AALSO Water Quality Level 1 Practice Test

Define 'reagent blank'.

A blank that is processed like a sample and can be used to zero or subtract out the small positive error that may arise in the reagents A blank used to calibrate instruments A control sample with a known concentration A bottle of deionized water used for rinsing

Correct Answer:

A blank that is processed like a sample and can be used to zero or subtract out the small positive error that may arise in the reagents

Explanation:

The idea behind a reagent blank is to measure the background signal that comes from reagents and labware by running a blank through every step of the method, so that this background can be zeroed out or subtracted from the sample readings. It contains all the reagents but no analyte, so any signal it produces represents contamination or baseline noise instead of the actual analyte. By using this blank to set the zero or to subtract from the samples, you ensure the measured value reflects only what’s in the sample, not what the reagents themselves contribute. This is why a reagent blank is described as a blank processed like a sample and used to correct small positive errors from the reagents.

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