LaMotte AUXILIARY PHOSPHORUS TEST KIT APT - Manual (Page 2)

IN TRO DUC TION
The determination of orthophosphate (A), is made by testing a filtered
water sample. The determination of hydrolyzable phosphorus
(polyphosphate) and orthophosphate is made by testing a filtered water
sample which has been treated with a sulfuric acid digestion. This
converts hydrolyzable phosphorus (polyphosphate) to orthophosphates.
This determination (B) minus the orthophosphate determination (A) will
give the hydrolyzable or polyphosphate concentration.
A = Orthophosphate
B = Hydrolyzable Phosphorus + Orthophosphate
Hydrolyzable Phosphorus = B - A
The determination of total phosphorus (C) is made by testing a filtered
water sample which has been treated with a sulfuric acid/ammonium
persulfate digestion. This converts organic phosphorus and hydrolyzable
phosphorus to orthophosphates.
C = Total Phosphorus
Organic Phosphorus = C - B
The determination of particulate phosphorus and total phosphorus is
made by determining total phosphorus on an unfiltered water sample.
All of the comparator readings are given as PO
4
-3 . To convert this to
phosphorus, multiply by the factor 0.326.
PRO CE DURE
A. ORTHOPHOSPHATE
Filter the sample and test it for orthophosphate according to the
procedure given for the particular phosphate test kit being used. This is
reading A.
Orthophosphate = Reading A
B. HYDROLYZABLE PHOSPHORUS
(POLYPHOSPHATES) & ORTHOPHOSPHATES
1. Fill 50 mL graduated cylinder (0418) to 50 mL line with filtered
water. Pour into a 125 mL Erlenmeyer flask.
2. Use a 1 mL pipet (0354) to add 1 mL of *Sulfuric Acid, 36% (7885)
to flask. Swirl to mix.
3. Add a few boiling stones (7888). Place flask on hot plate and boil
gently for 30 minutes. Add Deionized Water (5115PT) to the sample
during the boiling step to maintain a volume between 10 and 50 mL.
Or microwave on high power for 2 minutes. Permit the volume to
decrease to approximately 10 mL (about c inch of water) by the end