Tissue , generally samples

The general sample set for method validation parameters is the same for all matrices under consideration (except body fluids and tissues, see Section 4.2.5) ... 

In cases of suspected human toxicity, it would appear that the hair is the best tissue to sample as it is generally exposed to the likely cause of poisoning, i.e., particulate manganese-containing dust [65]. 

The quanitity of the raw material necessary to produce a reliable estimate of any element will depend on the selected detection instrument. In general, samples for uranium analysis are preconcentrated by evaporation, air-, freeze-, or oven-drying to remove water, and dry-ashing or wet-ashing to remove carbonaceous matter. For vegetation and soil, acid or alkali fusion followed by acid dissolution of the fusion cake is required to ensure dissolution of refractory materials. Aerosol, water, soft tissues, blood, and dry-ashed bone samples may be solubilized with mineral acids. 

Stability Assessment In general there is no formal stability study prior to the certification of a natural matrix S RM. H owever, the stability of the certified analytes is monitored on a regular basis, typically every 1-3 years depending on the analytes, as the SRMs are analyzed as control samples during the analyses of similar matrix samples. A recent study of PAHs in frozen mussel tissue over nearly 10 years found no significant changes in the concentrations of the measured PAHs (Schantz et al. 2000). 

The sample set must include two fortification levels appropriate to the proposed LOQ and likely residue levels or 10 times the LOQ, except for body fluids and tissues (considered in Section 5.2.3) where validation data at the LOQ are sufficient. Five determinations should be made at each fortification level. In general, mean... 

In general, the physical structure of the tissue must be broken down mechanically followed by an extraction procedure, before the sample can be analyzed. Homogenization using blenders, probe homogenizers, cell disrupters, sonicators, or pestle grinders is particularly useful for muscle, liver, and kidney samples. Regardless of the method used for tissue disruption, the pulse, volume of extraction solvent added, and temperature should be validated and standardized in order to ensure reproducible analytical results. During cell disruption, care should be taken to avoid heat build-up in the sample, because the analyte may be heat labile. 

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