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What problems should be paid attention to when obtaining turbidity parameters by water quality analyzer

by:BOQU     2021-05-13

The water quality analyzer performs measurement and uses a spectrophotometer to obtain accurate values. However, there are still many problems in the operation that require our attention. For example, we must pay more attention to the turbidity sensor of the water quality analyzer to prevent the sensor from affecting the entire Analysis of water quality. So we have summarized the issues that need attention in obtaining water turbidity.

When we use a water quality analyzer to measure turbidity, we need a container to contain our samples. Just like the colorimetric test using chlorine or COD, glassware is generally used, which can make the analytical instrument read the data better, but we must ensure that the cuvette is clear and scratch-free. Otherwise, these scratches will interfere with the way the light passes through the glass, leading to falsely high results.

1. Beware of scratches on the cuvette

Many operators of water quality analyzers neglect the scratches on the cuvettes, and the scratches and defects visible in the glass will affect the turbidity readings, even the smallest scratches can affect the detected data. Silicone oil can conceal small defects in glass in daily life. Silicone oil has the same refractive index as glass, so it will not interfere with readings. Just take a few drops of oil, add it to the cuvette and wipe it thoroughly with a lint-free cloth. Can be used normally

The demand reminds us that silicone oil is only effective when filling small defects in the glass. For some large scratches, we recommend replacing the cuvette.

2. Clean the cuvette

The stains on the cuvette can absorb light or spread. If stains are formed on the glass, please use dilute acid or other cleaning agents to remove the stains. After cleaning, use high-purity deionized water filtered by a filter membrane of ≤0.2μm to flush the utensils.

3. Use colorimetry

If the suspended particles in the sample are added when using the water quality analyzer, the sample will scatter and absorb and reflect light. This 'lost' light will cause the turbidity measurement to be different from the actual value.

You can deal with the problem of high turbidity samples through two methods. One method is to dilute any highly turbid samples with turbidity-free water. After dilution, the sample is measured according to the normal method, and then the dilution factor is used for proofreading. Before measuring any samples above 40NTU should be diluted.

Another way to compensate for backscattered or attenuated light is to use the ratio method. Many meters are equipped with other detectors at various angles to confirm and compensate for the lost light.

4. Prevent condensation in the cuvette

When using a water quality analyzer to detect turbidity, condensation will simply appear on the glass, especially if the sample is in a particularly cold environment. Condensation on the outside of the glass will block the light from the sample and cause incorrect turbidity readings.

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