Simultaneous analysis of buprenorphine,methadone, cocaine,opiates and nicotine metabolites in sweat by liquid chromatography tandem mass spectrometry

A liquid chromatography tandem mass spectrometry method for buprenorphine (BUP), norbuprenorphine (NBUP), methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), cocaine, benzoylecgonine, ecgonine methyl ester (EME), morphine, codeine, 6-acetylmorphine, heroin, 6-acetylcodeine, cotinine, and trans-3′-hydroxycotinine quantification in sweat was developed and comprehensively validated. Sweat patches were mixed with 6 mL acetate buffer at pH 4.5, and supernatant extracted with Strata-XC-cartridges. Reverse-phase separation was achieved with a gradient mobile phase of 0.1% formic acid and acetonitrile in 15 min. Quantification was achieved by multiple reaction monitoring of two transitions per compound. The assay was a linear 1–1,000 ng/patch, except EME 5–1,000 ng/patch. Intra-, inter-day and total imprecision were <10.1%CV, analytical recovery 87.2–107.7%, extraction efficiency 35.3–160.9%, and process efficiency 25.5–91.7%. Ion suppression was detected for EME (−63.3%) and EDDP (−60.4%), and enhancement for NBUP (42.6%). Deuterated internal standards compensated for these effects. No carryover was detected, and all analytes were stable for 24 h at 22 °C, 72 h at 4 °C, and after three freeze/thaw cycles. The method was applied to weekly sweat patches from an opioid-dependent BUP-maintained pregnant woman; 75.0% of sweat patches were positive for BUP, 93.8% for cocaine, 37.5% for opiates, 6.3% for methadone and all for tobacco biomarkers. This method permits a fast and simultaneous quantification of 14 drugs and metabolites in sweat patches, with good selectivity and sensitivity.     

Simultaneous quantification of nicotine,opioids, cocaine,and metabolites in human fetal postmortem brain by liquid chromatography tandem mass spectrometry

A validated method for simultaneous LCMSMS quantification of nicotine, cocaine, 6-acetylmorphine (6AM), codeine, and metabolites in 100 mg fetal human brain was developed and validated. After homogenization and solid-phase extraction, analytes were resolved on a Hydro-RP analytical column with gradient elution. Empirically determined linearity was from 5–5,000 pg/mg for cocaine and benzoylecgonine (BE), 25–5,000 pg/mg for cotinine, ecgonine methyl ester (EME) and 6AM, 50-5000 pg/mg for trans-3-hydroxycotinine (OH-cotinine) and codeine, and 250–5,000 pg/mg for nicotine. Potential endogenous and exogenous interferences were resolved. Intra- and inter-assay analytical recoveries were ≥92%, intra- and inter-day and total assay imprecision were ≤14% RSD and extraction efficiencies were ≥67.2% with ≤83% matrix effect. Method applicability was demonstrated with a postmortem fetal brain containing 40 pg/mg cotinine, 65 pg/mg OH-cotinine, 13 pg/mg cocaine, 34 pg/mg EME, and 525 pg/mg BE. This validated method is useful for determination of nicotine, opioid, and cocaine biomarkers in brain.     

Oral fluid cannabinoid concentrations following controlled smoked cannabis in chronic frequent and occasional smokers

Oral fluid (OF) is an alternative biological matrix for monitoring cannabis intake in drug testing, and drugged driving (DUID) programs, but OF cannabinoid test interpretation is challenging. Controlled cannabinoid administration studies provide a scientific database for interpreting cannabinoid OF tests. We compared differences in OF cannabinoid concentrations from 19 h before to 30 h after smoking a 6.8 % THC cigarette in chronic frequent and occasional cannabis smokers. OF was collected with the Statsure Saliva Sampler? OF device. 2D-GC-MS was used to quantify cannabinoids in 357 OF specimens; 65 had inadequate OF volume within 3 h after smoking. All OF specimens were THC-positive for up to 13.5 h after smoking, without significant differences between frequent and occasional smokers over 30 h. Cannabidiol (CBD) and cannabinol (CBN) had short median last detection times (2.5–4 h for CBD and 6–8 h for CBN) in both groups. THCCOOH was detected in 25 and 212 occasional and frequent smokers’ OF samples, respectively. THCCOOH provided longer detection windows than THC in all frequent smokers. As THCCOOH is not present in cannabis smoke, its presence in OF minimizes the potential for false positive results from passive environmental smoke exposure, and can identify oral THC ingestion, while OF THC cannot. THC?≥?1 μg/L, in addition to CBD?≥?1 μg/L or CBN?≥?1 μg/L suggested recent cannabis intake (≤13.5 h), important for DUID cases, whereas THC?≥?1 μg/L or THC?≥?2 μg/L cutoffs had longer detection windows (≥30 h), important for workplace testing. THCCOOH windows of detection for chronic, frequent cannabis smokers extended beyond 30 h, while they were shorter (0–24 h) for occasional cannabis smokers.     

Quantification of cocaine and metabolites in exhaled breath by liquid chromatography-high-resolution mass spectrometry following controlled administration of intravenous cocaine

Breath has been investigated as an alternative matrix for detecting recent cocaine intake; however, there are no controlled cocaine administration studies that investigated the drug’s disposition into breath. Breath was collected from 10 healthy adult cocaine users by asking them to breathe into a SensAbues device for 3 min before and up to 22 h following 25 mg intravenous (IV) cocaine dosing on days 1, 5, and 10, and assayed with a validated liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method to quantify breath cocaine, benzoylecgonine (BE), ecgonine methyl ester (EME), and norcocaine. The assay was linear from 25 to 1,000 pg/filter, extraction efficiencies were 83.6–126 %, intra- and inter-assay imprecision was <10.6 %, and bias was between ?8.5 and 16.8 %. No endogenous or exogenous interferences were observed for more than 75 tested. Analytes were generally stable under short-term storage conditions. Ion suppression was less than 46 %. Of breath specimens collected after controlled cocaine administration, 2.6 % were positive for cocaine (26.1–66 pg/filter, 1–9.5 h), 0.72 % BE (83.3–151 pg/filter, 6.5–12.5 h), and 0.72 % EME (50–69.1 pg/filter, 6.5–12.5 h); norcocaine was not detected. Methanolic extraction of the devices themselves, after filters were removed, yielded 19.2 % positive cocaine tests (25.2–36.4 pg/device, 10 min–22 h) and 4.3 % positive BE tests (26.4–93.7 pg/device, 10 min–22 h), explaining differences between the two extraction techniques. These results suggest that the device reflects the drug in oral fluid as well as lung microparticles, while the filter reflects only drug-laden microparticles. A sensitive and specific method for cocaine, BE, EME, and norcocaine quantification in breath was developed and validated. Cocaine in breath identifies recent cocaine ingestion, but its absence does not preclude recent use.

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Graphical abstract ?

     

Methadone concentrations in blood, plasma, and oral fluid determined by isotope-dilution gas chromatography–mass spectrometry

Methadone (MTD) is widely used for detoxification of heroin addicts and also in pain management programs. Information about the distribution of methadone between blood, plasma, and alternative specimens, such as oral fluid (OF), is needed in clinical, forensic, and traffic medicine when analytical results are interpreted. We determined MTD and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in blood, plasma, blood cells, and OF by gas chromatography–mass spectrometry (GC-MS) after adding deuterium-labeled internal standards. The analytical limits of quantitation for MTD and EDDP by this method were 20 and 3 ng/mL, respectively. The amounts of MTD and EDDP were higher in plasma (80.4 % and 76.5 %) compared with blood cells (19.6 % and 23.5 %) and we found that repeated washing of blood cells with phosphate–buffered saline increased the amounts in plasma (93.6 % and 88.6 %). Mean plasma/blood concentration ratios of MTD and EDDP in spiked samples (N?=?5) were 1.27 and 1.21, respectively. In clinical samples from patients (N?=?46), the concentrations of MTD in plasma and whole blood were highly correlated (r?=?0.92, p?<?0.001) and mean (median) plasma/blood distribution ratios were 1.43 (1.41). The correlations between MTD in OF and plasma (r?=?0.46) and OF and blood (r?=?0.52) were also statistically significant (p?<?0.001) and the mean OF/plasma and OF/blood distribution ratios were 0.55 and 0.77, respectively. The MTD concentration in OF decreased as salivary pH increased (more basic). These results will prove useful in clinical and forensic medicine when MTD concentrations in alternative specimens are compared and contrasted.     

Simultaneous quantification of 28 synthetic cathinones and metabolites in urine by liquid chromatography-high resolution mass spectrometry

Synthetic cathinones are novel stimulants derived from cathinone, with amphetamines or cocaine-like effects, often labeled “not for human consumption” and considered “legal highs”. Emergence of these new designer drugs complicate interpretation of forensic and clinical cases, with introduction of many new analogs designed to circumvent legislation and vary effects and potencies. We developed a method for the simultaneous quantification of 28 synthetic cathinones, including four metabolites, in urine by liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). These cathinones include cathinone, methcathinone, and synthetic cathinones position-3’-substituted, N-alkyl-substituted, ring-substituted, methylenedioxy-substituted, and pyrrolidinyl-substituted. One mL phosphate buffer pH 6 and 25 μL IStd solution were combined with 0.25 mL urine, and subjected to solid phase cation exchange extraction (SOLA SCX). The chromatographic reverse-phase separation was achieved with a gradient mobile phase of 0.1 % formic acid in water and in acetonitrile in 20 min. We employed a Q Exactive high resolution mass spectrometer, with compounds identified and quantified by target-MSMS experiments. The assay was linear from 0.5–1 to 100 μg/L, with limits of detection of 0.25–1 μg/L. Imprecision (n?=?20) was <15.9 % and accuracy (n?=?20) 85.2–118.1 %. Extraction efficiency was 78.9–116.7 % (CV 1.4–16.7 %, n?=?5), process efficiency 57.7–104.9 %, and matrix effects from ?29.5 % to 1.5 % (CV 1.9–13.1 %, n?=?10). Most synthetic cathinones were stable at 4 °C for 72 h (n?=?27) and after 3 freeze-thaw cycles (n?=?26), but many (n?=?19) were not stable at room temperature for 24 h (losses up to ?67.6 %). The method was applied to authentic urine specimens from synthetic cathinone users. This method provides a comprehensive confirmation method for 28 synthetic cathinones in urine, with good selectivity and specificity.     

Analysis of cocaine and its principal metabolites in waste and surface water using solid-phase extraction and liquid chromatography–ion trap tandem mass spectrometry

A validated method based on solid-phase extraction (SPE) and liquid chromatography-ion trap tandem mass spectrometry (LC-MS/MS) is described for the determination of cocaine (COC) and its principal metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME), in waste and surface water. Several SPE adsorbents were investigated and the highest recoveries (95.7 +/- 5.5, 91.8 +/- 2.2 and 72.5 +/- 5.3% for COC, BE and EME, respectively) were obtained for OASIS HLB(R) cartridges (6 mL/500 mg) using 100 mL of waste water or 500 mL of surface water. Extracts were analysed by reversed-phase (RP) or hydrophilic interaction (HILIC) LC-MS/MS in positive ion mode with multiple reactions monitoring (MRM); the latter is the first reported application of the HILIC technique for drugs of abuse in water samples. Corresponding deuterated internal standards were used for quantification. The method limits of quantification (LOQs) for COC and BE were 4 and 2 ng L(-1), respectively, when RPLC was used and 1, 0.5 and 20 ng L(-1) for COC, BE and EME, respectively, with the HILIC setup. For COC and BE, the LOQs were below the concentrations measured in real water samples. Stability tests were conducted to establish the optimal conditions for sample storage (pH, temperature and time). The degradation of COC was minimal at -20 degrees C and pH = 2, but it was substantial at +20 degrees C and pH = 6. The validated method was applied to a set of waste and surface water samples collected in Belgium.     

Determination of Meserine,a new candidate for Alzheimer’s disease in mice brain by liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic and tissue distribution study

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of Meserine ((?)-meptazinol phenylcarbamate), a novel potent inhibitor of acetylcholinesterase (AChE), was developed, validated, and applied to a pharmacokinetic study in mice brain. The lower limit of quantification (LLOQ) was 1 ng mL^?1 and the linear range was 1–1,000 ng mL^?1. The analyte was eluted on a Zorbax SB-Aq column (2.1?×?100 mm, 3.5 μm) with the mobile phase composed of methanol and water (70:30, v/v, aqueous phase contained 10 mM ammonium formate and 0.3 % formic acid) using isocratic elution, and monitored by positive electrospray ionization in multiple reaction monitoring (MRM) mode. The flow rate was 0.25 mL min^?1. The injection volume was 5 μL and total run time was 4 min. The relative standard deviation (RSD) of intraday and interday variation was 2.49–7.81 and 3.01–7.67 %, respectively. All analytes were stable after 4 h at room temperature and 6 h in autosampler. The extraction recoveries of Meserine in brain homogenate were over 90 %. The main brain pharmacokinetic parameters obtained after intranasal administration were T _max?=?0.05 h, C _max?=?462.0?±?39.7 ng g^?1, T _1/2?=?0.4 h, and AUC_(0-∞)?=?283.1?±?9.1 ng h g^?1. Moreover, Meserine was distributed rapidly and widely into brain, heart, liver, spleen, lung, and kidney tissue. The method is validated and could be applied to the pharmacokinetic and tissue distribution study of Meserine in mice.     

Determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples by cloud-point extraction and high-performance liquid chromatography

A highly sensitive method for the determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples is proposed. The method is based on analytes reacted with ammonium pyrrolidinedithiocarbamate (APDC) to give hydrophobic chelates (M–APDC), which were separated and enriched by cloud-point extraction (CPE) with non-ionic surfactant Tergitol TMN-6 as extractant. The surfactant-rich phase containing the chelates is determined with a high-performance liquid chromatography system. To achieve the best CPE method, the Box–Behnken design was used to study the concentration of Tergitol TMN-6, equilibrium temperature, equilibrium time as well as their interaction. What followed was the individual research for the pH of the sample solutions and the concentration of APDC. What is more, in the given optimized experimental conditions, calibration plots were found to be linear in the range of 0.0200–0.500 mg/L for Mn (VII) and Cr (VI), meanwhile 0.0500–1.00 mg/L for Ni (II), the linear correlation coefficients were between 0.996 and 0.999, the recoveries ranged from 91.8 to 97.8 % and the relative standard deviations were between 1.09 and 2.30 % (n = 3). The limits of detection were 0.164 μg/L for Mn (VII), 0.562 μg/L for Cr (VI) and 5.12 μg/L for Ni (II), respectively. The proposed method was applied to determine manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples with satisfactory results.     

Development and validation of a solid-phase extraction gas chromatography–mass spectrometry method for the simultaneous quantification of methadone, heroin, cocaine and metabolites in sweat

A sensitive and specific method is presented to simultaneously quantify methadone, heroin, cocaine and metabolites in sweat. Drugs were eluted from sweat patches with sodium acetate buffer, followed by SPE and quantification by GC/MS with electron impact ionization and selected ion monitoring. Daily calibration for anhydroecgonine methyl ester, ecgonine methyl ester, cocaine, benzoylecgonine (BE), codeine, morphine, 6-acetylcodeine, 6-acetylmorphine (6AM), heroin (5-1000 ng/patch) and methadone (10-1000 ng/patch) achieved determination coefficients of >0.995, and calibrators quantified to within +/-20% of the target concentrations. Extended calibration curves (1000-10,000 ng/patch) were constructed for methadone, cocaine, BE and 6AM by modifying injection techniques. Within (N = 5) and between-run (N = 20) imprecisions were calculated at six control levels across the dynamic ranges with coefficients of variation of <6.5%. Accuracies at these concentrations were +/-11.9% of target. Heroin hydrolysis during specimen processing was <11%. This novel assay offers effective monitoring of drug exposure during drug treatment, workplace and criminal justice monitoring programs.     

Determination of sulfadiazine in phosphate- and DOC-rich agricultural drainage water using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry

Trace levels of the veterinary antibiotic compound sulfadiazine (SDZ) can be determined in agricultural drainage water samples with this new method. Optimized sample pretreatment and solid-phase extraction was combined with liquid chromatography coupled to tandem mass spectrometry (SPE LC-MS/MS) using positive electrospray ionization. The linear dynamic range for the LC-MS/MS was assessed from 5 μg/L to 25 mg/L with a 15-point calibration curve displaying a coefficient of correlation r ²?=?0.9915. Agricultural drainage water spiked at a concentration of 25 ng/L gave recoveries between 63 and 98 % (relative standard deviation 15 %), while at 10 ng/L, it showed a lower recovery of 32 % (relative standard deviation 47 %). The final SPE LC-MS/MS method had a limit of detection (LOD)_Method and a limit of quantification (LOQ)_Method of 7.5 and 23 ng/L agricultural drainage water, respectively. Determination of SDZ, spiked at a realistic concentration of 50 μg/L, in artificial drainage water (ADW) containing common and high levels of phosphate (0.05, 0.5, and 5 mg/L) gave recoveries between 70 and 92 % (relative standard deviation 7.4–12.9 %). Analysis of the same realistic concentration of SDZ in ADW, spiked with common and high levels of dissolved organic carbon (2, 6, and 15 mg/L) confirmed the possible adaptation of a tandem solid-phase extraction (strong anion exchange (SAX)-hydrophilic-lipophilic balance (HLB)) followed by liquid chromatography-tandem mass spectrometry methodology. Recoveries obtained ranged from 104 to 109 % (relative standard deviation 2.8–5.2 %). The new methods enable determination of the veterinary antibiotic compound SDZ in agricultural drainage water from field experiments and monitoring schemes for phosphate- and dissolved organic carbon (DOC)-rich water samples in intensive farming areas.

Biotechnological Production of Xylitol: Enhancement of Monosaccharide Production by Post-Hydrolysis of Dilute Acid Sugarcane Hydrolysate

Dilute-acid hydrolysis pretreatment of sugarcane bagasse resulted in release of 48% (18.4 g/L) of the xylan in the hemicellulose fraction into the hydrolysate as monomeric xylose. In order to enhance the recuperation of this monomer, a post-hydrolysis stage consisted of thermal treatment was carried out. This treatment resulted in an increase in xylose release of 62% (23.5 g/L) of the hemicellulose fraction. Original and post-hydrolysates were concentrated to the same levels of monomeric xylose in the fermentor feed. During the fermentation process, cellular growth was observed to be higher in the post-hydrolysate (3.5 g/L, Y _x/s?=?0.075 g cells/g xylose) than in the original hydrolysate (2.9 g/L, Y _x/s?=?0.068 g cells/g xylose). The post-treated hydrolysate required less concentration of sugars resulting in a lower concentration of fermentation inhibitors, which were formed primarily in the dilute acid hydrolysis step. Post-hydrolysis step led to a high xylose–xylitol conversion efficiency of 76% (0.7 g xylitol/g xylose) and volumetric productivity of 0.68 g xylitol/L h when compared to 71% (0.65 g xylitol/g xylose and productivity of 0.61 g xylitol/L h) for the original hemicellulosic hydrolysate.     

Determination of Bromate in Bottled Drinking Water from Saudi Arabian Markets by HPLC/ICP-MS

The determination of bromate BrO₃ ^? in 50 different bottled drinking water samples collected from Saudi Arabian markets has been investigated using liquid chromatography inductively coupled plasma mass spectrometry (HPLC/ICP-MS). For analysis, samples were injected directly without any further pretreatment or dilution, using only a 50 μL injection volume. The method showed: detection limit of 0.5 μg/L, limit of quantification of 1.0 μg/L, 1.0 ? 200.0 μg/L linearity range (r² = 0.9998), relative standard deviation (%RSD) for reproducibility (inter-day precision) values of 14% and 4% for low and high concentration levels (10,100 μg/L), respectively. The results obtained for bromate showed that 30% of the samples are acceptable as US EPA standards (10 μg/L), 40% of the samples are acceptable as Gulf (Saudi Arabia) standards (25 μg/L), and almost 60% of the samples exceed the allowable limits for bromate in bottled drinking water.     

Exhaustive extraction of peptides by electromembrane extraction

This fundamental work illustrates for the first time the possibility of exhaustive extraction of peptides using electromembrane extraction (EME) under low system-current conditions (<50 μA). Bradykinin acetate, angiotensin II antipeptide, angiotensin II acetate, neurotensin, angiotensin I trifluoroacetate, and leu-enkephalin were extracted from 600 μL of 25 mM phosphate buffer (pH 3.5), through a supported liquid membrane (SLM) containing di-(2-ethylhexyl)-phosphate (DEHP) dissolved in an organic solvent, and into 600 μL of an acidified aqueous acceptor solution using a thin flat membrane-based EME device. Mass transfer of peptides across the SLM was enhanced by complex formation with the negatively charged DEHP. The composition of the SLM and the extraction voltage were important factors influencing recoveries and current with the EME system. 1-nonanol diluted with 2-decanone (1:1 v/v) containing 15% (v/v) DEHP was selected as a suitable SLM for exhaustive extraction of peptides under low system-current conditions. Interestingly, increasing the SLM volume from 5 to 10 μL was found to be beneficial for stable and efficient EME. The pH of the sample strongly affected the EME process, and pH 3.5 was found to be optimal. The EME efficiency was also dependent on the acceptor solution composition, and the extraction time was found to be an important element for exhaustive extraction. When EME was carried out for 25 min with an extraction voltage of 15 V, the system-current across the SLM was less than 50 μA, and extraction recoveries for the model peptides were in the range of 77–94%, with RSD values less than 10%.     

Biohydrogen Production Based on the Evaluation of Kinetic Parameters of a Mixed Microbial Culture Using Glucose and Fruit–Vegetable Waste as Feedstocks

Hydrogen (H₂) production from the organic fraction of solid waste such as fruit and vegetable waste (FVW) is a novel and feasible energy technology. Continuous application of this process would allow for the simultaneous treatment of organic residues and energy production. In this study, batch experiments were conducted using glucose as substrate, and data of H₂ production obtained were successfully adjusted by a logistic model. The kinetic parameters (μ _max?=?0.101 h^?1, K _s?=?2.56 g/L) of an H₂-producing microbial culture determined by the Monod and Haldane–Andrews growth models were used to establish the continuous culture conditions. This strategy led to a productive steady state in continuous culture. Once the steady state was reached in the continuous reactor, a maximum H₂ production of 700 mL was attained. The feasibility of producing H₂ from the FVW obtained from a local market in Mexico City was also evaluated using batch conditions. The effect of the initial FVW concentration on the H₂ production and waste organic material degradation was determined. The highest H₂ production rate (1.7 mmol/day), the highest cumulative H₂ volume (310 mL), and 25 % chemical oxygen demand (COD) removal were obtained with an initial substrate (FVW) concentration of 37 g COD/L. The lowest H₂ production rates were obtained with relatively low initial substrate concentrations of 5 and 11 g COD/L. The H₂ production rates with FVW were also characterized by the logistic model. Similar cumulative H₂ production was obtained when glucose and FVW were used as substrates.     

Simultaneous Determination of Buprenorphine, Norbuprenorphine and Naloxone in Human Plasma by LC-MS-MS

A novel sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS-MS) method simultaneously determined buprenorphine (BUP) and its active metabolite, norbuprenorphine (NBUP), and a coformulant, naloxone was developed, validated and applied successfully in humans. Buprenorphine-d ₄ and norbuprenorphine-d ₃ were used as the internal standard. The analysis was performed on a silica column, and the mobile phase was isocratic and composed of acetonitrile:2 mM ammonium formate in H2O (82:18, v/v). Mass spectrometry employed multiple reaction monitoring modes with transitions of m/z 468.1?C55.2 for BUP, 414.2?C101.2 for NBUP, 328.3?C310.3 for naloxone, 472.1?C59.2 for buprenorphine-d ₄ and 417.2?C101.2 for norbuprenorphine-d ₃. Lower limit of quantification (LLOQ) of the analytical method was 0.05 ng mL^?1 for BUP, 0.1 ng mL^?1 for NBUP and 0.025 ng mL^?1 for naloxone, respectively. The standard calibration curves of BUP, NBUP and naloxone were linear over the concentration range of 0.05?C20 ng mL^?1, 0.1?C20 ng mL^?1 and 0.025?C20 ng mL^?1, respectively. The precisions (RSD) and accuracies (RE) of LLOQ and other QC samples were in acceptable range, with RSD < 20% and RE ± 20% for LLOQ and RSD < 15% and RE within ±15% for QC samples. The method was accurate, precise and specific, and was applied to the pharmacokinetic study of buprenorphine in healthy volunteers.     

Electromembrane extraction and anodic stripping voltammetric determination of mercury(II) using a glassy carbon electrode modified with gold nanoparticles

This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg^.L^?1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg^.L^?1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy.

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Graphical abstract Hg(II) ions were extracted from a donor phase into an acidic acceptor phase (15 μL) placed in the lumen of a hollow fiber using electromembrane extraction. The acceptor phase was then analyzed using anodic stripping voltammetry.

     

Selenium speciation in paired serum and cerebrospinal fluid samples

Se speciation was performed in 24 individual paired serum and cerebrospinal fluid (CSF) samples from neurologically healthy persons. Strong anion exchange (SAX) separation, coupled to inductively coupled plasma–dynamic reaction cell–mass spectrometry (ICP-DRC-MS), was employed. Species identification was done by standard matched retention time, standard addition and by size exclusion chromatography followed from SAX (2-D SEC-SAX-ICP-DRC-MS) and by SAX followed from CE-ICP-DRC-MS (2-D SAX-CE-ICP-DRC-MS). Limit of detection (LoD, 3?×?standard deviation (SD) of noise) was in the range of 0.026–0.031 μg/L for all investigated species and thus was set uniformly to 0.032 μg/L. Quality control for total Se determination was performed by analysing control materials “human serum” and “urine”, where determined values met target values. Several Se species were found in both sample types having following median values (sequence: serum/CSF, each in μg Se/L): total Se, 58.39/0.86; selenoprotein P (SePP), 5.19/0.47; Se-methionine (SeM), 0.23/<LoD; glutathione peroxidase (GPx), 4.2/0.036; thioredoxinreductase (TrxR), 1.64/0.035; Se IV, 12.25/0.046; Se-human serum albumin (Se-HSA), 18.03/0.068. Other Se species, such as Se-cystine (SeC), Se VI and up to four non-identified compounds were monitored (if ever) only in very few samples usually close to LoD. Therefore, their median values were <LoD. Linear relationships based on median values provide information about Se-species passage across neural barriers (NB): SePP_-serum is significantly correlated to total Se_-serum when the latter was >?65 μg/L; however, SePP_-CSF appeared independent of SePP_-serum. For Se-HSA_-serum versus (vs.) Se-HSA_-CSF, a weak linear relationship was found (r ²?=?0.1722). On the contrary, for anti-oxidative Se-enzymes, higher r ² values were calculated: GPx_-serum vs. GPx_-CSF, r ²?=?0.3837; TrxR_-serum vs. TrxR_-CSF, r ²?=?0.6293. Q _-Se-species values (= ratios of CSF_-Se-species/serum_-Se-species) were compared with the Q _-Alb value (HSA_-CSF/HSA_-serum?=?clinical index of NB integrity) for deeper information about NB passage of Se species. The Q _-Se-HSA value (3.8?×?10^?3) was in accordance to the molecular mass dependent restriction at NB (Q _-Alb at 5.25?×?10^?3). Increased Q values were seen for TrxR (21.3?×?10^?3) and GPx (8.3?×?10^?3) which are not (completely) explained by molecular size. For these two anti-oxidative Se-enzymes (GPx, TrxR), we hypothesize that there might be either a facilitated diffusion across NB or they might be additionally synthesized in the brain.     

Simultaneous determination of opiates, methadone, amphetamines, cocaine, and metabolites in human placenta and umbilical cord by LC-MS/MS

LC-MS/MS methods for the quantification of morphine, morphine-3-glucuronide, morphine-6-glucuronide, codeine, 6-acetylmorphine, cocaine, benzoylecgonine, ecgonine methyl ester, hydroxybenzoylecgonine, cocaethylene, amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), methadone, and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in human placenta and umbilical cord were developed and validated. Specimens (1?±?0.02 g) were homogenized with the Ultra-Turrax T8 disperser and centrifuged, and the supernatant was submitted to solid-phase extraction with Oasis MCX cartridges. Chromatographic separation was performed using an Atlantis T3 analytical column (100?×?2.1 mm, 3 μm) and a gradient of 0.1 % formic acid and acetonitrile. Selectivity was verified in 10 different blank specimens. The method was linear from 1–5 to 100–500 ng/g, depending on the analyte. Limits of detection and quantification ranged from 0.5 to 2.5 ng/g and 1 to 5 ng/g, respectively. Method imprecision was ≤15.3 %, except for MDMA at low quality control (18.1 %); accuracy, 87.1 to 114 %; extraction efficiency, 16.3 to 154.0 % (%CV?=?1.8-39.4 %); matrix effect, ?75.7 to 449.9 % (%CV?=?3.5–50 %); and process efficiency, 8.7 to 316.0 %. The method was applied to authentic placenta and umbilical cord specimens from drug-user pregnant women.     

Rapid isolation of angiotensin peptides from plasma by electromembrane extraction

The present study has for the first time demonstrated the isolation of peptides from human plasma by electromembrane extraction (EME). Angiotensin 1, angiotensin 2, and angiotensin 3 migrated from 500 μL of diluted plasma, through a thin layer of 1-octanol and 8% di-(2-ethylhexyl) phosphate immobilized as a supported liquid membrane (SLM) in the pores of a porous hollow fiber, and into a 25 μL aqueous acceptor solution present inside the lumen of the fiber. The driving force for the extraction was a 15 V potential difference applied across the SLM. After only 10 min of EME, the peptides were isolated from diluted plasma (pH 3) with extraction recoveries between 25 and 43%. After optimization, the extraction system was evaluated using spiked plasma samples of angiotensin 2. The evaluation was performed by liquid chromatography electrospray mass spectrometry, showing linearity of angiotensin 2 in the range 2.5–125.0 ng/mL (r² = 0.989), and repeatability (RSD) between 5.6 and 11.6% (n = 6). The results demonstrate the possibility of isolating angiotensin peptides from plasma in only 10 min, using electromembrane extraction. The experimental findings are therefore promising with regard to future peptide extractions.