Hach DR/700 - Page 14

xiv
PHOSPHORUS, REACTIVE, continued
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions, using one DR/700, matched sample cells and two representative
lots of testing reagents. Testing 1.60 mg/L PO
4
3-
concentration samples, the
standard deviation was ±0.007 mg/L PO
4
3-
.
Testing zero concentration samples, the limit of detection was 0.019 mg/L
PO
4
3-
. The limit of detection was calculated as three times the standard
deviation when testing zero concentration samples (Adapted from Analytical
Chemistry, 1980, 52, 2242-2249.
Using two representative lots of AccuVacs, the standard deviation was ±0.008
mg/L PO
4
3-
and the limit of detection was 0.021 mg/L PO
4
3-
.
SUMMARY OF METHOD
Orthophosphate reacts with molybdate in an acid medium to produce a
phosphomolybdate complex. Ascorbic acid then reduces the complex, giving
an intense molybdenum blue color.
REQUIRED REAGENTS (Using Powder Pillows)
Quantity
Description Per Test Unit Cat. No.
PhosVer 3 Phosphate Reagent
Powder Pillows . . . . . . . . . . 1 Pillow . . . . . 100/pkg . . . . . . . . 2125-99
REQUIRED REAGENTS (Using AccuVac Ampuls)
PhosVer 3 Phosphate Reagent
AccuVac Ampuls . . . . . . . . 1 ampul . . . . . . 25/pkg . . . . . . . . . 25080-25
REQUIRED APPARATUS (Using Powder Pillows)
Clippers, for opening
powder pillows . . . . . . . . . . 1. . . . . . . . . . . .each . . . . . . . . . . . . . 968-00
DR/700 Filter Module
Number 81.01 . . . . . . . . . . . 1. . . . . . . . . . . . each . . . . . . . . . . . 46281-00
REQUIRED APPARATUS (Using AccuVac Ampuls)
Beaker, 50 mL . . . . . . . . . . . . . 1. . . . . . . . . . . . each . . . . . . . . . . . . . 500-41
Cap, ampul, blue . . . . . . . . . . . 1. . . . . . . . . . . .25/pkg . . . . . . . . . . 1731-25
DR/700 Filter Module
Number 81.01 . . . . . . . . . . . 1. . . . . . . . . . . . each . . . . . . . . . . . 46281-00
81-54
Expected
repeatability
of the
procedure
Concise
explanation
of method
The amount
of reagents
and apparatus
needed to
perform the
procedure as
written
Items needed
to perform the
procedure, not
included with
the instrument