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Environmental Analysis
Utilisation of GCxGC-TOFMS as a Broad-Spectrum Analysis for Endocrine Disruptor Compounds in Urban and Rural Watersheds
Endocrine disrupting compounds (EDCs) encompass a variety of chemical classes, including drugs, pesticides, polymer additives, coatings materials, personal consumer products, industrial by- products and pollutants. There is worldwide concern over long term environmental exposure to EDCs leading to serious health effects including a range of reproductive problems such as reduced fertility, male and female reproductive abnormalities, skewed male/female sex ratios, brain and behavior problems, impaired immune functions, and various cancers.
The research presented in this study emphasises the need for instrumentation that will detect and identify sources of long term environmental exposure to EDCs that can lead to ecological destruction and serious health effects.
This research presents a robust, broad range analysis for the detection of EDC’s in impacted natural waters using Comprehensive two-dimensional gas chromatography – Time of Flight Mass Spectrometry (GCxGC-TOFMS). GCxGC facilitates enhanced detection, chromatographic resolution, and peak capacity while TOFMS allows the fast acquisition (up to 500 spectra per second) necessary to successfully acquire the data density needed to fully characterise low levels of targeted and untargeted compounds in complex samples. A reference standard of 108 known endocrine disrupting compounds was prepared and analysed. Methods for solid phase extraction and GCxGC-TOFMS analysis were developed. GCxGC-TOFMS analysis was conducted on multiple water samples from a rural and urban Midwestern U.S. watershed. Extraction of 1.0 liter water samples was conducted using Supel-Select HLB SPE cartridges (Supelco Analytical, Sigma-Aldrich) designed to recover a wide range of analytes. Subsequent analysis was conducted by GCxGC-TOFMS and the data was processed using a 152 component reference standard. The results are reported as targeted and untargeted analytes found. This research study presents a practical, robust, sensitive, and reliable method for the detection of EDCs in urban and rural watersheds.
Experimental Methods Reference Standard Preparation
• An endocrine disruptor reference stock standard at 1ng/µL was prepared in acetone with EPA Method standards purchased from Restek Corp.
•The commercial standards purchased were Method 8270 Megamix, Method 527 pesticide mix # 1, Method 551.1 pesticide/ herbicide mix, plus Bisphenol A. Solid Phase Extraction Procedure
Author Details:
John Heim, Joe Binkley, and Doug Staples LECO Corporation
3000 Lakeview Avenue St. Joseph, MI 49085
Phone: 800-292-6141 Fax: 269-982-8977 Email:
info@leco.com Web:
www.leco.com
Table 2: An example of a peak table is shown below for the EDC Reference used for this analysis. The columns show the Compound Name, Type of Match, the Match similarity score, retention time, peak area, unique mass, signal to noise, and the library used to identify the mass spectral peak.
•Adjust 1 liter water sample to pH 2 with 37% HCl. •Condition SPE Supel™ Select HLB, 500mg cartridge with 5mL HPLC Water/ 5%Methanol, then 5mL Acetone, followed by 5mL HPLC water.
•Load 1 Liter of water using the Supelco Visiprep Vacuum Manifold (Supelco Analytical, Sigma –Aldrich) slowly unto the SPE cartridge.
•Dry SPE tube with vacuum for approximately 15 minutes.
•Elute slowly, 3mL of acetone/5% methanol into a 20mL clean glass test tube.
•Elute slowly, 3mL of dichloromethane into the same 20mL glass test tube.
•Speedvac to dryness for approximately 2 hours.
•Reconstitute dried residue in 500µL of acetone, vortex, and pipet into auto sampler vial,
•Inject 1uL sample for GCxGC-TOFMS analysis. Method Development
•The solid phase extraction (SPE) procedure was developed using 1 liter of HPLC water spiked with the EDC reference standard at 50ppb.
•The GCxGC-TOFMS method was developed using the EDC reference standard injected at 5ng on-column.
Using The Reference Standard Feature
A Reference Method is built in ChromaTOF® software from a user created standard that is applied and compared to a sample. The purpose of a Reference Method is to determine the component differences between a sample and a reference standard within user defined limits of retention time, peak area, and spectral match. In this study, untargeted components found in the water extracts were added to the original 108 component reference standard. The final Reference used in data analysis contained 152 compounds. The Reference is applied as part of the data processing method. The processed sample peak table displays each compound from the reference in the Type column as either a “Match”, found but “Out of Tolerance” by percent, or “Not Found”.
IET March / April 2012
www.envirotech-online.com
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