CCIL Sample Management and Preparation 3

Question 1

Which preservation chemical is added to water samples collected for nitrate/nitrite analysis?

Accepted Answer

Sulfuric acid

Answer

Sulfuric acid lowers the pH to ≤2, inhibiting microbial conversion of nitrate and nitrite in water samples.

Question 2

What does the term 'matrix spike' refer to in sample preparation quality control?

Accepted Answer

Adding a known concentration of analyte to a sample to assess recovery efficiency

Answer

A matrix spike involves fortifying a sample with a known analyte amount to evaluate method recovery in that specific matrix.

Question 3

When subsampling a heterogeneous solid sample such as contaminated soil, which technique best ensures representativeness?

Accepted Answer

Cone and quarter or riffle splitting after thorough mixing

Answer

Cone and quarter or riffle splitting reduces heterogeneous bulk samples to representative subsamples with minimal bias.

Question 4

A laboratory must analyze water for mercury. Which container material is MOST appropriate?

Accepted Answer

Glass bottle with Teflon-lined cap

Answer

Mercury adsorbs to plastic and can permeate through standard containers, so borosilicate glass with Teflon-lined caps is required.

Question 5

What is the function of an equipment blank (also called a rinsate blank) in field sampling?

Accepted Answer

To confirm that sampling equipment was adequately decontaminated between samples

Answer

Equipment blanks use analyte-free water rinsed through sampling gear to detect cross-contamination from inadequate decontamination.

CCIL - Canadian Council of Independent Laboratories Practice Test