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 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 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.     

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.     

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.     

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.     

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 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.     

Determination of tramadol and O-desmethyltramadol in human plasma by high-performance liquid chromatography with mass spectrometry detection

A new simple, sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS) method for quantification of tramadol and its active metabolite O-desmethyltramadol in human plasma was validated. The tramadol and its metabolite were separated on a reversed phase column (Zorbax SB-C18, 100 mm x 3.0 mm I.D., 3.5 microm) under isocratic conditions using a mobile phase of a 10:90 (v/v) mixture of acetonitrile and 0.2% (v/v) trifluoroacetic acid in water. The flow rate was 1 ml/min at the column temperature 45 degrees C. In these chromatographic conditions, the retention times were 2.3 min for O-desmethyltramadol and 3.5 min for tramadol, respectively. The detection of both analytes was in SIM mode using an ion trap mass spectrometer with electrospray positive ionisation. The monitored ions were m/z 264 for tramadol and m/z 250 for its metabolite. The sample preparation was very simple and rapid and consisted in plasma protein precipitation from 0.2 ml plasma using 0.2 ml solution of perchloric acid 7%. Calibration curves were generated over the range of 2-300 ng/ml for both analytes with values for coefficient of correlation greater than 0.998 and by using a weighted (1/y) quadratic regression. The values of precision and accuracy for tramadol at quantification limit were less than 10.9% and 5.1, respectively, both for within- and between-run. For O-desmethyltramadol, precision and accuracy at quantification limit were 10.1% and -9.9% for within-run determinations and 6.7% and 10.4% for between-run determinations, respectively. The mean recovery for both analytes was 96%. Both tramadol and its metabolite demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. This is the first reported method for analysis of tramadol and O-desmethyltramadol in human plasma that uses protein precipitation as sample processing procedure. The method is very simple and allows obtaining a very good recovery of both analytes. The validated LC/MS method has been applied to a pharmacokinetic study of 50 mg tramadol tablets on healthy volunteers.     

Azithromycin quantitation in human plasma by high-performance liquid chromatography coupled to electrospray mass spectrometry: application to bioequivalence study

A sensitive and specific liquid chromatography-electrospray ionization mass spectrometry method is developed and validated for the identification and quantitation of azithromycin in human plasma. After the addition of the internal standard and 1.0M sodium hydroxide solution, plasma samples are extracted with a methylene chloride-ethyl acetate mixture (20:80, v/v). The organic layer is evaporated under a stream of nitrogen at 40 degrees C. The residue is reconstituted with 200 microL of the mobile phase. The compounds are separated on a prepacked Shimadzu Shim-pack VP-ODS C18 (5 microm, 150 mm x 2.0 mm) column using a mixture of acetonitrile-water (65:35) (0.5% triethylamine, pH was adjusted to 6.2 with acetic acid) as the mobile phase. Detection is performed on a single quadrupole mass spectrometer by selected ion monitoring mode via electrospray ionization source. The method is fully validated and linear calibration curves are obtained in the concentration ranges from 5 to 2000 ng/mL. The intra- and inter-batch relative standard deviations at four different concentration levels are all < 10%. The limit of detection and quantitation are 2 ng/mL and 5 ng/mL, respectively. The proposed method enables the unambiguous identification and quantitation of azithromycin for pharmacokinetic, bioavailability, or bioequivalence studies.     

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.     

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 Aroclor 1260 in soil samples by gas chromatography with mass spectrometry and solid‐phase microextraction

A novel fast screening method was developed for the determination of polychlorinated biphenyls that are constituents of the commercial mixture, Aroclor 1260, in soil matrices by gas chromatography with mass spectrometry combined with solid‐phase microextraction. Nonequilibrium headspace solid‐phase microextraction with a 100 μm polydimethylsiloxane fiber was used to extract polychlorinated biphenyls from 0.5 g of soil matrix. The use of 2 mL of saturated potassium dichromate in 6 M sulfuric acid solution improved the reproducibility of the extractions and the mass transfer of the polychlorinated biphenyls from the soil matrix to the microextraction fiber via the headspace. The extraction time was 30 min at 100°C. The percent recoveries, which were evaluated using an Aroclor 1260 standard and liquid injection, were within the range of 54.9–65.7%. Two‐way extracted ion chromatogram data were used to construct calibration curves. The relative error was <±15% and the relative standard deviation was <15%, which are respective measures of the accuracy and precision. The method was validated with certified soil samples and the predicted concentrations for Aroclor 1260 agreed with the certified values. The method was demonstrated to be linear from 10 to 1000 ng/g for Aroclor 1260 in dry soil.     

Simultaneous determination of ramipril, ramiprilat and telmisartan in human plasma using liquid chromatography tandem mass spectrometry

A rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed and validated for the simultaneous determination of ramipril, ramiprilat and telmisartan in human plasma. The solid-phase extraction technique was used for the extraction of ramipril, ramiprilat and telmisartan from human plasma. Trandolaprilat and hydrochlorothiazide were used as the internal standards (ISs). Chromatography was performed on a Hypurity C18, 5 μm, 50 mm × 4.6 mm column, with the mobile phase consisting of ammonium acetate and acetonitrile (in a 20:80 ratio), followed by detection using mass spectrometry. The method involves a simple reversed isocratic chromatography condition and mass spectrometry detection, which enables detection at sub-nanogram levels. The method was validated and the lower limit of quantification for ramipril, ramiprilat and telmisartan was found to be 0.1 ng mL⁻¹, 0.1 ng mL⁻¹ and 2 ng mL⁻¹, respectively. The mean recovery for ramipril, ramiprilat and telmisartan ranged from 90.1 to 104.1%. This method increased the sensitivity and selectivity; resulting in high-throughput analysis of ramipril, ramiprilat and telmisartan using two different ISs in a single experiment for bioequivalence studies, with a chromatographic run time of 1.5 min only.     

Novel solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods for the rapid analysis of triazine herbicides in real waters

Novel, fast, selective, eco‐friendly and reproducible solid‐phase membrane tip extraction and gas chromatography with mass spectrometry methods were developed and validated for the analysis of triazine herbicides (atrazine and secbumeton) in stream and lake waters. The retention times of atrazine and secbumeton were 7.48 and 8.51 min. The solid‐phase membrane tip extraction was carried out in semiautomated dynamic mode on multiwall carbon nanotubes enclosed in a cone‐shaped polypropylene membrane cartridge. Acetone and methanol were found as the best preconditioning and desorption solvents, respectively. The extraction and desorption times for these herbicides were 15.0 and 10.0 min, respectively. The percentage recoveries of atrazine and secbumeton were 88.0 and 99.0%. The linearity range was 0.50–80.0 μg/L (r² > 0.994), with detection limits (<0.47 μg/L, S/N = 3) and good reproducibility (<8.0%). The ease of operation, eco‐friendly nature, and low cost of solid‐phase membrane tip extraction made these methods novel. The Solid‐phase membrane tip extraction method was optimized by considering the effect of extraction time, desorbing solvents and time.