Yoshihiro Saito

Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples

A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography-mass spectrometry (GC-MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.

Needle-type extraction device for the purge and trap analysis of 23 volatile organic compounds in tap water.

We developed a rapid determination technique for trace volatile organic compounds (VOCs) in tap water by introducing a novel needle-type extraction device coupled to a purge-and-trap method. To extract a wide range of VOCs, a new extraction needle containing particles of divinylbenzene and activated carbon was developed in this study. During the active sampling of the headspace gas in a glass vial by the extraction needle, pure N2 gas was used for purging the aqueous sample. After the optimization of several experimental parameters, such as the addition of the salt and conditions of dry purging and desorption, the extraction performance of the device and method was evaluated for 23 VOCs that are typically found in tap water samples. The quantification limits of the method were 0.6 μg/L for 1,1-dichloroethylene and less than 0.5 μg/L for other VOCs, with good repeatability being confirmed for all the target compounds. Taking advantage of the excellent recovery of VOCs, the determination of VOCs in real tap water samples was carried out successfully. Because the developed method does not require sample heating and/or cryogenic focusing, simple and rapid analyses can be performed along with satisfactory sensitivity for typical tap water samples.

Determination of breath isoprene and acetone concentration with a needle-type extraction device in gas chromatography–mass spectrometry

BACKGROUNDnIsoprene in human breath is said to be related to cholesterol metabolism, and the possibility of the correlations with some clinical parameters has been studied. However, at this stage, no clear benefit of breath isoprene has been reported for clinical diagnosis. In this work, isoprene and acetone concentrations were measured in the breath of healthy and obese subjects using a needle-type extraction device for subsequent analysis in gas chromatography-mass spectrometry (GC-MS) to investigate the possibility of these compounds as an indicator of possible diseases.nnnMETHODSnAfter measuring intraday and interday variations of isoprene and acetone concentrations in breath samples of healthy subjects, their concentrations were also determined in 80 healthy and 17 obese subjects. In addition, correlation between these breath concentrations and the blood tests result was studied for these healthy and obese subjects.nnnRESULTSnThe results indicated successful determination of breath isoprene and acetone in this work, however, no clear correlation was observed between these measured values and the blood test results.nnnCONCLUSIONSnBreath isoprene concentration may not be a useful indicator for obesity or hypercholesterolemia.

Determination of very volatile organic compounds in water samples by purge and trap analysis with a needle-type extraction device.

Very volatile organic compounds (VVOCs), such as methanol, acetaldehyde, ethanol, acetone, acetonitrile, and dichloromethane, were extracted from water samples using a needle-type extraction device based on purge and trap analysis. The extracted analytes could then be determined by gas chromatography-mass spectrometry. By introducing carbon molecular sieves as the extraction medium, aqueous VVOCs could be successfully extracted using the extraction needle. The limit of quantification for methanol, acetaldehyde, ethanol, acetone, acetonitrile, and dichloromethane were 75, 75, 7.5, 0.5, 10 and 0.5 μg/L, respectively. This newly developed method was also successfully applied to the determination of VVOCs in commercial samples, such as fruit juice.

A novel miniaturized extraction capillary for determining gaseous formaldehyde by high-performance liquid chromatography

A novel miniaturized sample extraction capillary was developed to provide a simple and sensitive method for analyzing gaseous formaldehyde (FA) using conventional high-performance liquid chromatography (HPLC). The extraction capillary was prepared by packing silica gel particles in a stainless steel capillary with a 1.6-mm o.d. Before the gaseous samples were collected, the silica gel particles were impregnated with a derivatizing reagent 2,4-dinitrophenylhydrazine (DNPH) by passing a solution of DNPH through the extraction capillary. FA was derivatized to form the corresponding hydrazone during the active sampling of a gaseous sample, and the derivative was sorbed by the silica gel. The capillary was then directly connected to a six-port valve, and desorption from the capillary and injection into the HPLC were achieved simultaneously by passing a solvent through the capillary. The run-to-run and device-to-device variabilities, as relative standard deviations, were both less than 6.9xa0%. The limit of detection for FA was 2.5xa0ng/L using a sampling volume of 100xa0mL, and a sample collection time of 2xa0min. Acetaldehyde and acetone in a gaseous sample could also be simultaneously extracted and determined using this method. The applicability of the developed method for determining FA in real indoor air samples was confirmed by comparing the results obtained using the proposed method and a conventional sample preparation method. The developed method enables the rapid and simple sample preparation of gaseous FA and gives a good level of sensitivity.

Determination of Formaldehyde in Aqueous Samples with a Miniaturized Extraction Capillary Coupled to High-Performance Liquid Chromatography

A novel analytical method for determining formaldehyde (FA) in aqueous samples was developed with a miniaturized extraction capillary in high-performance liquid chromatography (HPLC). The extraction capillary was prepared by packing silica gel particles in a stainless steel capillary of 0.8 mm i.d. and 1.6 mm o.d. A derivatization reagent of 2,4-dinitrophenylhydrazine (DNPH) was impregnated on the silica gel particles by pumping a solution of DNPH to the capillary. Two extraction methods; dynamic extraction and purge-and-trap (PT) methods, were investigated for derivatizing and extracting FA from water samples onto the silica gel in the extraction capillary. The extraction capillary was directly connected to a six-port valve, and then desorption of the derivative from the capillary and injection to conventional HPLC system were simultaneously achieved with a flow of acetonitrile through the capillary. In the dynamic extraction, FA was determined with a simple sample preparation procedure, and the limit of detection (LOD) was 18 μg L(-1) at a sample volume of 20 mL, while several limitations were found in the method, such as bleeding of the derivatization reagent and the corresponding derivatized FA from the capillary during the sample load/extraction process. The sensitivity was significantly improved by introducing a PT technique, where the LOD was 6.9 μg L(-1) at a sample volume of 20 mL with a sampling time of approximately 20 min. With the PT method, successful recoveries of FA were confirmed for spiked tap water, river water and fruit juice samples.