Answer | common problems and solutions of aquatic product testing

2018-03-23 Reagent technology

Common problems and solutions of aquatic product detection

1, said the sample, the sample is on the bottom of the tube or nozzle, if put in nozzle have what effect on the test results?
Answer: in the process of weighing, the sample should be weighed at the bottom of the test tube as far as possible, if the sample adhesion in the tube mouth, can make the extract can't fully contact with the sample, cause extraction is not sufficient, thus affecting the test results.
2. can you weigh the sample in advance to the centrifuge tube for cold storage in the refrigerator for the next day's experiment?
A: freezing preservation is recommended and care should be taken to avoid cross - contamination.
3, add organic reagent, organic reagent is easy to drip from the spear, how to avoid?
Answer: pick up organic reagents should use a graduated straw or bottle dispenser. The use of pipettes to aspirate organic reagents can result in damage to the pipettes and inaccurate pipettes. The higher the saturated vapor pressure of liquid ( volatile liquid ) is more likely to appear drop phenomenon, if must use pipette suction, gun head and pipette can be closely connected, reduce the occurrence of dripping phenomenon.
4. requirements for water quality in drug residue detection experiment: distilled water, distilled water, purified water or deionized water?
Answer: in theory, these kinds of water can meet the analysis requirements, but there are certain differences for some projects. Deionized water and distilled water are recommended. distilled water and purified water are generally used only for the preparation of cleaning solutions.
5, sample test results outside the curve how to determine?
Answer: the treated sample solution can be diluted with complex solution gradient, and then tested to make its od value in the curve approximate linear range is the best.
6. the od value of the kit is low within the shelf life, but the standard product has gradient. can you continue to use it?
Answer: general manufacturers have minimum requirements for zero standard od value, if the experimental data standard gradient is good and zero standard od value meets the manufacturer's requirements, can be used for results analysis.
7. when one of the six points of the standard curve is obviously abnormal, the judgment of the result will be affected. how to deal with it?
Answer: can refer to the previous experimental data and the quality control report in the kit, selectively remove the abnormal point, can determine the yin and yang of the sample out first. For some samples which are difficult to judge yin and yang, re-examination is recommended.
8, emulsifying phenomenon how to solve?
Answer: emulsifying phenomenon is due to the detected tissue fat content is higher, after adding organic solvents and aqueous solution without layering, appear " water in oil" phenomenon.
Solution: if the re-dissolution of emulsifying phenomenon is generally added n-hexane to remove fat, because n-hexane only play a role in removing fat and impurities, so you can increase n-hexane dosage to reduce emulsification.
If the emulsifying phenomenon occurs in other experimental links: heating in a water bath at 80 deg c for 3 to 5 minutes, whirling and high-speed centrifugation; Rapidly freezing at low temperature for 10 - 20min and centrifuging; Adde salt such as sodium chloride and that like, and whirling and centrifuge.
9. do you need to remove n-hexane before testing after adding n-hexane and complex solution to the sample for vortex centrifugation?
A: n - hexane has a great influence on the experimental results. it is suggested to remove n-hexane and directly absorb the lower complex solution for detection. After redissolving centrifugation, the upper layer of n-hexane should be removed and left open for 10 minutes to allow the residual n-hexane to volatilize.
10, for furan four pretreatment, if there is no 50 ml specifications of centrifuge tube, can will weigh the sample amount and the amount of added solution all halved to 15 ml specifications of centrifuge tube operation?
Answer: if the laboratory conditions are really limited, you can cut the sample and the amount of solution added by half to 15 ml size centrifuge tube operation, but should pay attention to all the solutions and reagents used in the process of experiment should be halved ( except n - hexane ).
11, furan four take the upper organic solvent nitrogen blowing, if not carefully to the lower water phase?
Answer: the whole experimental process should be strictly in accordance with the requirements of the instructions. If that wat phase in the lower lay is taken, all the liquid in the suction head needs to be pumped into a centrifugal pipe, re - centrifuged, and the supernatant taking operation is carry out again.