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ChlorAC™ Buffer
For Preservation of Aqueous Carbamate Samples
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INTRODUCTION
Trace analysis of carbamate insecticide residues in water
is a routine requirement in the U.S. Since several of the
common carbamates — Carbaryl, Oxamyl, Hydroxycarbofuran
— are labile in water due to oxidation or hydrolysis,
the samples and standards must be preserved in order to obtain
valid results.
USEPA Method 531.1 specifies pH adjustment, dechlorination,
and cold storage to preserve the samples. The optimum pH is
3.0 ± 0.2. The specified preservative buffer is made
from Monochloroacetic acid and Potassium acetate.
Unfortunately, the commercial grades of Monochloroacetic
acid are not specified to be free of contaminants that interfere
with carbamate analysis. Laboratories have reported varying
levels of fluorescent interferences from 99% crystalline material.
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ChlorAC Buffer from Pickering Laboratories is a highly purified
Chromatographic Grade™ preservative. It is ready-to-use and
prepared to EPA specifications. ChlorAC is guaranteed to be free
of co-eluting interferences for the analytes in EPA 531.1.
EPA Sampling Protocol
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Add 1.8 mL of ChlorAC Buffer to each pre-cleaned 60 mL sample
vial.
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If the water sample is chlorinated, dechlorinate with 5 mg of
Sodium thiosulfate per 60 mL sample.
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Fill the sample vials with the dechlorinated water, seal, and
mix well.
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Maintain the samples at 4 °C for transportation, and at
-10 °C during storage for up to 28 days.
When preparing standards and blanks for chromatographic analysis,
use 10 mL ChlorAC Buffer diluted to 1000 mL with HPLC-grade water.
NOTE:
Well and river waters contain colloidal iron which would dissolve
if samples are preserved prior to filtration only to precipitate
out again as the hydroxide in the reactor.
Reference:
M.W. Dong, M.V. Pickering, M.J.I.Mattina, and H.M.Pylypiw, Jr.,
LC•GC, 10 (6) (1992) 442–446
The shelf life of a factory-sealed 250 mL
bottle of ChlorAC is one year.
ChlorAC and Chromatographic Grade are trademarks
of Pickering Laboratories, Inc.
ORDERING INFORMATION
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1700-0132 |
ChlorAC Buffer preservative
for aqueous carbamate samples, 250 mL |
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