If a chlorine analyzer consistently reads lower while grab samples show levels are good, what should be troubleshot first?

When troubleshooting the issue of a chlorine analyzer consistently reading lower than expected while grab samples indicate that levels are good, the first step should be to examine the buffer. This is because the buffer solution plays a critical role in the chemical reaction that allows the analyzer to measure chlorine levels accurately. If there is a problem with the buffer, it can lead to incorrect or low readings by the analyzer.

Buffer effectiveness can decline over time due to contamination or degradation, which may affect the analyzer's accuracy. Ensuring that the buffer is fresh and properly maintained can resolve discrepancies between the analyzer readings and grab samples. This step is essential before investigating other potential factors such as calibration, sampling methods, or the condition of the probe, which may also affect readings but are secondary to ensuring that the buffer is functioning correctly.