Laboratory Practice Questions for Washington Level I

1. Question 1

   What is the main purpose of a **laboratory blank** used with a wastewater analysis?

   1. Compare repeated results to evaluate measurement precision
   2. Confirm recovery after adding a known analyte amount
   3. Establish instrument response with calibration standards
   4. Check for contamination introduced during analysis
   Show the answer

   Answer: D. Check for contamination introduced during analysis

   A laboratory blank contains no intended sample analyte and is processed to reveal contamination that may come from reagents, containers, equipment, or laboratory procedures.

2. Question 2

   Which sampling point is most likely to produce a **representative sample**?

   1. The location closest to the laboratory entrance
   2. A location that reflects the stream being evaluated
   3. A location where the wastewater appears clearest
   4. A quiet location separated from normal process flow
   Show the answer

   Answer: B. A location that reflects the stream being evaluated

   A representative sampling point should reflect the actual wastewater stream or process condition being evaluated, not simply the easiest or cleanest-looking location.

Operator Master has 2 Level I laboratory questions, free, with an explanation after every answer.

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