horiba TPNA-500, Инструкция по эксплуатации

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Before Using the Product
1
Before Using the Product
Preface
Total nitrogen (TN) and total phosphorus (TP) have been defined as “Living Environment
Items” under Environmental Quality Standards and Effluent Standards as part of measures to
control eutrophication of enclosed bodies of water. In addition to existing COD (chemical
oxygen demand), total nitrogen and total phosphorus were incorporated into regulations
governing total pollution loads beginning with the Fifth Total Pollutant Load Control
implemented in 2004. Measurement by automatic measurement instrument is mandatory for
factories and other establishments whose waste liquid discharge volume is greater than 400
m
3
, per day.
No principles or methods of measurement are specified for automatic measurement
instrument of the total nitrogen and total phosphorus under the Total Pollutant Load Control.
Any measurement instrument complying with the standards for performance, control, and
maintenance set forth in the “Manual of measurement methods for water quality pollutant load
using nitrogen/phosphorus automatic measurement instrument (published by Japan's Ministry
of the Environment)” can be used.
The TPNA-500 uses the ultraviolet oxidative dissolution method.

Ultraviolet oxidative dissolution method

Principle of measurement for total nitrogen
Alkaline potassium peroxodisulfate solution is added to the sample solution. Irradiation by
ultraviolet light then causes oxidative dissolution of nitrogen compounds to nitrite ions (NO
3
-
).
Total nitrogen (TN) concentration is obtained by measuring the nitrite ion concentration using
an ultraviolet absorption photometer. The advantage of this method is the simplified
architecture of the dissolution tanks that enables dissolution to be carried out under normal
atmospheric pressure at a lower temperature (100

C) than thermal decomposition methods
that require 120

C.

Principle of measurement for total phosphorus
Potassium peroxodisulfate solution is added to the sample solution followed by irradiation with
ultraviolet light, causing oxidative dissolution of phosphorus compounds to phosphoric ions
(PO
4
3-
). L-ascorbic acid solution mixed with a solution of ammonium molybdate and
potassium antimonyl tartrate are then added to the sample to bring about a chromogenic
reaction forming molybdenum blue. The total phosphorus (TP) concentration is obtained by
measuring the absorbance of the molybdenum blue at the absorption wavelength of 880 nm
using an absorption photometer. The advantage of this method is the simplified architecture of
the dissolution tanks that enables dissolution to be carried out under normal atmospheric
pressure at a lower temperature (100

C) than thermal decomposition methods that require
120

C.