Acknowledgements: A special thanks to Dr. Michelle Ward, Dr. Rena Robinson, Christina King, Liqing Gu, Yaphet Geadion, Lindsay Osentoski, and the company sponsors who made this session possible.

References: (1) Garcia-Reyes, Juan, Ayanna Jackson, Antonio Molina-Diaz, and R. Cooks. "Desorption

Electrospray Ionization Mass Spectrometry for Trace Analysis of Agrochemicals on Food." American Chemical Society 81.2 (2008): 820-29. Analytical Chemistry. ACS. Web. 27 Sept. 2015. <http://pubs.acs.org/doi/pdf/10.1021/ac802166v>.

(2) http://webbook.nist.gov/chemistry/ (3) http://www.chm.bris.ac.uk/ms/theory/esi-ionisation.html

Background• An ESI-MS determines the mass-to-charge ratio by

pumping the sample solution through the capillary needle which results in the charged spray of fine droplets. The resulting gaseous ions are analyzed by the detector. Experimental Design

Discussion

Conclusion• The data could have been better

quantified if an internal standard was used and the ESI-MS was coupled with the LC-MS.

• Further studies can be completed by analyzing different pesticides, produce, and instrument schemes.

• Some sources of error could have resulted in the analyte concentrations being lower than their LOD.

Introduction• The purpose of this experiment was to

detect trace amounts of various insecticides and fungicides on different types of produce since the presence of these chemicals and their degradation products could cause potential health hazards1.

• An Electrospray Ionization mass spectrometer was used for the identification of the various agrochemicals in both the standard and produce samples.

Figure 2: Ions were produced by applying a voltage to the sample and an aerosol was created.

Figure 1: ESI MS used direct infusion with LTQ ion trap with Finnigan Ion Max API source.The Thermo Finnigan LTQ MS was used with the following parameters: ESI+ Mode, Nitrogen Gas, Full Scan Mode, 500 Scans, 150-2000 m/z range.

A Qualitative Analysis of Pesticides on Produce Using ESI-MSMadison Gongaware, Michael McDaniels, Stephanie McPhillips*

CHEM 1250: Instrumental Analysis Laboratory Department of Chemistry, University of Pittsburgh

15 g of homogeniz

ed subsample

15 mL ACN Shake 1

min6 g MgSO4 1.5 g NaCl

Shake 20 sec

Centrifuge 3.7K rpm for 1 min

750 mg MgSO4 150 mg

PSA

Shake 20 sec

Centrifuge 3.7K rpm for 1 min

1 g of sample in 100% ACN

Results

Analyte 202.0 (m/z)

293.1 (m/z)

297.1 (m/z)

306.2 (m/z)

404.1 (m/z)

Kale (ppb) 0.9507 0.3415 2.2782 0.4711 0.0000

Apple (ppb) 0.6342 0.0000 3.6492 0.6703 11.6670

Organic Apple (ppb)

0.4037 0.0000 7.8169 0.0000 2.8863

Spinach (ppb) 4.0446 0.2367 2.3677 3.5713 2.4787

Organic Spinach

(ppb)0.0000 0.0000 0.0000 0.0000 0.0000

Orange (ppb) 0.6282 0.0000 0.7045 0.0000 0.9824

Orange Peel 2.4974 0.2825 2.6197 0.0000 11.8972LOD (ppb) 15.0000 2.0000 4.0000 5.0000 8.0000

Figure 3: Schematic of the Linear Ion Trap Detector that was used to analyze the ions.

Figure 4: Mass Spec of Thiabendazole Standard, 199 – 208 m/z.

Figure 4: ESI-MS Spectra for orange and orange peel samples, 195-415 m/z.

Figure 5: Identification of Thiabendazole in orange and orange peel samples, 201.8-202.8 m/z.