Main points of NY/T761 pretreatment operation

Pay attention to the standardization of pre-processing operations, especially in the process of skill competition

(1) The use of the balance should be regulated

(2) If adding standard solution, the addition volume should not exceed 1ml

(3) Check whether the knife head of the homogenizer is clean, rinse it with water and acetone idling, and then homogenize the sample

When homogenizing, the samples should be broken and evenly beaten to make the pesticides fully extracted.

(4) Put 7g NaCl in the graduated cylinder with stopper in advance (use weighing paper to feed it into the bottom)

(5) In the filtration step, filter with a funnel rack and stack the filter paper

(6) When shaking vigorously, the stopper must be tightly closed to prevent leakage

(7) When standing still, the time should not be less than 30min, otherwise the separation of the acetonitrile phase and the water phase will not be complete

(8) When using a pipette to pipette 10.

(9) Place the beaker on the nitrogen blowing instrument and blow dry, and take care that the pipe of the nitrogen blowing instrument does not touch the liquid surface

(10) For organic phosphorus, the recovery rate of methamidophos , dichlorvos, omethoate, etc.

(11) When transferring to a centrifuge tube, rinse the beaker with about 3ml of acetone in 3 times

(12) For the organochlorine part, during the column passing step, pre-rinsing and activating the solid phase extraction column, the column must not be allowed to dry (the liquid level is below the sieve plate), otherwise it will affect the recovery and cause errors

(13) For elution, put 10 mL of acetone and hexane into a test tube in advance

(14) Blow the centrifuge tube in a water bath at 40°C with ammonia to less than 5 mL, and use n-hexane to make the volume constant

(15) For the carbamate part, pay attention to the preservation of derivatization reagents and drugs to avoid invalidation
.
The prepared reagent was filled with nitrogen as much as possible , and the derivatization capacity was not significantly reduced within 2 weeks
.

(16) During the test, it should be noted that the record must be recorded when recording, and attention should be paid to the control time
.