Fast determination of Z-ligustilide in plasma by gas chromatography/mass spectrometry following headspace single-drop microextraction

Angelica sinensis (danggui in Chinese) is a common traditional Chinese medicine (TCM), and its essential oil has been used for the treatment of many diseases such as hepatic fibrosis. Z-Ligustilide has been found to be an important active component in the TCM essential oil. In this work, for the first time, headspace single-drop microextraction (HS-SDME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the determination of Z-ligustilide in rabbit plasma after oral administration of essential oil of danggui. The extraction parameters of solvent selection, solvent volume, sample temperature, extraction time, stirring rate, and ion strength were systemically optimized. Furthermore, the method linearity, detection limit, and precision were also investigated. It was shown that the proposed method provided good linearity (0.02-20 microg/mL, R2 = 0.997), low detection limit (10 ng/mL), and good precision (RSD value less than 9%). Finally, HS-SDME followed by GC/MS was used for fast determination of Z-ligustilide in rabbit plasma at different time intervals after oral administration of danggui essential oil. The experimental results suggest that HS-SDME followed by GC/MS is a simple, sensitive, and low-cost method for the determination of Z-ligustilide in plasma, and a low-cost approach to pharmacokinetics studies of active components in TCMs.     

Fast determination of paeonol in plasma by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry

Paeonol is the active component in the traditional Chinese medicines (TCMs), such as Cynanchum paniculatum, which has been used to treat many diseases, such as eczema. In this work, a simple, rapid and sensitive method was developed for the determination of paeonol in rabbit plasma, which was based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). The extraction parameters of fiber coating, sample temperature, extraction time, stirring rate and ion strength were systemically optimized; the method linearity, detection limit and precision were also investigated. It was shown that the proposed method provided a good linearity (0.02-20 μg mL⁻¹, R² > 0.990), low detection limit (2.0 ng mL⁻¹) and good precision (R.S.D. value less than 8%). Finally, GC/MS following HS-SPME was applied to fast determination of paeonol in rabbit plasma at different time point after oral demonstration of Cynanchum paniculatum essential oil. The experimental results suggest that the proposed method provided an alternative and novel approach to the pharmacokinetics study of paeonol in the TCMs.     

Detection of perfluorocarbons in blood by headspace solid-phase microextraction combined with gas chromatography/mass spectrometry.

A new method of detection of perfluorocarbon molecules (PFCs) in blood sample has been established. After an extraction and pre-concentration step performed by headspace solid-phase microextraction (HS-SPME), the PFCs are detected by gas chromatography-mass spectrometry (GC/MS) with an ion trap mass spectrometer in MS and MS/MS modes. The influence of different parameters on the SPME process is discussed. The limit of detection and the linearity of the procedure have been determined for two PFCs.     

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.     

Optimisation of a solid-phase microextraction method for the analysis of nicotine in hair

A headspace solid-phase microextraction method (HS-SPME) followed by gas chromatography with mass spectrometric detection (GC/MS) has been developed for the determination of low concentrations of nicotine in hair. Parameters affecting the SPME procedure including type of fiber coating, extraction mode, extraction temperature and time, desorption time, stirring, and salt addition have been evaluated and optimised. The method provided good linearity (r(2)≥0.9980) over the concentration range tested (0.2-20 ng/mg) and low detection limit (0.02 ng/mg). Precision expressed as relative standard deviation was <10%. The average accuracy was 95%. The proposed method was used to determine hair nicotine levels in 100 children in order to assess exposure to environmental tobacco smoke (ETS). The described HS-SPME procedure is fast, simple, sensitive, and solvent-free and is therefore suitable for studies involving ETS exposure assessment.     

Development of water-phase derivatization followed by solid-phase microextraction and gas chromatography/mass spectrometry for fast determination of valproic acid in human plasma

In this study, a simple, rapid, and sensitive method was developed and validated for the quantification of valproic acid (VPA), an antiepileptic drug, in human plasma, which was based on water-phase derivatization followed by headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS). In the proposed method, VPA in plasma was rapidly derivatized with a mixture of isobutyl chloroformate, ethanol and pyridine under mild conditions (room temperature, aqueous medium), and the VPA ethyl ester formed was headspace-extracted and simultaneously concentrated using the SPME technique. Finally, the analyte extracted on SPME fiber was analyzed by GC/MS. The experimental parameters and method validations were studied. The optimal conditions were obtained: PDMS fiber, stirring rate of 1100 rpm, sample temperature of 80 degrees C, extraction time of 20 min, NaCl concentration of 30%. The proposed method had a limit of quantification (0.3 microg/mL), good recovery (89-97%) and precision (RSD value less than 10%). Because the proposed method combined a rapid water-phase derivatization with a fast, simple and solvent-free sample extraction and concentration technique of SPME, the sample preparation time was less than 25 min. This much shortens the whole analysis time of VPA in plasma. The validated method has been successfully used to analyze VPA in human plasma samples for application in pharmacokinetic studies. All these results show that water-phase derivatization followed by HS-SPME and GC/MS is an alternative and powerful method for fast determination of VPA in biological fluids.     

Automated determination of ethyl carbamate in stone-fruit spirits using headspace solid-phase microextraction and gas chromatography-tandem mass spectrometry

A fully automated procedure using headspace solid-phase microextraction (HS-SPME) followed by gas chromatographic/tandem mass spectrometric (GC/MS/MS) detection was developed for the determination of the toxic contaminant ethyl carbamate (EC) in stone-fruit spirits. After addition of deuterated internal standard, the optimised HS-SPME extraction with carbowax/divinylbenzene fibres (30 min at 70 degrees C) was done applying salting out with sodium chloride in the presence of pH 7 buffer solution. For quantitative analysis the characteristic fragmentations of m/z 74>44 and m/z 62>44 for ethyl carbamate as well as m/z 64>44 for ethyl carbamate-d5 were monitored in the multiple reaction monitoring (MRM) mode using a triple quadrupole instrument. In the validation studies, ethyl carbamate exhibited good linearity with a regression coefficient of 0.998. The limits of detection and quantitation were 0.03 and 0.11 mg/l. The precision never exceeded 4.3% (intraday) and 8.2% (interday) at any of the concentrations examined. A good agreement of analysis results in comparison to conventional sample clean-up over diatomaceous earth columns was found (R = 0.956, Bias = 0.08 mg/l). The new HS-SPME/GC/MS/MS procedure is suitable for the fast, reliable and inexpensive determination of ethyl carbamate in alcoholic beverages in an automated, and therefore, convenient procedure.     

An improved method for cyanide determination in blood using solid-phase microextraction and gas chromatography/mass spectrometry

A new method is described for the qualitative and quantitative analysis of cyanide, a very short-acting and powerful toxic agent, in human whole blood. It involves the conversion of cyanide into hydrogen cyanide and its subsequent headspace solid-phase microextraction (HS-SPME) and detection by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Optimizing the conditions for the GC/MS (type of column, injection conditions, temperature program) and SPME (choice of SPME fiber, effect of salts, adsorption and desorption times, adsorption temperature) led to the choice of a 75-microm carboxen/polydimethylsiloxane SPME fiber, with D3-acetonitrile as internal standard, and a capillary GC column with a polar stationary phase. Method validation was carried out in terms of linearity, precision and accuracy in both aqueous solutions and blood. The limit of detection (LOD) and limit of quantitation (LOQ) were determined only in aqueous solutions. The assay is linear over three orders of magnitude (water 0.01-10, blood 0.05-10 microg/mL); and the LOD and LOQ in water were 0.006 and 0.01 microg/mL, respectively. Good intra- and inter-assay precision was obtained, always <8%. The method is simple, fast and sensitive enough for the rapid diagnosis of cyanide intoxication in clinical and forensic toxicology.     

Determination of diisopropylfluorophosphate in rat plasma and brain tissue by headspace solid-phase microextraction gas chromatography/mass spectrometry

A simple, sensitive and rapid method for the determination of diisopropylfluorophosphate (DFP) in rat plasma and brain tissue using headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. A 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was selected for sampling. The main parameters affecting the SPME process such as extraction and desorption temperature, extraction and desorption time, salt addition, and fiber preheating time were optimized in each matrix to enhance the extraction efficiency of the method. The lower limits of quantitation for DFP in plasma and brain tissue were 1 ng/mL and 3 ng/g, respectively. The method showed good linearity over the range from 1-100 ng/mL in plasma and 3-300 ng/g in brain tissue with correlation coefficient (R(2)) values higher than 0.995. The precision and accuracy for intra-day and inter-day were less than 10%. The relative recoveries in plasma and brain for DFP were greater than 50%. Stability tests including autosampler and freeze and thaw were also investigated. This validated method was successfully applied to study the neurobehavioral effects of low-level organophosphate exposures. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Solid-phase microextraction method for the quantitative analysis of styrene in water

A headspace solid-phase microextraction (HS-SPME) method is developed for the determination of styrene in drinking water. Gas chromatography (GC)-mass spectrometry is utilized for qualitative analysis. A manual SPME holder with 85-microm polyacrylate coating is used to extract the styrene from water, which is determined to have good linearity (correlation coefficient r = 0.9999 for 1.00-100.00 microg/L range), a relative standard deviation of 1.9%, and a detection limit of 0.30 microg/L. This method is compared with a classical headspace GC method.     

Determination of Volatile Nitrosamines in Latex Products by HS-SPME–GC–MS

Nitrosamines which have been detected in various latex products are carcinogens. The method for determination of volatile nitrosamines in latex products was developed using a combination of headspace solid phase micro-extraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS). A carboxen/polydimethylsiloxane (CAR/PDMS) fiber was used for HS-SPME involving the following variables: (1) agitation conditions, (2) extraction temperature (3) extraction time, and (4) salt concentration. The instrument performances of three detection systems including GC combined thermal energy analyzer, nitrogen chemiluminescence detector and MS were evaluated. The agitation conditions including magnetic stirring and ultrasonication were investigated by the comparison of extraction efficiency of HS-SPME for nitrosamines. Obtained optimal detection conditions of nitrosamines were HS-SPME at 45 °C for 60 min assisted with magnetic stirring and saturated NaCl followed by GC–MS. To evaluate this method performance, the commercial products including eleven latex products (gloves, balloons and condoms) and four liquid silicone nipples were analyzed with the method. The results revealed that the method is suitable for simple and effective determination of nitrosamines in latex products. The advantage of this HS-SPME–GC–MS method is simple treatment, fast analysis, adequate sensitivity and without organic solvent.

     

Determination of fluoride in toothpaste using headspace solid-phase microextraction and gas chromatography-flame ionization detection

A new method for determination of fluoride in toothpaste employing the headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/flame ionization detection (GC/FID) has been proposed. It is a development of the method for determination of fluoride using trimethylchlorosilane (TMCS) as the derivatization reagent to form trimethylfluorosilane (TMFS), with the liquid/liquid extraction (LLE) step replaced by HS-SPME. To introduce the latter, it was necessary to determine the conditions of the reaction and to optimize the two stages of the SPME procedure: extraction and desorption. The parameters of the SPME analysis using carboxen/polydimethylsiloxane (CAR/PDMS) fiber were defined and compared with the corresponding ones for the LLE method, used as a reference. Also, these two methods were compared with respect to their linearity, precision, and accuracy. Results from toothpaste analyses using these two methods were highly correlated, indicating the potential to use the SPME extraction as an inexpensive and solventfree alternative to the LLE method.     

Determination of Estragole in Fennel Herbal Teas by HS-SPME and GC–MS

Estragole, a volatile phenylpropanoid contained in a variety of edible herbs, has been demonstrated to be genotoxic and carcinogenic, and its addition as a flavoring substance to foodstuffs has been banned by the regulatory bodies of the European Union. Fast and accurate analytical methods for its determination in herbs are thus necessary to assess the dietary exposure of this substance in humans and, in particular, to sensitive groups. In the present study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC–MS) was applied for determination of estragole in infusions from different widely used commercial herbal teas based on Foeniculum vulgare (fennel) seeds. The optimized HS-SPME extraction conditions involved the use of a polydimethylsiloxane fiber exposed to the herbal infusion for 20 min at 50°C followed by GC–MS analysis. The method was fully validated for linearity, sensitivity, accuracy, and precision and applied to real samples; the level of estragole in infusions of commercial fennel seed teas was found to be within 50–250 µ`^?1.     

Rapid monitoring of sulfur mustard degradation in solution by headspace solid-phase microextraction sampling and gas chromatography mass spectrometry

A method using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography/mass spectrometry (GC/MS) analysis has been developed to gain insight into the degradation of the chemical warfare agent sulfur mustard in solution. Specifically, the described approach simplifies the sample preparation for GC/MS analysis to provide a rapid determination of changes in sulfur mustard abundance. These results were found to be consistent with those obtained using liquid-liquid extraction (LLE) GC/MS. The utility of the described approach was further demonstrated by the investigation of the degradation process in a complex matrix with surfactant added to assist solvation of sulfur mustard. A more rapid reduction in sulfur mustard abundance was observed using the HS-SPME approach with surfactant present and was similar to results from LLE experiments. Significantly, this study demonstrates that HS-SPME can simplify the sample preparation for GC/MS analysis to monitor changes in sulfur mustard abundance in solution more rapidly, and with less solvent and reagent usage than LLE.     

Multiple headspace solid-phase microextraction for eliminating matrix effect in the simultaneous determination of haloanisoles and volatile phenols in wines

This paper proposes a multiple headspace solid-phase microextraction (MHS-SPME) method coupled to gas chromatography-tandem mass spectrometry detection (GC/MS/MS) for the simultaneous determination of 2,4,6-trichloroanisole, 2,3,4,6-tetrachloroanisole, pentachloroanisole, 2,4,6-tribromoanisole, 4-ethylphenol, 4-ethylguaiacol, 4-vinylphenol and 4-vinylguaiacol in wines. These compounds are involved in the presence of "cork taint" and Brett character in wines. The MHS-SPME method is a modification of SPME developed for quantitative analysis that avoids possible matrix effects based on an exhaustive analyte extraction from the sample. After demonstrating the existence of matrix effect in the analysis of the target compounds by HS-SPME with a divinylbenzene/Carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre, the MHS-SPME method was developed and validated. The proposed method showed satisfactory linearity, precision and detection limits, all below the odour detection thresholds of the compounds in wine matrices. Good recoveries were observed for all compounds, always above 90%, and the repeatability obtained was considered acceptable, ranging between 2 and 11%. After checking the applicability of the method by comparing the results recorded with those obtained with the standard addition method, the method was applied successfully to the analysis of wine samples. To our knowledge, this is the first time that MHS-SPME combined with GC/MS/MS has been applied to simultaneously determine haloanisoles and volatile phenols in wine.     

Determination of different recreational drugs in hair by HS-SPME and GC/MS

A simple procedure combining headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC/MS) to detect and quantify amphetamines, ketamine, methadone, cocaine, cocaethylene and ∆⁹-tetrahydrocannabinol (THC) in hair is described. This procedure allows, in a single sample, even scant, analysis of drugs requiring different analytical conditions. A hair sample (10 mg) is washed and subjected to acidic hydrolysis. Then the HS-SPME is carried out (10 min at 90 °C) for amphetamines, ketamine, methadone, cocaine and cocaethylene. For derivatization of analytes, the fibre is introduced into the headspace of another closed vial containing acetic anhydride. After a chromatographic run, an alkaline hydrolysis for THC analysis is carried out in the same vial containing the hair sample previously used. For adsorption, the solid-phase microextraction needle is inserted into the headspace of the vial and the fibre is exposed for 30 min at 150 °C. For derivatization of analytes, the fibre is introduced into the headspace of another closed vial containing N-methyl-N-(trimethylsilyl)trifluoroacetamide. The GC/MS parameters were the same for both chromatographic runs. The linearity was proved to be between 0.01 and 10.00 ng/mg. The repeatability (intra- and interday precision) was below 10% as the coefficient of variation for all compounds. The accuracy, as the relative recovery, was 96.2–103.5% (spiked samples) and 88.6–101.7% (quality control sample). The limit of detection ranged from 0.01 to 0.12 ng/mg, and the limit of quantification ranged from 0.02 to 0.37 ng/mg. Application of the procedure to real hair samples is described. To the best of our knowledge, the proposed procedure combining HS-SPME and GC/MS is the first one be to successfully applied to the simultaneous determination of most of the common recreational drugs, including THC, in a single hair sample.     

Trace level determination of trichloroethylene in biological samples by headspace solid-phase microextraction gas chromatography/negative chemical ionization mass spectrometry

A gas chromatography/negative chemical ionization mass spectrometry (GC/NCIMS) method using headspace solid-phase microextraction (HS-SPME) was developed for the determination of trichloroethylene (TCE) in blood, liver, kidney, lung and brain. The method was optimized with respect to several parameters including extraction time, extraction temperature, desorption time and salt addition. The method showed good linearity over the range of 0.025-25 ng/mL in blood and 0.075-75 ng/g in tissues with correlation coefficient (R2) values higher than 0.99. The precision and accuracy for intra-day and inter-day measurements were less than 10%. The relative recoveries of all matrices were greater than 52%. Samples showed no significant loss during 8 h in the autosampler and following three freeze/thaw cycles. Validation results demonstrated that selected-ion monitoring of the 35Cl and 37Cl isotopes using NCI resulted in reliable and sensitive quantitation. This validated method was successfully applied to study the toxicokinetics of TCE following oral administration of extremely low doses of this potential human carcinogen to small test animals (rats).     

Determination of Volatile Nitrosamines in Latex Products by HS-SPME�CGC�CMS

Nitrosamines which have been detected in various latex products are carcinogens. The method for determination of volatile nitrosamines in latex products was developed using a combination of headspace solid phase micro-extraction (HS-SPME) and gas chromatography?Cmass spectrometry (GC?CMS). A carboxen/polydimethylsiloxane (CAR/PDMS) fiber was used for HS-SPME involving the following variables: (1) agitation conditions, (2) extraction temperature (3) extraction time, and (4) salt concentration. The instrument performances of three detection systems including GC combined thermal energy analyzer, nitrogen chemiluminescence detector and MS were evaluated. The agitation conditions including magnetic stirring and ultrasonication were investigated by the comparison of extraction efficiency of HS-SPME for nitrosamines. Obtained optimal detection conditions of nitrosamines were HS-SPME at 45 °C for 60 min assisted with magnetic stirring and saturated NaCl followed by GC?CMS. To evaluate this method performance, the commercial products including eleven latex products (gloves, balloons and condoms) and four liquid silicone nipples were analyzed with the method. The results revealed that the method is suitable for simple and effective determination of nitrosamines in latex products. The advantage of this HS-SPME?CGC?CMS method is simple treatment, fast analysis, adequate sensitivity and without organic solvent.     

Rapid determination of acetone in human blood by derivatization with pentafluorobenzyl hydroxylamine followed by headspace liquid-phase microextraction and gas chromatography/mass spectrometry

In the current work, a simple, rapid, accurate and inexpensive method was developed for the determination of acetone in human blood. The proposed method is based on derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA), followed by headspace liquid-phase microextraction (HS-LPME) and gas chromatography/mass spectrometry (GC/MS). In the present method, acetone in blood samples was derivatized with PFBHA and acetone oxime formed in several seconds. The formed oxime was enriched by HS-LPME using the organic solvent film (OSF) formed in a microsyringe barrel as extraction interface. Finally, the enriched oxime was analyzed by GC/MS in electron ionization (EI) mode. HS-LPME parameters including solvent, syringe plunger withdrawal rate, sampling volume, and extraction cycle were optimized and the method reproducibility, linearity, recovery and detection limit were studied. The proposed method was applied to determination of acetone in diabetes blood and normal blood. It has been shown that derivatization with HS-LPME and GC/MS is an alternative method for determination of the diabetes biomarker, acetone, in blood samples.     

Determination of pyrethroid,organophosphate and organochlorine pesticides in water by headspace solid-phase microextraction

Simultaneous determination of pyrethroid, organophosphate (OP) and organochlorine (OC) pesticides in water was achieved with headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron-capture detection (GC-ECD). The parameters affecting HS-SPME of pesticides from water were optimized, including extraction temperature, sample and headspace volumes, and sodium chloride amounts. The effects of desorption temperature, desorption time, and position of the fibre in the GC inlet were also investigated. Extraction temperature was the most important factor affecting the recoveries of analytes, and the optimized temperature was 96°C. The addition of salt did not increase extraction efficiencies of the pesticides from the water. The optimized desorption conditions in the GC were as follows: desorption time of 10?min; desorption temperature of 260°C; and a 2?cm position of the fibre in the inlet. The method detection limits were in the low-ng/L level with a linearity range of 50–1000?ng/L for the OCs, 50–5000?ng/L for the OP, and 50–20?000?ng/L for the pyrethroids. These data demonstrated that HS-SPME is a sensitive method for the determination of pyrethroid, OC, and OP pesticides in water.