Hach DR/850 Procedures Manual page 344

PHOSPHONATES,
Table 2
Sample Volume (mL)
(chosen in Step 3)
50
25
10
5
1
Phosphate concentration = Instrument Reading x
Multiplier
Sampling and Storage
Accuracy Check
Interferences
continued
Multiplier
0.1
0.2
0.5
1.0
5.0
Collect samples in clean plastic or glass bottles that have been
cleaned with 1:1 Hydrochloric Acid Solution and rinsed with
deionized water.
Do not use a commercial detergent. If prompt analysis is
impossible, adjust the pH to 2 or less with about 2 mL of sulfuric
acid, ACS, per liter of sample. Store at 4 °C (39 °F) or below.
Preserved samples can be stored at least 24 hours. See Section 1
for more information on dilution factors, cleaning instructions,
etc.
Ideally, a solution containing a known amount of the phosphonate
product being used should be prepared. This will check the UV
conversion of phosphonate to orthophosphate.
When testing a 5-mL sample volume, the following may interfere
when present in concentrations exceeding those listed below:
The interference levels will decrease as the sample size increases.
For example, copper does not interfere at or below 100 mg/L for
a 5.00 mL sample. If the sample volume is increased to 10.00 mL,
copper will begin to interfere above 50 mg/L.
344
Table 3
Phosphonate Type
PBTC
NTP
HEDPA
EDTMPA
HMDTMPA
DETPMPA
HPA
Active Phosphonate (mg/L) = Phosphate con-
centration from Step 15 x Conversion Factor
Conversion Factor
2.84
1.050
1.085
1.148
1.295
1.207
1.49