Agricultural products sample pretreatment and analysis

1. Sample pretreatment

Rice and rape samples are sent to the sample processing unit within 2 days after collection, and vegetable samples are usually arranged to be collected in the morning and sent to the sample processing unit on the same day. The sample processing methods for each type of sample are as follows:

Rice and rapeseed are sun-dried and hulled.

Tea samples are pre-dried at the sampling site (or at the premises) and then baked in a drying oven at about 70°C until dry.

Leafy vegetables are baked in a 100-120 ℃ blast drying oven (or vacuum drying oven) for 30min, and then dried in a drying oven at about 70 ℃.

The total amount of dried samples was not less than 100g, which was divided into 2 plastic bottles and set aside.

Soil samples were air-dried and cracked with a wooden stick to remove plant and animal remains, stones and other debris. Air-dried soil samples placed on a wooden grinder, all fine, all over the 20 mesh nylon sieve, <20 mesh sample amount should be > 700g, too much when the quadrature method of rounding off part. Divided into 2 parts, into plastic bottles, standby.

2. Analytical testing indicators

In the laboratory according to the corresponding standards, test method requirements, the samples to do further processing and send analysis.

Soil total indicators: As, Cd, Cr, Hg, Pb, Zn, Cu, Ni, Se, F and organic matter. Soil effective amount indicators: pH, As, Cd, Cr, Hg, Pb, Zn, Cu. Indicators of pesticide residue determination in soil are shown in Table 4-7.

Agricultural products indicators: elemental content of As, Cd, Cr, Hg, Pb, Zn, Cu, Ni, Se, F and pesticide indicators are shown in Table 4-8. Nitrates and nitrites were also determined in the vegetable samples.

Table 4-7 Indicators of pesticide residue determination in soil

Table 4-8 Indicators of pesticide residue determination in agricultural products

The analysis of the full and effective amount of soil elements and the content of elements in agricultural products was undertaken by the Central Laboratory of the Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences (IGGE, Chinese Academy of Geological Sciences). The analysis of pesticide residues in soil and agricultural products is undertaken by the Pesticide Testing Institute of Zhejiang Provincial Department of Agriculture. Zhejiang University Testing Center to undertake the determination of nitrate and nitrite content of vegetable samples.