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Take accurate readings with a Photometer

Written by Janice M on . Posted in Technical Tips

How do you get more accurate readings with a digital photometer when measuring elements such as Chlorine?

Keep in mind that you are measuring minute quantities within a sample, eg when measuring Chlorine, you are looking for changes like 1 mg / 1000ml – in a sample this equates to 0.0001 mg in 10 ml. Imagine how small this amount is?

glass sample cell

Preparation of the sample is very important:

  1.  KEEP YOUR FINGERS OFF THE SAMPLE CELL AT ALL TIMES. Small amounts of sweat will have an effect on the result, as compounds in your skin can combine with elements in the sample. When closing the lid of the sample, touch the lid from the outside only. Hold the cell by the top corners.
  2. CLEANING A SAMPLE CELL:  Do NOT use dishwashing liquid / powder – small amounts stick on the walls and reduce the amount of Chlorine in a sample.
  3. Use special “Chlorine demand” glassware – the cells supplied with your instrument. Replacement cells are available.
  4. Use Phosphate Free Cleaning Solution / Teepol Orange OR store your cells in the pool water / water you are measuring. If you are going to wash the cells and leave them to dry, then rinse them twice with distilled water.
  5. Cleaning the instrument: all reagents are water soluble, so all     that is necessary is a simple cleaning with a tissue / a damp tissue. REMEMBER: water / humidity is not good for any instrument, so it is very important to close the battery chamber properly when changing batteries.
For replacement Lovibond® cells, click here

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