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Low Level Pyrethroids by GCMS/MS/NCI
 

Pyrethroid Pesticide Analysis of Aqueous Matrices by
GC-MS/MS-NCI-MRM/SIM Triple Quadrupole Detection

Introduction of the Triple Quadrupole GC-MS system to the evaluation of pyrethroid pesticides (along with select organo-phosphates) enables Caltest to achieve up to 40× lower method detection limits (MDL), 50× lower reporting limits (RL), better sensitivity and increased selectivity as compared to previous methods for analysis of aqueous matrices (e.g. surface waters, monitoring waters, etc.). This technology is applicable for ultra-trace, sub-part per trillion (ppt) residue determination, incorporating a hexapole mass collision cell blanketed with a combination of argon and helium gases to improve ion fragmentation prior to final filtration and detection quantification.1 The significantly improved detection capability is the product of a unique negative chemical ionization tuning procedure involving multiple gases (e.g. methane and ammonia).

Previously developed methods incorporating GC-MS-NCI-SIM (single quadrupole) technology and extensive clean-up steps have proven helpful in achieving trace-level pyrethroid determination of wastewater treatment plant effluent samples spiked at low levels (e.g. 20 ppt) down to a RL of 0.5 ng/L (ppt) for select compounds. This approach met EPA criteria and was in conformance to MDL and RL derivation criteria; however, the method had reached its limit with respect to sensitivity and could not achieve sub-ng/L chronic reporting limits currently of interest. 2,3 Incorporation of Triple Quadrupole technology surpasses the 0.5 ng/L RL, achieving sub-ppt RLs as low as 0.01 ng/L (10 ppq) and enables significantly lower spiking levels (0.15 ppt for all analytes of interest with the exception of permethrin which is spiked at 0.75 ppt due to lack of sensitivity). This information demonstrates Caltest's dedication to continuously improve detection limits and is offered as a progress report of on-going method development efforts.

If Caltest is your selected laboratory, and you are required matrix spike evaluation of your sample(s), at least two additional 1-L samples must be provided in order to accommodate these analyses (an additional charge may also apply). If matrix spike evaluation is not a necessity of your testing prerequisites, but sufficient volume of additional samples is available for collection, Caltest would appreciate receiving at least two additional 1-L samples which may be randomly selected for use as batch QC. These fortified analyses assist in method performance evaluation for the specific matrix assayed and provides for increased accuracy of reported values.

Brief Summary:

Approximately 1-L of sample is extracted, passed through a multi-step clean-up process (as needed) and brought to final volume. Analysis is performed by Gas Chromatography-Mass Spectrometry/Mass Spectrometry operated in negative chemical ionization multiple reaction mode for all compounds with the exception of two (allethrin and fenpropathrin) which do not produce transition ions are analyzed in the selected ion monitoring mode.

Typical calibration range is 0.01 ng/L (ppb) to 2.5 ng/L (ppb) (quantification concentrations may vary due to specific analyte response). Analyses are accompanied by a Method Blank, Laboratory Control Samples (LCS and LCSD, as applicable) and Matrix Spikes (MS and MSD, as applicable). It is important during sample collection to provide two additional 1-L samples per event/batch to use for Matrix Spikes (total of three 1-L aqueous samples collected; four liters preferred if extra volume is available in the event that sample re-extraction is needed).

System sensitivity check standards are run at a mid-point calibration and at the lowest calibration standard to verify that the instrument is withholding sensitivity and that samples have not contributed to system degradation.

The summarized method incorporates EPA SW-846 Method 8270D4 with modifications.

Limitations: Current compounds evaluated along with respective RLs and MDLs are listed below. Samples with matrix interferences or excessive target concentrations may require dilutions which would elevate reported RLs and MDLs.

Pyrethroid Analytes
(November 2016)

Analyte PQL
(ng/L; ppt)
RL
(ng/L; ppt)
MDL –
(ng/L; ppt)a
LCS/LCSD % Recovery Range LCS/LCSD Acceptable
% RPD
MS/MSD
%
Recovery Range
MS/MSD Acceptable
% RPD
Allethrin 0.03 0.04 0.0264 50 - 150 30 35 - 165 50
Bifenthrin 0.02 0.02 0.0182 50 - 150 30 35 - 165 50
Cyfluthrinb 0.02 0.02 0.0124 50 - 150 30 35 - 165 50
λ-Cyhalothrin 0.04 0.04 0.0339 50 - 150 30 35 - 165 50
Cypermethrinb 0.04 0.04 0.0357 50 - 150 30 35 - 165 50
Deltamethrin/ Tralomethrin 0.03 0.08 0.0255 50 - 150 30 35 - 165 50
Esfenvalerate/ Fenvalerateb 0.05 0.05 0.0466 50 - 150 30 35 - 165 50
Fenpropathrin 0.06 0.1 0.0556 50 - 150 30 35 - 165 50
Permethrinb 0.5 0.5 0.2940 50 - 150 30 35 - 165 50
Tau-Fluvalinateb 0.16 0.2 0.0319 50 - 150 30 35 - 165 50
Tetramethrin 0.03 0.05 0.0248 50 - 150 30 35 - 165 50
a MDL values are determined at least annually, or when there is a change in the test method that affects sensitivity and are subject to change.
b Procedural refinements and MDL studies with extraction clean-up and without extraction clean-up are in progress.
c Analyte chromatographs with multiple peaks (isomers). RL and MDL adjusted to reflect a total (summation of all peaks).

Additional Analytes upon Request
(November 2016)

Analyte PQL
(ng/L; ppt)
RL
(ng/L; ppt)
MDL –
(ng/L; ppt)a
LCS/LCSD % Recovery Range LCS/LCSD Acceptable
% RPD
MS/MSD
%
Recovery Range
MS/MSD Acceptable
% RPD
Chlorpyrifos 0.5 1.0 0.4350 50 - 165 30 35 - 180 50
Diazinon 0.04 0.06 0.0185 50 - 150 30 35 - 165 50
a MDL values are determined at least annually, or when there is a change in the test method that affects sensitivity and are subject to change.

Permethrin remains ~10× less sensitive than the other analytes evaluated by this method and is fortified (spiked) at an enhanced level. Additionally, fenvalerate and esfenvalerate responses are indistinguishable and are co-reported; this is also the case for tralomethrin and deltamethrin.

Furthermore, MDL studies are determined at least annually, or when there is a change in the test method that affects sensitivity and are subject to change. If the date referenced on the above list of current compounds is older than one year, contact Caltest for potential updates.

Sample Preservation and Storage:

The containers used for sampling and storage shall be amber glass 1L and have screw caps with removable Teflon liners. Aqueous samples and extracts should be stored at 0-6 °C (not frozen). Aqueous samples should be extracted within 3 days of sampling, due to possible lack of stability for cyhalothrin and permethrin.5

Please contact Caltest Project Management for additional details or a quote at 707-258-4000 or info@caltestlabs.com.


  1. 1 Agilent 7000 Series Triple Quadrupole GC/MS System, Concepts Guide: The Big Picture. Second Edition,
    October 2011. Available online: http://www.agilent.com/cs/library/usermanuals/public/G7000-90031.pdf.
  2. 2 Fojut, T.L., Rering, C., Tjeerdema, R.S. Water Quality Criteria Report for Permethrin – Phase III: Application of the pesticide water quality criteria methodology. Sept. 2011. Available online:
    http://www.swrcb.ca.gov/rwqcb5/water_issues/tmdl/central_valley_projects/central_valley_pesticides/criteria_method/permethrin/permethrin_final_criteria.pdf.
  3. 3 Fojut, T., Central Valley Pyrethroid Pesticides Total Maximum Daily Load and Basin Plan Amendment. Presentation, May 2015. Available online:
    http://www.waterboards.ca.gov/centralvalley/water_issues/tmdl/central_valley_projects/central_valley_pesticides/pyrethroid_tmdl_bpa/2015_0505_pres.pdf.
  4. 4 EPA SW-846 Method 8270D, Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry. Revision 5, Update V, July 2014. Available online: https://www.epa.gov/sites/production/files/2015-12/documents/8270d.pdf.
  5. 5 According to USGS and the CA Department of Food and Agriculture.