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Do You Really Use An Uv Spectrophotometer?

August 10, 2020

UV spectrophotometer is a kind of precision instrument. Due to various reasons such as working environment and operation method during operation, its technical condition will inevitably undergo certain changes, which may affect the performance of the equipment, or even induce equipment failure and accident. Therefore, analysts must understand the basic principles and instructions of the spectrophotometer, and be able to detect and eliminate these hidden dangers in time, and repair the faults that have occurred in time to ensure the normal operation of the equipment.

UV-Vis spectrophotometer--use experience

1) If you change the test wavelength by a large margin, you need to wait a while, after the lamp heat balance, recalibrate "0" and "100%" and then measure again.

2) When the pointer type instrument is not connected to the power supply, the pointer of the electric meter must be on the zero scale. If this is not the case, mechanical zero adjustment is required.

3) After the cuvette is used, please rinse it off with distilled water immediately, and wipe off the water mark with a clean and soft gauze to prevent the surface finish from being damaged and affect the light transmittance of the cuvette.

4) Operators should not easily move the bulb and reflector lamp, so as not to affect the light efficiency.

5) The 1900 equal spectrophotometer, because its photoelectric receiving device is a photomultiplier tube, its own characteristic is a large magnification, so it can be used to detect weak photoelectric signals, but not strong light. Otherwise, signal drift is prone to occur and sensitivity decreases.

In view of the above-mentioned characteristics, care should be taken not to expose the photomultiplier tube to light for a long time when repairing and using this type of instrument. Therefore, when preheating, you should open the cuvette cover or use a light blocking rod to avoid prolonged exposure Performance drift causes unstable work.

6) After the amplifier sensitivity is shifted, it must be reset to zero.

7) Compatibility of the cuvette. The cuvette must be used in combination, otherwise the test result will be meaningless. A comparison should be made before each test.

Specific method: Pour the same solution into the two cups to be tested, put the instrument at a certain wavelength, quartz cuvette; 220nm, 700nm with distilled water, glass cuvette: 700nm with distilled water, set one Adjust the transmittance value of the cell to 100%, measure the transmittance values of other cells, and record the difference in indications and the direction of light. If the difference in transmittance is within ±0.5%, it can be used together. If it exceeds this range, it should Consider its impact on test results.

Ultraviolet Visible Spectrophotometer

Ultraviolet Visible Spectrophotometer

Electric box failure and troubleshooting

1) The instrument cannot be zeroed. possible reason:

a) The light door cannot be closed completely. Solution: Repair the light door component and make it completely closed.

b) The transmittance "100%" is turned to the end. Solution: Re-adjust the "100%" knob.

c) The instrument is seriously damp. Solution: Open the photoelectric tube cassette, blow it on with a hair dryer for a while to dry it, and replace the desiccant.

d) Circuit failure.

2) The instrument cannot be adjusted to "100%". possible reason:

a) Insufficient light energy. Solution: Increase the sensitivity magnification gear, or replace the light source lamp (although the lamp is still on).

b) The cuvette holder is not in place. Solution: Adjust the cuvette holder to position it.

c) The photoelectric conversion part is aging. Solution: Replace parts.

d) Circuit failure.

3) During the measurement process, the "100%" point often changes. possible reason:

a) The position of the cuvette in the cuvette holder is inconsistent, or there are droplets on the surface. Solution: Wipe the surface of the cuvette with lens cleaning paper, and then place it on the left side of the cuvette, and position it with a positioning clip.

b) Circuit failure (voltage, photoelectric receiving, amplifying circuit).

4) The digital display is unstable. possible reason:

a) Insufficient preheating time. Solution: Extend the warm-up time to about 30 minutes (some instruments may work unstable when they are in working condition for a long time due to aging and other reasons).

b) The desiccant in the photocell fails, causing the micro current amplifier to get wet. Solution: Bake the circuit, and replace or bake the desiccant.

c) Excessive environmental vibration, high air velocity near the light source, strong external light exposure, etc. Solution: Improve the working environment.

d) Other reasons such as photoelectric tube and circuit.

In the use or verification of Ultraviolet Visible Spectrophotometer, the accuracy of transmittance (absorbance) is an important indicator to measure the performance of the instrument, and its accuracy is directly related to the credibility of the measured data And scientific. Therefore, it is particularly important to improve the use of this indicator and the accuracy of verification.

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