Which type of water is typically used in travel blanks for VOC analysis?

• A. Distilled water
• B. ASTM Type II reagent water
• C. Tap water
• D. Seawater

Answer: (B)

Travel blanks must be filled with water that has a well-defined, very low level of contaminants so that any VOC signal in the blank can be attributed to the sampling process itself, not the water used to fill the blank. ASTM Type II reagent water is designed for general chemical analysis and provides a controlled, low-background level of impurities, including organic compounds. This makes it the most reliable option for travel blanks, ensuring that background VOCs are minimized and any contamination detected reflects the sampling and handling workflow.

Distilled water, while very pure for many purposes, can still introduce VOCs from the distillation system or storage materials. Tap water contains chlorine, disinfectants, and various organic contaminants, which would confound VOC measurements. Seawater has high salinity and a complex mix of contaminants that would overwhelm or mask the VOCs of interest.