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Comment
Response to the Comment on HRMS and APGC-MS measurement of TCDD Kari L. Organtini, Liad Haimovici, Karl J. Jobst, Eric J Reiner, Adam Ladak, Douglas Stevens, Jack W. Cochran, and Frank L. Dorman Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.5b03268 • Publication Date (Web): 21 Sep 2015 Downloaded from http://pubs.acs.org on September 26, 2015
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Analytical Chemistry
Response to the Comment on HRMS and APGC-MS measurement of TCDD Kari L. Organtini1 , Liad Haimovici2, Karl J. Jobst2,3, Eric J. Reiner 2,4, Adam Ladak,5, Douglas Stevens,5, Jack W. Cochran6,7 and Frank L. Dorman1,7* 1
Biochemistry, Microbiology, and Molecular Biology Department, The Pennsylvania State University, 107 Althouse Laboratory, University Park, PA 16802 2 Ontario Ministry of the Environment, 125 Resources Road, Toronto, ON, Canada M9P 3V6 3 Department of Chemistry, McMaster University, 1280 Main St. W., Hamilton, ON, Canada L8S 4M1 4 Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6 5 Waters Corporation, 34 Maple Street, Milford, MA 01757 6 Restek Corporation, 110 Benner Circle, Bellefonte, PA 16823 7 Forensic Science Program, The Pennsylvania State University, 107 Whitmore Laboratory, University Park, PA 16802 * Corresponding author
[email protected] 814-863-6805 Regarding the comments made by Hayward, regarding the published paper (AC-2015-01705x) we would like to further clarify our position. The focus of this paper was the comparison of APGC-QQQ with GCHRMS, considered the “gold standard”, for the analysis of polychlorinated dibenzo- dioxins and –furans in solid-waste-relevant matrices. A number of examples of quantitative accuracy using reference materials were presented, most of which are contaminated samples. These examples show that the results compare well within the limits reported for these reference materials. The detection limits (MDL’s) were determined using fortified samples that had been spiked consistent with concentrations meeting minimum levels as listed in EPA 1613 [http://water.epa.gov/scitech/methods/cwa/organics/dioxins/upload/2007_07_10_methods_method_dioxi ns_1613.pdf] Table 2; higher than those considered for food testing. All congeners in our study meet these minimum levels (1 ng/kg for tetra- congeners, 5 ng/kg for penta- to hepta- congeners and 10 ng/kg for octa- congeners) for soil samples for both APGC-QQQ and GC-HRMS. For the fish tissue samples, all congeners are significantly lower than these limits for APGC-QQQ. For GC-HRMS, TCDD, one hexa dioxin and one hexa furan exceed the minimum level. Given that we were most interested in solid waste samples, we did not choose to try to reduce the MDL’s for biota to lower levels, though we certainly could have done so. Testing food samples for dioxins and furans is very challenging and often requires significantly larger sample sizes to meet the desired (lower) detection limits. Methods are developed to be fit for the purpose they are intended. Methods used for contaminated samples use smaller sample sizes and lower concentration factors to minimize instances of severe instrument contamination. Ultimate sensitivity was not the focus of this comparison, however the sensitivity of APGC-QQQ is clearly better than classical GC-HRMS instruments and appears to potentially be an excellent alternative to GC-HRMS for food testing as well as solid waste.
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