How to maintain the UV detector

Ultraviolet absorption detector is a UV detector. It is a detector based on the principle of solute molecules absorbing ultraviolet light. Its working principle is Lambert-Beer's law, that is, when a bundle of monochromatic light passes through the flow cell, if the mobile phase does not absorb For light, the absorbance A is proportional to the concentration C of the light absorbing component and the optical path length L of the flow cell.

Usually, the maintenance of the UV detector is also very important. The following small series will introduce you how to maintain the UV detector:

Flow cell maintenance

For lightly polluted flow cells, the flow cell can be cleaned online. For heavily polluted flow cells, online flushing generally does not work. The flow cell assembly should be removed from the instrument for cleaning.

The procedure is as follows: Loosen the set screw located at the upper end of the sample flow cell. Take the flow cell assembly and remove the joints at the inlet and outlet respectively; then remove the screws of the three fixed windows and remove the stainless steel piece to remove the two quartz windows of the flow cell. Be careful not to lose the plastic king seal ring in the contact part of the window and the flow cell body. The window and the flow cell body were placed in two beakers containing methanol and ultrasonically cleaned for 20 minutes. If the pollution is particularly serious, the ultrasound can be continued for 20 minutes after the methanol is replaced: the window can also be cleaned with methanol on the cotton wool. Then ultrasound again. After cleaning, the solvent is dried and placed in an oven at 80 ° C. After 30 minutes, it is taken out and cooled to room temperature and assembled. When assembling the flow cell assembly, it is necessary to pay attention to the tightness of the three screws. After the flow cell is introduced into the mobile phase, the principle of not leaking is: the three screws on the flow cell must be cross-tightened, otherwise it will easily cause leakage: if 3 The screw is too tight. The quartz window will be broken.

Monochromator exit slit exit window cleaning

After pulling out the drawer, open the photodetector and loosen the screws on the top of the sample and reference cell. Remove the sample cell and reference cell. The window behind the sample cell and the reference cell is removed. Wipe the window separately with yi ether. After the solvent is evaporated, it can be reduced.

Photoelectric detection head photodiode window cleaning

Pull out the control box drawer, open the test head, you can observe the sample and the reference photodiode window, scrub with yi ether. After the solvent on the window is volatilized, the photodetecting head assembly is turned off.

Xenon lamp maintenance

Proper use and maintenance of xenon lamps can extend their life. The specific method is: after replacing the xenon lamp, the xenon lamp counter should be cleared to correctly display the time of its use. If the instrument is on, but it will not be analyzed for a while, the xenon lamp can be temporarily turned off to extend its service life. Clean the xenon window with methanol once every six months to prevent dust from attenuating the light energy. Note: If the wavelength used is shorter, such as 200 to 210 nm, the lamp life is shorter than the longer wavelength.

The instrument periodically sweeps dust

The instrument should be cleaned once every 3 years to ensure the performance of the instrument and reduce the occurrence of instrument failure. This maintenance requires two people to cooperate, remove the control box from the instrument, first clean the dust inside the instrument with a small brush, and then let the vacuum cleaner immediately suck away. In particular, the cooling fan located under the xenon lamp has accumulated dust and dirt and needs to be cleaned repeatedly. If the deposited dust contains oil, it is difficult to clean with a small brush. At this time, it can be cleaned with absorbent cotton dipped in ethanol [2].

Cleaning in the monochromator: Unscrew the top of the monochromator and open the top cover of the monochromator. The grating and the double-sided concave mirror were purged with dry nitrogen. Be careful not to wipe the grating with a mirror paper. If the concave mirror in the monochromator is found to be dirty, the method of purging with nitrogen cannot be cleaned. It can be washed with a neutral detergent and then rinsed with deionized water. If there is a large area of ​​mildew on the concave mirror, only new products can be replaced.

Monochromator grating motor mechanical drive maintenance

The mechanical drive of the grating motor consists of a motor, a lead screw and a guide rod. After 3 years of use, the mechanical drive part of the lubricating oil is dry and a layer of oil is formed on the surface. Increase the force of the motor, which will seriously damage the motor drive circuit. Maintenance steps: Take out the control box. Remove the monochromator top cover. Clean the residual oil from the screw and the guide rod with absolute ethanol or acetone. After drying, apply a few drops of light lubricating oil on the lead screw and the guide rod, and repeatedly rotate the motor to distribute the lubricating oil evenly. Screw and guide surface.

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