Key Takeaway
The hair sample washing procedure is one of the most important stages in preparing material for elemental analysis. Its purpose is to remove external contaminants that could interfere with analytical measurements. At the same time, overly aggressive cleaning may lead to the partial loss of certain elements. Therefore, standardization of the washing process is a critical component of quality assurance in laboratories performing hair analysis.
Why Does Hair Require Cleaning Before Analysis?
Hair is a biological material that is continuously exposed to the surrounding environment.
Its surface may accumulate:
- environmental dust,
- household dust,
- industrial contaminants,
- hair care products,
- styling products,
- minerals from water,
- metal particles present in occupational environments.
If these contaminants are not removed before analysis, they may influence the measured elemental concentrations.
For this reason, the washing procedure is a standard part of sample preparation in laboratories performing hair analysis.
Hair as a Biomonitoring Material
The value of hair in environmental research stems, among other factors, from its ability to reflect long-term exposure to selected elements.
The topic is discussed in greater detail in the article:
“Why Is Hair Used in Environmental Biomonitoring?”
In biomonitoring studies, it is essential to distinguish between elements incorporated within the hair structure and those present only on its surface.
This is precisely why sample cleaning plays such an important role.
What Is External Contamination?
External contamination refers to substances present on the surface of the hair that are not related to physiological processes occurring within the body.
Sources of contamination may include:
- occupational environments,
- atmospheric air,
- cosmetics,
- hair dyes,
- bleaching agents,
- tap water,
- contact with metals.
For certain elements, particularly heavy metals, external contamination may significantly influence analytical results.
What Does the Hair Washing Procedure Involve?
Laboratories use different protocols for hair sample preparation.
The process commonly includes:
- Assessment of sample quality.
- Sample sorting and preparation.
- Cleaning using appropriate solvents.
- Rinsing with high-purity water.
- Drying under controlled conditions.
- Sample digestion prior to analysis.
The objective is to remove surface contamination while preserving the elemental composition within the hair matrix.
Why Can Excessive Washing Be a Problem?
One of the most important methodological challenges is finding the balance between effective cleaning and preservation of sample integrity.
Overly aggressive washing procedures may:
- partially remove certain elements,
- alter sample composition,
- reduce result reproducibility.
Conversely, insufficient cleaning may leave contaminants on the hair surface that interfere with analysis.
Therefore, laboratories performing hair analysis should apply validated and reproducible sample preparation procedures.
Why Can Results Differ Between Laboratories?
Scientific literature identifies differences in sample preparation procedures as one of the reasons for variability between laboratories.
Different laboratories may use:
- different washing protocols,
- different solvents,
- different exposure times,
- different drying procedures.
As a result, measurements obtained from the same hair sample may vary to some extent.
This topic is discussed in more detail in the article:
Standardization as a Component of Laboratory Quality
In modern analytical laboratories, sample preparation procedures are an integral part of the quality system.
Standardization typically includes:
- standard operating procedures (SOPs),
- reagent quality control,
- method validation,
- personnel training,
- process documentation.
For biological materials such as hair, standardization is particularly important for achieving reproducible results.
The Role of Method Validation
To ensure reliability, sample preparation procedures should be validated.
Validation helps assess:
- method accuracy,
- precision,
- reproducibility,
- robustness against interference,
- process stability.
A more detailed discussion can be found in the article:
“How Are ICP-OES Methods Validated for Biological Material Analysis?”
Hair Washing and ICP-OES Analysis
Once the cleaning process is completed, the sample proceeds to subsequent preparation and analytical stages.
One of the most commonly used technologies in hair elemental analysis is ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry).
The effectiveness of this method depends not only on instrument performance but also on the quality of sample preparation.
More information can be found in the article:
“ICP-OES Spectrometry in Biological Material Elemental Analysis – Capabilities and Limitations”
The Importance of QA/QC in the Washing Process
The washing procedure should be incorporated into the laboratory quality control system.
In practice, this includes:
- implementation of standard operating procedures,
- monitoring reagent quality,
- documenting the process,
- regular method reviews,
- assessing result reproducibility.
Analytical data quality depends on every stage of sample preparation, not solely on the final measurement.
This topic is explored further in the article:
“Data Quality in Elemental Analysis – The Role of QA/QC Procedures in the Laboratory”
FAQ
No. Scientific literature documents significant differences between laboratories regarding washing and sample preparation procedures.
Because hair may contain contaminants originating from the environment, cosmetic products, or occupational exposure.
Yes. Over-cleaning may lead to the partial removal of certain elements from the sample.
Yes. In laboratories operating according to quality standards, sample preparation is an integral component of a validated analytical method.
Yes. Differences in sample preparation are among the most frequently reported reasons for discrepancies in HTMA results.
Summary
The hair washing procedure is one of the key stages of elemental hair analysis.
Its purpose is to remove external contamination while preserving the intrinsic elemental composition of the hair.
The reliability of the process depends on:
- standardized procedures,
- method validation,
- reagent quality,
- laboratory expertise,
- quality assurance systems.
Therefore, when evaluating a laboratory performing hair analysis, it is important to consider not only the analytical instrumentation but also the sample preparation procedures employed.
References
- Kempson IM, Lombi E. Hair analysis as a biomonitor for toxicology, disease and health status. Chemical Society Reviews. 2011;40(7):3915–3940..
- Rodrigues JL, Batista BL, Nunes JA, Passos CJ, Barbosa F Jr. Evaluation of the use of human hair for biomonitoring the deficiency of essential and exposure to toxic elements. Science of the Total Environment. 2008;405(1–3):370–376.
- Bass DA, Hickock D, Quig D, Urek K. Trace element analysis in hair: Factors determining accuracy, precision, and reliability. Biological Trace Element Research. 2001;83(1):1–16.
- Seidel S, Kreutzer R, Smith D, McNeel S, Gilliss D. Assessment of commercial laboratories performing hair mineral analysis. JAMA. 2001;285(1):67–72.
- Harkins DK, Susten AS. Hair Analysis: Exploring the State of the Science. Environmental Health Perspectives. 2003;111(4):576–578.
- Chojnacka K, Górecka H, Górecki H. The influence of living habits and family relationships on element concentrations in human hair. Science of the Total Environment. 2006;366(2–3):612–620.
- International Atomic Energy Agency (IAEA). Elemental Analysis of Biological Materials. Current Problems and Techniques with Special Reference to Trace Elements. Vienna.
Hair elemental analysis is a tool used in biomonitoring and environmental research. It is not a standalone diagnostic method and does not replace medical consultation or clinical diagnostics.