Water Quality Analyst Practice Test 2025 - Free Practice Questions and Study Guide for Water Quality Analyst Certification

Gas chromatography/mass spectrometry (GC/MS) is the preferred method for identifying volatile organic compounds (VOCs) in water due to its high sensitivity and specificity. This technique allows the separation of complex mixtures of compounds and provides precise identification and quantification.

In the context of testing for VOCs, GC is particularly effective because it heats the sample, causing the volatile compounds to vaporize and travel through a column. As they pass through, different compounds separate based on their chemical properties. Coupled with mass spectrometry, which analyzes the mass-to-charge ratio of ionized molecules, it enables analysts to precisely identify the individual VOCs present in a water sample, even at low concentrations.

Other methods like UV-Vis spectroscopy, HPLC, and ion chromatography are suitable for different types of analyses but are not optimal for VOCs. UV-Vis spectroscopy is primarily used for analyzing non-volatile compounds and can struggle with the detection of low-concentration VOCs. High-Performance Liquid Chromatography (HPLC) is designed for non-volatile and thermally unstable analytes and typically involves liquid phases rather than gas, which makes it less effective for VOCs. Ion chromatography focuses on charged species and is not suitable for the nonpolar nature of many