LC/MS Analysis of 52 Carbamates: A Fully Automated Protocol

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Kate Yu, Jim Krol, Michael Balogh
ASMS 2002; Orlando; 3 June 2002
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Introduction: In environmental chemistry, many of the same types of chemicals and pollutants continue to be of interest. Those most commonly measured include pesticides, surfactants, polychlorinated biphenyls (PCBs) etc. Over the years, the information that can be obtained for these compounds has changed and is enabling a better understanding of environmental processes. LC-MS has been regarded as a potential candidate of pesticide analysis due to the capability of the MS detector and the applicability of LC to wide range of molecules. The purpose of this work is to demonstrate the potential of LC-MS for quantitative carbamate analysis. A fully automated LC-MS protocol was developed for the direct analysis of 50 carbamate waste constituents in a single injection. The analysis was performed in wastewater and finished drinking water. Methods: The LC separation was performed on a 2.1 x 150 mm C8 reverse phase column with a 50-minute gradient. The mobile phase was 10 mM ammonium acetate in water (A) at pH 5.0 and 10 mM ammonium acetate in acetonitrile (B). The MS detection was performed on a single quadruple mass spectrometer. Data collection was full scan for optimization and single ion recording (SIR) for quantification. Once the separation for the 50 compounds was established for the LC, the MS optimization for each compound (tuning), the data acquisition for each standard mixture and analyte, and the post run process was all performed in one automated process. Preliminary Data: The 11 EPA regulated carbamtes pesticides presented in EPA method 531.1 (using post column derivatization with fluorescence detection) for drinking water analysis is currently the primary method for carbamate analysis due to its selectivity and sensitivity. However, some carbamates cannot be detected by this method due to chemistry limitations. We have compared the detection limits of the MS method to the fluorescence method using two different protocols. First, we manually performed the MS optimization, method set up plus data acquisition, and post run processing; Second, we repeated the whole process with a fully automated protocol offered by the MS software. For the fully automated protocol, using a 50uL injection volume, (8 times less than the EPA 531.1 requirement of 400 uL), we were able to achieve an LCD of 0.3 ppb (pg/ul); using a 200 uL injection, neither the chromatography nor detector response was compromised, an LOD of less than 0.1 ppb was obtained - both well below the EPA action limits. The above numbers were higher than what we could achieve with the manual protocol, however, the amount of operator time and expertise required for the automated protocol was significantly reduced. We have extended the automated protocol to an additional 39 carbamate analytes, not detected by EPA method 531.1 to enhance the scope of the MS approach. Once the MS method was established, it was applied to a local drinking water and wastewater to understand any matrix effects. This work can set a precedent for the use of single-quadrupole mass spectrometry as an environmental screening method tool.

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