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(2) Environmental impact. When preparing the standard solution, pay attention to the pollution of other organic gases and cosmetics such as balsam and perfume; avoid direct sunlight, and the room temperature requirement is within 20 °C ± 2 °C; during the preparation of the standard sample, the removal and weighing of the standard solution are required. Completed quickly.
(3) The influence of blank absorption liquid. The CCl4 blank values ​​of different batches and different bottles are highly discrete, which causes large errors in the measurement results. In order to make the measurement results accurate and reliable, the blank absorption liquid must use newly distilled CCl4.
(4) The impact of baseline taking. When using air as a reference, there are two ways to take the baseline. One is the tangent parallel to the abscissa from 3250cm-1 (referred to as baseline A), and the other is the tangent at 3000cm-1 and 2880cm-1 (referred to as the baseline). B). For baseline B, the absorbance at 3000cm-1 and 2880cm-1 not only increases with the concentration of mineral oil in the sample, but also the absorption peak at 2930cm-1; the difference is also different with the purity of CCl4 (different bottles). And the calculation of absorbance is also more troublesome. If the analytical peak is disturbed by the near-peak, a single-point horizontal tangent can be used as the baseline, so the method uses baseline A.
(5) The influence of silicon (milk) hoses. When CCl4 contacts the silicon (milk) hose, the absorbance A of CCl4 at 2930 cm-1 increases a lot, and the latex tube is particularly prominent. Therefore, when injecting CCl4 into a sealed gas cylinder, it is absolutely impossible to use a silicone (milk) hose as a conduit, otherwise the result is definitely high; the connection between the sealed gas cylinders is preferably as short as possible. Tube, and the glass tube mouth should be docked; after the absorption is completed, after removing the silicone tube, the outer wall of the glass at the joint is washed out with blank CCl4, and then transferred.
(6) The impact of the operation. CCl4 is extremely volatile, the speed of SF6 gas can not be too fast, the absorption must be carried out in the ice water bath, try to avoid taking CCl4 away. The CCl4 as the absorbing liquid and the CCl4 used as the blank must be newly distilled in the same batch.
What are the influencing factors of mineral oil determination results?
(1) The influence of the instrument. First of all, the selected glass container should be selected to prepare the standard solution after passing the measurement verification and the cleaning inspection is qualified; secondly, the measuring device with smaller capacity tolerance should be selected as much as possible, for example, when selecting the volumetric flask or the measuring cylinder, it should be selected. The volumetric flask is used to prepare the standard solution, and the colorimetric tube is selected instead of the measuring cup.