Determination of tandospirone in human plasma by a liquid chromatography–tandem mass spectrometry method

A rapid, sensitive, and selective liquid chromatography–tandem mass spectrometry method for the detection of tandospirone in human plasma is described. It was employed in a pharmacokinetic study. The analyte and internal standard diphenhydramine were extracted from plasma using liquid–liquid extraction, then separated on a Zorbax XDB C₁₈ column using a mobile phase of methanol–water–formic acid (80:20:0.5, v/v/v). The detection was performed with a tandem mass spectrometer equipped with an electrospray ionization source. Linearity was established in the concentration range of 10.0-5,000 pg/ml. The lower limit of quantification was 10.0 pg/ml. The intraday and interday relative standard deviation across three validation runs over the entire concentration range was less than 13%. Accuracy determined at three concentrations (25.0, 200, and 4,000 pg/ml for tandospirone) ranged from 94.4 to 102.1%. Each plasma sample was chromatographed within 3.4 min. The method proved to be highly selective and suitable for bioequivalence evaluation of different formulations containing tandospirone and clinical pharmacokinetic investigation of tandospirone.     

High-throughput and simultaneous analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry in the positive and negative ionization modes

In this report, a high-throughput and sensitive method for analysis of eight central-acting muscle relaxants in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) in the positive and negative ionization modes using tolbutamide as internal standard is presented. After pretreatment of a plasma sample by solid-phase extraction with an Oasis HLB cartridge, muscle relaxants were analyzed by UPLC with Acquity UPLC BEH C₁₈ column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration curves for muscle relaxants spiked into human plasma equally showed good linearities in the nanogram per milliliter order range. The detection limits (signal-to-noise ratio = 3) was as low as 0.1–2 ng/mL. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with muscle relaxants. To further validate the present method, 250 mg of chlorphenesin carbamate was orally administered to a healthy male volunteer, and the concentrations of chlorphenesin carbamate in plasma were measured 0.5, 1, 2, 4, 6, and 8 h after dosing; their concentrations in human plasma were between 0.62 and 2.44 μg/mL. To our knowledge, this is the first report describing simultaneous analysis of over more than two central-acting muscle relaxants by liquid chromatography–tandem mass spectrometry. This has been realized by the capability of our instrument for simultaneous multiple reaction monitoring of the target compounds in both positive and negative ionization modes. Therefore, the present method seems very useful in forensic and clinical toxicology and pharmacokinetic studies.     

Trimethylsilyldiazomethane derivatization coupled with solid-phase extraction for the determination of alendronate in human plasma by LC-MS/MS

Alendronate is an important representative of bisphosphonates, strongly polar compounds that lack chromophores. With rare exceptions, derivatization of the analytes is necessary for bioanalysis. In this study, a rapid liquid chromatography–tandem mass spectrometry method employing pre-column derivatization was developed and validated for the determination of alendronate concentrations in human plasma. The procedure was based on derivatization with trimethylsilyldiazomethane during solid-phase extraction on a weak anion-exchange solid-phase cartridge, which integrated sample purification and derivatization into one step. The alendronate derivative was eluted with methanol. Chromatographic separation was performed on a Capcell PAK-C18 column. The total run time was 6.5 min. The calibration curve was linear in the range 1.00–1,000 ng/mL using d6-alendronate as the internal standard. The lower limit of quantification was 1.00 ng/mL. The intra- and inter-assay precision (in RSD) calculated from quality control samples was less than 15%, and the accuracy was between 98.1% and 100.2%. The validated method was successfully applied to characterize the pharmacokinetic profiles of alendronate following the intravenous infusion of 5 or 10 mg alendronate sodium to healthy volunteers.     

反相高效液相色谱-串联质谱法测定尿液中儿茶酚胺和肾上腺素(英文)

The measurement of urine catecholamine and metanephrine concentrations is important for biochemical screening and diagnosis of pheochromocytoma.The goal of this work was to develop a simple liquid chromatography-tandem mass spectrometry(LC-MS/MS)method for determining catecholamines and metanephrines in urine to replace an existing liquid chromatographic method using electrochemical detection.Urine samples were prepared using Oasis weak-cation-exchange cartridges.The eluate was analyzed on an Agilent ZORBAX Eclipse Plus Phenyl-Hexyl column in 3 min.Adrenaline,noradrenaline,dopamine,metanephrine,normetanephrine,and their deuterated internal standards were monitored in positive electrospray ionization mode by multiple reaction monitoring(MRM).No evidence of ion suppression was observed.The assay was linear up to 5μmol/L for adrenaline,5μmol/L for noradrenaline,6.1μmol/L for dopamine,5.6μmol/L for metanephrine,and 34.6μmol/L for normetanephrine,with lower limits of quantification of 5,5,12,6 and 7nmol/L,respectively.The intra-day and inter-day precisions for all analytes ranged from 0.59%to 4.64%and1.98%to 4.80%,respectively.External quality assurance samples were assayed and showed excellent agreement with the target values.This simple method provides an improved assay for determining urine catecholamines and metanephrines.     

Determination of organophosphate flame retardants in sediments by microwave-assisted extraction and gas chromatography–mass spectrometry with electron impact and chemical ionization

An efficient microwave-assisted extraction (MAE) procedure coupled to gas chromatography–mass spectrometry (GC–MS) with electron impact (EI) and chemical ionization (CI) has been developed to determine five organophosphate flame retardants (OPFRs) in marine and river sediments. The effects of various operating parameters on the quantitative extraction of the OPFRs through MAE were systematically investigated. Selected OPFRs were extracted from the sediments through MAE using 40 mL of acetone at 120 °C for 20 min. The limits of quantitation ranged from 0.1 to 0.4 ng/g (dry weight) in 2 g of the sediment samples. Moreover, as the chlorinated alkyl phosphates present no molecular ions in EI, GC–MS with furan-CI (furan-CI) was applied to confirm their determination in complex environmental samples. The recoveries of the selected OPFRs in spiked sediment samples ranged from 62% to 106% (relative standard derivation, 1−11%). The total concentrations of the selected OPFR residues in marine and river sediments ranged from 1.0 to 12.6 ng/g.     

Quantitative analysis of eletriptan in human plasma by HPLC-MS/MS and its application to pharmacokinetic study

Authors developed a simple, sensitive, selective, rapid, rugged, and reproducible liquid chromatography–tandem mass spectrometry method for the quantification of eletriptan (EP) in human plasma using naratriptan (NP) as an internal standard (IS). Chromatographic separation was performed on Ascentis Express C18, 50 × 4.6 mm, 2.7 μm column. Mobile phase was composed of 0.1% formic acid: methanol (40:60 v/v), with 0.5 mL/min flow rate. Drug and IS were extracted by liquid–liquid extraction. EP and NP were detected with proton adducts at m/z 383.2→84.3 and 336.2→97.8 in multiple reaction monitoring (MRM) positive mode, respectively. The method was validated with the correlation coefficients of (r ²) ≥ 0.9963 over a linear concentration range of 0.5–250.0 ng/mL. This method demonstrated intra- and inter-day precision within 1.4–9.2% and 4.4–5.5% and accuracy within 96.8–103% and 98.5–99.8% for EP. This method is successfully applied in the bioequivalence study of 24 human volunteers.     

Application of silica-based monolith as solid phase extraction cartridge for extracting polar compounds from urine

The silica monolith with ionizable silanol groups and large surface area was found able to function as an offline cation exchange solid phase extraction (SPE) cartridge for extracting polar analytes. The prepared cartridge was housed in a 2-mL syringe fixed over a SPE vacuum manifold. The unique property of this silica monolithic cartridge was demonstrated by extracting epinephrine, normetanephrine and metanephrine from urine samples. These analytes were chosen as model compounds for testing because of their high hydrophilicity, and being candidates monitored for clinical diagnosis. The extracted analytes, after concentration and reconstitution were then quantitated by high-performance liquid chromatography coupled to mass spectrometer (HPLC/ESI/MS). Multiple reactions monitoring was carried out with transitions: 184 → 107, 184 → 134 and 198 → 148 for analyzing epinephrine, normetanephrine and metanephrine, respectively. The limit of detection was 3 ng/mL for metanephrine and 5 ng/mL for normetanephrine and epinephrine. The relative standard deviations of measurements ranged from 2 to 10%. The sorbent offered good linearity with coefficient of determination (r²) > 0.99, over a concentration range of 20-200 ng/mL. The relative recoveries ranged from 60 to 67%, 55 to 59% and 99 to 105% for epinephrine, normetanephrine and metanephrine, respectively. The prepared cartridge had shown potential and was found robust in extracting the polar analytes repeatedly without any significant loss in efficiency.     

Hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) determination of cocaine and its metabolites benzoylecgonine, ecgonine methyl ester, and cocaethylene in hair samples

This study reports the development and validation of a method using hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) for the analysis of cocaine and its metabolites benzoylecgonine (BE), ecgonine methyl ester (EME), and cocaethylene (CE) in hair samples. Decontamination was performed as follows: Firstly, the aliquot of hair was briefly rinsed with 2 mL dichloromethane, then was washed three times with 10 mL 0.01 M phosphate buffer, pH 6, for 15 min, followed by 2 mL 2-propanol for less than 2 min, and, finally, a last rinse with 2 mL dichloromethane was again done. Cocaine compounds were extracted from 10 mg of hair by incubation with 2 mL 0.1 M HCl at 50 °C for 12 h and purified by solid phase extraction with Oasis MCX cartridges. Analysis was performed by LC-MS/MS using an Atlantis HILIC silica chromatographic column. The method was fully validated. Linearity was established over the concentration range 0.020–10.0 ng/mg for cocaine (COC), 0.010–10.0 ng/mg for BE and CE, and 0.005–2.0 ng/mg for EME, and the correlation coefficients were all >0.99. Extraction efficiency was >70% for all analytes. Limits of detection were 0.0005 ng/mg for CE and 0.001 ng/mg for the other analytes (COC, BE, and EME). Lower limits of quantification were the lowest points of the calibration curves with acceptable accuracy and precision (coefficient of variation ≤20%). Intra- and inter-day imprecision ranged between 1.5% and 9.5% and 0.7% and 12.6%, respectively. Intra- and inter-day inaccuracy ranged from 0.5% to 12.3% and from 0.7% to 7.1%, respectively. With regard to matrix effects, suppression was <27.5% in all cases. The method was applied to the analysis of several samples derived from forensic cases.     

Determination of antibacterials in animal feed by pressurized liquid extraction followed by online purification and liquid chromatography-electrospray tandem mass spectrometry

A fully automated method has been developed for analysis of eighteen antibacterial compounds, including penicillins, cephalosporins and sulfonamides, in animal feed with limits of quantification in the range 0.25–5.79 μg kg⁻¹. The method is based on pressurized liquid extraction of 3 g homogenized feed with water and online clean-up of 500 μL of the extract with C₁₈HD cartridges. The purified sample was directly analysed by liquid chromatography–electrospray tandem mass spectrometry (SPE–LC–ESI-MS–MS). Chromatographic separation was achieved within 10 min by use of a C₁₂ Phenomenex Hydro-RP reversed-phase analytical column and a mobile phase gradient (water + 0.1% formic acid–methanol + 0.1% formic acid). The method was validated, revealing capability for detection of concentrations as low as 0.09 μg kg⁻¹, decision limits (CCα) and detection capabilities (CCβ) in the range 10–174 μg kg⁻¹ and 22–182 μg kg⁻¹, respectively, and inter-day precision ranging from 0.7 to 8.3%. Recovery, with internal standard correction, was in the range 93–134% for all analytes. The method was then applied to analysis of fifteen feed samples, nine of which contained at least one antimicrobial at concentrations between 0.006 and 1.526 mg kg⁻¹. The performance data and results from the method were compared with those from a previous method developed by our group, using offline SPE, by analyzing the same set of samples by both methods. The online SPE approach resulted in slightly improved sensitivity, with LODs of 0.09–2.12 μg kg⁻¹ compared with 0.12–3.94 μg kg⁻¹ by the offline approach. In general, better recovery was achieved by use of online purification (for 72% of the analytes) and the correlation between the two methods was good. The main advantages of the new online method are rapid and automated sample pre-treatment, and reduction of sample manipulation, enabling high-throughput analysis and highly accurate results. Because of all these characteristics, the proposed method is applicable and could be deemed necessary within the field of food control and safety.     

A simple assay for the simultaneous determination of rosuvastatin acid,rosuvastatin-5<Emphasis Type="Italic">S</Emphasis>-lactone,and <Emphasis Type="Italic">N</Emphasis>-desmethyl rosuvastatin in human plasma using liquid chromatography–tandem mass spectrometry (LC-MS/MS)

A simple and sensitive assay was developed and validated for the simultaneous quantification of rosuvastatin acid (RST), rosuvastatin-5S-lactone (RST-LAC), and N-desmethyl rosuvastatin (DM-RST), in buffered human plasma using liquid chromatography–tandem mass spectrometry (LC-MS/MS). All the three analytes and the corresponding deuterium-labeled (d6) internal standards were extracted from 50 μL of buffered human plasma by protein precipitation. The analytes were chromatographically separated using a Zorbax-SB Phenyl column (2.1 mm × 100 mm, 3.5 μm). The mobile phase comprised of a gradient mixture of 0.1% v/v glacial acetic acid in 10% v/v methanol in water (solvent A) and 40% v/v methanol in acetonitrile (solvent B). The analytes were separated at baseline within 6.0 min using a flow rate of 0.35 mL/min. Mass spectrometry detection was carried out in positive electrospray ionization mode. The calibration curves for all three analytes were linear (R ≥ 0.9964, n = 3) over the concentration range of 0.1–100 ng/mL for RST and RST-LAC, and 0.5–100 ng/mL for DM-RST. Mean extraction recoveries ranged within 88.0–106%. Intra- and inter-run mean percent accuracy were within 91.8–111% and percent imprecision was ≤15%. Stability studies revealed that all the analytes were stable in matrix during bench-top (6 h on ice–water slurry), at the end of three successive freeze and thaw cycles and at −80°C for 1 month. The method was successfully applied in a clinical study to determine the concentrations of RST and the lactone metabolite over 12-h post-dose in patients who received a single dose of rosuvastatin.     

Quantification of femtomolar concentrations of the CYP3A substrate midazolam and its main metabolite 1'-hydroxymidazolam in human plasma using ultra performance liquid chromatography coupled to tandem mass spectrometry

The benzodiazepine midazolam is a probe drug used to phenotype cytochrome P450 3A activity. In this situation, effective sedative concentrations are neither needed nor desired, and in fact the use of very low doses is advantageous. We therefore developed and validated an assay for the femtomolar quantification of midazolam and 1′-hydroxymidazolam in human plasma. Plasma (0.25 mL) and 96-well-based solid-phase extraction were used for sample preparation. Extraction recoveries ranged between 75 and 92% for both analytes. Extracts were chromatographed within 2 min on a Waters BEH C18 1.7 μm UPLC? column with a fast gradient consisting of formic acid, ammonia, and acetonitrile. Midazolam and 1′-hydroxymidazolam were quantified using deuterium- and ¹³C-labeled internal standards and positive electrospray tandem mass spectrometry in the multiple reaction monitoring mode, which yielded lower limits of quantification of 50 fg/mL (154 fmol/L) and 250 fg/mL (733 fmol/L) and a corresponding precision of <20%. The calibrated concentration ranges were linear for midazolam (0.05–250 pg/mL) and 1′-hydroxymidazolam (0.25–125 pg/mL), with correlation coefficients of >0.99. Within-batch and batch-to-batch precision in the calibrated ranges for both analytes were <14% and <12%. No ion suppression was detectable, and plasma matrix effects were minimized to <15% (<25%) for midazolam (1′-hydroxymidazolam). The assay was successfully applied to assess the kinetics of midazolam in two human volunteers after the administration of single oral microgram doses (1–100 μg). This ultrasensitive assay allowed us to quantify the kinetics of midazolam and 1′-hydroxymidazolam for at least 10 h, even after the administration of only 1 μg of midazolam.     

Metabolic profiling of major vitamin D metabolites using Diels–Alder derivatization and ultra-performance liquid chromatography–tandem mass spectrometry

Biologically active forms of vitamin D are important analytical targets in both research and clinical practice. The current technology is such that each of the vitamin D metabolites is usually analyzed by individual assay. However, current LC-MS technologies allow the simultaneous metabolic profiling of entire biochemical pathways. The impediment to the metabolic profiling of vitamin D metabolites is the low level of 1α,25-dihydroxyvitamin D₃ in human serum (15–60 pg/mL). Here, we demonstrate that liquid–liquid or solid-phase extraction of vitamin D metabolites in combination with Diels–Alder derivatization with the commercially available reagent 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) followed by ultra-performance liquid chromatography (UPLC)–electrospray/tandem mass spectrometry analysis provides rapid and simultaneous quantification of 1α,25-dihydroxyvitamin D₃, 1α,25-dihydroxyvitamin D₂, 24R,25-dihydroxyvitamin D₃, 25-hydroxyvitamin D₃ and 25-hydroxyvitamin D₂ in 0.5 mL human serum at a lower limit of quantification of 25 pg/mL. Precision ranged from 1.6–4.8 % and 5–16 % for 25-hydroxyvitamin D₃ and 1α,25-dihydroxyvitamin D₃, respectively, using solid-phase extraction. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Validation of ELISA screening and LC–MS/MS confirmation methods for cocaine in hair after simple extraction

This article describes an easy and innovative extraction procedure for cocaine and its primary metabolite, benzoylecgonine (BE), from hair consisting of sonication with H₂O/0.1% formic acid for 4 h. The same extract was used for screening with an enzyme-linked immunoassay (ELISA) and confirmation by liquid chromatography–tandem mass spectrometry (LC–MS/MS). For the ELISA screening test a cutoff of 0.5 ng/mg was used according to the Society of Hair Testing recommendations. LC–MS/MS limits of detection (LODs) were established to be 10 pg/mg and 1 pg/mg for cocaine and BE, respectively. Linearity was obtained over a range of 0.2–5 ng/mg for BE (target analyte) in the ELISA screening test, while in the LC–MS/MS method the range was 0.10–10 ng/mg for cocaine and 0.01–10 ng/mg for BE. Intra- and interbatch coefficients of variation and mean relative errors were less than 20% for all analytes and concentrations studied. The validated ELISA and LC–MS/MS methods were applied to 48 hair samples and the results of both methods were compared; ELISA demonstrated a sensitivity and specificity of 89.2% and 10.8%.     

A robust LC–MS/MS assay with online cleanup for measurement of serum testosterone

Accurate measurement of low levels of testosterone is critical for diagnosis and treatment of androgen disorders. The very low concentrations of testosterone in children, females, and males with androgen suppression therapies necessitate the use of mass spectrometry‐based methods. We aimed to develop a liquid chromatography with tandem mass spectrometry method with simplified sample preparation and online solid‐phase extraction cleanup to achieve enhanced precision, accuracy, robustness, and cost‐effectiveness. The assay was linear from 10 to 20 000 pg/mL with an analytical recovery of 93–104%. The total coefficient of variation was 2.5, 1.9, and 1.7% at concentration levels of 348, 5432, and 10 848 pg/mL, respectively. No significant carryover was observed from samples with concentrations up to 20 000 pg/mL. No significant interference was observed from androstenedione, dehydroepiandrosterone, epi‐testosterone, and estriol. Comparison with CDC Hormone Standardization program (HoSt) reference samples with defined values (n = 40) showed a Deming regression slope of 0.963, intercept of 28.06 pg/mL, standard error of estimate was 66.9, a correlation coefficient of 0.9996, and a mean bias of ?0.6%. The method met the accuracy criteria by the CDC HoSt program. In addition, we achieved >12 000 injections on a single analytical column without significant performance deterioration due to the specific online solid‐phase extraction settings.     

Quantification of atrazine and its metabolites in urine by on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry

We have developed a method using on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry (SPE-HPLC-MS/MS) and isotope dilution quantification to measure atrazine and seven atrazine metabolites in urine. The metabolites measured were hydroxyatrazine, diaminochloroatrazine, desisopropylatrazine, desethylatrazine, desethylatrazine mercapturate, atrazine mercaturate and atrazine itself. Our method has good precision (relative standard deviations ranging from 4 to 20% at 5, 10 and 50 ng/mL), extraction efficiencies of 67 to 102% at 5 and 25 ng/mL, relative recoveries of 87 to 112% at 5, 25, 50 and 100 ng/mL limits of detection (LOD) ranging from 0.03 to 2.80 ng/mL. The linear range of our method spans from the analyte LOD to 100 ng/mL (40 ng/mL for atrazine and atrazine mercapturate) with R ² values of greater than 0.999 and errors about the slope of less than 3%. Our method is rapid, cost-effective and suitable for large-scale sample analyses and is easily adaptable to other biological matrices. More importantly, this method will allow us to better assess human exposure to atrazine-related chemicals. Figure A schematic representation showing the elution of the analytes from the solid-phase extraction cartridge onto the analytical column for chromatographic separation prior to MS/MS analysis     

Quantitative determination of vitamin D metabolites in plasma using UHPLC-MS/MS

Vitamin D is an important determinant of bone health at all ages. The plasma concentrations of 25-hydroxy vitamin D (25-OH D) and other metabolites are used as biomarkers for vitamin sufficiency and function. To allow for the simultaneous determination of five vitamin D metabolites, 25-OH D₃, 25-OH D₂, 24,25-(OH)₂ D₃, 1,25-(OH)₂ D₃, and 1,25-(OH)₂ D₂, in low volumes of human plasma, an assay using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) was established. Plasma samples were spiked with isotope-labeled internal standards and pretreated using protein precipitation, solid-phase extraction (SPE) and a Diels–Alder derivatization step with 4-phenyl-1,2,4-triazoline-3,5-dione. The SPE recovery rates ranged from 55% to 85%, depending on the vitamin D metabolite; the total sample run time was <5 min. Mass spectrometry was conducted using positive ion electrospray ionization in the multiple reaction monitoring mode on a quadrupole–quadrupole-linear ion trap instrument after pre-column addition of methylamine to increase the ionization efficiency. The intra- and inter-day relative standard deviations were 1.6–4.1% and 3.7–6.8%, respectively. The limit of quantitation for these compounds was determined to be between 10 and 20 pg/mL. The 25-OH D results were compared with values obtained for reference materials (DEQAS). In addition, plasma samples were analyzed with two additional Diasorin antibody assays. All comparisons with conventional methods showed excellent correlations (r ² = 0.9738) for DEQAS samples, demonstrating the high degree of comparability of the new UHPLC-MS/MS technique to existing methods.     

Cannabinoids and metabolites in expectorated oral fluid after 8 days of controlled around-the-clock oral THC administration

Oral fluid (OF) is an increasingly accepted matrix for drug testing programs, but questions remain about its usefulness for monitoring cannabinoids. Expectorated OF specimens (n = 360) were obtained from 10 adult daily cannabis smokers before, during, and after 37 20-mg oral Δ⁹-tetrahydrocannabinol (THC) doses over 9 days to characterize cannabinoid disposition in this matrix. Specimens were extracted and analyzed by gas chromatography–mass spectrometry with electron-impact ionization for THC, 11-hydroxy-THC, cannabidiol, and cannabinol, and negative chemical ionization for 11-nor-9-carboxy-THC (THCCOOH). Linear ranges for THC, 11-hydroxy-THC, and cannabidiol were 0.25–50 ng/mL; cannabinol 1–50 ng/mL; and THCCOOH 5–500 pg/mL. THCCOOH was the most prevalent analyte in 344 specimens (96.9%), with concentrations up to 1,390.3 pg/mL. 11-hydroxy-THC, cannabidiol, and cannabinol were detected in 1, 1, and 3 specimens, respectively. THC was detected in only 13.8% of specimens. The highest THC concentrations were obtained at admission (median 1.4 ng/mL, range 0.3–113.6) from previously self-administered smoked cannabis. A total of 2.5 and 3.7% of specimens were THC-positive at the recommended Substance Abuse and Mental Health Services Administration (2 ng/mL) and Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) (1 ng/mL) confirmation cutoffs, respectively. THC is currently the only analyte for monitoring cannabis exposure in OF; however, these data indicate chronic therapeutic oral THC administration and illicit oral THC use are unlikely to be identified with current guidelines. Measurement of THCCOOH may improve the detection and interpretation of OF cannabinoid tests and minimize the possibility of OF contamination from passive inhalation of cannabis smoke.     

High-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometric method for the analysis of catecholamines and metanephrines in human urine

An assay of norepinephrine (NE), epinephrine (E), dopamine (DA), normetanephrine (NE) and metanephrine (MN) based on high-performance liquid chromatography (HPLC) in combination with atmospheric pressure chemical ionization mass spectrometry (APcI-MS) is described. The catecholamines and metanephrines were extracted from urine and aqueous samples using Bio-Rex 70 cation-exchange resin and subjected to analysis by HPLC/APcI-MS. The separation was performed on a C18 column in 50 mM ammonium formate buffer, pH 3.0, using a flow rate of 0.8 mL/min. Acetonitrile was added post-column at a flow rate of 0.2 mL/min via a post-column addition tee. The total analysis time was 6.5 min. The quantitative analysis was performed using 3,4-dihydroxybenzylamine (DHBA) as the internal standard (I.S.). Selected ion monitoring detection was applied: m/z 170 (for NE), 184 (for E and NM), 154 (for DA), 198 (for MN) and 140 (for DHBA, I.S.). The limits of quantitation were 5 ng/mL for NE, E and DA and 2.5 ng/mL for NM and MN. The recovery ranged from 75 to 83% for each analyte. The method was found to be simple and highly selective for the determination of catecholamines and metanephrines in the urine of patients suspected of pheochromocytoma.     

Determination of basic drugs of abuse in human serum by online extraction and LC–MS/MS

A new quantitation method for the determination of drugs of abuse (opiates, amphetamine and derivatives, cocaine, methadone and metabolites) in serum by using online extraction coupled to liquid chromatography (LC)–mass spectrometry (MS)/MS has been developed. The online extraction is carried out using two extraction columns simultaneously and one analytical column. One extraction column is loaded, while the other one is eluted by a gradient. The elution gradient also separates the analytes in the analytical column. For the sample preparation, serum is spiked with a mixture of deuterated analogues of the drugs. After protein precipitation with methanol/zinc sulphate, centrifugation, evaporation and reconstitution, the sample is injected into the LC system. The quantitation is based on the analysis of two multiple reaction monitoring transitions per drug. The recovery of the protein precipitation step is over 80% for all analytes. Intra- and interday precision, as relative standard deviation, is lower than 6%, and in the case of accuracy, RE is lower than 15%. Only the most polar analytes showed matrix effects. The limits of quantitation for the analysed compounds vary between 0.5 and 2.8 ng/mL. The developed method was used to quantify basic drugs in samples “from driving under the influence of drugs” cases. The results were compared with those obtained by using solid-phase extraction–GC–MS.     

Selective ion exchange separation of uranium from concomitant impurities in uranium materials and subsequent determination of the impurities by ICP-OES

An ion exchange method has been developed for the separation of uranium from trace level metallic impurities prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES) in uranium materials. Selective separation of uranium from trace level metallic impurities consisting Cr, Co, Cu, Fe, Mn, Cd, Gd, Dy, Ni, and Ca was achieved on anion exchange resin Dowex 1 × 8 in sulphate medium. The resin (100–200 mesh, in chloride form) was packed in a small Teflon column (7.8 cm × 0.8 cm I.D.) and brought into sulphate form by passing 0.2 N ammonium sulphate solution. Optimum experimental conditions including pH and concentration of sulphate in the liquid phase were investigated for the effective uptake of uranium by the column. Uranium was selectively retained on the column as anionic complex with sulphate, while impurities were passed through the column. Post column solution was collected and analyzed by ICP-OES for the determination of metallic impurities. Up to 2,500 μg/mL of uranium was retained with >99% efficiency after passing 25 mL sample through the column at pH 3. Percentage recoveries obtained for most of the metallic impurities were >95% with relative standard deviations <5%. The method established was applied for the determination of gadolinium in urania–gadolinia (UO₂–Gd₂O₃) ceramic nuclear fuel and excellent results were achieved. Solvent extraction method using tributylphosphate (TBP) as extractant was also applied for the separation of uranium in urania–gadolinia nuclear fuel samples prior to the determination of gadolinium by ICP-OES. The results obtained with the present method were found very comparable with those of the solvent extraction method.