Screening for Hazardous Chemicals in Homeland Security and Environmental Samples Using a GC/MS/ECD/FPD with a 731 Compound DRS Database Application Note

Screening for Hazardous Chemicals in Homeland Security and Environmental Samples Using a GC/MS/ECD/FPD with a 731 Compound DRS Database Application Note Homeland Security, Environmental Authors interpretation of the MS data, especially in samples with high matrix contamination. The combination of selective Bruce Quimby GC detectors, SIM/Scan, and deconvolution makes a Mike Szelewski very powerful hazardous chemical analysis system that Agilent Technologies, Inc. shows significant progress toward the above goals. 2850 Centerville Road Wilmington, DE 19808 UASA Introduction In recent years, there has been increasing concern Abstract over the release of hazardous chemicals through either accidental or intentional acts. Both the Response to homeland security or environmental inci- homeland security and environmental communi- dents involving hazardous chemicals requires first, the ties recognize the need for preparing analytical rapid and accurate identification of the chemical agent(s) laboratories that can respond quickly to such inci- involved and second, the quantitative measurement of dents. The terms toxic industrial chemicals/toxic that agent in large numbers of samples to aid in managing industrial materials (TIC/TIM) are used in home- the response. Given the unknown nature of the analytes land security to refer to hazardous chemicals, and the complexity of matrices that could be encountered, while the environmental community uses different developing analytical methods for this analysis is chal- terminology like hazardous materials. In either lenging. The approach described in this work uses a gas case, the challenge is to develop laboratory meth- chromatography/mass spectrometry (GC/MS) system ods with the capability of identifying any with a micro-fluidic splitter added to the end of the hazardous chemical(s) involved in an incident and column. The splitter divides the column effluent between to be able to measure its concentration in collected the MS and either a dual-wavelength flame photometric samples. detector (DFPD) or a micro electron-capture detector There are several significant challenges to face (µECD) and a single-wavelength FPD. This approach when developing methods for this analysis. The allows the simultaneous collection of MS and two chan- methods must able to: nels of selective GC detector data from a single injection. This multisignal configuration provides: full-scan MS data • Rapidly and accurately identify the specific for library searching, selective ion monitoring (SIM) data toxic agents involved for trace analysis, µECD and FPD data for excellent selec- • Measure concentration correctly at high levels tivity and sensitivity in complex matrices. The systems of agent at the epicenter (high dynamic range) use retention time locking (RTL) to produce retention times (RTs) that precisely match those in a 731 compound • Measure concentration correctly at low levels of database of hazardous chemicals. Deconvolution Report- agent at perimeters and during decontamination ing Software (DRS) is used to provide fast and accurate (low detection limits) • Be highly selective over matrix interferences • The time required for data review of hundreds (wood smoke, fuels, burning tires, etc.) to mini- of targets in complex matrices can become mize both false positives and false negatives unmanageably large. • Indentify as many toxic agents as possible • Even with a very large database of targets, it is possible that hazardous chemicals not in the • Handle large numbers of samples target list could be present in a sample. It is clear that there is no single analytical tech- Recently, several techniques have become nique that can be used for detecting all possible available to help address the above set of chal- hazardous chemicals. However, one technique that lenges. RTL produces RTs that precisely match is widely applicable for the identification and mea- from instrument-to-instrument and to those in a surement of broad classes of hazardous chemicals database [1]. This eliminates the need for recali- is GC/MS. GC/MS is widely used in laboratories bration of the individual RTs and timed events. The worldwide for the analysis of thousands of introduction of reliable and inert microfluidic different chemicals. splitters allows for the simultaneous collection of GC/MS methods are typically developed to analyze mass spectral data and, for example, phosphorus, between 10 and 100 individual compounds. A sulfur, and/or electron capture data [2]. The selec- target compound is deemed to be present if the tive detector chromatograms can highlight suspect target ion and two or three qualifier ions, with spe- compounds even if they are not in the MS target cific abundance ratios, fall within a defined RT list. They can also offer an alternative means for window. The identity of the target may be further quantitation of target analytes. confirmed by comparison of the scan at the apex of The introduction of the synchronous SIM/Scan the peak with a library reference spectrum. feature allows for the simultaneous acquisition of Matrix interferences are usually minimized by both full scan and SIM data from the same injec- optimizing a combination of the sample preparation [2, 3]. The scan data can be used for screening tion, GC, and MS parameters. Since most methods the full list of targets in the database while the SIM only deal with at most a few matrix types, the ions data looks for a high priority subset of compounds chosen for identification purposes can be selected down to very low levels. such that they are minimized in the matrix. With One of the most significant tools developed for the limited number of targets addressed by the dealing with complex matrices is Agilent’s Decon- method, recalibration of response factors, RTs, volution Reporting Software (DRS) [4]. It uses and qualifier ion abundance ratios can be accom- advanced computational techniques to extract the plished with the injection of a few calibration spectra of targets from those of overlapped inter- mixtures. ference peaks. It then compares the extracted General screening methods for very large numbers spectrum with a library to determine if the target of targets in widely varying and complex matrices is present. Any hits are confirmed by searching offer a new set of challenges for the method devel- against the main NIST MS reference library. This oper. When screening for hundreds of targets, process is automated and provides significant time several factors must be addressed: savings in data interpretation. Since it deals with the entire spectrum instead of just four ions, DRS • Use of sample preparation to reduce matrix can often correctly identify a target in the presence interferences is now significantly limited of interferences where the typical approach would because rigorous cleanup steps may uninten- fail. The use of DRS substantially reduces the tionally remove targets. This reduced level of number of both false positives and false negatives. cleanup can result in significantly higher levels of matrix interferences to contend with. This application note describes the combination of the above techniques with a database of • Recalibration of response factors, RTs, and 731 hazardous chemicals, the Agilent Hazardous qualifier abundance ratios is difficult or impos- Chemical DBL (HCD), to be used for screening sible because of the large number of targets. purposes. The compounds were chosen because of • The methods may be deployed in laboratories their significance in environmental or food safety without access to standards for all of the analysis. The reasoning is that if the materials are targets. manufactured in significant quantities and are toxic, they would be likely to appear in an 2 environmental method. The pesticides are and where the fuel components are not of interest. included because many exhibit toxicity. In the examples shown below the database with hydrocarbons removed was used, since fuels were The list is comprised of: used as prototype matrices. • Chlorinated Dioxins and Furans: EPA 8280A, 10 compounds System Configuration • Polychlorinated biphenyls: EPA 8082, 19 compounds The system configurations used are shown in Figure 1A and 1B. • Volatiles: EPA 502/524, 60 compounds • Semivolatiles: EPA 8270C Appendix IX, 140 compounds A • Pesticides: Agilent RTL Pesticide Database Auto-sampler (adapted), 567 compounds Phosphorus FPD • Total: 796 compounds, with 65 compounds in 3-Way effluent two groups, or 731 individual compounds AUX EPC µECD splitter with 3.8 psig makeup The names of all the compounds in the database are listed in Appendix A at the end of this note. The above list by no means contains all of the haz- 5975 Inert ardous chemicals that could be encountered. How- Column MSD ever, it does screen for a large number of known 6890N hazards and with the addition of selective detec- GC tion can highlight other nontarget compounds that may be of interest. B The chromatographic conditions chosen for devel- Auto-sampler opment of the database are general in nature and Dual Flame Photometric Detector are compatible with the analysis of other types of Sulfur Phosphorus compounds beyond those in the table. For example, laboratories with access to calibration stan- 3-Way effluent AUX EPC splitter with dards for chemical warfare agents (CWA) can add 3.8 psig makeup CWA data to the tables and screen for them as well. 5975 Inert The RTs for compounds in the database were col- MSD lected with the column outlet pressure at 3.8 psig Column + Performance using a microfluidic splitter. This was done to 6890N electronics assure that the RTs observed during sample analy- GC sis would closely match those in the database when a microfluidic splitter or QuickSwap is used. Figure 1. System configurations. A). GC/MS/ECD/FPD The chromatographic conditions for the database system used for 1X and 3X screening analyses. were chosen to be compatible with the method B). GC/MS/DFPD system used for 7X screening translation technique. Constant pressure mode analyses. was used in the GC inlet so that method transla- Key components are: tion can be used to precisely time scale the methods for faster operation [5].

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