of this approach for different matrices ranging from tablets to syrups, different techniques such as liquid chromatography, or UV spectrophotometry, and for different categories of assays commonly encountered in the pharmaceutical industry i.e. content assays, dissolution assays, and quantitative impurity assays. The accuracy profile approach assesses the fitness of purpose of these methods for their future routine application. It also allows the selection of the most suitable calibration curve, the adequate evaluation of a potential matrix effect and propose efficient solution and the correct definition of the limits of quantification of the studied analytical procedures.

CEC-atmospheric pressure ionization MS of pesticides using a surfactant-bound monolithic column

A surfactant bound poly (11-acrylaminoundecanoic acid-ethylene dimethacrylate) monolithic column was simply prepared by in situ co-polymerization of 11-acrylaminoundecanoic acid and ethylene dimethacrylate with 1-propanol, 1,4-butanediol and water as porogens in 100 microm id fused-silica capillary in one step. This column was used in CEC-atmospheric pressure photoionization (APPI)-MS system for separation and detection of N-methylcarbamates pesticides. Numerous parameters are optimized for CEC-APPI-MS. After evaluation of the mobile phase composition, sheath liquid composition and the monolithic capillary outlet position, a fractional factorial design was selected as a screening procedure to identify factors of ionization source parameters, such as sheath liquid flow rate, drying gas flow rate, drying gas temperature, nebulizing gas pressure, vaporizer temperature and capillary voltage, which significantly influence APPI-MS sensitivity. A face-centered central composite design was further utilized to optimize the most significant parameters and predict the best sensitivity. Under optimized conditions, S/Ns around 78 were achieved for an injection of 100 ng/mL of each pesticide. Finally, this CEC-APPI-MS method was successfully applied to the analysis of nine N-methylcarbamates in spiked apple juice sample after solid phase extraction with recoveries in the range of 65-109%.