When is it necessary to fill a sample bottle completely with no air space?

Filling a sample bottle completely with no air space is crucial for certain types of analyses, particularly when analyzing sulfides, ammonia, and volatile organics. The presence of air in a sample bottle can lead to reactions that may alter the concentration of these chemicals before testing occurs.

For volatile organics, any air space could allow those compounds to evaporate, resulting in a lower measured concentration when the sample is tested. Similarly, sulfides and ammonia can react with oxygen in the air, which may result in the conversion of these substances into other forms that do not accurately reflect the original concentration in the sample.

In contrast, while some analyses, such as those for metals or turbidity, might have different sample handling requirements, they do not necessitate that the sample bottles be filled to the brim to the same extent as volatile organics or ammonia. Microbiological testing also has specific procedures but does not typically require the complete absence of air space in the sample bottle to the same critical degree. Overall, ensuring a complete fill without air space is essential for preventing interference in the results for sulfides, ammonia, and volatile organics.