Method for testing permanganate index though gas phase molecular absorption spectroscopy

Abstract

The invention discloses a method for testing a permanganate index though gas phase molecular absorption spectroscopy. The method comprises the steps of measuring and picking a defined amount of water to be tested, placing the water into a reaction vessel, adding sulfuric acid so that the mixture can be acidic, or adding sodium hydroxide so that the mixture can be alkaline, then adding a given mass of potassium permanganate solutions, conducting heating reaction for a period of time, so that reducible substances in the mixture are oxidized by potassium permanganate, adding excessive nitrite solutions for conducting reduction on residual potassium permanganate, and then adding hydrochloric acid and ethanol solutions. When ethyl alcohol is added to hydrochloric acid mediums and serves as a catalyst, nitrite can be transformed into NO<2> instantly. Carrier gas is blown into the reaction vessel for loading NO<2> into a gas phase molecular absorption spectrometer, and the watery potassium permanganate content and the watery permanganate index can be obtained through calculation. The method is simple, rapid and convenient in operation step, by using hydrochloric acid and ethyl alcohol as the catalysis solutions, the reaction is greatly accelerated, the testing result is free of tailing peak phenomenon, and errors are minor.

Description

technical field [0001] The invention belongs to the field of chemical analysis, in particular to a gas-phase molecular absorption spectrometry test method for permanganate index. Background technique [0002] The permanganate index is a comprehensive indicator of the pollution degree of surface water bodies by organic pollutants and reducing inorganic pollutants. It refers to the oxygen consumed when treating water samples with permanganate as an oxidant in acidic or alkaline media. Expressed in mg / L of oxygen. Reductive inorganic substances such as nitrite, ferrous salt, sulfide in water and organic substances that can be oxidized under these conditions can consume potassium permanganate. Therefore, the permanganate index is often used as a comprehensive indicator of the pollution degree of surface water bodies by organic pollutants and reducing inorganic substances. [0003] Gas-phase molecular absorption spectroscopy (hereinafter referred to as GPMAS) is based on the pr...

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Problems solved by technology

[0006] (1) It is necessary to use the color change to determine the consumption of reagents and the reaction standard, and the requirements for the clarity of the test water sample are relatively high, and it is difficult to measure samples with high turbidity and color;

[0007] (2) There are many steps such as titration and color difference judgment that require manual operation during the test process, which is easy to introduce manual operation errors and requires high quality of operators;

[0009] (4) The consumption of samples and reagents is large, and the standard method needs to take 100ml of mixed water samples for each test;

[0010] (5) There are many operation steps, the result calculation parameters are many, the calculation is complicated, and it is easy to introduce errors or calculation errors;

[0011] (6) It is difficult to realize high-precision automatic operation, and the number of samples that can be measured every day is small