Help needed regarding the slit width of an ultraviolet spectrophotometer
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When measuring the content of dehydroabietic acid in disproportionated rosin in the laboratory, by using slit widths of 1 nm and 2 nm to test the same sample, different values for the dehydroabietic acid content were obtained. Could someone explain why this is the case? Also, is it true that the smaller the slit, the better the data? ?
The slit width refers to the width of the incident slit. It controls the light flux entering the spectrophotometer (in simple terms, it controls the total amount of energy of light that enters per unit of time); the wider the slit, the more energy enters. The slit width also affects the resolution of the spectrophotometer; the wider the slit, the lower its resolution. The slit width cannot be too small either, as the detector has a minimum sensitivity; if the incoming energy is too low, the detector does not respond accordingly. At the same time, due to the influence of noise, the energy is too low, resulting in a very poor signal-to-noise ratio. Therefore, the width of a typical incident slit is on the order of um-mm. As long as the resolution requirements are met, the wider the incident slit, the better (of course, it must not exceed the detector’s range)