Evaluation of Permethrin-treated Uniforms
Kristin Rury Armed Forces Pest Management Board
The George Washington University
Uniform to be tested (permethrin treatment
by factory impregnation, IDA kit,
aerosol spray can, or air compressed sprayer
methods)
1. Each uniform is
washed 0, 20 or 50 times
2. Two samples are cut from each washed
uniform
5A. The untested
sample of the same uniform is sent to CMAVE after passing
step 43. Using an ASE, the permethrin
is extracted from one of the
cut samples 5B. If the concentration
of permethrin in sample is not
within the minimum to
maximum range (in milligrams/ cm2) a single
retest is allowed
4. A GC is used to analyzed the
permethrin concentration in
the sample*
6. Female mosquitoes are
collected
7. Volunteer arm with
uniform sample is placed in a chamber with
live mosquitoes
8. Testing the efficacy of bite
protection from the permethrin
treatment is conducted by
counting number of bites in each 0, 20 or
50 washing sample
Soldier Systems Technology Research Laboratories
Center for Medical, Agricultural and Veterinary Entomology
* Testing the concentration of permethrin is important to ensure the concentration left in the garment is not too high (a potential health hazard) or
too low (ineffective in protecting against vector
bites)
GC: Gas ChromatographASE: Accelerated Solvent Extractor
Soldier Systems Technology Engineering Research Laboratories
• Contracted textile lab where permethrin is tested for binding and retention to the fabric after a set number of washings
• Lab receives pre-treated fabric from each company
Instruments/products used for testing one uniform sample
• Analytical Balance• 10-100 mL volumetric
flasks• Funnel• Pipettes• Automatic Die Cutter• Three inch cutting die• Extraction Process
– ASE– Soxhlet
• Gas Chromatograph• Mass Spectrometer• Reagents
– Permethrin analytical standard
– Solvent mixture– Helium carrier gas
Sample Preparation
• The uniforms are washed using AATCC 135, 3, V, III to the specified number of cycles (0, 20, or 50)
• A three inch diameter circle is cut from the uniform using a 3 inch cutting die from single ply areas only
Sample Preparation
– Samples are weighed to the nearest milligram
– A second sample is cut from the same uniform for bite protection and insect resistance testing at a separate lab
Standard Preparation
• Standards are used to compare the amount of permethrin in the uniform– Six concentrations of
permethrin standards which are 20, 50, 75, 100, 150, and 200ng/µL
– The concentrations of the standards are calculated based on the weight of the permethrin.
Accelerated Solvent Extractor (ASE)
• Preparing the Specimens– Each circular uniform
sample is rolled and placed into an ASE cell fitted with a cellulose filter
– To ensure procedural quality, a control is used during each run of the ASE to detect any permethrin distribution to other vials
Extraction Procedure• The permethrin is extracted
from the treated specimens for 6 hours or until and extraction recovery of 95% or greater has been achieved.
• The extract is then re-concentrated to a final volume of 40mL. – A 1mL aliquot (a small portion
of the solution) is prepared from every specimen extraction for GC analysis.
– Permethrin recovery must be 95% or greater.
Quality Control
• “Blank vials” containing no permethrin or solution are used to ensure samples are contaminant free and to ensure there is no cross contamination during a run. – If any blank, after multiplying
concentration by five, is greater than any specimen concentration result, the data becomes invalid and the system is checked.
Gas Chromatograph (GC) Procedure
• One µL of the solution from the ASE is placed into the Gas Chromatograph equipped with Mass Spectrometer. – Helium carrier gas is used – Rinse vials are used and contain 80%
acetonitrile and 20% methanol
• The concentration of permethrin in each sample is found by:– Extracting the ion chromatograms
183 and 163 with the GC.
Concentration Calculation• The concentration of permethrin
is determined through:– Area under the chromatographic
curve expressed in mass of permethrin per surface area (mg/cm2)
• If the concentration of permethrin in a sample is not within the minimum to maximum range (in milligrams/cm2) a single retest is allowed, otherwise the sample fails testing and is not distributed to troops.
Bite Protection Testing
• USDA Center for Agricultural and Veterinary Entomology (CMAVE) lab in Gainesville, FL
• The fabric is tested against live mosquitoes after a certain # of washings at the Soldier Systems Technology Engineering Research Laboratories– 0, 20, 50 times