Hair Analysis Panel Discussion: Section 3.2
3.2 Sample Preparation Methods
Panel discussions on sample preparation focused on washing protocols. The group agreed that washing hair prior to analysis was an important consideration when external sources of the substance(s) being studied exist. Panelist-specific comments follow.
One panelist stated that no washing method can distinguish
between external contamination and internally deposited
elements. She noted that a number of washing procedure "camps"
exist, including the "no wash hypothesis" (Chittleborough
1980), use of a mild detergent, the washing procedure recommended
by the International Atomic Energy Agency that uses a solvent
in water (adopted by many research groups), and more radical
procedures that use chelating agents. Wide differences in
results have been observed depending on the washing method
External interferences can be especially significant
with small children, so CDC uses a standard washing protocol
The extent to which washing is necessary depends on the substance being studied and how the sample is being used. For example, washing is not necessary when one is testing for a substance for which no external source exists (e.g., methyl mercury). Other key questions to consider include: Are you looking at a spectrum or a specific agent/element at a hazardous waste site? Are you sampling for exposure information? Are you sampling to determine changes in exposures over time? (TC)
See Section 4 for additional discussions on hair washing, specifically as it relates to distinguishing between endogenous and exogenous sources of metals.