Simultaneous quantitation of morphine, 6-acetylmorphine, codeine, 6-acetylcodeine and tramadol in hair using mixed-mode solid-phase extraction and gas chromatography–mass spectrometry

A simple procedure has been developed and validated for the qualitative and quantitative analysis of several opiates (morphine, 6-acetylmorphine, codeine, 6-acetylcodeine) and tramadol in hair. The analytes were extracted from within the matrix via an overnight incubation with methanol at 65 °C, and afterwards the samples were cleaned up by mixed-mode solid-phase extraction. The extracts were derivatized with N-methyl-N-(trimethylsilyl) trifluoroacetamide with 5% trimethylchlorosilane and analyzed by gas chromatography–mass spectrometry in the selected ion monitoring mode. The method was linear from 0.05 (lower limit of quantitation) to 50 ng/mg (40 ng/mg for tramadol), with correlation coefficients higher than 0.99 for all compounds, accomplishing the cut-off values proposed by the Society of Hair Testing for the detection of these substances in hair (0.2 ng/mg). Intra- and interday precision and trueness were in conformity with the criteria normally accepted in bioanalytical method validation, and the sample cleanup step presented a mean efficiency higher than 90% for all analytes. Furthermore, using these incubation conditions, 6-acetylmorphine did not significantly hydrolyze to morphine. For these reasons, and because of its simplicity, the proposed method can be successfully applied in the determination of these compounds in hair samples, and is suitable for application in routine analysis with forensic purposes.     

Simultaneous determination of phthalates and adipates in human serum using gas chromatography–mass spectrometry with solid‐phase extraction

A gas chromatography–mass spectrometry assay was developed and validated for the simultaneous determination of phthalates and adipates in human serum. The phthalates and adipates studied were dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzylbutyl phthalate, di‐2‐ethylhexyl phthalate, di‐n‐octyl phthalate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis(2‐butoxyethyl) adipate and di‐2‐ethylhexyl adipate, with diisooctyl phthalate as internal standard. The extraction and cleaning up procedure was carried out with solid‐phase extraction cartridges containing dimethyl butylamine groups, which showed extraction efficiencies over 88% for each analyte and the internal standard. The calibration curves obtained were linear with correlation coefficients greater than 0.98. For all analytes, the assay gave CV% values for intra‐day precision from 4.9 to 13.3% and mean accuracy values from 91.4 to 108.4%, while inter‐day precision was 5.2–13.4% and mean accuracy 91.0–110.2%. The limits of detection for the assay of phthalates and adipates were in the range 0.7–4.5 ng/mL. The method is simple, sensitive and accurate, and allows for simultaneous determination of nanogram levels of phthalates and adipates in human serum. It was successfully applied to an investigation on the level of phthalates and adipates in a non‐occupationally exposed population.     

Simultaneous determination of ten antihistamine drugs in human plasma using pipette tip solid-phase extraction and gas chromatography/mass spectrometry

Ten antihistamine drugs, diphenhydramine, orphenadrine, chlorpheniramine, diphenylpyraline, triprolidine, promethazine, homochlorcyclizine, cyproheptadine, cloperastine and clemastine, have been found to be extractable from human plasma samples using MonoTip C18 tips, inside which C18- bonded monolithic silica gel was fixed. Human plasma (0.1 mL) containing the ten antihistamines was mixed with 0.4 mL of distilled water and 25 microL of a 1 M potassium phosphate buffer (pH 8.0). After centrifugation of the mixture, the supernatant fraction was extracted to the C18 phase of the tip by 25 repeated aspirating/dispensing cycles using a manual micropipettor. The analytes retained on the C18 phase were then eluted with methanol by five repeated aspirating/dispensing cycles. The eluate was injected into a gas chromatography (GC) injector without evaporation and reconstitution steps, and was detected by a mass spectrometer with selected ion monitoring in the positive-ion electron impact mode. The separation of the ten drugs from each other and from impurities was generally satisfactory using a DB-1MS column (30 m x 0.32 mm i.d., film thickness 0.25 microm). The recoveries of the ten antihistamines spiked into plasma were 73.8-105%. The regression equations for the ten antihistamines showed excellent linearity with detection limits of 0.02-5.0 ng/0.1 mL. The within-day and day-to-day coefficients of variation for plasma were not greater than 9.9%. The data obtained from determination of diphenhydramine and chlorpheniramine in human plasma after oral administration of the drugs are also presented.     

Simultaneous determination of seven nitrogen‐containing phenyl ethers in cosmetics by gas chromatography with mass spectrometry and dispersive solid‐phase extraction

An analytical method was established for the simultaneous determination of seven nitrogen‐containing phenyl ethers (2‐anisidine, 3‐anisidine, 4‐anisidine, 2‐nitroanisole, 3‐nitroanisole, 4‐nitroanisole, and 3,3'‐dimethoxybenzidine) in cosmetics by gas chromatography with mass spectrometry in this work. The samples were extracted with ethyl acetate and purified with primary secondary amine during the dispersed solid‐phase extraction. The analytes were separated by a DB‐17MS column and detected in the electron ionization mode of mass spectrometry in the selected ions monitoring mode. The extraction solvent, purification adsorbents, and chromatographic column behavior were optimized. The results indicated that the seven analytes show good linear relationship (R ² > 0.9965) in the concentrations of 5.0–5000 μg/L. The quantitation limits of the method ranged from 19.0 to 84.8 μg/kg. The recovery rates of seven analytes were in the range of 72.6–114% with the relative standard deviations of 1.1–7.5%. Real sample analyses showed that this accurate and precise method could be appropriate for simultaneous determination of seven nitrogen‐containing phenyl ethers in cosmetics.     

Azithromycin extraction from municipal wastewater and quantitation using liquid chromatography/mass spectrometry

Azithromycin is a broad spectrum antimicrobial agent that is approved in the United States for use in humans. Due to azithromycin's low rate of metabolism it is likely to be found in wastewater treatment plants, where its broad spectrum of antimicrobial activity could lead to development of resistance in bacteria. A liquid-liquid extraction using K2CO3 and methyl-t-butyl ether (MTBE) was used to extract azithromycin from 10 ml aliquots of wastewater. Liquid chromatography was performed using a Luna C18(2) (30 mm x 2.0 mm) column with a mass spectrometer friendly mobile phase containing 50:24:2:24 acetonitrile, methanol, tetrahydrofuran, and 0.04 M ammonium hydroxide. The mass spectrometer used an electrospray source with positive ionization and an ion trap detector. A linear standard curve from 5 to 200pg/ml was validated and used to quantitate azithromycin in wastewater.     

Method validation for the determination of propellant components by Soxhlet extraction and gas chromatography/mass spectrometry

A fast, sensitive, and accurate GC/MS method for the quantification of aliphatic nitroesters (ethylene glycol dinitrate, nitroglycerin, and triethylene glycol dinitrate) and aromatic amines (diphenylamine, 2-nitrodiphenylamine, and triphenylamine) in propellants was developed and validated. This method comprises a Soxhlet extraction step with dichloromethane, followed by separation on a capillary column MDN-5. Ionization of the analytes is carried out using electron ionization. The limit of quantification of the method was 1% w/w for aliphatic nitroesters and 0.1% w/w for aromatic amines (diphenylamine and triphenylamine). Values of repeatability and reproducibility for analyzed compounds were smaller than values of the maximum allowed tolerances of the Horwitz-equation RSD(max) and 2/3 RSD(max). Values of accuracy for selected compounds were below the acceptable threshold of 15% for all tested levels in the range of calibration curve excepting the lowest concentration of calibration curve for nitroglycerin and aromatic amines. During the validation of method, temperature instability in injection port of gas chromatograph and column was observed for 2-nitrodiphenylamine. Hence, it follows worse results of accuracy and linearity and 2-nitrodiphenylamine was not validated successfully.     

Simultaneous determination of haloanisoles and halophenols in water using in situ acylation combined with solid‐phase microextraction with gas chromatography and mass spectrometry

In this work, an in situ acylation combined with solid‐phase microextraction coupled to gas chromatography and mass spectrometry method has been developed for simultaneously determining haloanisoles (2,4,6‐trichloranisole, 2,4,6‐tribromoanisole), and their direct precursors (2,4,6‐trichlorophenol, 2,4,6‐tribromophenol) and indirect precursors (2‐chloropenol, 2,4‐dichlorophenol, 2‐bromophenol, 2,4‐dibromophenol) in water. The key parameters for the solid‐phase microextraction were determined by using Plackett–Burman screening and optimized by central composite optimization. Under optimal conditions, the eight compounds can be analyzed in a short time (33 min) with a strong linearity ranging from 2 to 200 ng/L (correlation coefficient greater than 0.996), showing good sensitivities with the limit of detection in a range of 0.23–0.91 ng/L and a limit of quantification of 0.77–3.03 ng/L, good repeatability (2.00–9.10%) and interday precision (1.67–11.3%). When environmental water samples were treated, the recoveries of target compounds were 75.5–127.3%, suggesting that the developed method could be applied in probing the origin of haloanisoles and monitoring halophenols and haloanisoles in natural waters at concentration levels of ng/L.     

Determination of chlorinated polycyclic aromatic hydrocarbons in water by solid‐phase extraction coupled with gas chromatography and mass spectrometry

Given the potential risks of chlorinated polycyclic aromatic hydrocarbons, the analysis of their presence in water is very urgent. We have developed a novel procedure for determining chlorinated polycyclic aromatic hydrocarbons in water based on solid‐phase extraction coupled with gas chromatography and mass spectrometry. The extraction parameters of solid‐phase extraction were optimized in detail. Under the optimal conditions, the proposed method showed wide linear ranges (1.0–1000 ng/L) with correlation coefficients ranging from 0.9952 to 0.9998. The limits of detection and the limits of quantification were in the range of 0.015–0.591 and 0.045–1.502 ng/L, respectively. Recoveries ranged from 82.5 to 102.6% with relative standard deviations below 9.2%. The obtained method was applied successfully to the determination of chlorinated polycyclic aromatic hydrocarbons in real water samples. Most of the chlorinated polycyclic aromatic hydrocarbons were detected and 1‐monochloropyrene was predominant in the studied water samples. This is the first report of chlorinated polycyclic aromatic hydrocarbons in water samples in China. The toxic equivalency quotients of chlorinated polycyclic aromatic hydrocarbons in the studied tap water were 9.95 ng the toxic equivalency quotient m^?3. 9,10‐Dichloroanthracene and 1‐monochloropyrene accounted for the majority of the total toxic equivalency quotients of chlorinated polycyclic aromatic hydrocarbons in tap water.     

Simultaneous quantitation of enalapril and enalaprilat in human plasma by 96-well solid-phase extraction and liquid chromatography/tandem mass spectrometry

A sensitive and rapid method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) combined with rapid solid-phase extraction (SPE) has been developed and validated for the quantitative determination of enalapril and its active metabolite enalaprilat in human plasma. After addition of internal standard to human plasma, samples were extracted by 96-well SPE cartridge. The extracts were analyzed by HPLC with the detection of the analyte in the multiple reaction monitoring (MRM) mode. This method for the simultaneous determination of enalapril and enalaprilat was accurate and reproducible, with respective limits of quantitation of 0.2 and 1.0 ng/mL in plasma. The standard calibration curves for both enalapril and enalaprilat were linear (r(2) = 0.9978 and 0.9998) over the concentration ranges 0.2-200 and 1.0-100 ng/mL in human plasma, respectively. The intra- and inter-day precision over the concentration range for enalapril and enalaprilat were lower than 13.3 and 15.4% (relative standard deviation, %RSD), and accuracy was between 89.2-105.0 and 91.9-104.7%, respectively.     

Simultaneous determination of five phthalate esters and bisphenol A in milk by packed‐nanofiber solid‐phase extraction coupled with gas chromatography and mass spectrometry

A novel polystyrene/pyridine composite nanofiber was synthesized and utilized as the sorbent material for the solid‐phase extraction of bisphenol A and five common phthalate esters in milk. The method of extraction integrated extraction and preconcentration of target analytes into a single step. Bisphenol A and five common phthalate esters were selected as target compounds for the development and evaluation of the method. The effects of operating parameters for nanofiber‐based solid‐phase extraction, such as selection and amount of sorbent, the volume fraction of perchlorate (precipitate protein), desorption solvent, volume of desorption solvent, and effect of salt addition were optimized. Under optimal conditions, higher extraction recoveries (89.6–118.0%) of the six compounds in milk spiked at three levels were obtained, and the satisfied relative standard deviation were ranged from 0.6 to 10.9%. The detection limits and quantification limits of the method ranged from 0.01 to 0.06 μg/L and 0.05 to 0.53 μg/L, respectively. Matrix effects were also verified and well controlled in the range of 91.3–109.3%. The new method gave better performance metrics than Chinese standard method and other published methods. Thus, the proposed method may be applied to the analysis of the phthalate esters and bisphenol A in complex matrixes.     

Simultaneous quantitation of acetylsalicylic acid and clopidogrel along with their metabolites in human plasma using liquid chromatography tandem mass spectrometry

The interest in therapeutic drug monitoring has increased over the last few years. Inter‐ and intra‐patient variability in pharmacokinetics, plasma concentration related toxicity and success of therapy have stressed the need of frequent therapeutic drug monitoring of the drugs. A sensitive, selective and rapid liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS) method was developed for the simultaneous quantification of acetylsalicylic acid (aspirin), salicylic acid, clopidogrel and carboxylic acid metabolite of clopidogrel in human plasma. The chromatographic separations were achieved on Waters Symmetry Shield^TM C₁₈ column (150 × 4.6 mm, 5 µm) using 3.5 mm ammonium acetate (pH 3.5)–acetonitrile (10:90, v/v) as mobile phase at a flow rate of 0.75 mL/min. The present method was successfully applied for therapeutic drug monitoring of aspirin and clopidogrel in 67 patients with coronary artery disease. Copyright © 2015 John Wiley & Sons, Ltd.     

Arsenic extraction and speciation in carrots using accelerated solvent extraction, liquid chromatography and plasma mass spectrometry

Arsenic present in freeze-dried carrots was extracted using accelerated solvent extraction (ASE). Several parameters, including selection of the dispersing agent, extraction time, number of extraction cycles, particle size and extraction temperature, were evaluated to optimize the ASE method. Filtering and treatment with C-18 SPE cartridges were also evaluated as part of the sample preparation procedure before speciation analysis. The method was validated by spiking single arsenical and mixed arsenical standards on the dispersing agent and on portions of freeze-dried carrot prior to extraction. LC-ICP-MS was used to determine individual arsenic species in the carrot extracts. A weak anion-exchange column was used for the separation of As(III), As(v), monomethylarsonic acid (MMA), dimethylarsinic acid and arsenobetaine. Optimized sample preparation conditions were applied to the extraction of arsenic in nine freeze-dried carrot samples. Total arsenic concentration in the carrot samples ranged from less than 20 ng g(-1) to 18.7 microg g(-1), dry mass. Extraction efficiency, defined as the ratio of the sum of individual arsenic species concentrations to total arsenic, ranged from 80 to 102% for freeze-dried carrots with arsenic concentrations greater than the limit of quantitation. Inorganic As(III) and As(v) were the only species found in samples that contained less than 400 ng g(-1) total arsenic. MMA and an unidentified arsenic compound were present in some of the samples with higher total arsenic content.     

Imatinib assay by high‐performance liquid chromatography in tandem mass spectrometry with solid‐phase extraction in human plasma

We have developed a method of liquid chromatography in tandem with mass spectrometry to monitor therapeutic levels of imatinib in plasma, a selective inhibitor of protein tyrosine kinase. After solid‐phase extraction of plasma samples, imatinib and its internal standard, imatinib‐D8, were eluted with Zorbax SB‐C₁₈ at 60 °C, under isocratic conditions through a mobile phase consisting of 4 mm ammonium formate, pH: 3.2 (solution A) and acetonitrile solution B. The flow rate was 0.8 mL/min with 55% solution A + 45% solution B. Imatinib was detected and quantified by mass spectrometry with electrospray ionization operating in selected‐reaction monitoring mode. The calibration curve was linear in the range 10–5000 ng/mL, the lower limit of quantitation being 10 ng/mL. The method was validated according to the recommendations of the Food and Drug Administration, including tests of matrix effect (bias < 10%) and recovery efficiency (>80 and <120%). The method is precise (coefficient of variance intra‐day <2% and inter‐day <7%), accurate (95–108%), sensitive and specific. It is a simple method with very fast recording time (1.2 min) that is applicable to clinical practice. This will permit improvement of the pharmacological treatment of patients. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of polycyclic aromatic hydrocarbons in water samples by gas chromatography coupled to triple quadrupole tandem mass spectrometry using macroporous resin solid‐phase extraction

A method for the determination of 16 polycyclic aromatic hydrocarbons in water has been developed. First, we made a solid‐phase extraction column. After this, the parameters affecting the efficacy of the experimental method were optimized, including appropriate selection of a solid‐phase extraction column and cleanup conditions on columns. The separation was achieved by gas chromatography and detection with triple quadrupole tandem mass spectrometry. The method showed satisfactory linearity (R² > 0.999) over the range assayed (0.01–1 μg/mL), and limits of quantification ranging from 0.0011 to 0.0199 μg/L. The recoveries ranged from 83 to 113%. The relative standard deviation is in the range 0.86–3.1%. The results indicated that this method had high selectivity and precision that was suitable for the simultaneous determination of 16 polycyclic aromatic hydrocarbons in water.     

Storage stability studies for tributyltin determination in human urine samples using headspace solid‐phase microextraction and gas chromatography mass spectrometry

A headspace solid‐phase micro‐extraction (HS‐SPME) method was employed in order to study the effect of storage conditions of human urine samples spiked with tributyltin (TBT) using gas chromatography and mass spectrometry. To render the analyte more volatile, the derivatization (ethylation) was made in situ by sodium tetraethylborate (NaBEt₄), which was added directly to dilute unpreserved urine samples and in buffers of similar acidity. The stability of TBT in human urine matrix was compared with the stability of TBT in buffer solutions of similar pH value. Critical parameters of storage conditions such as temperature and time, which affect the stability of TBT in this kind of matrix, were examined extensively. The tests showed that the stability of TBT remains practically satisfactory for a maximum of 2 days of storage either at +4 or 20°C. Greater variations were observed in the concentration of TBT in human urine samples at +4°C and lower ones at ?20°C over a month's storage. The freeze–thaw cycles have negative effect on the stability and should be kept to a minimum. The results from spiked urine samples are also discussed in comparison to those acquired from buffer solutions of equal TBT concentration. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of a magnetic solid‐phase extraction coupled with gas chromatography and mass spectrometry method for the analysis of semivolatile organic compounds

Semivolatile organic compounds are a category of organic micropollutants including phthalate esters, polycyclic aromatic hydrocarbons and so on, which are commonly analyzed by solid‐phase extraction followed by gas chromatography with mass spectrometry. In this work, a highly sensitive and feasible method of magnetic solid‐phase extraction combined with gas chromatography with mass spectrometry was established for the determination of semivolatile organic compounds in water. The novel method was based on a permanent magnetic resin with uniform particle size and high surface area (1154.3 m²/g). The results demonstrated that the extraction efficiency of the resin was superior to that of a C₁₈ cartridge. The method was proved to be of satisfactory recoveries (75–115.7%) and limits of detection and quantification (0.063–6.524 and 0.212–21.745 μg/L, respectively). The method was applied to the analysis of semivolatile organic compounds in the midstream Huai River. It was observed that polychlorinated biphenyls exceeded current water standards. To further illustrate the potential effects on human health, health risk assessment was conducted based on the obtained data. The existence of health risk was proved, with hexachlorobenzene and 2,2’,4,4’‐tetrachlorobiphenyl as the major causes. The method possesses the characteristics of high efficiency and rapid analysis, offering a good prospect of applications in large quantities of practical water.     

Determination of glycosylation degree for glycoconjugate vaccines using a solid‐phase extraction combined with liquid chromatography and tandem mass spectrometry method

In this study, a solid‐phase extraction with liquid chromatography and tandem mass spectrometry method was developed to determine the degree of glycosylation of glycosylation sites and the ratio of free carrier protein to total carrier protein for glycoconjugate vaccines. To remove and enrich the glycosylated peptides, a solid‐phase extraction method was developed, optimized, and hyphenated to liquid chromatography?tandem mass spectrometry. The developed solid‐phase extraction with liquid chromatography?tandem mass spectrometry method was shown to possess a wide linear dynamic range (0.03?100 μg/mL), a high sensitivity (0.03 μg/mL for CRM197), good interday and intra‐day precision (relative standard deviation of peak area < 3.3%), and good recoveries from vaccine matrix (90?105%). Finally, the method was utilized to determine the degree of glycosylation and free carrier protein to total carrier protein ratio for pneumococcal conjugate vaccines and meningococcal vaccines. For quality evaluation of glycoconjugate vaccines, the method could provide more information than the traditional size exclusion chromatography method. Fourteen and twelve reported glycosylation sites for CRM197‐ and tetanus toxin‐based vaccines can be detected, respectively.