Shigeki Daishima

Determination of chloramphenicol residues in fish meats by liquid chromatography-atmospheric pressure photoionization mass spectrometry

A liquid chromatography-atmospheric pressure photoionization (APPI) mass spectrometry method was developed for the determination of chloramphenicol (CAP) in fish meats (young yellowtail and flatfish). For the optimization of APPI, several APPI ion source parameters and mobile phases were investigated. CAP with APPI using the optimized parameters gave simple mass spectra and a strong signal corresponding to [M-H]- was observed. Further, APPI was compared with atmospheric pressure chemical ionization (APCI) and APPI gave similar results in terms of structural information and a better signal-to-noise ratio. The samples were extracted with acetonitrile and evaporated to dryness followed by a clean-up step using the liquid-liquid distribution between acetonitrile and n-hexane. The mean recoveries of chloramphenicol from a young yellowtail meat and a flatfish meat spiked at 0.1-2 ng/g were 89.3-102.5 and 87.4-94.8%, respectively. The limit of detection (signal-to-noise ratio = 3) of the young yellowtail meat and the flatfish meat were 0.1 and 0.27 ng/g.

Determination of stale-flavor carbonyl compounds in beer by stir bar sorptive extraction with in-situ derivatization and thermal desorption-gas chromatography-mass spectrometry.

A method for the determination of stale-flavor carbonyl compounds including E-2-octenal, E-2-nonenal, E,Z-2,6-nonadienal and E,E-2,4-decadienal in beer was developed using stir bar sorptive extraction (SBSE) with in-situ derivatization followed by thermal desorption-GC-MS analysis. The derivatization conditions with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and the SBSE conditions--sampling mode, salt addition, sample volume, polydimethylsiloxane volume (sample/polydimethylsiloxane phase ratio) and extraction time--were examined. The method showed good linearity over the concentration range from 0.1 to 10 ng ml(-1) for all analytes and the correlation coefficients were higher than 0.9993. The limits of detection ranged from 0.021 to 0.032 ng ml(-1) for all analytes. The recoveries (98-101%) and precision (RSD 2.4-7.3%) of the method were examined by analyzing beer samples fortified at the 0.5-ng ml(-1) level. The method was successfully applied to low-level concentration samples.

Determination of estrogens in river water by gas chromatography–negative-ion chemical-ionization mass spectrometry

A method for the determination of estrogens (17alpha-estradiol, 17beta-estradiol, estrone, ethynyl estradiol, and estriol) as pentafluorobenzyl-trimethylsilyl (PFB-TMS) derivatives by gas chromatography-mass spectrometry (GC-MS) with negative-ion chemical-ionization (NICI) is described. The NICI of all the derivatives produced an intense [M-PFB]- ion as the base peak. The reagent gas (methane) flow-rate and the ion source temperature were determined to be 2.0 ml/min and 240 degrees C, respectively, for the optimized NICI-selected ion monitoring (SIM) conditions. The sensitivities of the PFB-TMS derivatives in the NICI mode were 8.0-130 times higher than those of the PFB-TMS derivatives in electron ionization (EI) mode, and 12-25 times higher than those of all the TMS derivatives in the EI mode. This method was applied to the analysis of estrogens in river water using a solid-phase extraction as the sample preparation. The recoveries of the target chemicals from a river-water sample spiked with standards at 2 ng/l level were 85.8-126.5% (RSD, 6.2-13.0%). The methodical detection limits ranged from 0.10 to 0.28 ng/l.

Determination of trace amounts of off-flavor compounds in drinking water by stir bar sorptive extraction and thermal desorption GC-MS

A method for the determination of trace amounts of off-flavor compounds including 2-methylisoborneol, geosmin and 2,4,6-trichloroanisole in drinking water was developed using the stir bar sorptive extraction technique followed by thermal desorption-GC-MS analysis. The extraction conditions such as extraction mode, salt addition, extraction temperature, sample volume and extraction time were examined. Water samples (20, 40 and 60 ml) were extracted for 60-240 min at room temperature (25 degrees C) using stir bars with a length of 10 mm and coated with a 500 microm layer of polydimethylsiloxane. The extract was analyzed by thermal desorption-GC-MS in the selected ion monitoring mode. The method showed good linearity over the concentration range from 0.1 or 0.2 or 0.5 to 100 ng l(-1) for all the target analytes, and the correlation coefficients were greater than 0.9987. The detection limits ranged from 0.022 to 0.16 ng l(-1). The recoveries (89-109%) and precision (RSD: 0.80-3.7%) of the method were examined by analyzing raw water and tap water samples fortified at the 1 ng l(-1) level. The method was successfully applied to low-level samples (raw water and tap water).

Analysis of volatile sulphur compounds in breath by gas chromatography-mass spectrometry using a three-stage cryogenic trapping preconcentration system

A method for the determination of trace volatile sulphur compounds (VSCs) including methanethiol, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) at low ppbv (volume/volume) in breath has been developed using a large volume preconcentration technique prior to capillary GC-MS analysis. The breath sample was collected in a 6-1 fused-silica-lined stainless steel canister and introduced into the three-stage cryogenic trapping preconcentration system by GC-MS in the total ion monitoring (scan) mode. The water condensation effect of breath sample inside the canister, which is due to the difference between human body temperature and laboratory temperature, was examined. The condensed water in the fused-silica-lined canister at 24 degrees C did not affect the recoveries of VSCs within 12 h. As this three-stage cryogenic trapping preconcentration technique made it possible to remove excess water [relative humidity (RH) >95%] and carbon dioxide (3.8%) without loss of the VSCs, more than 400 ml of the breath sample could be concentrated. The detection limits of methanethiol, DMS and DMDS in a breath sample using this method were 0.13, 0.09 and 0.15 ppbv, respectively.

Determination of polycyclic aromatic hydrocarbons by liquid chromatography–electrospray ionization mass spectrometry using silver nitrate as a post-column reagent

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) using silver nitrate as a post-column reagent has been used for the determination of 10 polycyclic aromatic hydrocarbons (PAHs) in river water. In this method, after all the PAHs were separated by reversed-phase liquid chromatography, analytes formed complexes with silver cation by mixing with silver nitrate solution. The complexes then transfer the molecular ion, [M]+, of the PAHs by charge transfer using in source collision-induced dissociation. The positive ion ESI mass spectra of all PAHs tested in this study showed [M]+ as the base peak and abundant [M+Ag]+, [2M+Ag]- with very weak or no [2M+Ag]+. For the sample extraction, several solid-phase extraction parameters using the blue-chitin column were optimized. The limits of detection (S/N=3) of all PAHs for the spiked river water sample ranged from 0.001 to 0.03 ng/ml, and the detector responses were linear up to I ng/ml (correlation coefficients > or =0.0998). Repeatability and reproducibility were in the range from 4.3 to 6.8% and from 6.2 to 9.5%, respectively.

Trace analysis of pesticide residues in water by high-speed narrow-bore capillary gas chromatography–mass spectrometry with programmable temperature vaporizer

A method for the rapid trace analysis of 17 residual pesticides in water by narrow-bore capillary (I.D. 100 microm) gas chromatography-mass spectrometry (GC-MS) using a programmable temperature vaporizer (PTV) was discussed. The method consisted of a large-volume injection (40 microl) by a PTV, high-speed analysis using a narrow-bore capillary column and MS detection. The PTV with solvent vent mode was very useful for large-volume injection into a narrow-bore capillary column because the injected solvent volume could be reduced to less than 2 microl. The analysis time was 8.5 min [less than 50% of the analysis time using conventional columns (I.D. 250 microm)]. A 10-ml volume of river water was extracted by dichloromethane (4 ml), and then the extract was condensed to 1 ml. This extract was analyzed. Mean recoveries for river water spiked at 100 pg/ml ranged from 83.4 to 96.7%. The limit of detections of the 17 pesticides ranged from 1 to 100 pg/ml.

Automated on-line in-tube solid-phase microextraction followed by liquid chromatography/electrospray ionization-mass spectrometry for the determination of chlorinated phenoxy acid herbicides in environmental waters

A method for the determination of six chlorinated phenoxy acid herbicides in river water was developed using in-tube solid-phase microextraction (SPME) followed by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from a sample directly into an open tubular capillary by repeated draw/eject cycles of the sample solution. Simple mass spectra with strong signals corresponding to [M-H]- and [M-RCOOH]- were observed for all herbicides tested in this study. The best separation of these compounds was obtained with a C18 column using linear gradient elution with a mobile phase of acetonitrile-water containing 5 mmol l-1 dibutylamine acetate (DBA). To optimize the extraction of herbicides, several in-tube SPME parameters were examined. The optimum extraction conditions were 25 draw/eject cycles of 30 microliters of sample in 0.2% formic acid (pH 2) at a flow rate of 200 microliters min-1 using a DB-WAX capillary. The herbicides extracted by the capillary were easily desorbed by 10 microliters acetonitrile. Using in-tube SPME-LC/ESI-MS with time-scheduled selected ion monitoring, the calibration curves of herbicides were linear in the range 0.05-50 ng ml-1 with correlation coefficients above 0.999. This method was successfully applied to the analysis of river water samples without interference peaks. The limit of quantification was in the range 0.02-0.06 ng ml-1 and the limit of detection (S/N = 3) was in the range 0.005-0.03 ng ml-1. The repeatability and reproducibility were in the range 2.5-4.1% and 6.2-9.1%, respectively.

Determination of haloacetic acids in water by liquidchromatography-electrospray ionization-mass spectrometry using volatileion-pairing reagents

A method for the determination of nine haloacetic acids (HAAs) in drinking water was developed using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) employing volatile ion-pairing reagents. The separation and sensitivity of all the compounds were optimized using three volatile amines (di-n-butylamine, N,N-dimethyl-n-butylamine and tri-n-butylamine) and optimized conditions were obtained with 5 mmol l−1 dibutylamine (DBA). The sample preparation of this method was very simple involving filtration of the sample and the addition of 100 mmol l−1 DBA. With DBA as ion-pairing reagent and propan-2-ol as mobile phase modifier, a water sample spiked with 0.1–100 ng ml−1 of nine HAAs could be determined by LC-ESI-MS using time-scheduled selected ion monitoring. The correlation coefficients for all target analytes were higher than 0.999. The detection limits ranged from 24 to 118 pg ml−1. The repeatability and reproducibility were in the range 1.5–9.1% and 5.9–12.4%, respectively.

Analysis of anatoxin-a in freshwaters by automated on-line derivatization–liquid chromatography–electrospray mass spectrometry

Anatoxin-a is a toxin produced from cyanobacterial blooms in freshwaters. In order to determine trace anatoxin-a in freshwaters, an automated on-line derivatization procedure with fluorenyl methylchloroformate using liquid chromatography-electrospray ionization mass spectrometry was developed. Anatoxin-a was extracted using solid-phase extraction with adequate recovery (75.7+/-7.2%, n=6) at 20 ng/l. The limits of quantification and detection were calculated to be 15.2 ng/l and 2.1 ng/l, respectively, using selected ion monitoring.