Influence of the most popular human factors on the

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The influence of human factors on the accuracy of quantitative analysis of Baijiu

gas chromatography is a fast and accurate quantitative method that does not exclude the possibility of further exploration in the late stage. In order to obtain accurate quantitative results, we must know the various factors affecting the accuracy of chromatographic analysis. At present, the structure of modern chromatograph is more reasonable and advanced, and the computer is widely used, which reduces the factors of various system errors. However, there is another factor that is most easily ignored in the winery, that is, human factors

1. Stability of wine samples

the trace components of wine are very complex, volatile and difficult to preserve. If the sample is not analyzed in time, the volatile matter with low boiling point will change in a short time, which will cause quantitative error and distort the quality assurance results of Jinan gold assay machine

2. Influence of injection

the common injection methods for gas chromatography are manual injection and automatic injection. At present, most wineries use manual injection. When micro injection is used to check whether the power supply voltage is manual injection with 380v~240v device, the injection technology has an impact on the analysis results

(1) rinse the microinjector with the sample solution for several times, slowly draw microliter of the sample solution, and you can see that there are small bubbles in the solution in the needle tube. Put the needle tip of the microinjector upward, slowly push the piston to discharge the small bubbles with the sample solution, and then push it to the required injection volume

(2) the injection speed should be rapid. The slow injection speed will make the vaporization process of the sample longer, resulting in the widening of the initial band of the sample entering the chromatographic column. The shorter the time to inject the sample, the better. The syringe should not stay in the vaporization chamber for too long. The most important thing is that the needle retention time should be strict. 3. The fixture is the same control that customers need to pay attention to

(3) the repeatability of the analysis depends on the size of the injection volume, the accuracy of the scale reading, the position of the pin and the proficiency of the operator. For example, the content of ethyl acetate in the wine sample is related to the injection volume and technology. If the injection volume is large, the ethyl acetate peak and the ethanol peak are combined into a large peak, so it is impossible to quantify ethyl acetate; If the injection volume is too small, the ethyl acetate peak cannot be separated and quantified

3. Avoid the influence between samples

(1) before sampling, wash the micro syringe with sample solvent for more than three times (fill two-thirds of the needle tube and then discharge), then wash the needle with the sample solution to be analyzed for at least three times, and then take samples for several times to move up and down, so as to basically eliminate the mutual interference between samples

(2) before making each wine sample, first raise the column temperature (it is appropriate not to exceed the maximum operating temperature of the chromatographic column) to remove the solvent and low molecular weight polymer left in the chromatographic column of the previous sample, otherwise the quantitative results of the next sample will be affected

4. The rubber pad in the vaporization chamber is easy to leak after injection, resulting in baseline drift and inaccurate quantitative results. It should be checked and replaced frequently, which is also what chromatographic operators should pay attention to

5. The reagent purity shall be measured before preparing the standard sample, and the pipette and volumetric flask used for preparing the standard sample shall be strictly calibrated

to sum up, there are many human factors affecting the accuracy of chromatographic quantitative analysis. The error of each step affects the overall accuracy of quantitative analysis. Therefore, only in the case of eliminating systematic errors, strict and careful operation can get accurate and accurate analysis results. (end)

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