Field Analytical Chemistry & Technology最新文献

Aerosol particulate species of the gram-negative bacterium Erwinia herbicola (EH) were detected by stand-alone, analytical instrumentation in an outdoor western United States desert test site. The device consisted of an aerosol collector interfaced to a quartz-tube pyrolysis–gas chromatography/ion-mobility spectrometer (Py-GC/IMS). The detector is about the size of a shoebox, that is, 12 × 9 × 6 in. Bacterial aerosols and background particulates in the 2 to 10 μm-diameter range were collected by a 1000-l/min aerosol concentrator and deposited onto a filter in a quartz tube. Rapid heating to 350 °C in 5 s effected vaporization, and a portion of the pyrolyzate was directed into a GC column. The eluate was detected by the atmospheric-pressure–based IMS. A distinct peak in the GC/IMS data window was used to signal the presence of the EH bacterial aerosol. The sensitivity of this method was relatively good in that values down to five EH-containing aerosol particles per liter of air could be detected in approximately 2.5 min. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 111–126, 2000

This article discusses a feasibility demonstration for a 30-lb field-portable chemical analysis system with detection capability comparable to that of a benchtop system. Syagen constructed and operated a prototype instrument with the use of a novel atmospheric sampling photoionization source coupled to a quadrupole-ion-trap, time-of-flight mass spectrometer (QitTof). The keys to reducing weight and power were the development of a notebook-computer data-acquisition system and a new low-power ion-trap RF source. Detection limits of 10–100 ppb and 5–50 pg were measured for a variety of compounds including phosphonates and aromatics. An air and liquid sampler was developed and shown to have a response time of 1–10 s, depending on mode of operation. The QitTof analyzer and processor can record mass spectra at 200 Hz, making it suitable for fast gas chromatography. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 204–215, 2000

In the case of accidents at chemical plants, during transportation of chemicals or during terrorist attacks, hazardous compounds may be released and may harm emergency personnel and population. To prevent this a simple chemical hazard monitor is required to help locate the dangerous area, its border, and the safe area, as recently pointed out by Overton¹ in a FACT editorial.

Normally, only one or a few compounds are released, but a wide range of compounds has to be considered and must be measurable. In such cases, single-compound detectors may not provide any information or may provide misleading information. Alternative systems that determine sum parameters will give insufficient information to make a decision plan for environmental-protection activities or intervention by firefighters. However, there is always the danger of failing to detect important toxic substances if only one sensing technology is used.

In principle, all relevant compounds can be measured at low concentrations by laboratory analysis. However, techniques for task forces in the field are usually limited to simple equipment^2,3 and are useful for only a limited range of substances. Making laboratory analytical techniques available to the firefighter is the first successful step in accident analysis. However, devices such as mobile GC/MS and optical systems^4,5 need to be operated by specially trained personnel. Furthermore, because of relatively high costs only few special-purpose forces use this equipment.

Given the large amount of chemical hazardous compounds produced nowadays and the frequency of accidents reported in the past and anticipated accidents in the future, guidelines with lists of the major fraction of hazardous substances have been established in the United States (Emergency Response Planning Guidelines, ERPG2⁶) and in Germany (Einsatz Toleranz-Werte: ETW, tolerable concentration values⁷). In addition to the substances in these lists, chemical warfare agents have to be considered, for example, in the case of terrorism.

Detecting these substances in the field has been the objective of incident detection and measurement device developments. One result of our development efforts is the portable gas detector array (GDA). Its analytical task, selected sensors, signal interpretation, and measuring strategy as well as first experiences from the fire brigades using the prototype instruments are presented here. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 195–203, 2000

A fast gas chromatograph (GC) equipped with a pulsed-flame photometric detector (PFPD) was designed and built with the intention of facilitating field analysis of the full range of chemical warfare agents (CWA). This GC-PFPD system was tested with five organophosphorus and organosulfur CWA simulants that cover the volatility range of common CWA. Fast repetitive analysis was demonstrated with a cycle time as short as 30 s, combined with very low detection limits of 20 ng/m³ for organophosphorus CWA simulants and 200 ng/m³ for organosulfur compounds. With a longer analysis time of 80 s, a 3-ng/m³ detection limit was demonstrated for DMMP. In the GC-PFPD system, the separation power of each of these techniques is orthogonal and independent; thus, this hyphenated combination is characterized by a very low false-alarm rate, combined with CWA identification capability at the molecular level. The large improvement in system selectivity is demonstrated in the direct analysis of a low level of triethylphosphate in the headspace of diesel fuel without any interference. The system inlet was heated and the sample path was inert without any metal, enabling fast response time and low detection limits for a low volatility agent such as VX. The same fast GC-PFPD system could also be quickly and easily switched to a continuous sampling “sniff” mode of operation with 2-s response time. Alternatively, it could be operated in a novel mode of thermally modulated inlet (TMI) that provided intermediate results between those of GC and “sniff” in terms of the trade-off of response time and performance. The fast GC-PFPD system is also characterized by low average hydrogen consumption (about 4 ml/min), small size, and low weight. No attempt was made to complete the system in terms of portable control electronics. The advantages and unique features of this system, as well as the importance of CWA identification at the molecular level, are discussed. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 170–194, 2000

An ion mobility spectrometer (IMS) equipped with a 10.6 eV low-pressure gas-discharge lamp usually used in photoionization detectors for gas chromatographic applications was developed for the continuous detection of benzene, toluene, and m-xylene. To improve the resolution of the IMS for single substances a customized IMS with a doubled drift tube length was built. The responses of both IMS (drift tube lengths of 6 and 12 cm) to the compounds selected were determined and compared. The advantages of the combination of multi-capillary columns with IMS are discussed with the aim of achieving further enhancements to the resolution of the instrument. This coupling leads to a significant increase in the scope of application of ion mobility spectrometry for environmental applications. The influence of intermolecular charge-transfer reactions on the peak can be reduced and more complex matrices considered. The presented three-dimensional correlation supports the interpretation of the spectra acquired from the mixtures. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 157–169, 2000

We are developing a method for the real-time analysis of airborne microparticles based on laser-ablation mass spectroscopy. Airborne particles enter an ion trap mass spectrometer through a differentially pumped inlet, are detected by light scattered from two continuous-wave (CW) laser beams, and sampled by a 10-ns excimer laser pulse at 308 nm as they pass through the center of the ion trap electrodes. Following the laser pulse the stored ions are mass analyzed with the use of conventional ion trap methods. In this work thousands of positive and negative ion spectra were collected for 18 different samples: six species of bacteria, six types of pollen, and six types of particulate matter. The data were averaged and analyzed with the use of the multivariate patch algorithm (MPA), a variant of traditional multivariate analysis. The MPA successfully differentiated between all of the average positive ion spectra and 17 of the 18 average negative ion spectra. In addition, when the average positive and negative spectra were combined the MPA correctly identified all 18 types of particles. Finally, the MPA is also able to identify the components of computer-synthesized mixtures of spectra from the samples studied. These results demonstrate the feasibility of using a less-specific real-time analytical monitoring technique to detect substantial changes in the background concentration of environmental organisms, indicating that a more selective assay should be initiated. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 31–42, 2000

Recently, much progress has been made in developing and characterizing new types of immunoadsorbers that aim at a more selective and efficient enrichment of target analytes from complex environmental matrices. A bioceramic immunosorbent prepared by the incorporation of pyrene antibodies into glasses with the sol-gel glass technique was investigated for the direct extraction of polycyclic aromatic hydrocarbons from wet precipitation. The bioceramic support was filled into a specially manufactured adsorber cartridge and inserted in an outdoor rainwater collector. The capacity of the immunosorbent was affected neither by changes in the sample's pH value from 2–9, nor by increases in temperatures of up to 40 °C. The maximum binding capacity of the immunosorbent did not significantly decrease over a 4-week field test at a rural area near Munich in the summer of 1998. The retention of the 16 EPA PAHs depended on the total amount of the analytes and their distribution in the sample, the capacity of the immunosorbent, and the affinity of the used antibody for the single compounds. In the field experiment only nanogram amounts of fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene were detected in the eluate of the immunoadsorber cartridge, which corresponds to concentrations clearly below 30 ng/l⁻¹ for these analytes in rainwater. According to these results, sol-gel glass immunosorbents also seem to be useful as selective adsorber materials in the field, although further studies are necessary. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 43–52, 2000

Lower-flammability-limit (LFL) sensors have recently been installed in the drying ovens and web tunnel of a commercial tape manufacturing process line. Calibration of the LFL sensors by the sensor manufacturer was accomplished by creating a cocktail of solvents that was similar in composition to tape formulations that are used at the manufacturing plant, and then exposing a calibration LFL sensor to various amounts of the cocktail. A calibration curve was generated from the response of this sensor to various concentrations of the cocktail, and then it was exported to all of the process LFL sensors. To verify the accuracy of the process LFL sensors, extractive Fourier-transform infrared (FTIR) spectroscopy was used to measure the concentrations of solvents present at the LFL sensor probe locations while the LFL sensor readouts were read and recorded. The extractive FTIR solvent concentration measurements were converted to % LFL and compared to the readings generated by the LFL sensors. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 62–69, 2000

Two different direct-sampling ion-trap mass spectrometry (DSITMS) methods are evaluated for monitoring trace levels of volatile organic compounds (VOCs) in air. The first is based on the use of a sample introduction system that mixes the air sample into a helium stream prior to introduction into the ion trap through an open-split interface. The second utilizes a valve and uses zero air to flush the contents of the sample loop into the ion trap. Unique features of this system are its use of air in place of helium as a buffer gas for the ion trap, and the optimization of experimental parameters to maintain sensitivity and unit mass resolution. Dichlorodifluoromethane (CFC12) and carbon tetrachloride (CCl₄) were employed as test compounds for this study. Figures of merit for both sample introduction methods were comparable. Detection limits were approximately 50 parts per billion by volume in MS, selected ion monitoring (SIM), and MS/MS modes. Analysis speeds were on the order of 20 s or less per sample. The sensitivity of the ion trap, inherent selectivity of MS/MS, and fast response times of these sample introduction systems make these DSITMS techniques suitable for many applications that require on-line, real-time monitoring of VOCs in air. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 14–30, 2000