Determination of Organochlorine Pesticides in Serum via QuEChERS and GC–MS

June 1, 2015
Xiaoyan Wang, UCT, LLC

The Application Notebook

Issue 0

Organochlorine (OC) pesticides are hydrocarbons with multiple chlorine substitutions primarily used as insecticides. OC pesticides do not break down easily as the chlorine-carbon bonds are very strong.

Organochlorine (OC) pesticides are hydrocarbons with multiple chlorine substitutions primarily used as insecticides. OC pesticides do not break down easily as the chlorine-carbon bonds are very strong. They remain in the environment long after application and bio-accumulate in organisms long after exposure. They are toxic, and some are known or suspected human carcinogens, such as 4,4'-DDT, 4,4'-DDD, and the lindanes. Many OC pesticides are banned or have restricted use. These chemicals are frequently found in human body tissue, blood, fat, and breast milk. This application employs a modified QuEChERS extraction and a fast, push-through cartridge clean-up for the determination of OC pesticides in human serum.

Sample Preparation

1) Add 2 mL acetonitrile containing internal standard (IS) to a 15-mL centrifuge tube with 800 mg MgSO4 and 200 mg NaCl (ECQUUS1115CT).

2) Add 1 mL serum sample and 1 mL reagent water into the 15-mL centrifuge tube. Shake for 1 min manually or use a Spex 2010 Geno-Grinder at 1000 strokes/min.

3) Centrifuge at 3000 g for 5 min.

4) Load 1.5 mL supernatant using a disposable syringe and attach a push through cartridge (ECPURMPSMC) to the Luer tip of the syringe.

5) Push the syringe plunger slowly, discard the first 3–5 drops (to remove any trapped airborne contaminants in the cartridge), then collect 0.5 mL extract into a 2-mL auto-sampler vial.

Instrumental

GC–MS: Agilent 6890N GC coupled to 5975C MSD
Injection: 1 μL splitless at 250 °C
Column: Restek Rxi®-5sil MS 30 m × 0.25 mm × 0.25 μm
Carrier gas: He at a constant flow of 1.2 mL/min
Oven temp program: 50 °C hold for 1 min, ramp at 10 °C/min to 310 °C and hold for 3 min
Detection: ESI/SIM mode, 25 ms dwell time


Figure 1: Spiked serum sample.

Results

Matrix matched calibration curves were constructed for analyte quantitation. The responses were linear over the analytical range from 20 to 2000 ng/mL with R2 greater than 0.9970. The average recoveries (Rec%) and relative standard deviations (RSD%) of 5 replicated samples are listed in Table I.

Conclusion

This application provides a simple, fast, and efficient method for the determination of organochlorine pesticides in serum.

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