Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was reviewed?
This review evaluates elemental hair analysis for heavy metal certification, synthesizing procedures and applications reported over roughly the prior decade. It explains hair morphology, mechanisms of metal incorporation, and the analytical landscape, emphasizing ICP-MS (including LA-ICP-MS) for multi-element ultra-trace quantification, isotope ratios, and speciation. Particular attention is given to sampling, standardized washing, digestion, quality assurance, and the persistent challenge of distinguishing endogenous from exogenous contamination. For HTMC, the paper is valuable because it links analytical choices to data reliability and shows where reference ranges and inter-laboratory comparability break down—critical for any certification standard. It also surveys clinical, environmental, and forensic use-cases, and trends such as isotope ratio applications and spatially resolved strand profiling.
Who was reviewed?
The article synthesizes studies of human hair across diverse geographies, ages, and exposure contexts, with occasional comparisons to animal keratin (e.g., whiskers) to illustrate diet/exposure tracing. Populations include children, adults, occupationally exposed workers, patients with specific diseases, residents near mining or industrial sites, and general reference cohorts, enabling assessment of variability due to sex, age, diet, cosmetics, smoking, environment, and analytical protocol differences that directly affect elemental hair analysis for heavy metal certification thresholds and interpretability.
Most important findings
| Critical point | Details for HTMC |
|---|---|
| ICP-MS is the workhorse | ICP-MS delivers multi-element, ultra-trace sensitivity and wide dynamic range; coupling to chromatography enables speciation, and coupling to laser ablation yields spatially and temporally resolved profiles along single hairs, powerful for exposure reconstruction relevant to certification audits. |
| Sampling and washing dominate uncertainty | Standardized scalp sampling is advised; washing must remove surface contamination without extracting endogenous metals. IAEA’s acetone–water protocol is common but not universally effective (e.g., Hg, U), and aggressive reagents (e.g., EDTA, ultrasonication) can strip internal elements; washing reagents themselves may introduce contamination. HTMC should mandate validated wash protocols per analyte and analysis of wash liquors. |
| Digestion and matrix effects | Microwave acid digestion is prevalent; incomplete decomposition leaves carbon that alters ionization. Acid strength mismatches between samples and standards bias Hg; memory effects necessitate carriers or flow injection. Internal standards and carbon buffering are recommended. Certification labs must document digestion completeness and matrix matching. |
| Interferences and instrumentation | Polyatomic interferences (e.g., ArCl on As) require collision/reaction cells or sector-field instruments; Si is notably difficult and demands glass-free introduction systems. Method selection should be specified by HTMC for interference-prone analytes. |
| Endogenous vs exogenous discrimination | No universal wash can fully remove exogenous load without affecting endogenous signal; thus, differentiation often relies on speciation, isotope ratios, or LA-ICP-MS depth/longitudinal profiling. HTMC acceptance criteria should incorporate confirmatory evidence when exogenous contamination is plausible. |
| Reference ranges are site- and cohort-specific | Reported “reference” intervals vary widely with age, sex, hair color, diet, and locale; cross-study comparability is poor. HTMC should adopt matrix- and region-specific interpretive ranges and require co-analysis of appropriate CRMs. |
| Speciation is essential for risk relevance | For arsenic and mercury, species—iAs vs organo-As; MeHg vs inorganic Hg—determine toxicity. Extraction can induce interconversion; species-specific isotope dilution is recommended to correct de-methylation. HTMC needs species-level targets and validated extraction QA/QC. |
| Isotope ratios enhance source apportionment | Pb, U/Pu, and Hg isotope signatures enable source tracing, metabolism insights, and historical exposure reconstruction. Inclusion of isotopic criteria can strengthen HTMC adjudication for disputed exposure sources. |
| LA-ICP-MS for time-resolved certification evidence | Direct ablation of single strands provides chronological exposure profiles, confirming acute events, treatment adherence (e.g., Pt after cisplatin), and diet-driven Hg fluctuations, with S as an internal standard. HTMC could allow LA-ICP-MS as confirmatory testing for suspected episodic exposures. |
| QA/QC gaps limit regulatory confidence | Many studies omit CRMs or recovery tests; inter- and intra-laboratory reproducibility remains limited. HTMC should enforce CRMs for total elements and, where available, species CRMs, along with method blanks, wash-liquor checks, spikes, and IS use. |
Key implications
For regulators, consistent sampling, analyte-specific washing, and interference-aware ICP-MS are primary regulatory impacts; certification requirements should include CRMs, isotope/speciation confirmation for As and Hg, and optional LA-ICP-MS for time-stamped evidence. Industry applications include exposure reconstruction and supply-chain audits. Research gaps span standardized washing, Si/As interference control, and broader speciation. Practical recommendations emphasize matrix-matched calibration, internal standards, wash-liquor analysis, and region-specific reference intervals.
Citation
Pozebon D, Scheffler GL, Dressler VL. Elemental hair analysis: A review of procedures and applications. Analytica Chimica Acta. 2017. doi:10.1016/j.aca.2017.09.017
