Continuous Flow Colorimetric Assay for ortho-Phosphate
Last revised July 22, 1997
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[Details of the method]
[Sample preparation and handling]
Details of the method
The color reaction chemistry used in this process (automated
Murphy/Riley 1962) is appropriate for water samples containing
native ortho-phosphate and for other liquid samples in which ortho-P
is present as the product of a digest or extract procedure.
Sample preparation and handling
A discussion of principles and practical considerations in
continuous-flow colorimetry is available in the
[Colorimetry Overview] document. The ortho-PO4 procedure
is specified in replicable detail in [assay
for Phosphorus-all forms].
Samples must be free of turbidity and particulate matter and must
not contain any color that absorbes at the same wavelength as the
analytical color chemistry tint. Liquid samples which cannot be
analyzed immediately after collection must be preserved for
shipment. The U.S. E.P.A. has published a table of [acceptable preservation methods] and
holding times for many analytes. Detailed sample-handling
instructions specific to this laboratory are available in the [Sample collection] instructions.