Method of on-line monitoring total chromium in water with potassium chlorate as oxidant

Abstract

The invention relates to a method of monitoring total chromium in water and discloses a method of on-line monitoring total chromium in water with potassium chlorate as an oxidant, wherein the method includes following steps: (1) sampling: adding 10 ml of a water sample being 6-9 in pH value from exterior to a reaction chamber of an instrument through an extraction apparatus; (2) addition of the oxidant: adding 5ml of the oxidant, a saturated potassium chlorate solution, to the reaction chamber of the instrument and stirring the mixed liquid uniformly; (3) sealed heating: sealedly heating the mixed liquid at a constant temperature of 100 DEG C for 10 min, and cooling the mixed liquid to room temperature; (4) color development: adding 1.5 ml of a mixed acid solution composed of sulfuric acid, phosphoric acid and water according to the volume ratio of 1:1:15, and adding 1.5 ml of a color development agent, which is an ethanol solution containing diphenylcarbazide and phthalic anhydride, with stirring uniformly, and performing a color development reaction for 2 min; and (5) measurement: measuring the absorbance with a 540 nm light source and substituting the absorbance into a standard operation curve according to the absorbance of series standard solutions to calculate the concentration of total chromium in the water sample, wherein the result is displayed on and stored in the instrument or is sent to a data acquisition instrument. The method can save time and energy and is simple and accurate.

Description

technical field [0001] The invention relates to a monitoring method for total chromium in water, in particular to a method capable of accurately testing total chromium in water samples by using an online monitor. Background technique [0002] Chromium is a highly toxic heavy metal that easily enters human cells, causing damage to liver, kidney and other internal organs and DNA. Accumulation in the human body is carcinogenic and may induce gene mutations. At present, the methods for analyzing total chromium in my country include potassium permanganate oxidation-diphenylcarbazide spectrophotometry, ferrous ammonium sulfate titration, catalytic polarography, flame atomic absorption spectrophotometry, and graphite furnace atomic absorption spectrometry. Wait. However, in the field of online monitoring of water quality, diphenylcarbazide spectrophotometry has been widely used because of its strong selectivity, high sensitivity, anti-interference and ease of use. In the field of ...

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Problems solved by technology

But this method will cause the waste of diphenylcarbazide, and the diphenylcarbazide consumed to eliminate the oxidant potassium permanganate is more than the actual color development needs; and because the total chromium in the water sample is a variable, the consumed Potassium permanganate and the remaining diphenylcarbazide will also change, resulting in inconsistencies in the amount of the color developer during the color reaction, which will affect the kinetic reaction of the color system, and also affect the quality of the color reaction. speed and stability

And publication number is CN103822883A " monitoring method of total chromium in water " proposes to use hydrogen peroxide as oxidant, and this method does not need to heat, but because the low symmetry of hydrogen peroxide molecular structure and the existence of peroxygen bond, cause hydrogen peroxide to self-decompose easily, stability Not good, the shelf life is short, not suitable for online monitors

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