Yoshikatsu Takazawa

Stir bar sorptive extraction and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry for ultra-trace analysis of organochlorine pesticides in river water

A method for the determination of ultra-trace amounts of organochlorine pesticides (OCPs) in river water was developed by using stir bar sorptive extraction (SBSE) followed by thermal desorption and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (SBSE-TD-GC×GC-HRTOF-MS). SBSE conditions such as extraction time profiles, phase ratio (β: sample volume/polydimethylsiloxane (PDMS) volume), and modifier addition, were examined. Fifty milli-liter sample including 10% acetone was extracted for 3 h using stir bars with a length of 20 mm and coated with a 0.5 mm layer of PDMS (PDMS volume, 47 μL). The stir bar was thermally desorbed and subsequently analyzed by GC×GC-HRTOF-MS. The method showed good linearity over the concentration range from 50 to 1000 pg L(-1) or 2000 pg L(-1) for all analytes, and the correlation coefficients (r(2)) were greater than 0.9903 (except for β-HCH, r(2)=0.9870). The limit of detection (LOD) ranged from 10 to 44 pg L(-1). The method was successfully applied to the determination of 16 OCPs at pg L(-1) to ng L(-1) in river water. The results agree fairly well with the values obtained by a conventional liquid-liquid extraction (LLE)-GC-HRMS (selected ion monitoring: SIM) method using large sample volume (20 L). The method also allows screening of non-target compounds, e.g. pesticides and their degradation products, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pharmaceuticals and personal care products (PPCPs) and metabolites in the same river water sample, by using full spectrum acquisition with accurate mass in GC×GC.

Global and selective detection of organohalogens in environmental samples by comprehensive two-dimensional gas chromatography–tandem mass spectrometry and high-resolution time-of-flight mass spectrometry

We successfully detected halogenated compounds from several kinds of environmental samples by using a comprehensive two-dimensional gas chromatograph coupled with a tandem mass spectrometer (GC×GC-MS/MS). For the global detection of organohalogens, fly ash sample extracts were directly measured without any cleanup process. The global and selective detection of halogenated compounds was achieved by neutral loss scans of chlorine, bromine and/or fluorine using an MS/MS. It was also possible to search for and identify compounds using two-dimensional mass chromatograms and mass profiles obtained from measurements of the same sample with a GC×GC-high resolution time-of-flight mass spectrometer (HRTofMS) under the same conditions as those used for the GC×GC-MS/MS. In this study, novel software tools were also developed to help find target (halogenated) compounds in the data provided by a GC×GC-HRTofMS. As a result, many dioxin and polychlorinated biphenyl congeners and many other halogenated compounds were found in fly ash extract and sediment samples. By extracting the desired information, which concerned organohalogens in this study, from huge quantities of data with the GC×GC-HRTofMS, we reveal the possibility of realizing the total global detection of compounds with one GC measurement of a sample without any pre-treatment.

Selective extraction of halogenated compounds from data measured by comprehensive multidimensional gas chromatography/high resolution time-of-flight mass spectrometry for non-target analysis of environmental and biological samples.

We developed a method that selectively extracts a subset from comprehensive 2D gas chromatography (GC×GC) and high-resolution time-of-flight mass spectrometry (HRTOFMS) data to detect and identify trace levels of organohalogens. The data were obtained by measuring several environmental and biological samples, namely fly ash, soil, sediment, the atmosphere, and human urine. For global analysis, some samples were measured without purification. By using our novel software, the mass spectra of organochlorines or organobromines were then extracted into a data subset under high mass accuracy conditions that were approximately equivalent to a mass resolution of 6000 for some samples. Mass defect filtering as pre-screening for the data extraction was very effective in removing the mass spectra of hydrocarbons. Those results showed that data obtained with HRTOFMS are valuable for global analysis of organohalogens, and probably of other compounds if specific data extraction methods can be devised.

Thermal desorption - comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry for determination of trace polycyclic aromatic hydrocarbons and their derivatives.

We developed a highly sensitive method for determination of polycyclic aromatic hydrocarbons (PAHs) and their derivatives (oxygenated, nitrated, and methylated PAHs) in trace particulate samples by using thermal desorption followed by comprehensive two-dimensional gas chromatography coupled with tandem mass spectrometry (TD-GC×GC-MS/MS) with a selected reaction monitoring mode. The sensitivity of TD-GC×GC-MS/MS was greater than that of TD-GC-HRMS and TD-GC×GC-QMS by one or two orders of magnitude. The instrumental detection limits were 0.03-0.3pg (PAHs), 0.04-0.2pg (oxygenated PAHs), 0.03-0.1pg (nitrated PAHs), and 0.01-0.08pg (methylated PAHs). For small amounts (10-20μg) of standard reference materials (SRMs 1649a and 1650b, urban dust and diesel exhaust particles, respectively), the values measured by using TD-GC×GC-MS/MS agreed with the certified or reference values within a factor of two. Major analytes were quantified successfully by TD-GC×GC-MS/MS from diesel exhaust nanoparticles (18-32nm) and accumulation-mode particles (100-180nm) from an 8-L diesel engine with no exhaust after-treatment system. The PAH profiles differed among driving conditions but they did not differ markedly among the particle sizes.

Rapid automatic identification and quantification of compounds in complex matrices using comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry with a peak sentinel tool.

Comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) is a powerful tool for comprehensive analysis of organic pollutants. In this study, we developed a powerful analytical method using GC×GC for rapid and accurate identification and quantification of compounds in environmental samples with complex matrices. Specifically, we have developed an automatic peak sentinel tool, T-SEN, with free programming software, R. The tool, which consists of a simple algorithm for on peak finding and peak shape identification, allows rapid screening of target compounds, even for large data sets from GC×GC coupled to high resolution time of flight mass spectrometry (HRTOFMS). The software tool automatically assigns and quantifies compounds that are listed in user databases. T-SEN works on a typical 64 bit workstation, and the reference calculation speed is 10-20 min for approximately 170 compounds for peak finding (five ion count setting) and integration from 1-2GB of sample data acquired by GC×GC-HRTOFMS. We analyzed and quantified 17 PCDD/F congeners and 24 PCB congeners in a crude lake sediment extract by both GC×GC coupled to quadrupole mass spectrometry (qMS) and GC×GC-HRTOFMS with T-SEN. While GC×GC-qMS with T-SEN resulted in false identification and inaccurate quantification, GC×GC-HRTOFMS with T-SEN provided correct identification and accurate quantification of compounds without sample pre-treatment. The differences between the values measured by GC×GC-HRTOFMS with T-SEN and the certified values for the certified reference material ranged from 7.3 to 36.9% for compounds with concentrations above the limit of quantification. False positives/negatives were not observed, except for when co-elution occurred. The technique of GC×GC-HRTOFMS in combination with T-SEN provides rapid and accurate screening and represents a powerful new approach for comprehensive analysis.

Selective and comprehensive analysis of organohalogen compounds by GC × GC–HRTofMS and MS/MS

Thousands of organohalogen compounds, including hazardous chemicals such as polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs), were selectively and simultaneously detected and identified with simple, or no, purification from environmental sample extracts by using several advanced methods. The methods used were software extraction from two-dimensional gas chromatography–high-resolution time-of-flight mass spectrometry (GC × GC–HRTofMS) data, measurement by negative chemical ionization with HRTofMS, and neutral loss scanning (NLS) with GC × GC–MS/MS. Global and selective detection of organochlorines and bromines in environmental samples such as sediments and fly ash was achieved by NLS using GC × GC–MS/MS (QQQ), with the expected losses of 35Cl and 79Br. We confirmed that negative chemical ionization was effective for sensitive and selective ionization of organohalogens, even using GC × GC–HRTofMS. The 2D total ion chromatograms obtained by using negative chemical ionization and selective extraction of organohalogens using original software from data measured by electron impact ionization were very similar; the software thus functioned well to extract organohalogens. Combining measurements made by using these different methods will help to detect organohalogens selectively and globally. However, to compare the data obtained by individual measurements, the retention times of the peaks on the 2D chromatograms need to match.

A method to circumvent the lot number of activated carbon affecting the performance of activated carbon silica gel columns used for cleanup of blood samples for analysis of 29 hazardous organochlorine compounds

We have previously described the use of a tandem simplified multilayer silica gel-activated carbon dispersed silica gel (TS-ML-AC) column for the cleanup of blood samples for the analysis of 29 hazardous organochlorine compounds (OCs)--the 17 major polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) and 4 non-ortho- and 8 mono-ortho-polychlorinated biphenyls (PCBs). We noted that the performance of the activated carbon-silica gel (ACS) column (lower column) varied with the lot number of the ACS. In this study, we compared the elution profiles of OCs eluted on 5 ACS columns, each with a different ACS lot number, and found that only mono-ortho-PCBs #114 and #123 were affected by lot number. The problem was that the 50 ml of n-hexane required to elute all the OCs from the simplified multilayer silica gel (MLS) column (upper column) into the AC column (lower column) also eluted varying amounts of PCBs #114 and #123 from the ACS column by ACS lot number. Although we could prevent PCBs #114 and #123 from being eluted from the ACS column by reducing the n-hexane volume to 10 ml, this volume was not sufficient to elute all the OCs from the MLS column. We solved this by separating the two columns; the sample solution was eluted with 50 ml of n-hexane from the MLS column, this eluate was concentrated to about 0.3 ml using a rotary evaporator, and then the concentrated solution was cleaned up on the ACS column. The recovery rates of #114 and #123 from blood samples were above 70% and the relative standard deviations of their concentration were below 10%, irrespective of the lot number, compared with recovery rates of 45-79% for #114 and 59-89% for #123, and relative standard deviations of their concentration above 15% when 50 ml of n-hexane was run through the tandem column. Our modified method affords reliable and reproducible cleanup of blood samples for analysis of 29 OCs, irrespective of the ACS lot number.