Hair decontamination procedure prior to multi-class pesticide analysis Radu-Corneliu Duca, Emilie Hardy, Guillaume Salquèbre and Brice M. R. Appenzeller* Although increasing interest is being observed in hair analysis for the biomonitoring of human exposure to pesticides, some limitations still have to be addressed for optimum use of this matrix in that specific context. One main possible issue concerns the need to differentiate chemicals biologically incorporated into hair from those externally deposited on hair surface from contaminated air or dust. The present study focuses on the development of a washing procedure for the decontamination of hair before analysis of pesticides from different chemical classes. For this purpose, three different procedures of artificial contamination (with silica, cellulose, and aqueous solution) were used to simulate pesticides deposition on hair surface. Sev- eral washing solvents (four organic: acetone, dichloromethane, methanol, acetonitrile; and four aqueous: water, phosphate buffer, shampoo, sodium dodecylsulfate) were evaluated for their capacity to remove artificially deposited pesticides from hair surface. The most effective washing solvents were sodium dodecylsulfate and methanol for aqueous and organic solvents, respectively. Moreover, after a first washing with sodium dodecylsulfate or methanol, the majority of externally deposited pesticides was removed and a steady-state was reached since significantly lower amounts were removed by additional second and third washings. Finally, the effectiveness of a decontamination procedure comprising washing with sodium dodecyl- sulfate and methanol was successively demonstrated. In parallel, it was determined that the final procedure did not affect the chemicals biologically incorporated, as hair strands naturally containing pesticides were used. Such a procedure appears to remove in one-shot the fraction of chemicals located on hair surface and does not require repeated washing steps. Copyright © 2014 John Wiley & Sons, Ltd. Keywords: hair; decontamination; washing procedure; pesticides; multi-class analysis Introduction Although increasing interest is being observed in hair analysis for the biomonitoring of human exposure to pesticides, some limita- tions still have to be addressed for optimum use of this matrix in that specific context. One main possible issue concerns the need to differentiate chemicals biologically incorporated into hair from those externally deposited on hair surface due to contaminated air or dust. Chemicals incorporated by means of biological mech- anisms, likely to be located in the whole hair structure, can be interpreted as representative of the internal dose people have undergone during the period of hair growth. On the contrary, chemicals externally deposited only represent recent contamina- tion and are therefore less biologically relevant. Ideal decontam- ination procedure therefore has to remove external chemicals (deposited on the cuticle surface) without affecting internally incorporated compounds (present in the bulk of the matrix). In forensic sciences, decontamination of hair prior to drug analysis is an important step, since false positive samples might have legal implications. Thus, decontamination has been extensively documented and several washing procedures with different degrees of complexity have been proposed. [1] Hair decontamination before drug testing is generally performed with organic solvents (e.g. dichloromethane, acetone, methanol, acetonitrile) and/or with aqueous solutions of detergents (e.g. sodium dodecylsulfate) or buffers (e.g. phosphate buffer). [1–6] Unlike for drug testing, the decontamination with organic solvents before environmental pollutants analysis was less used [7–11] and more gentle decontamination solvents like water [12–14] and water with shampoo [15–20] were preferred. Nevertheless, no standardized washing procedure removing the totality of the external contami- nation without affecting the drugs biologically incorporated into hair is available yet. [21] Still, the importance of hair decontamination was acknowledged by the Society of Hair Testing (SoHT) and rec- ommendations for washing were made: both organic and aqueous solvents should be used, the efficiency of the washing procedure should be tested and, if required, additional clean-up steps should be taken. [21] An important step in the development of a decontamination procedure is to produce artificially contaminated specimens to be used for testing the efficiency of the washing to remove chemicals deposited on hair surface. The most classic contamina- tion procedure is the utilization of a soaking aqueous solution containing the compounds of interest. [4,6,22,23] Even if this artifi- cial contamination is effective, it reflects neither the external de- position of compounds on hair surface by biological fluids nor the environmental contamination occurring mainly through air- borne dust particles. Moreover, an important limitation associ- ated with hair dipping in aqueous solutions is the possible irreversible penetration of the compounds within the hair shaft. [6] * Correspondence to: Brice M. R. Appenzeller, Laboratory of Analytical Human Biomonitoring, Centre de Recherche Public de la Santé (CRP-Santé), 162A, Avenue de la Faïencerie, L-1511 Luxembourg, Luxembourg. E-mail: brice. appenzeller@crp-sante.lu Laboratory of Analytical Human Biomonitoring, CRP-Santé, 162A avenue de la Faïencerie, L-1511 Luxembourg, Luxembourg Drug Test. Analysis 2014, 6, 55–66 Copyright © 2014 John Wiley & Sons, Ltd. Research article Drug Testing and Analysis Received: 31 October 2013 Revised: 7 February 2014 Accepted: 24 February 2014 Published online in Wiley Online Library (www.drugtestinganalysis.com) DOI 10.1002/dta.1649 55