Precision Of Quality Control Samples Research Articles

Development and validation of a simple ultra‐high‐performance‐tandem mass spectrometry method for the simultaneous determination of five bioactive components in rat plasma of Hedysari Radix

AbstractHedysari Radix is a commonly used traditional Chinese medicine that improves immunity; formononetin, ononin, calycosin, medicarpin, and vanillic acid play an important role in achieving this effect. Herein, a precise and sensitive ultra‐high‐performance‐tandem mass spectrometry method was developed and validated for the determination of five bioactive components that were extracted from plasma using a protein precipitation method. A Waters CORTES C18 (4.6 × 50 mm, 2.7 µm) and a mobile phase composed of methanol and water (containing 0.2% formic acid) were used for the separation. The method was linear within the concentration range of 19.53–625.00 ng/mL for formononetin; 0.01–3.13 ng/mL for ononin; 0.01–3.13 ng/mL for calycosin; 0.16–5.00 ng/mL for medicarpin; and 19.53–625.00 ng/mL for vanillic acid. This method has a lower limit of quantification, is simple, and has a short analysis time and a high degree of separation. The intra‐day precisions and inter‐day precisions of quality control samples were traced to be below 8.58% and 12.64%, respectively. Fidelity intervened from −8.61% to 10%. Finally, the developed method was used to determine the concentrations of the five bioactive components in rat plasma after the administration of rubbing‐ and non‐rubbing processed Hedysari Radix.

Simultaneous determination of 24 antiepileptic drugs and their active metabolites in human plasma by UHPLC-MS/MS

Antiepileptic drugs (AEDs) have narrow therapeutic ranges with large individual variability. Routine therapeutic drug monitoring of AEDs was useful for dose optimization, but the common immunoassays could not meet the detection requirements of AEDs, especially for new generation AEDs. The aim of this study was to validate an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for simultaneously quantification of 24 AEDs and their active metabolites in human plasma and comparison with a chemiluminescent immunoassay (Simens ADVIA Centaur). The method validation was performed according to FDA and EMEA guidelines. A one-step protein precipitation by acetonitrile followed a five-fold dilution was performed for sample pretreatment. A 5.2 min gradient separation by methanol and 10 mM ammonium acetate was used for separation at 0.6 mL/min under 45 °C. Both positive and negative electrospray ionization were used. Isotopic internal standard was used for all analytes. The inter-day (36 days) accuracy and precision of quality control samples were − 1.07–13.69% and < 6.70% for all analytes. The stability was acceptable for all analytes under routine storing conditions. A total of 436 valproic acid, 118 carbamazepine, and 65 phenobarbital samples were determined twice by each of the UHPLC-MS/MS and immunoassay. Evaluated by Bland-Altman plot, the mean overestimation of the immunoassay compared to UHPLC-MS/MS was 16.5% for valproic acid, 5.6% for carbamazepine, and 40.3% for phenobarbital.

An electrochemiluminescence assay for quantification of Denileukin Diftitox and its anti-drug antibodies in rat serum

Denileukin Diftitox (DD), comprising fragments of diphtheria toxin (DT) and interleukin-2 (IL2), was developed for the treatment of lymphoma and has been approved for marketing in Japan. Toxicological evaluation including pharmacokinetics and immunogenicity in preclinical animals is important for drug development and thus the assays of DD and anti-drug antibody (ADA) were developed by electrochemiluminescence (ECL) detection. For the DD assay, ruthenium-labeled anti-DT Ab and biotinylated anti-IL2 Ab were mixed with serum samples and the mixture was captured by streptavidin-coated wells for ECL detection. For the ADA assay, signals of immuno-complex of biotinylated DD, ruthenium-labeled DD, and ADA, bound to streptavidin plate were determined. DD was quantifiable from 10 ng/mL. Accuracy and precision of quality control samples were within ±20% and 20%, respectively, and stability of DD in rat serum was successfully assessed. Precision of positive control samples of ADA was within the acceptance criteria and cut point values for ADA detection in the screening and confirmatory assay were determined by statistical analysis. Drug-induced ADA was detected by screening assay followed by confirmatory assay. The developed method was successfully applied to assess pharmacokinetics and immunogenicity to support toxicity studies in rats.

Development and validation of a liquid chromatography coupled to tandem mass spectrometry method for the simultaneous quantification of five analgesics and sedatives, and six of their active metabolites in human plasma: Application to a clinical study on the determination of neurological death in the intensive care unit

A sensitive and selective high-performance liquid chromatographic method coupled to tandem mass spectrometry was developed and validated for the quantification of morphine, hydromorphone, fentanyl, midazolam and propofol and their metabolites morphine-3-β-d-glucuronide, morphine-6-β-d-glucuronide, hydromorphone-3-β-d-glucuronide, 1′-hydroxymidazolam-β-d-glucuronide, α-hydroxymidazolam and 4-hydroxymidazolam in human plasma using potassium oxalate/sodium fluoride mixture as anticoagulant. Human plasma samples (0.4 mL) to which were added a mixture of eleven deuterated internal standards were subjected to solid phase extraction using a mixed-mode polymeric Oasis PRiME MCX in 96-well format. Propofol was selectively eluted and further derivatized using 2-Fluoro-1-methylpyridinium p-toluenesulfonate, whereas the remaining 10 analytes were eluted separately and further concentrated. The derivatized propofol was analyzed separately in a second injection. The analytes were chromatographically separated on a Kinetex phenyl-hexyl analytical column in gradient elution mode, using a mobile phase consisting of aqueous ammonium formate/formic acid buffer and methanol. The overall run time was 8 min. Detection was performed using an AB/SCIEX 4000 QTRAP instrument with positive electrospray ionization employing scheduled multiple reaction monitoring mode. The lower limits of quantification ranged from 0.02 to 5 ng/mL depending on the analyte. Calibration curves covered a concentration range of 1000× in all cases but 1′-hydroxymidazolam-β-d-glucuronide where it covered a range of 500 × . The validated method was accurate and precise, the intra-day accuracy and precision of quality control samples (4 concentration levels, n = 6 each) being within 91.5–112 % and 1.3–13.2 % (coefficient of variation), respectively, and inter-day (n = 24; 4 days) accuracy and precision of quality control samples (3 concentration levels) being within 94.8–103.5 % and 3.2–11.2 % (coefficient of variation). Mean absolute extraction recoveries were above 60 % for all compounds, except for hydromorphone-3-β-d-glucuronide (44 %) and for 1′-hydroxymidazolam-β-d-glucuronide (33 %). Internal standard corrected matrix effect ranged from −4.8 to 3.8 % in normal plasma and in plasma containing 1 % hemolyzed blood. Analytes were stable (above 90 %) in plasma and blood for 19 h at 22 °C, in blood for 90 h at 5 °C, in plasma for 60 days at −20 °C, for 4 months at −70 °C and after three freeze-thaw cycles, and in the injection solvent for at least 3 days in the autosampler. The present method is successfully being applied in a multicenter clinical study for the analysis of plasma samples from patients in intensive care units from a number of Canadian hospitals.

Application of an electrochemiluminescence assay for quantification of E6011, an antifractalkine monoclonal antibody, to pharmacokinetic studies in monkeys and humans.

E6011, a humanized antifractalkine monoclonal antibody, is under development for the treatment of various inflammatory diseases, such as rheumatoid arthritis. A reproducible assay method has been developed for the determination of E6011 in monkey and human serum by electrochemiluminescence (ECL) assay. E6011 in serum was captured by fractalkine and detected by ruthenium-labeled rabbit anti-E6011 Fab polyclonal antibodies for ECL detection. E6011 in serum was quantifiable from 0.02 and 0.1μg/mL in monkey and human serum, respectively, with minimum required dilution of 500. The method was then validated in accordance with bioanalytical guidelines. Accuracy and precision of quality control samples at five concentrations in intra- and interbatch reproducibility demonstrated that relative error and relative standard deviation were within acceptable criteria. Recovery of E6011 was 92.9%-121.7% and 85.0%-109.3% in humans and monkeys. Dilution integrity, no prozone effects, and no impacts by antigen were also ensured. Parallelism was also confirmed using incurred clinical sample analysis. Various types of stability were assessed, which confirmed that E6011 in serum was stable for 367 and 735days in monkey and human sera, respectively, under frozen conditions. The developed method was successfully applied supporting pharmacokinetic studies in monkeys and humans.

Quantification of triacontanol and its PEGylated prodrug in rat plasma by GC–MS/MS: Application to a pre-clinical pharmacokinetic study

PEGylation techniques have been increasingly employed in drug delivery system and chemical modification of compounds with low aqueous solubility. Triacontanol (TA) is a natural product with several pharmacological activities, but its low aqueous solubility significantly limited its application. PEGylated triacontanol (PEG-TA) was designed as the prodrug to improve the aqueous solubility and pharmacokinetic properties of TA. On the basis of salting-out assisted liquid-liquid extraction (SALLE) and saponification sample preparation procedure, a reliable gas chromatography tandem mass spectrometric (GC–MS/MS) method was developed and validated for the quantification of PEG-TA and its metabolite TA in rat plasma after separation and transformation. Acetonitrile-methanol (9:1, v/v) and ammonium acetate (10 M) were utilized to separate PEG-TA and TA (including conjugated TA with fatty acid). Saponification facilitated the complete conversion of PEG-TA into TA, so PEG-TA could be indirectly quantified. The results revealed that the GC–MS/MS method had excellent selectivity, accuracy and linearity. Calibration curves were linear (R2>0.99) within the range of 20.0–1000.0 ng/mL for TA and 100.0–10,000.0 ng/mL for PEG-TA. The intra- and inter-day precision of quality control samples were within 15%, and their accuracy values varied from 93.54% to 113.38%. This analytical method has been successfully applied to pharmacokinetic study of PEG-TA. This study can facilitate the further exploration and quantification of PEGylated prodrugs.

Analytical Method To Detect and Quantify Avocatin B in Hass Avocado Seed and Pulp Matter.

Avocatin B, an avocado-derived compound mixture, was demonstrated recently to possess potent anticancer activity by selectively targeting and eliminating leukemia stem cells. Avocatin B is a mixture of avocadene and avocadyne, two 17-carbon polyhydroxylated fatty alcohols (PFAs), first discovered in avocado seeds; their quantities in avocado pulp are unknown. Analytical methods to detect avocado seed PFAs have utilized NMR spectroscopy and GC-MS; both of these lack quantitative capacity and accuracy. Herein, we report a sensitive LC-MS method for the quantitation of avocadene and avocadyne in avocado seed and pulp. The method has a reliable and linear response range of 0.1-50 μM (0.03-17.2 ng/μL) for both avocadene and avocadyne ( r2 > 0.990) with a lower limit of quantitation (LLOQ) of 0.1 μM. The intra- and interassay accuracy and precision of the quality control (QC) samples at LLOQ showed ≤18.2% percentage error and ≤14.4% coefficient of variation (CV). The intra- and interassay accuracy and precision for QC samples at low and high concentrations were well below 10% error and CV. This method was successfully applied to quantify avocadene and avocadyne in total lipid extracts of Hass avocado pulp and seed matter.

Determination of dexmedetomidine by UHPLC–MS/MS and its application to evaluate the effect of dexmedetomidine concentration on the target-controlled infusion concentration of propofol

The combination of dexmedetomidine (DEX) and propofol (PPF) is extensively used in the field of anaesthesiology. This study aimed to develop and validate a rapid, simple and sensitive ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) method for the determination of DEX in human plasma. The method was applied to evaluate the effect of DEX concentration on the target-controlled infusion (TCI) concentration of PPF. Analytes were separated on a Waters XTERRA® MS C18 column with a mobile phase of acetonitrile-methanol-water containing 0.1% formic acid and 5 mM ammonium acetate (70:10:20, v/v/v) at a flow-rate of 0.3 mL/min. Mass spectrometry was performed in the positive selection reaction monitoring mode. The 201.12 → 95.12 and 515.29 → 275.68 mass transitions of DEX and IS (telmisartan), respectively, were monitored. The calibration curve of DEX was linear over the concentrations of 0.1–10 ng/mL. The intra-batch and inter-batch precisions of quality control samples were less than 10.05% and had accuracies of less than 6.25%. The newly developed method was successfully applied to quantify the DEX concentrations of plasma samples from 34 patients who were co-medicated with DEX prior to receiving anaesthesia by PPF. Results showed that comedication with DEX could reduce the requirements of PPF. Specifically, it was firstly found that the concentration of DEX is negatively correlated with the TCI concentration of PPF at the time of loss of consciousness.

Development and validation of a sensitive assay for analysis of midazolam, free and conjugated 1-hydroxymidazolam and 4-hydroxymidazolam in pediatric plasma: Application to Pediatric Pharmacokinetic Study.

Pharmacokinetic, pharmacodynamic and pharmacogenomic studies of midazolam are currently being performed in critically ill children to find suitable dose regimens. Sensitive assays using small volumes of plasma are necessary to determine the concentrations of midazolam and its respective metabolites in pediatric studies. Midazolam is metabolized to hydroxylated midazolam isomers, which are present as free as well as the corresponding glucuronide conjugates. A high-performance liquid chromatographic method with tandem mass spectrometry has been developed and validated for the quantification of midazolam, and free and total 1-hydroxymidazolam and 4-hydroxymidazolam metabolites in small volumes of plasma. Cleanup consisted of 96-well μ-elution solid phase extraction (SPE). The analytes were separated by gradient elution using a C18 analytical column with a total run time of 5min. Multiple reaction monitoring was employed using precursor to product ion transitions of m/z 326.2→291.3 for midazolam, m/z 342.1→203.0 for 1-hydroxymidazolam, m/z 342.1→325.1 for 4-hydroxymidazolam and m/z 330.2→295.3 for 2H4-midazolam (internal standard). Since authentic hydroxymidazolamglucuronide standards are not available, samples were hydrolyzed with β-glucuronidase under optimized conditions. Assay conditions were modified and optimized to provide appropriate recovery and stability because 4-hydroxymidazolam was very acid sensitive. Standard curves were linear from 0.5 to 1000ng/mL for all three analytes. Intra- and inter day accuracy and precision for quality control samples (2, 20, 200 and 800ng/mL) were within 85-115% and 15% (coefficient of variation), respectively. Stability in plasma and extracts were sufficient under assay conditions. Plasma samples were processed and analyzed for midazolam, and free 1-hydroxymidazolam and 4-hydroxymidazolam metabolites. Plasma samples that were hydrolyzed with β-glucuronidase were processed and analyzed for midazolam, and total 1-hydroxymidazolam and 4-hydroxymidazolam metabolites under the same assay conditions. The difference in concentration between the total and free hydroxymidazolam metabolites provided an estimate of conjugated hydroxymidazolam metabolites. The combination of 96-well μ-elution SPE and LC-MS/MS allows reliable quantification of midazolam and its metabolites in small volumes of plasma for pediatric patients. This assay is currently being successfully utilized for analysis of samples from ongoing clinical trials.

Development and validation of LC-MS/MS methods for the measurement of ribociclib, a CDK4/6 inhibitor, in mouse plasma and Ringer's solution and its application to a cerebral microdialysis study.

LC-MS/MS methods to measure ribociclib in mouse plasma and Ringer's solution were successfully developed and validated. Reverse phase chromatography was performed with gradient elution using C18 (100A, 50×4.6mm, 3μ) and C8-A (50×2.0mm, 5μ) columns for plasma and Ringer's samples, respectively. Mouse plasma samples were extracted using solid phase extraction method, whereas no extraction was required for the Ringer's solution samples. Analytes were detected using positive ion MRM mode. The precursor to product ions (Q1→Q3) selected for ribociclib and d6-ribociclib were (m/z) 435.2→252.1 and 441.2→252.1, respectively. The linear range of quantification of ribociclib was 62.5-10,000ng/ml for plasma method and 0.1-100ng/ml for Ringer's solution method. The results for the inter-day and intra-day accuracy and precision of quality control samples were within the acceptable range. The lower limit of quantitation (LLOQ) for plasma and Ringer's samples were 62.5ng/ml (S/N>30) and 0.1ng/ml (S/N>13), respectively, whereas the limit of detection (LOD) was 6.9ng/ml (S/N>7) and 0.05ng/ml (S/N>3), respectively. The developed methods were successfully applied to the analysis of ribociclib in mouse plasma and dialysate samples collected during a cerebral microdialysis study of ribociclib in a non-tumor bearing mouse.

Novel psychoactive substances: Epidemiology, mechanisms of action, and human metabolism of synthetic cannabinoids

Pharmacokinetic, pharmacodynamic and pharmacogenomic studies of midazolam are currently being performed in critically ill children to find suitable dose regimens. Sensitive assays using small volumes of plasma are necessary to determine the concentrations of midazolam and its respective metabolites in pediatric studies. Midazolam is metabolized to hydroxylated midazolam isomers, which are present as free as well as the corresponding glucuronide conjugates. A high-performance liquid chromatographic method with tandem mass spectrometry has been developed and validated for the quantification of midazolam, and free and total 1-hydroxymidazolam and 4-hydroxymidazolam metabolites in small volumes of plasma. Cleanup consisted of 96-well μ-elution solid phase extraction (SPE). The analytes were separated by gradient elution using a C18 analytical column with a total run time of 5 min. Multiple reaction monitoring was employed using precursor to product ion transitions of m/z 326.2 → 291.3 for midazolam, m/z 342.1 → 203.0 for 1-hydroxymidazolam, m/z 342.1 → 325.1 for 4-hydroxymidazolam and m/z 330.2 → 295.3 for 2H4-midazolam (internal standard). Since authentic hydroxymidazolamglucuronide standards are not available, samples were hydrolyzed with β-glucuronidase under optimized conditions. Assay conditions were modified and optimized to provide appropriate recovery and stability because 4-hydroxymidazolam was very acid sensitive. Standard curves were linear from 0.5 to 1000 ng/mL for all three analytes. Intra- and inter day accuracy and precision for quality control samples (2, 20, 200 and 800 ng/mL) were within 85–115% and 15% (coefficient of variation), respectively. Stability in plasma and extracts were sufficient under assay conditions. Plasma samples were processed and analyzed for midazolam, and free 1-hydroxymidazolam and 4-hydroxymidazolam metabolites. Plasma samples that were hydrolyzed with β-glucuronidase were processed and analyzed for midazolam, and total 1-hydroxymidazolam and 4-hydroxymidazolam metabolites under the same assay conditions. The difference in concentration between the total and free hydroxymidazolam metabolites provided an estimate of conjugated hydroxymidazolam metabolites. The combination of 96-well μ-elution SPE and LC–MS/MS allows reliable quantification of midazolam and its metabolites in small volumes of plasma for pediatric patients. This assay is currently being successfully utilized for analysis of samples from ongoing clinical trials.

Simultaneous Measurement of 3-Chlorotyrosine and 3,5-Dichlorotyrosine in Whole Blood, Serum and Plasma by Isotope Dilution HPLC-MS-MS.

Chlorine is a public health concern and potential threat due to its high reactivity, ease and scale of production, widespread industrial use, bulk transportation, massive stockpiles and history as a chemical weapon. This work describes a new, sensitive and rapid stable isotope dilution method for the retrospective detection and quantitation of two chlorine adducts. The biomarkers 3-chlorotyrosine (Cl-Tyr) and 3,5-dichlorotyrosine (Cl2-Tyr) were isolated from the pronase digest of chlorine exposed whole blood, serum or plasma by solid-phase extraction (SPE), separated by reversed-phase HPLC and detected by tandem mass spectrometry (MS-MS). The calibration range is 2.50-1,000 ng/mL (R2 ≥ 0.998) with a lowest reportable limit (LRL) of 2.50 ng/mL for both analytes, an accuracy of ≥93% and an LOD of 0.443 ng/mL for Cl-Tyr and 0.396 ng/mL for Cl2-Tyr. Inter- and intra-day precision of quality control samples had coefficients of variation of ≤10% and ≤7.0%, respectively. Blood and serum samples from 200 healthy individuals and 175 individuals with chronic inflammatory disease were analyzed using this method to assess background levels of chlorinated tyrosine adducts. Results from patients with no known inflammatory disease history (healthy) showed baseline levels of <LRL-4.26 ng/mL Cl-Tyr and <LRL Cl2-Tyr. Patients with inflammatory disease had baseline levels of <LRL-15.4 ng/mL Cl-Tyr and <LRL-5.22 ng/mL Cl2-Tyr. Blood exposed to 2.02 ppm chlorine gas for 15 min produced 941 ng/mL Cl-Tyr and 223 ng/mL Cl2-Tyr. This high-throughput method has been developed and analytically validated for the diagnosis of human exposure to chlorine.

Toxicological screening of human plasma by on-line SPE-HPLC-DAD: identification and quantification of acidic and neutral drugs.

A multi-analyte screening method for the quantification of 50 acidic/neutral drugs in human plasma based on on-line solid-phase extraction (SPE)-HPLC with photodiode array detection (DAD) was developed, validated and applied for clinical investigation. Acetone and methanol for protein precipitation, three different SPE materials (two electro-neutral, one strong anion-exchange, one weak cation-exchange) for on-line extraction, five HPLC-columns [one C18 (GeminiNX), two phenyl-hexyl (Gemini C6 -Phenyl, Kinetex Phenyl-Hexyl) and two pentafluorophenyl (LunaPFP(2), KinetexPFP)] for analytical separation were tested. For sample pre-treatment, acetone in the ratio 1:2 (plasma:acetone) showed a better baseline and fewer matrix peaks in the chromatogram than methanol. Only the strong anion-exchanger SPE cartridge (StrataX-A, pH 6) allowed the extraction of salicylic acid. Analytical separation was carried out on a Gemini C6 -Phenyl column (150 × 4.6 mm, 3 µm) using gradient elution with acetonitrile-water 90:10 (v/v) and phosphate buffer (pH 2.3). Linear calibration curves with correlation coefficients r ≥ 0.9950/0.9910 were obtained for 46/four analytes. Additionally, this method allows the quantification of 23 analytes for therapeutic drug monitoring. Limits of quantitation ranged from 0.1 (amobarbital) to 23 mg/L (salicylic acid). Inter-/intra-day precisions of quality control samples (low/high) were better than 13% and accuracy (bias) ranged from -14 to 10%. A computer-assisted database was created for automated detection of 223 analytes of toxicological interests. Four cases of multi-drug intoxications are presented.

On-cartridge derivatization coupled with solid-phase extraction for the ultra-sensitive determination of minodronic acid in human plasma by LC–MS/MS method

Minodronic acid (MA) is a third-generation bisphosphonate (BP). Its high potency allows lower doses to be administered in clinical settings compared with other BPs, which results in extremely low systemic exposure. Therefore, it is essential to develop an ultra-sensitive bioassay for pharmacokinetics studies of MA. In this work, we used on-cartridge derivatization of MA with trimethylsilyldiazomethane to extract MA from plasma samples and improve its LC–MS/MS behavior. The reaction produced a known derivative, tetramethylated MA, and a novel derivative, pentamethylated MA (PMMA). PMMA exhibited a better signal-to-noise ratio, and was monitored for the quantification of MA. However, the derivatization yield of d4-PMMA was much lower and more variable than that of PMMA, which decreased the effectiveness of its correction function as an internal standard. Therefore, a two-cycle derivatization approach was introduced to increase its yield and improve the reproducibility. The calibration curves of MA showed good linearity over the range of 10.0–1000pg/mL. A lower limit of quantification of 10.0pg/mL was achieved with acceptable precision (<10.5%) and accuracy (5.0%). The intra- and inter-batch precision of quality control samples was <9.5%, and the accuracy ranged from −2.8% to 0.6%. The stability results showed that MA was stable in human plasma for 6h at room temperature (25°C), for 115 days at −20°C, during three freeze/thaw cycles (from −20°C to 25°C), and in post-preparative samples for 24h at 4°C. The method was successfully used to characterize the pharmacokinetic profile of MA following an oral dose of 1.0mg MA hydrate to healthy volunteers (n=12). The proposed derivatization procedure was also extended to measure other BPs (risedronic acid and zoledronic acid) in human plasma at low pg/mL.

Toxicological screening of human plasma by on-line SPE-HPLC-DAD: identification and quantification of basic drugs and metabolites.

An automated multi-analyte screening method for the identification and quantification of 92 drugs and metabolites based on on-line solid-phase extraction-high-performance liquid chromatography-diode array detection technique was developed and successfully validated. In addition, a database with 870 entries including UV-spectra, relative/retention times and response factors of toxicologically relevant compounds was created. Plasma samples (0.2 mL) were treated with methanol, diluted with buffer and on-line extracted (Strata X, 20 ×2 mm, 25 µm) at pH 9. Analytical separation was carried out on a Gemini NX column (150 ×4.6 mm, 3 µm) using gradient elution with acetonitrile-water (90:10,v/v) and 0.05 m potassium dihydrogen phosphate buffer (pH 2.3). Linear calibration curves with correlation coefficients ≥0.9950 were obtained for 78 analytes. As an additional benefit, the newly developed method allows the quantification of 42 analytes (e.g. antidepressants, neuroleptics and anticonvulsants) in a concentration range suitable for therapeutic drug monitoring. Limits of quantitation ranged from 0.02 mg/L (chlordiazepoxide) to 3.4 mg/L (mexiletine). Inter- and intra-day precisions of quality control samples (low/high) were better than 15% (zolpidem) and accuracy (bias) ranged from -11% (opipramol, venlafaxine) to 11% (venlafaxine, trazodone). Tests for carry-over and sample stability under different storage conditions were also performed and stability was adequate. Four cases of poisoning analysis are presented.

LC-MS/MS METHOD FOR SIMULTANEOUS QUANTIFICATION OF SERIES OF AMINOPROPAN-2-OL DERIVATIVES-APPLICATION TO IN VIVO PHARMACOKINETIC STUDY

A selective and a sensitive liquid chromatography-tandem mass spectrometry method for simultaneous determination of new aminopropan-2-ol derivatives with β-adrenolytic activity briefly called 2F109-(2RS)-1-(1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol, ANBL-(2RS)-1-(5-methoxy-1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol, and TWo8-(2RS)-1-(7-methoxy-1H-indol-4-yloxy)-3-(2-(2-methoxyphenoxy)ethylamino)propan-2-ol in rat serum was developed. The pharmacokinetics of 2F109, ANBL, and TWo8 in rats was performed following a single intravenous or intragastric administration of studied substances at a dose of 1 mg/kg. The work-up procedure involves a liquid–liquid extraction step using ethyl acetate and followed by gradient chromatography on a reversed-phase XBridge C18 column. Quantification analysis was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique, operating in the positive ionization and selected reaction monitoring mode. The limit of detection was found to be 0.5 ng/mL, the limit of quantification was 2 ng/mL. The intra-day and inter-day precision for quality control samples ranged from 6.3% to 14.2%, and intra-day and inter-day accuracy ranged from −0.8% to 10%. The terminal half-lives for 2F109, ANBL, and TWo8 after intravenous administration were 39.2 min, 262.3 min, and 169.4 min, respectively. The absolute bioavailability for 2F109, ANBL, and TWo8 were 40.2, 26.2, and 14.7%, respectively.

Simultaneous and sensitive analysis of fourth-generation antidepressants in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry

A sensitive method for simultaneous analysis of nine fourth-generation antidepressants in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS) is presented. The method was used with a Waters Acquity UPLC LC system, an Acquity TQD MS–MS system, and a Poroshell 120 EC-C18 separation column. For extraction of the target compounds, solid-phase extraction with Oasis HLB cartridges was used. All compounds were detected with retention times lower than 3 min. The calibration curves for the antidepressants spiked into human plasma showed similar good linearities in the range of subnanogram to nanogram per milliliter. The detection limits (signal-to-noise ratio = 3) were in the range of 0.2–100 pg/ml. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with these drugs. To further validate the present method, 25 mg of milnacipran was orally administered to a healthy male volunteer, and the drug concentrations in plasma were measured in samples collected 0.5, 1, 2, 4, and 8 h after dosing. The concentrations were in the range of 31.2–56.8 ng/ml. To our knowledge, this is the most sensitive quantitative method for fourth-generation antidepressants so far reported, and should prove very useful in forensic and clinical toxicology. In addition, the quantitative analysis of tianeptine by LC–MS–MS is first described in this study.

High-throughput analysis of ramelteon, agomelatine, and melatonin in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry

A high-throughput method for analysis of ramelteon, agomelatine, and melatonin in human plasma by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS–MS) is presented. The LC system, MS–MS system, and separation column used were Waters Acquity UPLC, Acquity TQD, and Poroshell 120 EC-C18, respectively. For extraction of the target compounds, solid-phase extraction was performed with Oasis HLB cartridges. All compounds were detected with retention times of <3 min. The calibration curves for the compounds spiked into human plasma showed good linearities in the nanogram-per-milliliter range. The detection limit (signal-to-noise ratio = 3) was as low as 0.2–0.5 ng/ml. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with these drugs. The present method should prove very useful in forensic and clinical toxicology and pharmacokinetic studies, because of its high sensitivity and rapidness. To our knowledge, this is the first trial to analyze ramelteon in a biological sample by LC–MS–MS.

A rapid and simultaneous analysis of theophylline and its metabolites in human whole blood by ultra-performance liquid chromatography-tandem mass spectrometry

A rapid and sensitive method for analysis of theophylline and its six metabolites in human whole blood by ultra-performance liquid chromatography (UPLC)–tandem mass spectrometry (MS/MS) using 3-isobutyl-1-methylxanthine as internal standard is presented. After pretreatment of a blood sample by liquid–liquid extraction with acetonitrile, theophylline and its metabolites were analyzed by UPLC with a Poroshell 120 EC-C18 column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration curves for theophylline and its metabolites spiked into human blood showed equally good linearities in the microgram per milliliter range. The detection limits (signal-to-noise ratio 3) were as low as 0.1–1.0 ng/ml. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with theophylline and its metabolites. To further validate the present method, 100 mg of theophylline was orally administered to a healthy male volunteer and the concentrations of theophylline and its metabolites in blood were measured 0.5, 1, 2, 4, and 8 h after dosing. The concentrations of theophylline in human blood were between 0.82 and 2.38 μg/ml. The present method should be very useful in forensic and clinical toxicology and pharmacokinetic studies.

Development of a quantification method for digoxin, a typical P-glycoprotein probe in clinical and non-clinical studies, using high performance liquid chromatography–tandem mass spectrometry: The usefulness of negative ionization mode to avoid competitive adduct-ion formation

Highly sensitive and accurate liquid chromatography–tandem mass spectrometry (LC/MS/MS) methods have been developed and validated for measuring digoxin (DGX), a typical P-glycoprotein probe, in human plasma, rat plasma, and rat brain. We extracted DGX and deuterium-labeled DGX (as internal standard) from sample fluids under basic conditions using acetonitrile and sodium chloride-saturated 0.1 mol/L sodium hydroxide. The upper organic layer was diluted with distilled water, and the resulting solution was injected into an LC/MS/MS system in negative ionization mode. Chromatographic separation was achieved on a C 18-ODS column in the gradient mobile phase, which comprised 0.05% (w/v) ammonium carbonate (pH 9.0) and methanol at a flow rate of 0.7 mL/min. Regardless of the type of biological matrix, intra-day and inter-day validation tests demonstrated good linearity of calibration curves within ranges of 0.1–10 ng/mL for plasma and 0.5–50 ng/g for rat brain and gave excellent accuracy and precision of quality control samples at 4 concentration levels. Unlike existing methods, our approach uses negative ionization to avoid competitive adduct formation of DGX. Our method showed higher sensitivity and wider applicability to various types of biological matrices than existing methods. Our method will support clinical and preclinical investigation of in vivo P-glycoprotein functionality using DGX.