Sample treatment of human biological materials

Human biological materials to be investigated include (a) hard calcified tissues, e.g. bone, teeth, other calcified formations (b) semi-hard tissue, e.g. hair, nails (c) soft body tissues and (d) various biological fluids and secretions in the human body. The treatment of each of these materials varies from one material to another and, as stated earlier, is often determined by the instrumental method to be employed for measuring the analytical signal, the elements to be determined and the concentration levels at which these are present. For the purposes of this discussion, it shall be generally assumed that the analytical techniques employed include atomic absorption spectrometry both with (F-AAS) as well as with a furnace (GF-AAS), neutron activation analysis (NAA), flame emission spectrometry (FES) voltammetric methods and the three inductively coupled plasma spec-trometric methods viz. ICP-atomic emission spectrometry, ICP-mass spectrometry and ICP-atomic fluorescence spectrometry. The sample preparation of biological methods for all ICP techniques is usually similar (Guo, 1989). 

The separation of dentin and enamel is usually carried out mechanically by chipping the enamel in a mortar made of an inert material (Helsby, 1974 Retief et al, 1974) or by grinding with a diamond disc (Steinnes et al, 1974 Stack et al, 1977). A carbide steel 

CLASSIFICATION OF ASHING METHODS FOR HUMAN BIOLOGICAL MATERIAL IN TRACE ELEMENT ANALYSIS 

1 High Temperatures 2.1 High temperatures 3.1 High temperatures 

1 Combustion with air/oxygen 2.1.1 Normal pressure 3.1.1 Oxidative fusion 

---

Chapter 2 Sample treatment of human biological materials... 

SUGGESTED PROCEDURES FOR SAMPLE TREATMENT OF HUMAN BIOLOGICAL MATERIALS... 

The human biological materials may be solid (bone, teeth, hair, nails, tissue), semisolid (blood, faeces, viscera) or liquids (body fluids). Treatment of the solid samples usually demands some extra steps during sample manipulation, e.g. particle size reduction, homogenisation, sub-sampling etc. Heterogeneous liquid phases, e.g. blood and certain body fluids, additionally need stabilisation and homogenisation so as to avoid occurrence of any changes in their composition, prior to actual analysis (Anand et al., 1975). It is also advisable to keep the total number of transfers to a minimum, and use accessories made of non-wettable and inert materials in case of the liquids. 

The packing material first described for direct injection of biological samples was prepared by simply saturating the accessible adsorption sites of a Cis reversed-phase silica with human plasma proteins (105). After saturation, the human plasma proteins were denatured at the external surface, and their native conformation was destroyed. With this treatment, the proteins formed a hydrophilic layer with weak ion-exchange properties, which provided protection from contact with the sample proteins, whereas the alkyl ligands inside the pores remained unchanged and thus served for analyte retention. The retention behavior of the saturated phase did not alter with this treatment, but the efficiency was reduced dramatically. Such protein-coated columns have shown a lifetime of several months (106). 

---