Accuracy andPrecisionData fromFourDeterminations of
Method 549.1Analytes (Paraquat andDiquat) usingResprep
™
C8Disk
Extraction and Ion-PairHPLCAnalysiswithUVDetection.
Paraquat
Diquat
Sample#1
95.5
88.6
Sample#2
97.0
89.7
Sample#3
98.4
89.2
Sample#4
93.9
85.5
Average
96.2
88.3
%RSD
1.8
1.9
Concentration=200ug/Lof eachanalyte
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above the surface of the disk.
3. Add10mLofConditioningSolu-
tionAdirectly to thewater on the
surface of the disk. Continue todraw
throughunder lowvacuumuntil the
top surface of the liquid is just above
the surface of the disk.
4. Add two10mL aliquots of deion-
izedwater directly to the liquidon
the surface of the disk. Continue to
draw throughunder lowvacuumuntil
the top surface of thewater is just
above the surface of the disk.
5. Add10mLofConditioningSolu-
tionBdirectly to thewater on the
surface of the disk. Continue todraw
throughunder lowvacuumuntil the
top surface of the liquid is just above
the surface of the disk.
SampleAddition
Pour the 250mL sample into the appa-
ratus, adding it directly to the layer of
liquid left on the disk from the condi-
tioning step. Increase the vacuum to
approximately10 in.Hg (35kPa) for a
flow rateof approximately100mLper
minute. Once the sample additionhas
begun, the diskmust not godryuntil the
entire samplehas beenprocessed.
AnalyteElution
Release systemvacuum. Insert a
silanizedglass sample collection tube.
Reassemble the apparatus. Add ap-
proximately1mLmethanol to thedisk,
exercising care to cover the entire top
surface of the disk. Immediately add4
mLof disk eluting solution to the disk,
anddraw the solvent through the disk at
1-2 in.Hg (3-7kPa) until the top sur-
face of the liquid is just above the sur-
face of the disk. Add an additional 4
mLof disk eluting solutiondirectly to
the liquidon the disk, anddraw com-
pletely through thedisk.
FinalAnalysis
Add100µLof ion-pair concentrate.
Adjust final samplevolume as neces-
sarywith elution solvent. Analyze 100
µLbyHPLCusing aRestekPinnacle
ODS (Part #9114565) columnwithUV
detection at 257nm and308nm.
