[Preservative Content] In Bakery Products Has Large Fluctuations In Detection, Why?
Apr 23, 2020
4. Different pH adjusted during sample pretreatment may lead to deviations in test results
According to the national standard GB 5009.121, when testing the content of sodium dehydroacetate in the sample, the pH of the sample treatment solution needs to be adjusted to 7-8. Because it is a range value, when different operators do sample pre-processing, the pH adjustment will be different. Some inspectors do not even perform pH adjustment. This will affect the subsequent peak time and area, and cause deviations in the results. However, this point has been clearly adjusted in the new national standard to be implemented on March 1, 2017 to adjust the pH of the treatment solution to 7.5, and this error will be reduced in the future.
Five, the reason for the instrument itself
When using high performance liquid chromatography for detection, the number of pedals is often reduced due to incomplete flushing of impurities in the chromatographic column or excessive use time; contamination of the sampler or dead volume in the pipe gap makes the flow of the sample liquid unstable and causes serious peak patterns Tailing; the sample concentration is too high or the bed at the end of the column collapses, and the measured components cannot be better separated. The decrease in the number of pedals, tailing of peaks, and poor resolution of the column will greatly affect the determination results of sodium dehydroacetate content.
Liquid chromatography is a precision instrument. The daily maintenance of the machine and the operating habits of the personnel are very important, which will directly affect the accuracy of the test results.
Six, different detection methods may lead to deviations in the detection results
For the same product, using liquid chromatography or gas chromatography, the results are very different, so the appropriate detection method should be selected according to the characteristics of the product.
Considering all factors, it is generally considered reasonable that the test results of the same batch of products have a deviation of less than 20%. If the difference is too large, it is recommended that the manufacturer send the same batch of products (preferably products in the same position on the baking tray) to different Testing agencies to verify the rationality of their results.
