As early as the sixties and seventies, the determination of nicotine used silicotungstic acid precipitation method, this method requires distillation, precipitation, filtration, high temperature burning, weighing and other steps, more cumbersome. In the 1980s, people used a more advanced instrument for the determination of nicotine by ultraviolet spectrophotometry. Although it is much advanced than the silicotungstic acid precipitation method, distillation is still required, and distillation is performed using a conventional distillation apparatus. Not only the instrument is installed, but also Disassembly is troublesome, and distillation is slow and cannot be distilled continuously. This article describes the rapid distillation of nicotine using a Kjeldahl apparatus, followed by a UV spectrophotometric method. Due to the application of the Kjeldahl nitrogen analyzer, the distillation process is simple, rapid and continuous, with high accuracy and good attention. A cycle can be completed in just over ten minutes, greatly improving work efficiency.
Test method 1. 38 samples of materials for testing were provided by the topic of flue-cured tobacco from Inner Mongolia College of Agriculture and Animal Husbandry.
Second, the instrument equipment BUCHI321 Kjeldahl, UVIKON81O ultraviolet Spectrophotometer, 25Oml flask, 250ml volumetric flask, Tops agricultural experiment dedicated distiller.
Third, reagent 23% NaOH solution, 1:4 hydrochloric acid solution.
Fourth, test procedure
1. Test method: Accurately weigh and take a representative representative sample of 0.2000g in a Kjeldahl bottle, add NaCI (AR) lOg, distilled water 50ml, 23% NaOH 10ml, and immediately install the Kjeldahl bottle in a 250ml flask Put 10ml l: 4 hydrochloric acid solution, the end of the condensation tube into the hydrochloric acid solution in the flask, distillation timing of 6 minutes, began to distill, adjust the distillation volume of about 200ml, until the end of the distillation distillate volume to In a 250 ml volumetric flask, shake well. Absorbance values ​​were measured at wavelengths of 259 nm, 236 nm, and 282 nm in the UV spectrophotometer, and the readings were recorded.
2, conditional test face
(l) Selection of Distillation Time The distillation time was plotted against the nicotine content. Distillation time was set for 6 minutes. Nicotine content appeared on the plateau and distillation time was chosen for 6 minutes.
(2) Selection of distillation volume When the distillation time is fixed, the nicotine content is the same when the distillation volume is 250 ml and 500 ml, and the distillation volume is selected to be 2 m1.
(3) The amount of 23% NaOH solution was added. The volume of 23% NaOH was added to the curve of nicotine. The content of nicotine was stable when 10 ml of alkali was added, and the volume of 23% of NaOH was set as 10 ml.
(4) The choice of the amount of NaCL added The amount of NaCL added to the nicotine content curve, when the NaCL added 109, the nicotine content appears platform, the amount of NaCL added 10g.
3, the result of calculation
1.059- Correction Factor
Volume volume of Vo-distillate, l
F-dilution multiple, this article is 1
W-weight, g
34.3-specific absorbance of nicotine. That is, when the nicotine concentration was 1 g/L, the absorbance calculated as a measured value was 34.3. D259 D236 D282---absorbance values ​​measured at wavelengths of 259 nm, 236 nm, and 282 nm, respectively.
Sample tests In this paper, 38 samples were tested. The results show that the method is of good importance and accuracy, and the calibration error of repeated measurements does not exceed 1%.
The conclusion test shows that the use of traditional distillation equipment for distillation, not only the operation is complex, but also time-consuming, power, water, low efficiency; using the Kjeldahl instrument described in this article for distillation, not only reproducible, accurate results, And it is easy to operate, saving time and electricity, and greatly improving work efficiency.
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