Which sampler is used to collect water samples with volatile organic compounds (VOCs) in wells and storage tanks?

• A. Kemmerer bottles
• B. The DPD kit
• C. Weighted bottle samplers
• D. Plastic Bottles

Answer: (C)

Volatile organic compounds are easily lost to the air, so you need a sampling method that keeps the water from contacting air as much as possible and from changing while you collect it at depth. A weighted bottle sampler is designed for this purpose: you lower it to the desired depth in a well or storage tank, it fills as it sinks, and when retrieved it closes off, leaving little to no headspace. This minimizes degassing and preserves the VOC concentration for an accurate measurement.

Kemmerer bottles are traditional sampling bottles with a stopcock and can introduce air during filling and retrieval, which increases the risk that VOCs will volatilize and alter the sample. The DPD kit is a chlorine testing tool, not a sampling device for VOCs. Plastic bottles are just containers and don’t provide a mechanism to isolate the sample from air or seal at depth, making VOC losses more likely.