Massachusetts Wastewater Practice Exam

If a calibrated pH probe is slow to respond, what might be a possible issue?

1. Wrong buffer solution

2. Broken bulb

3. Bulb is coated

4. Contaminated reagents

The correct answer is: Bulb is coated

A slow response time in a calibrated pH probe can be attributed to the bulb being coated. When the glass bulb of the pH probe becomes coated with contaminants such as grease, proteins, or other substances, it hinders the probe's ability to respond quickly to changes in pH levels. The coating can create a barrier that prevents the glass membrane from effectively interacting with the solution being measured, leading to sluggish readings. In comparison to other possible issues, a broken bulb would typically render the probe unusable entirely rather than just slow. Using the wrong buffer solution could affect the calibration accuracy but wouldn't directly slow response time. Contaminated reagents might lead to inaccurate readings or other chemical interactions but would not primarily cause a delay in the probe’s response. Therefore, the condition of the bulb is crucial for the performance and responsiveness of the pH probe in measuring acidity or alkalinity.