Check the amount of copper that is in your Whatman filter paper.  When I
was working at a power plant doing total and dissolved copper studies
for discharge, we almost reported a copper violation. It was found
through the use of Acidified blanks that depending on the paper used
from Whatman, copper can be a contaminate at the levels of 100-200 ppb.
 ----------
From: Anthony Balraj
To: [log in to unmask]
Subject: analysis method for copper in effluent
Date: Tuesday, March 25, 1997 10:44PM


 recently we found variation in results we obtained by 2 test methods
whether
 we acidify the sample or not.
 normally we discharge our effluent slightly alkaline (Ph 7.5 to
8.5).The
normal
procedure for analysis is collect sample filter in through whatman
filter
paper
take to AAS for analysis.when we acidified the sample after filteration
we
found
copper indicated to be vary high ( showing 50 to 100 % higher value)

so we did an experiment and used 2 different methods.one AAS (flame) and
Neocupione method .the neoprione method is described below :
 50ml of sample in a separting flask
add 5 ml hydrooxyamine-hydrochloride (200gm in 1000ml watere)
add 10 ml sodium citrate solution (250gm in 1000ml water)
add 10 ml neocuprione solution (1 gm dissolved in  500ml
isopropylalcohol
then made up to 1000ml with water)
add twice20 ml chloroform,shakefor 1 minute allow layer to separate and
collectextracts in 50 ml flask and make up volume to 50 ml with IPA.
check absorbance at 457 nm and from standards similarly prepared and
extracted
plot calibration curveand find value.


SAMPLE EFFLUENT TAKEN AT PH OF 8.4

           EXPERIMENT                             BY AAS        BY
NEOCUPRIONE


 1)  sample filter through 0.45micron
     absolute filter                               0.4           0.62

  2) filtered sample of (1) acidify
     to ph of 1.5 to 2                             0.68           1.6

  3) acidified sample of (2),raise
     ph to 8.5 allow for15 minutes
     filter through 0.45 micron                    0.39           0.65


all analysis were done by same analyst on same day andstandards prepared
from certified copper standrd.

. since we have filtered through 0.45 micron filter only dissolved
copper
should be present in the sample.then why copper increases when we
acidify
the sample by both methods.what is the correct ph or method for
analysis.

when samples have to be preserved for regulatory requrements, the
samples
are acidified and preserved. with this high variation between acidified
and
non acidified samples it can be make or break with the maximum
permissible
limits

can any technetter throw light? thanks in advance




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