CIF soil heavy metal constant temperature electric heating plate digestion method

In this paper, the content of heavy metals in soil and slag was analyzed by means of digestion method of constant temperature electric heating plate, and the contents of five metal elements of lead, cadmium, chromium, zinc and nickel were determined for soil and slag samples.

With the development of the economy, human over-exploitation of resources, massive discharge of harmful wastewater, excessive use of pesticides, and arbitrary dumping and stacking of tailings have led to an increasing trend in the types and concentrations of heavy metals in the soil. With the concern of food safety, the state has paid more and more attention to the problem of heavy metal pollution in water bodies and soils. At the same time, it has become an important evaluation object in environmental pollution investigation and evaluation research, and has been listed as a priority control pollutant list by countries. However, for the determination of heavy metal content in soil, different sample processing methods will seriously affect the measurement results. How to quickly and accurately analyze its content becomes especially important. Different methods of digestion of soils have different operational difficulties and sometimes different digestion effects.

In this paper, the method of digestion and determination of soil samples was carried out by using constant temperature electric heating plate digestion method, and the influence of two digestion methods on the determination results of five heavy metal elements of lead, cadmium, chromium, zinc and nickel was analyzed, which is the method for digestion of heavy metals in soil samples. Choose to provide.

1. Method for determination of heavy metals in soil samples

1.1 Main instruments and reagents

CIF constant temperature electric heating plate (PH43-260), Cu, Zn, Pb, Cd, Cr, Ni standard solution 1 000 mg / L, ultrapure water, all experimental acids are excellent grade pure. Soil sample

1.2 Preparation of soil samples

The collected soil samples (not less than 500 g) were mixed and divided by a quartering method to about 100 g. After the shrinking soil sample is air-dried (naturally dried or freeze-dried), remove foreign matter such as stones and animal and plant residues in the soil sample, and grind with a wooden rod (or agate rod) through a 2 mm nylon sieve (remove 2 mm). Mix the above grit). The soil sample that had passed through a 2 mm nylon mesh was ground to a nylon mesh with a pore size of 0.150 mm using an agate mortar, and mixed for use.

1.3 Digestion of soil samples

1.3.1 Heat plate digestion method accurately weigh 2g (accurate to 0. 000 1 g) sample in a 50ml triangle bottle, wet the sample with a small amount of water, add 20ml of aqua regia, gently shake, cover with a small funnel, Place on a hot plate and heat it to a slight boiling in a fume hood (140-160 °C). After the brown NOx is almost finished, remove the cooling. Add 10-20ml of perchloric acid along the wall, continue to heat and digest to produce a thick white smoke volatilizing most of the perchloric acid. The sample in the flask is gray paste and is cooled. The inner wall of the Erlenmeyer flask was washed with hot distilled water and made up to volume in a 100 ml volumetric flask. Filter through a medium speed quantitative filter paper into a plastic bottle. Determined on the machine.

1.4 Determination of samples

According to the national standard, the treated digestion solution is determined by spectrometry using plasma emission spectrometer for Cu, Zn, Pb, Cd, Cr, Ni, Se, Ag in the samples treated by the two methods, and according to the standard curve. Calculate the sample content.

1.5 Data measurement result mg/L

2. Analysis and discussion of results