Sampling principle
3. 1 sampling shall be conducted by professional and technical personnel.
3.2 The collected samples shall be representative.
3.3 In the process of sample collection and preparation, chemical changes and losses of the components to be tested should be prevented to avoid pollution.
3.4 In the process of sampling, relevant sampling information shall be recorded timely and accurately.
4 sampling method
4. 1 Sampling of samples of origin
4. 1. 1 sample collection
According to different regions and topography, random method, diagonal method, five-point method, Z-shape method, S-shape method and chessboard method are used for multi-point sampling. When the production area is less than 1 hm2, the sampling units should be divided according to NY/T398. When the producing area is greater than 1 hm2 and less than 10 hm2, take 1 hm2~3 hm2 as the sampling unit; When the production area is greater than 10 hm2, the sampling unit is 3 hm2~5 hm2. Collect representative samples in each sampling unit. Sick and too small samples should not be taken. When sampling fruit trees, samples should be taken from all parts of the plant (up, down, inside, outside, sunny and shady).
4. 1.2.6 fruits and vegetables (edible peels)
The whole fruit after removing the fruit stalk. The sample size is 6 ~ 12 individuals, not less than 3 kg. Representative varieties are: cucumber, pepper, eggplant, zucchini, tomato and okra.
4. 1.2.7 fruits and vegetables (the peel is inedible)
After removing the stalk, the peel and pulp of the whole fruit were measured respectively. The sample size is 4 ~ 6 individuals. Representative varieties: cantaloupe, pumpkin, melon, watermelon and wax gourd.
4. 1.2.9 Citrus fruits
Take the whole fruit. The skin and pulp were determined separately. At least 6 ~ 12 individuals, not less than 3 kg. Representative varieties are: orange, grapefruit, orange, lemon and so on.
4. 1.2. 10 pear fruit
Measurement of peeled pulp of pedicled and pitted parts (including seeds). At least 12 individuals, not less than 3 k. Representative species are: apple, pear, etc.
4. 1.2. 1 1 drupe
The whole fruit except the stalk and stone, but the residue calculation includes the stone. At least 24 individuals, not less than 2 kg. Representative varieties are: apricot, nectarine, cherry, peach and plum.
4. 1.2. 12 Small fruits and berries
Take the whole fruit out of the fruit stem and fruit holder, and the sample collection amount is not less than 3kg. Representative varieties are: grapes, strawberries, blackberries, gooseberries, blueberries, arhat, Kharkov berries, cranberries, blackcurrants and raspberries.
4. 1.2. 13 edible fruit with skin
Jujube and olive: The whole fruit is analyzed after the stem and stone are removed, but the residue is counted as the whole fruit. Figs take away the whole fruit. The sample collection amount shall not be less than 1 kg. Representative varieties are: jujube, olive and fig.
4. 1.2. 14 fruit with inedible skin
Unless otherwise specified, you should eat the whole fruit. Avocado and mango: the whole sample is pitted, but the residue is counted as the whole fruit. Pineapple: Take off the crown. The sample collection amount is 4 ~ 12 individuals, not less than 3 kg. Representative varieties are avocado, mango, banana, papaya, guava, passion fruit, New Zealand fruit and pineapple.
4.2 Sampling of field test samples of pesticide residues
According to the purpose of the test and the actual situation of sample types, multi-point sampling is carried out in each sampling unit according to random method, diagonal method or five-point method.
4.3. 1 bulk sample
For bulk samples, samples should be taken from the upper, middle and lower layers according to different pile heights, and the number of layers can be increased if necessary. Each layer should be randomly sampled from the center and five points around. The sampling quantity of the sampling sample shall comply with the provisions of GB/T 8855. Sample pretreatment method shall be carried out according to 4. 1.2.
4.3.2 Packaging products
For packaged products, the sampling amount of sampling samples shall be randomly sampled according to GB/T 8855. Sampling should be carried out by stacking or throwing boxes, that is, a corresponding number of samples should be taken from the upper, middle, lower or four corners of different parts on both sides of stacking. If the location is narrow, sampling should be carried out by stacking.
When it is difficult, you can throw a box every few boxes during the piling process and take out the required samples. Sample pretreatment method shall be carried out according to 4. 1.2.
5.3 A small amount of vegetables and fruits
After mixing, it is divided into four parts, treated with a tissue masher or a homogenizer, and stored in 250 g~500 g for testing.
5.4 Bulk Vegetables and Fruits
Chopped and divided into four parts, 600 g~800 g stored for testing.
5.5 Frozen samples
Crush in the frozen state and then shrink. If it needs to be thawed, it must be determined immediately.
6 sample packaging and storage
6. 1 sample packaging
Put the collected samples into inert packaging bags (boxes), and write down the labels (one inside the package and one outside the package) and serial numbers (together with the samples at all stages until the results are reported). Samples and related materials (sample name, sampling time, place and matters needing attention, etc. ) was transported to the laboratory within 24 hours and was in transit.
During transportation, samples should be prevented from deterioration, damage, water loss or pollution.
6.2 Storage of samples
6.2. 1 Samples containing unstable pesticide residues should be determined immediately.
6.2.2 Perishable samples shall be immediately mashed and frozen below -20℃.
6.2.3 Water samples are stored in cold storage or treated by extraction. Obtain extract, and storing unde freezing condition.
6.2.4 Samples stored for a short period (less than 7 days) shall be kept as they are at 1℃~ 5℃~ 5℃.
6.2.5 If it is stored for a long time, it should be frozen below -20℃. Analysis should be made immediately after thawing. When the frozen sample is taken for testing, water and ice crystals cannot be separated from the sample, and should be homogenized again when the separation is serious.
6.2.6 Test samples shall be backed up and kept for a specified time for reinspection.
7 sample record
The sample record form includes the following basic contents:
A) Name, type and variety of samples;
B) Identification mark or batch number and sample number;
C) sampling date;
D) sampling time;
E) sampling position;
F) sample base and quantity;
G) packaging method;
H) Signature or seal of sampling (sampling) unit and sampling (sampling) person;
I) storage method, storage location and storage time;
J) Environmental and climatic conditions during sampling;
K) The original number, production date and sampled unit shall be marked on the market sample, and the sampled unit shall sign or seal it.