Hach DR/850, Procedures Manual, Page: 357 / 460

357
Summary of Method
Phosphates present in organic and condensed inorganic forms
(meta-, pyro- or other polyphosphates) must be converted to
reactive orthophosphate before analysis. Pretreatment of the
sample with acid and heat provides the conditions for hydrolysis
of the condensed inorganic forms. Organic phosphates are
converted to orthophosphate by heating with acid and persulfate.
Organically bound phosphates are thus determined indirectly by
subtracting the result of an acid hydrolyzable phosphorus test
from the total phosphorus result.
This procedure must be followed by one of the reactive
phosphorus (orthophosphate) analysis methods for determination
of the phosphorus content of the sample. If the ascorbic acid
(PhosVer 3) method is used to measure the reactive phosphorus,
this method is EPA approved for NPDES reporting.
The following reagents and apparatus are required in addition to
those required for the reactive phosphorus test.
REQUIRED REAGENTS
Quantity Required
Description Per Test Unit Cat. No.
Potassium Persulfate Powder Pillows ..................... 1 pillow................100/pkg ............2451-99
Sodium Hydroxide Solution, 5.0 N........................... 2 mL .......100 mL
*
MDB ............2450-32
Sulfuric Acid Solution, 5.25 N.................................. 2 mL ......100 mL* MDB ............2449-32
REQUIRED APPARATUS
Cylinder, graduated, 25 mL...........................................2 ...........................each ..............508-40
Flask, erlenmeyer, 50 mL..............................................1 ...........................each ..............505-41
Sample Cell, 10-20-25 mL, w/caps...............................2 .........................6/pkg ..........24019-06
OPTIONAL REAGENTS
Drinking Water Standard, Inorganic, F – , NO
3
–N, PO
4
3– , SO
4
2– ................. 500mL ..........28330-49
Hydrochloric Acid, 6 N......................................................................... 500 mL ..............884-49
Sodium Hydroxide Solution, 5.0 N.............................................................. 1 L ............2450-53
Sulfuric Acid .................................................................. ...................... 500 mL ..............979-49
Wastewater Effluent Standard, Inorganic
(NH
3
–N, NO
3
–N, PO
4
, COD, SO
4
, TOC) ..................................... 500 mL ..........28332-49
Wastewater Influent Standard, Inorganic
(NH
3
–N, NO
3
–N, PO
4
, COD, SO
4
, TOC) ..................................... 500 mL ..........28331-49
Water, deionized ........................................................................................... 4 L ..............272-56
* Marked Dropper Bottle - Contact Hach for larger sizes.
PHOSPHORUS, TOTAL,
continued