YSI 9300 Photometer - Manual (Page 135)

Test Procedure - Total Chromium
1 Fill the pretreatment tube with sample to the 20 ml mark.
2 Add one level spoonful of Chromicol CR powder. Replace screw cap and
shake tube well for two minutes.
3 Allow tube to stand for two minutes.
4 Filter a portion of the solution dropwise into a round glass test tube. Discard
the first few drops and then fill to the 10 ml mark.
5 Add one Chromicol No 1 tablet, crush and mix to dissolve.
6 Add one Chromicol No 2 tablet, crush and mix to dissolve.
7 Stand for 10 minutes without disturbing the solution to allow full color
development and to enable any undissolved particles to settle.
8 Select Phot 100 on photometer.
9 Take photometer reading in usual manner (see photometer instructions).
10 The result represents the total soluble chromium concentration (trivalent and
hexavalent) as mg/l Cr (Result B).
11 The trivalent Chromium (Cr III ) concentration is obtained by subtracting Result
A from Result B :-
Trivalent Chromium = Result B - Result A
Interferences
Levels of dissolved iron above 1 mg/l cause low results for chromium. To increase
the tolerance, repeat the test using two Chromicol No 1 tablets and one
Chromicol No 2 tablet. Tannin causes complexation which prevents a response in
the test.
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