GC/MS/MS Screening for Pyrethroid Insecticides in Sediment

By AZoM

Table of Contents

Introduction
Experimental
Sample Preparation
Results
Conclusion
About Bruker

Introduction

The article describes a simple screening method for Pyrethoid insecticides in sediment samples. Electron impact ionization along with MS/MS in combination with programmed temperature vaporization injection (PTV) were used in order to obtain high specificity and low limits of detection. Pyrethroids are synthetic chemical insecticides having chemical structures that have been adapted from the chemical structures of the pyrethrins.

A modification has been made to the pyrethoids in order to improve their stability in sunlight. They are poisonous to aquatic organisms at very low concentrations, especially to invertebrates that are at the bottom of the food chain. Most of these compounds are found in wastewater outfalls because of ineffective water treatment.

Consequently, State and federal agencies have begun monitoring programs to characterize the extent of contamination in water supplies and their potential impact on aquatic life. Generally, there are no set requirements for minimum detection or reporting levels. The Scion TQ triple quadrupole mass spectrometer in EI mode with PTV injection is ideal for screening sediment extracts at low to sub-part-per-billion concentrations.

Experimental

Table 1. Experiment Specifications

451-GC Gas Chromatographic Conditions
Column BR-5ms, 30 m x 0.25 mm x 0.25 um
Carrier He 1.0 mL/min
Injector PTV with 3.4 mm ID Siltek Fritted Liner, 8 uL injection
Injector Conditions 60 C hold 0.4 min to 310 C at 200 C/min, hold 30 min
Column Temperature Program 55 C, hold 3 min, ramp to 200 at 40 C/min, hold 1 min; ramp to 310 C at 5 C/min, hold 1 min.
Scion TQ MS Conditions
Ion Source Temperature 250 C
Transferline Temperature 280 C
Filament Delay time 12 min
Filament Emission Current 80 uA
Dwell Time 100 ms each transition

Table 2. MS/MS Parameters for Pyretroids Insecticides

Compound Name RT (min) RT Window Precursor Product Collision Energy
Lambda Cyhalothrin_Ep1+2 19.150 1.000 208 181 -10
  19.150 1.000 181 152 -20
Fenvalerate+Esfenvalerate 24.230 1.000 167 125 -15
  24.230 1.000 225 91 -25
  24.230 1.000 225 119 -10
Bifenthrin 17.560 0.500 181 165 -18
  17.560 0.500 181 166 -10
  17.560 0.500 181 115 -40
trans+cis-Permethrin 20.880 1.000 183 168 -18
  20.880 1.000 183 128 -20
  20.880 1.000 183 152 -20
Cypermethrin-Isomers 22.580 1.200 181 152 -20
  22.580 1.200 181 127 -30
Cyfluthrin-Isomers 21.980 1.200 226 206 -15
  21.980 1.200 206 151 -15
Resmethrin_1+2 16.690 1.000 171 128 -12
  16.690 1.000 171 143 -12
Fenpropathrin 17.860 0.500 265 181 -20
  17.860 0.500 265 210 -10
Deltamethrin-1+2 25.200 1.000 253 174 -10
  25.200 1.000 253 172 -10

Calibration standards in hexane were prepared at 0.1, 1, 5, 10, 25, 50, 100, and 200 ppb. In addition, a blank sediment matrix was spiked at concentrations of 0.5, 5, 10, 25, 50, 100, and 200 ppb.

Sample Preparation

The sample is prepared by adding 5 g copper powder/magnesium sulfate to 20 g wet sediment. The mixture was extracted with 2 x 75ml 50:50 acetone:hexane using a shaker at 185 rpm (2 x15 minutes). The extracts were concentrated to a final volume of 2 mL and cleaned up on Florisil® Sep Pak.

Results

The Scion TQ has an innovative software feature known as Compound Based Scanning (CBS) that was used to easily set up the MRMs required for the analysis. The pyrethroids were found using the CBS software equipped with the Factory Library and were directly downloaded into the scan acquisition method as shown in Figure 1.

Figure 1. Optimized scan information for each compound is downloaded directly from the factory installed library. Bifenthrin MRM transitions are shown here.

Furthermore, the data handling table is automatically created and linked to the scan acquisition method. Hence time is saved as the person need not create any more tables or manage changes to the analytical method. Using MS/MS offered excellent sensitivity and specificity for the analysis. Compounds that were found in the sediment sample spiked at 0.5 ppb are shown in Figure 2. Calibration curves prepared in pure solvent (hexane) and in blank sediment extracts were linear showing no matrix interference from the sediment extract. Figure 3 shows an example calibration curve.

Figure 2. MS/MS for Bifenthrin (top), two epimers of lamda-cyhalothrin (mid), and cyfluthrin isomers (bottom) in the sediment matrix

Figure 3. Calibration curves for Bifenthrin prepared in hexane from 0.1 to 200 ppb (plot at top) and those prepared in a spiked sediment extract (plot at bottom) calibrated from 0.5 ppb to 200 ppb.

Conclusion

PTV injection along with the specificity and sensitivity of MS/MS result in excellent low-level screening of pyrethroids in river and lake sediments. The Scion TQ with Compound Based Scanning helps convenient set-up and management of the pyrethroid MRM parameters. Compound MRM information is directly loaded into the method by choosing them from a factory or user created library. It links the mass spectrometer acquisition table directly with data handling parameters, streamlining the data process.

About Bruker

Bruker is the new name in chemical analysis. Accurate and comprehensive analysis of exogenous and discrete elements in a wide range of sample matrices are key applications for many analytical chemistry groups. To address the needs and challenges of analysts working in those areas, Bruker has expanded their product family to provide, and expertly support, a series of fully integrated solutions including:

  • Gas Chromatography-Mass Spectrometers (GC/MS and GC/MS/MS)
  • Inductively Coupled Plasma Mass Spectrometers (ICP-MS)
  • Gas Chromatography Systems (GC)

Widely used in food and consumer safety testing, forensic, industrial, environmental, and clinical laboratories, these systems are well accepted and established market leaders that universally deliver outstanding performance at a premium value.

This information has been sourced, reviewed and adapted from materials provided by Bruker.

For more information on this source, please visit Bruker.

Date Added: Nov 9, 2012 | Updated: Sep 27, 2013
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