|
|
Problems, benefits and limitations of the determination of trace elements in hair.
ŽIŽKOVÁ, Věra
The thesis focuses on an evaluation of own experience in determining trace elements in hair and on gathering literature data from this area. The thesis concurrently attempts to answer the question of whether the determination of trace elements in hair is always relevant and beneficial or whether it poses certain limitations. The determination of trace elements in hair presents a number of advantages (i.e. easy and non-invasive sample collection, sample durability, small quantity) and it allows researchers to obtain otherwise hardly accessible retrospective information on the condition of the human body over a longer time horizon, often extending over several years. However, the determination of trace elements in hair also has its drawbacks and it requires researchers to resolve multiple problems. The use of hair cosmetics, for example, may have a potentially negative effect and there is the possible risk of hair contamination in the external or working environment. Therefore, when performing hair analysis, the first step is to clean (wash) the hair in an adequate manner so that external contaminants are removed as much as possible while endogenous elements are left intact. For this purpose, the methods recommended by IAEA, which include repeated washing and rinsing with the use of water and acetone, are often applied. The second critical step is hair mineralization, i.e. conversion to a solution. The common risks associated with this procedure are possible element loss due to e.g. evaporation caused by heat on one side and sample contamination by used reagents on the other side. Microwave mineralization with concentrated HNO3 and H2O2 additives seems as an ideal procedure in this respect. The own hair analysis may be effected by means of polarography or mass spectrometry with inductively coupled plasma. Nevertheless, the most frequently implemented method employs atomic absorption spectroscopy, namely flame atomisation for sufficiently high concentrations and electrothermal atomisation for low concentrations. Furthermore, method validation and standardisation are necessary for obtaining relevant information. For example, trueness should be verified through interlaboratory crosschecks (almost unavailable in the Czech Republic for the time being) or by using available reference material (e.g. BCR CRM 397). Precision is verified rather easily by repetitive homogenous sample analysis. In contrast to the discussed issues, commercial advertisements promise trouble-free, simple and easy, and sometimes even miraculous mapping of the health condition with distinct results and recommendations in the form of various food supplements. All may be naturally obtained after the payment of a specific amount (often paid repeatedly). How to answer, after summarizing data gathered from literature and own experience, the presented basic question on whether hair analysis is beneficial and generally applicable. In many cases, the answer may be yes. The thesis details examples of successful application when obtaining retrospective data on high expositions to Pb, Ni, Cd, Hg, and Fe: lead intoxication in a patient due to the long-term intake of a herbal concentrate containing lead, multiple-week monitoring of nickel content in the hair of a volunteer after a one-week exposition in an NiSO4 production environment, verification of Fe loss in a hemato-oncology patient, lead intoxication of an entire family as a result of long-term use of poor quality tableware, lead intoxication in historical painting conservators. As regards the commercial use of the individual result of the general population, it still seems rather problematic and the answer to the basic question is no. The determination of trace elements in hair is not beneficial and it cannot be generally applied that easily.
|
guest ::
