title: Comparison of Digestion Methods for the Determination of Trace Elements and Heavy Metals in Human Hair and Nails.
abstract: BACKGROUND
  Microwave is the most reliable sample digestion method. However, it requires expensive microwave digester automation and has relatively low productivity. In this study, three non-automated digestion methods, i.e. wet acid digestion using nitric acid (HNO3) and hydrogen peroxide (H2O2), wet acid digestion using HNO3, and dry washing, are compared in order to determine the best approach.
  
  
  METHODS
  Certified reference material IAEA-086 (International Atomic Energy Agency, Austria) and hair and nail samples from 20 female students of Universiti Kebangsaan Malaysia, aged 19 to 30 years, were collected and analysed using the three digestion methods.
  
  
  RESULTS
  For hair samples, analysis of variance of repeated measures showed significant differences in the level of all elements (P< 0.001) between the three methods. For nail samples, only the copper (Cu) level showed no significant difference (P= 0.100) between methods. Wet acid digestion using HNO3and H2O2showed the best within- and between-run relative standard deviation (RSD) values, with within-run RSD for all elements, except for selenium (Se), < 5%. The between-run precision ranges from 6.14% to 17.96% for hair and from 3.53% to 11.52% for nail samples. Wet acid digestion using HNO3and H2O2showed both good accuracy and precision for manganese (Mn) and magnesium (Mg), with percentage recoveries of 110% and 96.9%, respectively. All elements show higher method detection limit (MDL) values than the previous study: 0.05 μg/g Mg for wet acid digestion using HNO3, 0.02 μg/g Se for wet acid digestion using HNO3and H2O2, and 0.2 μg/g Mg for dry ash method.
  
  
  CONCLUSIONS
  Wet acid digestion using HNO3and H2O2proved to be the best method in terms of precision, accuracy, recovery, and MDL. However, only Mn and Mg showed adequate precision, accuracy, and percentage of recovery.
authors.affiliation: Biomedical Science Programme, Faculty of Health Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia.
authors.forename: Ismarulyusda
authors.initials: I
authors.lastname: Ishak
authors.affiliation: Biomedical Science Programme, Faculty of Health Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia.
authors.forename: Farah Dayana
authors.initials: FD
authors.lastname: Rosli
authors.affiliation: Biomedical Science Programme, Faculty of Health Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia.
authors.forename: Jamaludin
authors.initials: J
authors.lastname: Mohamed
authors.affiliation: Biomedical Science Programme, Faculty of Health Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia.
authors.forename: Muhammad Faiz
authors.initials: MF
authors.lastname: Mohd Ismail
keywords: digestion; hair; heavy metal; nails; trace element