Atomic absorption spectrometry microwave digestion method

Determination of arsenic in water by Hydride Generation Atomic Absorption Spectrometry

Principle: Potassium borohydride or sodium borohydride in acidic solution, the production of new ecological hydrogen, water samples of inorganic arsenic reduction to hydrogen arsenide gas, N2 gas loaded into the quartz tube, the quartz tube heated by electricity to 900 ~ 1000 degrees Celsius. At this temperature, hydrogen arsenide is decomposed into arsenic vapor, which absorbs the characteristic electromagnetic radiation from arsenic source. The absorbance of arsenic in water sample is compared with the standard absorbance to determine the content of arsenic in water sample.

Hydride atomization is a low-temperature atomization method, which is mainly used to determine As, Sb, Bi, Sn, Ge, Se, Pb and Te. These elements react with strong reductant sodium borohydride (or potassium) in acidic medium to form gaseous hydride. The hydride was then sent to the atomization system for determination.

Hydride atomization has the advantage of high efficiency in reducing to hydride, resulting in hydride generation at lower temperatures (typically 700-900). C) Atomization, and the hydride generation process itself is a separation process, so this method has the advantages of high sensitivity, less matrix interference and chemical interference.

Atomic absorption spectrophotometry, microwave digestion.

This method is a new method developed in recent years. It has the advantages of fast, high efficiency, simple, saving reagents and low blank value. However, it needs to be equipped with a microwave sample dissolving furnace. It can be used for the determination of various samples, such as tobacco, vegetables, hair, peanut, Chinese patent medicine, soil, and health care products. Especially for volatile elements, this method is most suitable. The principle is that polar molecules change their positive and negative directions at a rate of 2.45 billion times per second under the action of microwave electric field, resulting in high temperature due to high-speed collision and friction of molecules. At the same time, some substances dissolve in water, the molecules ionize into ions, and then under the action of microwave, make directional movement, form current, ion flow process. It has high-speed friction and collision with surrounding molecules and ions, so that microwave energy can be turned into heat energy. Microwave digestion is carried out in a fully enclosed state to avoid the loss of volatile elements, so the recovery rate is high, the accuracy is good, but also to reduce the sample pollution and environmental pollution. Lin Jie and others used microwave dissolving technology to treat tea as an example to illustrate the use of this method. The steps are as follows: grind the tea sample into powder by food grinder, accurately weigh 0.500g in the polytetrafluoroethylene sample dissolving cup, add 3ml HNO3, 2ml H2O2, after the reaction is stable, cover the cup, put the engineering plastic coat in the microwave sample dissolving furnace, set the pressure from 1 to 3 gear (0.5mPa, 1.0mPa, 1.5mPa) quantitative gradient addition. Pressure digestion. The digestion time is 5-10 minutes. Remove the digestion tank, open the lid after cooling. Put the PTFE sample cup on the heating plate at 120 C to drive the nitrogen oxide to the solution about 1 ml. Transfer to 10 ml colorimetric tube after cooling, rinse the digestive cup with a little deionized water, then add the lotion into the colorimetric tube, dilute to the scale, shake well to be measured.

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