[Dust collection efficiency of commercial gas collection tubes].

OBJECTIVES: Gas sampling tubes are essential tools for the evaluation of air quality in work environments. It adsorbs toxic gaseous matters onto the surface of various granular adsorbents, such as silica gel or activated carbon packed in a thin glass tube, for quantitative analysis by gas chromatography. Currently, most of the semi-volatile matters are evaluated via aerosol filtration or solid-phase gas adsorption depending on the main phase of the substances; however, only a few substances have a sampling protocol regarding both solid and gaseous phases. Therefore, semi-volatile components evaluated by the solid-phase adsorption may result in the underestimation of the component concentrations due to particulate components passing through and remaining in the adsorbent. To highlight issues on sampling of semi-volatile matters by the solid-phase adsorption method, the collection efficiency of aerosol particles by 17 commercial gas sampling tubes were measured via pressure drop. METHODS: To measure the particle collection efficiency of the gas collection tubes, precise control and dilution of the aerosol particle monitors are essential. However, we cannot apply typical filter test methods at a lower filtration flow rate than that of the aerosol particles monitors. Therefore, we developed a new experimental method that considers flow adjustment between the aerosol monitors. By assuming two specific particle size distributions and five inlet conditions, the collection efficiencies of total mass particles are estimated. From the gas-particle partitioning ratio of 16 polycyclic aromatic hydrocarbons (PAHs) in a coal tar pitch manufacturing industry, the underestimation of the concentration of semi-volatile matters using the gas collection tubes has been discussed. RESULTS: The aerosol particles were collected in all kinds of layers in the gas sampling tubes, such as in the glass wool cap, gas adsorbent granular bed, and polyurethane foam. Furthermore, the collection efficiency curve of all 17 gas sampling tubes tested showed similar trends; a valley around particle sizes ranging from 0.2-0.3 µm between high collection zones below 0.1 µm and above 1 µm was observed. The observations suggested granular bed filters collection mechanisms such as inertial impaction, Brownian diffusion, gravity, and interception as same as air filters. CONCLUSIONS: Solid-phase collection can underestimate the concentrations of multi-phase matters. Thus, we wish to highlight the importance of solid-phase collection methods along with filtration collection methods to collect all phases of semi-volatile matters.

Development of an analytical method for the determination of arsenic in urine by gas chromatography-mass spectrometry for biological monitoring of exposure to inorganic arsenic.

OBJECTIVES: The purpose of this study was to develop an analytical method for the simultaneous determination of inorganic arsenic [As(III) and As(V)] and monomethylarsonic acid (MMA) in urine by gas chromatography-mass spectrometry (GC-MS) for the biological monitoring of exposure to inorganic arsenic. METHODS: Arsenic compounds (after reduction of arsenic to the trivalent state) were derivatized with 2,3-dimercapto-1-propanol and then analyzed using a GC-MS. The proposed method was validated according to the US Food and Drug Administration guidelines. The accuracy of the proposed method was confirmed by analyzing Standard Reference Material (SRM) 2669 (National Institute of Standards and Technology). RESULTS: Calibration curves showed linearity in the range 1-100 µg/l for each of the arsenic species, with correlation coefficients of >0.999. For each of the arsenic species, the limits of detection and quantification were 0.2 µg/l and 1 µg/l, respectively. The recoveries were 96-100%, 99-102% and 99-112% for As(III), As(V) and MMA, respectively. Intraday accuracy and precision were 82.7-99.8% and 0.9-7.4%, respectively. Interday accuracy and precision were 81.3-100.0% and 0.8-9.9%, respectively. The analytical values of SRM 2669 obtained by the proposed method were sufficiently accurate. CONCLUSIONS: The proposed method overcame the disadvantages of high-performance liquid chromatography with inductively coupled plasma mass spectrometry. It was a robust, selective and cost-effective method suitable for routine analyses and could be useful for the biological monitoring of occupational exposure to inorganic arsenic.

Determination method for xylidines in workplace air.

OBJECTIVES: The purpose of this research was to develop a determination method for xylidines (XLDs) in workplace air for risk assessment. METHODS: The characteristics of the proposed method, such as recovery, detection limit, reproducibility, and storage stability of the samples were examined. RESULTS: An air sampler cassette containing two sulfuric acid-treated glass fiber filters was chosen as the sampler. The XLDs were extracted from the sampler filters, derivatized with heptafluorobutyric anhydride, and then analyzed by a gas chromatograph equipped with a mass spectrometer. The average recoveries of XLDs from the spiked sampler were 83-101% for personal exposure monitoring. The recovery after 5 days of storage in a refrigerator exceeded 90%. The overall limit of quantitation (LOQ) was 0.600 g/sample. The relative standard deviation, which represents the overall reproducibility defined as precision, was 0.8-10.3%. CONCLUSIONS: The proposed method enables 4-hour personal exposure monitoring of XLDs at concentrations equaling 0.001-2 times the threshold limit value-time-weighted average (TLV-TWA: 0.5 ppm) adopted by the American Conference of Governmental Industrial Hygienists, and is useful for estimating worker exposure to XLDs.

Determination method for nitromethane in workplace air.

OBJECTIVES: The purpose of this research was to develop a determination method for nitromethane (NM) in workplace air for risk assessment. METHODS: A suitable sampler and appropriate desorption condition were selected by a recovery test in which a spiked sampler was used. The characteristics of the proposed method, such as recovery, detection limit, and reproducibility, and the storage stability of the sample were examined. RESULTS: A sampling tube containing bead-shaped activated carbon was chosen as the sampler. NM in the sampler was desorbed with acetone and analyzed by a gas chromatograph equipped with a flame ionization detector. The recoveries of NM from the spiked sampler were 81-97% and 80-98% for personal exposure monitoring and working environment measurement, respectively. On the first day of storage in a refrigerator, the recovery from the spiked samplers exceeded 90%; however, it decreased dramatically with increasing storage time. In particular, the decrease was more remarkable for the smaller spiked amounts. The overall LOQ was 2 microg/sample. The relative standard deviation, which represents the overall reproducibility, was 1.1-4.0%. CONCLUSIONS: The proposed method enables 4-hour personal exposure monitoring of NM at concentrations equaling 0.001-2 times the threshold limit value-time-weighted average (TLV-TWA: 20 ppm) proposed by the American Conference of Governmental Industrial Hygienists, as well as 10-minute working environment measurement at concentrations equaling 0.02-2 times TLV-TWA. Thus, the proposed method will be useful for estimating worker exposure to NM.