Determination of Atenolol in Pharmaceutical Preparations by Gas Chromatography with Flame Ionization and Mass Spectrometric Detection

The present work describes the methodology and validation of gas chromatography with flame ionization (FID) and mass spectrometric (MS) detection after derivatization with N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) for determination of atenolol with an internal standard (metoprolol) in pharmaceutical preparations. The linearity was established over the concentration range of 0.5–20 μg/mL for GC/FID and 12.5–500 ng/mL for GC/MS method. The intra- and inter-day relative standard deviation was less than 4.72 and 5.80%, respectively. Limit of quantification was determined as 500 ng/mL and 12.5 ng/mL for GC/FID and GC/MS, respectively. No interference was found from tablet excipients at the selected assay conditions. Developed GC/FID and GC/MS methods in this study are accurate, sensitive, and precise and can be easily applied to Tensinor tablet as pharmaceutical preparation.     

Rapid screening of drugs of abuse and their metabolites by gas chromatography/mass spectrometry: application to urinalysis

This paper describes a rapid gas chromatographic/mass spectrometric (GC/MS) screening method for the detection of drugs of abuse and/or their metabolites in urine. Synthetic stimulants, opiates, cocaine metabolites, cannabinoids--and specifically the acid metabolite of tetrahydrocannabinol (THC-COOH)--can be simultaneously extracted by a single liquid/liquid separation step, at alkaline pH, and assayed as trimethylsilyl derivatives by GC/MS in SIM (selected ion monitoring) mode. All the analytes show a good linearity (R2 > 0.99 for most of the considered substances) in the range 25-1000 ng/mL, with a good reproducibility of both the retention times (CV% <0.7) and the relative abundances of the characteristic diagnostic ions (CV% <13). The limit of detection (LOD) of the method is 25 ng/mL of target compound in human urine for most of the substances investigated, 3 ng/mL for THC-COOH, and 10 ng/mL for norbuprenorphine. Validation of the method allows its application to different fields of forensic analytical toxicology, including antidoping analysis.     

Determination of residual clopidol in chicken muscle by capillary gas chromatography/mass spectrometry

Clopidol was extracted from chicken with acetonitrile, and the extract was evaporated to about 5 mL. The concentrated solution was centrifuged and applied to a glass column filled with basic alumina. The column was eluted with methanol and the methanol was evaporated to dryness. The residue was derivatized with Sylon BFT and analyzed by gas chromatography/mass spectrometry (GC/MS). Mass characteristics of trimethylsilyl derivative of clopidol were interpreted manually. The selected-ion monitoring mode was performed at m/z 191, 248, 263, and 265. A sensitive, reproducible GC/MS method was developed for monitoring residues of clopidol in chickens. All recoveries of the drug from chicken muscle fortified at 1, 10, and 100 ng/g were > 65%, and relative standard deviations were < 15%. The detection limit was about 0.5 ng/g, and the quantitation limit was the lower limit of the standard curve, which was about 1 ng/g.     

Development and validation of automated SPE-HPLC-MS/MS methods for the quantification of asenapine, a new antipsychotic agent, and its two major metabolites in human urine

To support the evaluation of the pharmacokinetic parameters of asenapine (ASE) in urine, we developed and validated online solid‐phase extraction high‐performance liquid chromatography methods with tandem mass spectrometry detection (SPE‐LC‐MS/MS) for the quantification of ASE and two of its major metabolites, N‐desmethylasenapine (DMA) and asenapine‐N⁺‐glucuronide (ASG). The linearity in human urine was found acceptable for quantification in a concentration range of 0.500–100 ng/mL for ASE and DMA and 10.0–3000 ng/mL for ASG, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal properties of poly(butylene oxalate) copolymerized with azelaic acid

Poly(butylene oxalate) (PBO) and poly(butylene oxalate/butylene azelate) random copolymers (PBOBAz) of various compositions were synthesized in bulk and characterized in terms of chemical structure and thermal properties. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All copolymers were found to be partially crystalline and thermally stable up to about 290 °C. The main effect of copolymerization was a decrease in melting and glass transition temperatures with respect to PBO homopolymer. The pure crystalline phase characteristic of PBO was evidenced by means of X-ray measurements in all the copolymers under investigation. The fusion temperatures appeared to be well correlated to composition by Baur's equation.Amorphous samples were obtained after melt quenching and showed a monotonic decrease of glass transition temperatures as the content of the flexible butylene azelate units is increased. Fox equation described well the T_g-composition data. Lastly, the overall crystallization rate of PBO was found to decrease regularly with increasing butylene azelate unit content.     

A fast,sensitive, and high‐throughput method for the simultaneous quantitation of three ellagitannins from Euphorbiae pekinensis Radix in rat plasma by ultra‐HPLC–MS/MS

A fast, sensitive, and high‐throughput ultra‐HPLC–MS/MS method has been developed and validated for the simultaneous determination of three main active constituents of Euphorbiae pekinensis Radix in rat plasma. After addition of the internal standard, plasma samples were extracted by liquid–liquid extraction with ethyl acetate/isopropanol (1:1, v/v) and separated on a CAPCELL PAK C₁₈ column (100 × 2.0 mm, 2 μm, Shiseido, Japan), using a gradient mobile phase system of methanol/water. The detection of the analytes was performed on a 4000Q UHPLC–MS/MS system with turbo ion spray source in the negative ion and multiple reaction‐monitoring mode. The linear range was 1.0–1000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐glucopyranoside (i), 1.5–1500 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐xylopyranoside (ii), and 5.0–5000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid (iii). The intra‐ and interday precision and accuracy of all the analytes were within 15%. The extraction recoveries of the three analytes and internal standard from plasma were all more than 80%. The validated method was first successfully applied to the evaluation of pharmacokinetic parameters of compounds 1 , 2 , and 3 in rat plasma after intragastric administration of the Euphorbiae pekinensis Radix extract.     

Simultaneous determination of tryptophan,kynurenine, kynurenic acid,xanthurenic acid and 5‐hydroxytryptamine in human plasma by LC‐MS/MS and its application to acute myocardial infarction monitoring

Reliable methods for the determination of tryptophan and its metabolites are vital to the monitoring of biochemical states during the initiation and progression of cardiovascular disease. In the present study, a single‐run liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed for the simultaneous determination of tryptophan (Trp) and its metabolites, including kynurenine (Kyn), kynurenic acid (KA), xanthurenic acid (XA) and 5‐hydroxytryptamine (5‐HT), in human plasma. The plasma samples were prepared using a protein precipitation approach, and the chromatographic separation was performed by gradient elution on a C₁₈ column within a total analysis time of 3.5 min. The calibration ranges were 40–20,000 ng/mL for Trp, 4–2000 ng/mL for Kyn, 0.2–100 ng/mL for KA, 0.4–200 ng/mL for XA and 1–500 ng/mL for 5‐HT, and the precision and accuracy were acceptable. The evaluation of recovery and internal standard‐normalized matrix effect proved that the sample preparation approach was effective and the matrix effect could be negligible. The newly developed method was successfully applied to the analysis of plasma samples from healthy individuals and myocardial infarction patients. The findings suggested that the plasma concentrations of Trp, Kyn, 5‐HT as well as the concentration ratios of Kyn/Trp and Trp/5‐HT might serve as biomarkers for the monitoring of acute myocardial infarction.     

Kinetic Spectrophotometric Determination of Trace Amounts of Nitrite by Catalytic Reaction between Methylthymol Blue and Bromate

A kinetic spectrophotometric method for determination of trace nitrite in two dynamic ranges (2–100 and 100–500 ng/mL) based on its catalytic effect on the reaction between methylthymol blue and potassium bromate in acidic (sulfuric acid) media is described. The reaction was monitored spectrophotometrically by measuring the decreasing color of methylthymol blue at 437 nm by the fixed‐time method of 4.0 min at 30°C. The detection limit is 0.6 ng/mL, and the relative standard deviations for 50.0 and 250.0 ng/mL nitrite are 1.6% and 1.3%, respectively. The method was used for the determination of nitrite in water samples.     

Simultaneous quantification of Delta9-tetrahydrocannabinol, 11-hydroxy-Delta9-tetrahydrocannabinol, and 11-nor-Delta9-tetrahydrocannabinol-9-carboxylic acid in human plasma using two-dimensional gas chromatography, cryofocusing, and electron impact-mass spectrometry

A two-dimensional (2D) gas chromatography/electron impact-mass spectrometry (GC/EI-MS) method for simultaneous quantification of Delta(9)-tetrahydrocannabinol (THC), 11-hydroxy-Delta(9)-tetrahydrocannabinol (11-OH-THC), and 11-nor-Delta(9)-tetrahydrocannabinol-9-carboxylic acid (THCCOOH) in human plasma was developed and validated. The method employs 2D capillary GC and cryofocusing for enhanced resolution and sensitivity. THC, 11-OH-THC, and THCCOOH were extracted by precipitation with acetonitrile followed by solid-phase extraction. GC separation of trimethylsilyl derivatives of analytes was accomplished with two capillary columns in series coupled via a pneumatic Deans switch system. Detection and quantification were accomplished with a bench-top single quadrupole mass spectrometer operated in electron impact-selected ion monitoring mode. Limits of quantification (LOQ) were 0.125, 0.25 and 0.125 ng/mL for THC, 11-OH-THC, and THCCOOH, respectively. Accuracy ranged from 86.0 to 113.0% for all analytes. Intra- and inter-assay precision, as percent relative standard deviation, was less than 14.1% for THC, 11-OH-THC, and THCCOOH. The method was successfully applied to quantification of THC and its 11-OH-THC and THCCOOH metabolites in plasma specimens following controlled administration of THC.     

New application of chitosan‐grafted polyaniline in dispersive solid‐phase extraction for the separation and determination of phthalate esters in milk using high‐performance liquid chromatography

Chitosan‐grafted polyaniline was synthesized and applied as a sorbent for the preconcentration of phthalate esters in dispersive solid‐phase extraction. By coupling dispersive solid‐phase extraction with high‐performance liquid chromatography and response surface methodology (central composite design), a reliable, sensitive, and cost‐effective method for simultaneous determination of phthalate esters including dimethyl phthalate, di‐n‐butyl phthalate, and di(2‐ethylhexyl)phthalate was developed. The morphology of sorbent had been studied by scanning electron microscopy and its chemical structure confirmed by Fourier transform infrared spectroscopy. Under optimum condition, good linearity was observed in the range of 5.0–5000.0 ng/mL. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were 0.1–0.3 and 0.3–1 ng/mL, respectively. The relative standard deviations were less than 8.8%. Finally, this procedure was employed for extraction of trace amounts of phthalic acid esters in milk samples, the relative recoveries ranged from 82 to 103%.     

Simultaneous determination of dimethylarsinic acid and monomethylarsonic acid after derivatization with thioglycol methylate by gas chromatography/mass spectrometry

A gas chromatography/mass spectrometry (GC/MS) method has been developed to determine two methylated arsenic species in human urine samples. The yield of derivatization for dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) using thioglycol methylate (TGM) was measured. The detection limit for the derivatized DMA and MMA using the GC/MS method are 0.95 and 0.8 ng cm-3, respectively. This simple and rapid method has good precision and accuracy. Fragmentation routes of derivatized MMA and DMA are suggested on accurate mass measurements.     

Analysis of fragrance compounds in blood samples of mice by gas chromatography, mass spectrometry, GC/FTIR and GC/AES after inhalation of sandalwood oil.

After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and alpha-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: alpha-santalol 6.1 ng/mL, beta-santalol 5.3 ng/mL and alpha-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with alpha-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively.     

Simultaneous determination of niacin and its metabolites—nicotinamide,nicotinuric acid and N‐methyl‐2‐pyridone‐5‐carboxamide—in human plasma by LC‐MS/MS and its application to a human pharmacokinetic study

An LC‐MS/MS method for the simultaneous quantitation of niacin (NA) and its metabolites, i.e. nicotinamide (NAM), nicotinuric acid (NUA) and N‐methyl‐2‐pyridone‐5‐carboxamide (2‐Pyr), in human plasma (1 mL) was developed and validated using nevirapine as an internal standard (IS). Extraction of the NA and its metabolites along with the IS from human plasma was accomplished using a simple liquid–liquid extraction. The chromatographic separation of NA, NAM, NUA, 2‐Pyr and IS was achieved on a Hypersil‐BDS column (150 ¥ 4.6 mm, 5 mm) column using a mobile phase consisting of 0.1% formic acid : acetonitrile (20:80 v/v) at a flow rate of 1 mL/min. The total run time of analysis was 2 min and elution of NA, NAM, NUA, 2‐Pyr and IS occurred at 1.37, 1.46, 1.40, 1.06 and 1.27 min, respectively. A detailed validation of the method was performed as per the FDA guidelines and the standard curves were found to be linear in the range of 100–20000 ng/mL for NA; 10–1600 ng/mL for NUA and NAM and 50–5000 ng/mL for 2‐Pyr with mean correlation coefficient of ≥0.99 for each analyte. The method was sensitive, specific, precise, accurate and suitable for bioequivalence and pharmacokinetic studies. The developed assay method was successfully applied to a pharmacokinetic study in humans. Copyright © 2010 John Wiley & Sons, Ltd.     

Use of gas chromatography/mass spectrometry with positive chemical ionization for the determination of opiates in human oral fluid

An analytical method for the simultaneous determination of codeine, morphine and 6-acetylmorphine (6AM) in human oral fluid was developed. The method involves liquid-liquid extraction in Toxitubes A, derivatization with 99:1 (v/v) N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)/trimethylchlorosilane (TMCS), and gas chromatography/mass spectrometry with positive chemical ionization (GC/PCI-MS) determination. The detector response was linear over the concentration range 30-500 ng/mL with coefficients of correlation higher than 0.99. The precision was acceptable with coefficients of variation less than 7.5%. The limits of detection achieved were 0.7 ng/mL for codeine, 2.0 ng/mL for morphine, and 0.6 ng/mL for 6AM. The method proposed was applied to 80 oral fluid samples from opiates users, 98% of which were positive for the three analytes. Human oral fluid is a suitable biological fluid for the determination of opiates by GC/PCI-MS.     

Quantitative analysis of ezetimibe in human plasma by gas chromatography‐mass spectrometry

A new, specific and sensitive GC‐MS method with electron impact ionization technique was developed for quantitative analysis of ezetimibe (EZE) in human plasma. Prior to GC analysis, EZE was derivatized with N‐methyl‐N‐trimethylsilyl‐trifluoroacetamide (MSTFA), which is a trimethyl silylating reagent. The derivatization reaction was optimized and parameters such as catalyst, derivatization time, temperature, solvent and the volume of silylating reagent were investigated. Trimethylsilyl ether derivative of EZE was determined in selected ion monitoring (SIM, mass‐to‐charge ratio (m/z): 326) mode. The method was validated with respect to LOD and LOQ, precision, accuracy, linearity, specificity, stability, and recovery. The LOQ and LOD were found as 15 and 10 ng/mL, respectively. The linearity of the method ranged from 15 to 250 ng/mL. The correlation coefficient of the calibration curve was 0.9977 ± 0.0004 (± S.E.M.). The intra‐ and inter‐day precisions (RSD) were less than 6% and accuracies (bias) for intra‐ and inter‐day accuracy were found between –4.04 and 9.71% at four different concentration levels (15, 40, 100, 250 ng/mL). The proposed method was successfully applied to real human plasma samples for determination of total EZE.     

Fast simultaneous LC/MS/MS determination of 10 active compounds in human serum for therapeutic drug monitoring in psychiatric medication

A UPLC/MS/MS method with simple protein precipitation has been validated for the fast simultaneous analysis of agomelatine, asenapine, amisulpride, iloperidone, zotepine, melperone, ziprasidone, vilazodone, aripiprazole and its metabolite dehydro‐aripiprazole in human serum. Alprenolol was applied as an internal standard. A BEH C₁₈ (2.1 × 50 mm, 1.7 µm) column provided chromatographic separation of analytes using a binary mobile phase gradient (A, 2 mmol/L ammonium acetate, 0.1% formic acid in 5% acetonitrile, v/v/v; B, 2 mmol/L ammonium acetate, 0.1% formic acid in 95% acetonitrile, v/v/v). Mass spectrometric detection was performed in the positive electrospray ionization mode and ion suppression owing to matrix effects was evaluated. The validation criteria were determined: linearity, precision, accuracy, recovery, limit of detection, limit of quantification, reproducibility and matrix effect. The concentration range was as follows: 0.25–1000 ng/mL for agomelatine; 0.25–100 ng/mL for asenapine and iloperidone; 2.5–1000 ng/mL for amisulpride, aripiprazole, vilazodone and zotepine; 2.3–924.6 ng/mL for dehydroaripiprazole; 2.2–878.4 ng/mL for melperone; and 2.2–883.5 ng/mL for ziprasidone. Limits of quantitation below a therapeutic reference range were achieved for all analytes. Intra‐run precision of 0.4–5.5 %, inter‐run precision of 0.6–8.2% and overall recovery of 87.9–114.1% were obtained. The validated method was successfully implemented into routine practice for therapeutic drug monitoring in our hospital. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative determination of octadecenedioic acid in human skin and transdermal perfusates by gas chromatography-mass spectrometry

A gas chromatographic (GC) method with mass spectrometric (MS) detection is developed and validated for the accurate and precise determination of octadecenedioic acid (C18:1 DIOIC) in human skin samples and transdermal perfusates. C18:1 DIOIC is extracted using methanol. The saturated analogue 1,18-octadecanedioic acid (C18:0 DIOIC) is added as internal standard. Prior to analysis, both compounds are converted to their trimethylsilylated derivatives using N,O-bis(trimethylsilyl)trifluoroacetamide with 15% trimethylchlorosilane. Quantitation is performed in selected ion monitoring mode with a limit of quantitation of 250 ng/mL. Linearity with a correlation coefficient of 0.998 is obtained over a concentration range of 250-2000 ng/mL. Values for within-day accuracy range from 94.5% to 102.4%, and from 97.5% to 105.8% for between-day accuracy. Within- and between-day precision values are better than 5% and 7%, respectively. The recovery values from the various matrices vary from 92.6% to 104.0%. The GC-MS method is employed for the determination of C18:1 DIOIC after application of an emulsion containing the active ingredient onto human skin in vitro. The results demonstrate that the method is suitable for the determination of C18:1 DIOIC in human skin samples and transdermal perfusates.     

Simultaneous determination of rabeprazole and its two active metabolites in human urine by liquid chromatography with tandem mass spectrometry and its application in a urinary excretion study

A simple and rapid liquid chromatography with tandem mass spectrometry method has been developed and validated for the determination of rabeprazole and its two active metabolites, rabeprazole thioether and desmethyl rabeprazole thioether, in human urine using donepezil as the internal standard. The sample preparation procedure involved a simple dilution of urine sample with methanol (1:3, v/v). The chromatographic separation was achieved on a Hedera ODS‐2 C₁₈ column using a mixture of methanol/10 mmol/L ammonium acetate solution (containing 0.05% formic acid; 55:45, v/v) as the mobile phase. The method was validated over the concentration ranges of 0.15–100 ng/mL for rabeprazole, 0.30–400 ng/mL for rabeprazole thioether, and 0.05–100 ng/mL for desmethyl rabeprazole thioether. The established method was highly sensitive with a lower limit of quantification of 0.15 ng/mL for rabeprazole, 0.30 ng/mL for rabeprazole thioether, and 0.05 ng/mL for desmethyl rabeprazole thioether. The intra‐ and interbatch precision was <4.5% for the low, medium, and high quality control samples of all the analytes. The recovery of the analytes was in the range 95.4–99.0%. The method was successfully applied to a urinary excretion profiles after intravenous infusion administration of 20 mg rabeprazole sodium in healthy volunteers.     

A sensitive LC–MS/MS‐based bioanalytical method for quantification of salviaflaside and rosmarinic acid in rat plasma and its application in a pharmacokinetic study

A selective and sensitive liquid chromatography tandem mass spectrometry method was developed for the simultaneous determination of salviaflaside and rosmarinic acid in rat plasma. Sample preparation was carried out through liquid–liquid extraction with ethyl acetate using curculigoside as internal standard (IS). The analytes were determined by selected reaction monitoring operated in the positive ESI mode. Chromatographic separation was performed on an Agilent Eclipse Plus C₁₈ column (100 × 4.6 mm, 1.8 μm) with a mobile phase consisting of methanol–water–formic acid (50:50:0.1, v/v/v) at a flow rate of 0.3 mL/min. The run time was 1.9 min per sample and the injection volume was 5 μL. The method had an LLOQ of 1.6 ng/mL for salviaflaside and 0.94 ng/mL for rosmarinic acid in plasma. The linear calibration curves were fitted over the range of 1.6–320 ng/mL for salviaflaside and 0.94–188 ng/mL for rosmarinic acid in plasma with correlation coefficients (r²) >0.99. Intra‐ and inter‐day precisions (relative standard deviation) were < 13.5%, and accuracies (relative error) were between −8.6% and 14.5% for all quality control samples. The method was validated and applied to the pharmacokinetics of salviaflaside and rosmarinic acid in plasma after oral administration of Prunella vulgaris extract to rats.     

Simultaneous determination of niflumic acid and its prodrug, talniflumate in human plasma by high performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of niflumic acid and its prodrug, talniflumate, in human plasma. Niflumic acid and talniflumate were eluted isocratically with methanol-water (73:27, v/v, adjusted to pH 3.5 by acetic acid) at a fl ow rate of 1 mL/min. Indomethacin was used as an internal standard. Signals were monitored by an UV detector at 288 nm. Retention times of indomethacin, niflumic acid and talniflumate were 5.9, 7.2 and 13.5 min, respectively. Calibration plots were linear over the range 50-5000 ng/mL for niflumic acid and 100-5000 ng/mL for talniflumate. The limits of quantitation were 50 ng/mL for niflumic acid and 100 ng/mL for talniflumate. The intra- and inter-day relative standard deviations (RSD) of niflumic acid and talniflumate were less than 10% and the accuracies were higher than 90%. This method is rapid, sensitive and reproducible for the determination of niflumic acid and talniflumate in human plasma.