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United States Department of Agriculture

Agricultural Research Service

Research Project: VIRUS-VECTOR-HOST INTERACTIONS OF ARBOVIRAL DISEASES OF LIVESTOCK

Location: Arthropod-Borne Animal Diseases Research

Title: Atmospheric Pressure-Thermal Desorption (AP-TD)/Electrospray Ionization-Mass Spectrometry for the Rapid Analysis of Bacillus Spores

Authors
item Basile, Franco -
item Zhang, Shaofeng -
item Shin, Yong-Seung -
item Drolet, Barbara

Submitted to: Analyst
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2010
Publication Date: April 1, 2010
Repository URL: http://pubs.rsc.org/en/Content/ArticleLanding/2010/AN/c0an00071j
Citation: Basile, F., Zhang, S., Shin, Y., Drolet, B.S. 2010. Atmospheric Pressure-Thermal Desorption (AP-TD)/Electrospray Ionization-Mass Spectrometry for the Rapid Analysis of Bacillus Spores. Analyst.

Interpretive Summary: A mass spectrometry (MS) technique is described where spores of a bacterium called Bacillus were rapidly detected and analyzed from complex samples. Bacterial spores were detected even in the presence of growth media in crude lyophilized samples. Repetitive analyses could be performed in less than 5 min total analysis time (including sample loading, heating and data acquisition). This approach was more successful than other direct ambient MS approaches to detect the biomarker from Bacillus spores. A detection limit for the biomarker was estimated at 1 part per million, which corresponded to a calculated detection limit of 100,000 spores or 0.1% by weight spore composition in solid samples (assuming a 1 mg sample size). The technique allowed the differentiation of bacterial spores from other ‘suspicious white powders’ using a single stage for mass analysis and with minimum sample preparation, making this approach suitable for simple field-portable MS instrumentation and pattern recognition data analysis.

Technical Abstract: A technique is described where an atmospheric pressure-thermal desorption (AP-TD) device and electrospray ionization (ESI)-mass spectrometry are coupled and used for the rapid analysis of Bacillus spores in complex matrices. The resulting AP-TD/ESI-MS technique combines the generation of volatile compounds and/or pyrolysis products with soft-ionization MS detection. In the AP-TD/ESIMS approach, an electrospray solvent plume was used as the ionization vehicle of thermally desorbed neutrals at atmospheric pressure prior to mass spectrometric analysis using a quadrupole ion trap mass spectrometer. The approach is quantitative as tested with the volatile standard dimethyl methylphosphonate (DMMP) and with the use of an internal standard (diethyl methylphosphonate, DEMP), with a linear response as tested in the 1–50 ppm range (R2 ¼ 0.991) and a standard error of the estimate of 0.193 (0.9% RSD, n ¼ 5). Bacterial spores were detected by performing pyrolysis in situ methylation with the reagent tetramethylammonium hydroxide (TMAH) for the detection of the bacterial spore biomarker dipicolinic acid (DPA) as the dimethylated derivative of dipicolinic acid (2Me-DPA). This approach allowed spore detection even in the presence of growth media in crude lyophilized samples. Repetitive analyses could be performed with a duty cycle of less than 5 min total analysis time (including sample loading, heating and data acquisition). This strategy proved successful over other direct ambient MS approaches like DESI-MS and AP-TD/ESI-MS without the in situ derivatization step to detect the dipicolinic acid biomarker from spores. A detection limit for the dimethylated DPA biomarker was estimated at 1 ppm (equivalent to 0.01 mg of DPA deposited in the thermal desorption tube), which corresponded to a calculated detection limit of 105 spores deposited or 0.1% by weight spore composition in solid samples (assuming a 1 mg sample size). The AP-TD/ESI source used in conjunction with the in situ methylation step allowed the differentiation of bacterial spores from other ‘suspicious white powders’ using a single stage for mass analysis and with minimum sample preparation, making this approach suitable for simple field-portable MS instrumentation and pattern recognition data analysis.

Last Modified: 8/30/2014
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