Measurement Notes; Measurement Techniques; Cleaning Sample Cells - Hach 2100N Instruction Manual

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SECTION 2,
continued

2.4.1 Measurement Notes

2.5 Measurement Techniques

2.5.1 Cleaning Sample Cells

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Always cap the sample cell to prevent spillage of sample into the instrument.
•
Always close the sample compartment lid during measurement.
•
Do not leave a sample cell in the cell compartment for extended periods
of time.
•
Empty the cell compartment and turn off the power if the instrument is stored
for extended periods of time.
•
Always use clean, scratch-free sample cells and caps.
•
Always apply silicone oil.
•
Always observe measurement techniques described in Section 2.5.
Accurate and repeatable turbidity measurements depend on good, consistent
measurement techniques. Measurements are more accurate and repeatable if close
attention is paid to proper measurement techniques. Four important
considerations are:
•
Use clean sample cells.
•
Use sample cells in good condition.
•
Remove air bubbles (degassing).
•
Apply silicone oil to the sample cell.
Measure samples immediately to prevent changes in sample characteristics due to
temperature shifts and settling. Avoid dilution whenever possible; particles
suspended in the original sample may dissolve or otherwise change characteristics
when the temperature changes or the sample is diluted. Thus, the measurement
may not be representative of the original sample.
Cells must be meticulously clean and free from significant scratches. Glass
imperfections and superficial scratches from manufacturing are effectively
masked by the silicone oiling procedure outlined in Section 2.6.1. Clean the inside
and outside of the cells by washing thoroughly with a nonabrasive laboratory
detergent. Then continue cleaning with a 1:1 HCl bath followed by multiple rinses
with distilled or deionized water. Air dry the cells. Handle sample cells by the top
only to minimize dirt and fingerprints.
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