Answer to Question #12023 Submitted to "Ask the Experts"

Category: Instrumentation and Measurements — Surveys and Measurements (SM)

The following question was answered by an expert in the appropriate field:

Q

What is the best compatible scintillator for tritium sampling using ethylene glycol?

A

Ethylene glycol contains two hydroxyl groups, which add considerable polarity to the molecule. Consequently, the scintillation cocktail solvent must contain sufficient "polarphilic" components to allow the ethylene to go into uniform solution. In the past before the advent of some of the newer scintillator preparations, which are more environmentally friendly and less toxic to people, preparations such as Bray's solution (which contained a number of constituents, including dioxane, ethylene glycol, methanol, and naphthalene) were often used to accommodate various polar molecules present in samples. Other mixes often used toluene or xylene as the major solvent and incorporated emulsifiers/surfactants to accommodate more polar samples. While some people still use such preparations, many have opted for the newer, generally safer commercial products that use less toxic/more environmentally friendly solvents. Depending on sample characteristics, there may sometimes be a loss of counting efficiency for some of the newer scintillator mixes, but these are often offset by their added convenience and safety.

One of the larger suppliers of scintillation cocktail mixes is Perkin Elmer, which bought out several other producers/suppliers of liquid scintillation products. Their product Ultima Gold is a very popular and effective mix for handling various polar samples as well as some less polar constituents. Its major solvent component is di-isopropylnaphthalene (DIPN), a high flashpoint solvent with good biodegradability. This reference is not intended as a product endorsement but simply as an example of a popular product with which I am familiar. Other suppliers of other products are available, and you may want to check out some of them—e.g., VWR, Fisher Scientific, Meridian Biotechnologies, GE Healthcare Life Sciences, EcoLite+™ cocktail through Thomas Scientific. Additional suppliers can be found by searching the internet.

George Chabot, PhD, CHP

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