What is the preservation for Conductivity samples?

• A. Cool <=6C; 28D
• B. No preservation; analyze immediately
• C. Add acid; pH<2
• D. Freeze; 7 days

Answer: (A)

The main idea here is keeping the ionic content stable by controlling temperature, because conductivity is highly sensitive to temperature. Cooling the sample to 6°C or below slows down any biological or chemical changes that could alter the ion concentrations and thus the conductivity reading. A hold time of 28 days reflects a standard practice: if the sample is kept refrigerated, you can delay analysis for up to about a month without significantly affecting the result. Other options would distort the measurement—adding acid introduces extra ions and lowers pH, which would change conductivity; freezing can cause changes in the sample matrix and affect the reading upon thawing; and while analyzing immediately is ideal, it isn’t always practical. So, cooling to ≤6°C and holding for up to 28 days is the appropriate preservation approach.