YSI 9300 Photometer - Manual (Page 82)

Reagents and Equipment
YSI Nitratest Powder (Spoon Pack)
YSI Nitratest Tablets
YSI Nitricol Tablets
YSI Nitratest Tube, 20 ml (PT 526)
YSI 9300 or 9500 Photometer
Round Test Tubes, 10 ml (PT 595)
Test Procedure
1 Fill the Nitratest Tube with sample to the 20 ml mark.
2 Add one level spoonful of Nitratest Powder and one Nitratest tablet. Do not
crush the tablet. Replace screw cap and shake tube well for one minute.
3 Allow tube to stand for about one minute then gently invert three or four
times to aid flocculation. Allow tube to stand for two minutes or longer to
ensure complete settlement.
4 Remove screw cap and wipe around the top of the tube with a clean tissue.
Carefully decant the clear solution into a round test tube, filling to the 10 ml
mark.
5 Add one Nitricol tablet, crush and mix to dissolve.
6 Stand for 10 minutes to allow full color development.
7 Select Phot 23 on photometer for result as mg/l N, or Phot 63 for result as
mg/l NO
3
.
8 Take photometer reading in usual manner (see photometer instructions).
NOTE
To convert mgll N to mgll NO
3
multiply result by 4.4.
Concentrations of nitrate greater than 1.0 mg/l may be determined by diluting
the original sample with deionised water. The test can be conveniently carried
out over a range 0 - 20 mg/l N as follows :-
Take a clean Nitratest Tube. Add 1 ml of sample using a pipette or graduated
dropper. Fill the Nitratest Tube to the 20 ml mark with deionised water.
Continue the test procedure as given in steps 2 to 9 above. Multiply the chart
reading obtained by 20 to obtain the nitrate concentration in the original sample.
Nitrite Correction
The Nitratest method will also respond to any nitrite present in the sample. In
most natural and drinking waters the amount of nitrite will be small in
comparison to the nitrate concentration. If it is desired to correct for nitrite,
determine nitrite concentration (as mg/l N) in the prescribed manner (see
PHOT.24.) and deduct from the nitrate concentration (as mg/l N) obtained from
the Nitratest procedure.
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