When filling a sample bottle, which condition must be met for certain analyses?

For certain analyses, particularly those involving the measurement of dissolved gases or volatile compounds, it is necessary that the sample bottle is completely filled with no air space. This ensures that there is no air in the bottle that could interact with the sample, potentially altering the concentration of gases or introducing contaminants. The absence of air space prevents additional gases from dissolving or escaping, which is critical for maintaining the integrity of the sample and obtaining accurate analytical results.

In contrast, leaving air space in the bottle could introduce variables that compromise the sample's conditions and lead to unreliable data. Therefore, filling the bottle completely is a standard practice in environmental sampling, especially when the analysis relies on the precision of the sample's physical and chemical properties.