Nitrogen, Total, Persulfate Digestion Method 10072 for DR/800, Test 'N Tube 第5页

哈希 HACH Nitrogen, Total, Persulfate Digestion Method 10072 for DR①800, Test 'N Tube 第5页

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Accuracy Check
This method generally yields 95-100% recovery on organic
nitrogen standards. For proof of accuracy Hach offers a set of
three Primary Standards for Kjeldahl Nitrogen.
1. Prepare one or more of the following three solutions. Each
preparation is for an equivalent 120 mg/L N standard. Use
water that is free of all organic and nitrogen-containing
species.
a) Weigh 1.6208 g of Ammonium p-Toluenesulfonate
(PTSA). Dissolve in a 1000-mL volumetric flask with
deionized water. Add deionized water to the
1000-mL mark.
b) Weigh 2.1179 g of Glycine p-Toluenesulfonate. Dissolve
in a 1000-mL volumetric flask with deionized water. Add
deionized water to the 1000-mL mark.
c) Weigh 2.5295 g of Nicotinic p-Toluenesulfonate. Dissolve
in a 1000-mL volumetric flask with deionized water. Add
deionized water to the 1000-mL mark.
2. Analyze each of these solutions using the test procedure
above. Calculate the percent recovery for each using
this formula:
The percent recovery should be:
Hach analysts have found Ammonia-PTSA to be the most
difficult to digest. Other compounds may yield different
percent recoveries.
Standard Solution Method
For proof of accuracy, substitute 0.5 mL of a 125 mg/L ammonia
nitrogen standard solution for the sample in the procedure. To
prepare a 125-mg/L standard, use a 25-mL Class A pipet to
transfer 25.00 mL of a 1000-mg/L Ammonia Nitrogen Standard
Compound Lowest Expected % Recovery
Ammonia-PTSA 95%
Glycine-PTSA 95%
Nicotinic-PTSA 95%
% recovery measured concentration
120
---------------------------------------------------------------- = x 100
NITROGEN, TOTAL, HR, Test ’N Tube, continued