An operator is preparing to measure the pH of a raw influent sample. According to standard laboratory practice, which of the following describes the correct procedure for calibrating a pH meter?
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A
Calibrate using a single buffer solution closest to the expected sample pH.
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B
Rinse the probe with tap water, calibrate with pH 7.0 buffer, then measure the sample.
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C
Rinse the probe with deionized water, calibrate with a pH 7.0 buffer, rinse again, then calibrate with a second buffer (e.g., pH 4.0 or 10.0).
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D
Immerse the probe in the sample first to acclimate it, then perform a two-point calibration.