SCIENCE
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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the use of proper containers,
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temperature control
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addition of preservatives
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observance of recommended sample holding time
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Detailed explanation-1: -Freezing the samples is a common preservation procedure. Samples that cannot be frozen or that do not need to be frozen (with nonvolatile matrix and analytes, or stable at ambient temperature) are usually stored at 0–5° C.
Detailed explanation-2: -A “holding time” is the elapsed amount of time from the point of collection to the moment of preparation or analysis.
Detailed explanation-3: -Methods 9040 and 9045 for pH both say that samples should be analyzed as soon as possible. 40 CFR 136 Table II defines the maximum holding time for Hydrogen ion (pH) as 15 minutes.
Detailed explanation-4: -Preserve sample. Special sample handling and storage are often required to prevent potential changes in sample morphology and/or composition between time of sampling and analysis. Oxidation, evaporation, thermal degradation, or chemical interaction may occur if samples are not properly preserved.