| In this paper, the quantitative analysis method of Digital enhanced- TLC was used to detect ethyl carbamate(EC) in alcoholic beverages based on MATLAB digital image processing technique. The main results are as follows:A digital enhanced- TLC(DE-TLC) device which consists of ZF-90 D obscure ultraviolet analyzer and Nikon L330 digital camera was constructed. With this device, we can get the digital images from the silica gel plates after the specific derivatization can be collected. The images can be used to quantify the content of ethyl carbamate(EC) of each spot on the TLC plates. A dipping machine was also designed to accurately control the dip step. The device comprised an Arduino UNO R3 development board, a TB6560 step motor driver, one 03C0-455 wire slide, and some physical blocks were made of PLA 3D printing material after 3D modeling. It was very easy to manipulate, not expensive and operates stably.An ethyl carbamate quantifying software(ECQ) based on MATLAB GUI was designed. The software has necessary functions as color channel filtering, image segmentation, image enhancement, image smearing, binary image threshold adjustment, integral calculating, etc. For verifying the feasibility of determining one target spot boundry by gray scale, a spot model and datas got from tests were performed.Research on single factor has been studied through the digital enhanced-TLC device, the dipping device, and the ECQ software. The result showed that the best conditions of quantifying EC in DE-TLC method were as follows: derivation: 40 m L acetone, 250 μL cinnamaldehyde, 3 μL phosphoric acid, 4 s dipping time, 120 ℃heating temperature, 4min heating time. Chromatography: 25 ℃room temperature, 36% room humidity, unsaturated plate developing, developing solvent(methyl-t-buthyl ether: n-hexan: emethanol =5:7:2, V/V), 7 cm developing distance. The Rf value of the EC spot was 0.42. The methodological evaluation showed that the accuracy RSD of 10 ng EC spot was 9.70%(n=5), the brightness of the EC spot became stably after 2 min, the content of EC was of positive relevance with the mean gray value of EC spots ranging from 8 ng/spot to 18 ng/spot, R2 was 0.992, the limit of detection was 0.595 mg/L, the recovery ranged from 60.12% to 84.70%.To get the investigation results of the content of ethyl carbamate(EC) in different alcohol beverages in Guangzhou market, a gas chromatography-mass spectrometry(GC/MS) with internal standard method was adopted to perform the analysis, in which solid phase extraction was used as pretreatment method and D5-ethyl carbamate was used as internal standard. In beer and rice wine EC was not detected, whereas in brandy, EC showed the highest(2.0846 mg/kg), plum wine, yellow rice wine, medicinal liquor, fruit wine, grape wine sorted from most to least by average content of EC were discovered. The DE-TLC method was also directly used to detect the content of EC among 4 samples(white spirit, rice wine, brandy, red wine) which had been studied in GC/MS method. The result showed that EC was detected in brandy, nevertheless, in other 3 wines EC were not detected. After the 4 samples concentrated by nitrogen blowing concentrator, the EC spot of white spirit was detected, while others were too ropy to apply because of high concentration of sugar and protein, etc. The detection value in DE-TLC method was lower than that in GS/MS method. |
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