Sampling biological materials

Figure 6.1. Influence of time on the extraction efficiency of methylmercury from CRM-463 sample (biological material) with ( ) and without (m) US assistance. (Reproduced with permission of Elsevier, Ref [10].)...

Although infrared photoacoustic spectra have been collected of gaseous samples 3,44 the primary advantage appears to lie in the area of solid and surface samples. Very little has been published thus far in the area of FT-IR-PAS, however, several publications have involved the measurement of solid samples. 6,47 the measurement of surface samples,biological materials,and binary mixtures.50... 

As a special development in recent years, SEMs have been designed which no longer necessitate high vacuum (enviromnental SEM, ESEM variable pressure SEM, VPSEM). This development is important for the imaging of samples with a residual vapour pressure, such as aqueous biological or medical samples, but also samples in materials science (wet rock) or organic chemistry (polymers). 

The infonuation that can be extracted from inorganic samples depends mainly on tlie electron beam/specimen interaction and instrumental parameters [1], in contrast to organic and biological materials, where it depends strongly on specimen preparation. 

There are problems in use of the frit nebulizer. Memory effects tend to be severe, and each sample needs to be followed by several wash-outs with clean solvent before the pores of the frit become free of residual sample. Biological samples frequently contain detergent-like materials, and... 

Comprehensive accounts of the various gravimetric, polarographic, spectrophotometric, and neutron activation analytical methods have been pubHshed (1,2,5,17,19,65—67). Sampling and analysis of biological materials and organic compounds is treated in References 60 and 68. Many analytical methods depend on the conversion of selenium in the sample to selenous acid, H2Se02, and reduction to elemental selenium when a gravimetric deterrnination is desired. 

The use of mutant 34486 of Neurospora crassa for the microbiological assay of ch oline has been described (8). A physiological method has also been used in which the ch oline is extracted after hydrolysis from a sample of biological material and acetylated. The acetylcholine is then assayed by a kymographic procedure, in which its effect in causing contraction of a piece of isolated rabbit intestine is measured (33). 

Polarographic methods can be used to examine food and food products biological materials herbicides, insecticides and pesticides petroleum and petroleum products pharmaceuticals. The examination of blood and urine samples is frequently carried out to establish the presence of drugs and to obtain quantitative results. 

In more recent times chemically defined basal media have been elaborated, on which the growth of various lactic acid bacteria is luxuriant and acid production is near-optimal. The proportions of the nutrients in the basal media have been determined which induce maximum sensitivity of the organisms for the test substance and minimize the stimulatory or inhibitory action of other nutrilites introduced with the test sample. Assay conditions have been provided which permit the attainment of satisfactory precision and accuracy in the determination of amino acids. Experimental techniques have been provided which facilitate the microbiological determination of amino acids. On the whole, microbiological procedures now available for the determination of all the amino acids except hydroxy-proline are convenient, reasonably accurate, and applicable to the assay of purified proteins, food, blood, urine, plant products, and other types of biological materials. On the other hand, it is improbable that any microbiological procedure approaches perfection and it is to be expected that old methods will be improved and new ones proposed by the many investigators interested in this problem. 

This method is especially valuable for identifying metabolites and other trace biological materials. A small portion of the sample is dissolved in the minimum amount of solvent and the solution is divided... 

The reliability of the results may be judged from the following. In sections of biological materials, about 10 pt thick, the absolute errors in the determination of calcium ranged between 0.15 and 0.2 g per square micron those for phosphorus and sulfur between 0.06 and 0.1 /igg per square micron. These errors often corresponded to less than 5% of the amount of element present in the sample. 

The obtaining of such reliable results on minute samples makes it possible to discover how the chemical composition of biological materials varies from one small section to another. The data thus obtained can be combined with dry-weight data from absorptiometry with polychromatic beams to yield conclusions of the,kind listed in Table 11-4. 

A more thorough review of analytical methods can be found in ATSDR (2003). Sample detection limits for biological material are typically in the range of 1-5... 

In order to determine the identity and quantity of each amino acid in a sample of biologic material, it is first necessary to hydrolyze the peptide bonds that fink the amino acids together by treatment with hot HCl. The resulting... 

Error 1 CRMs completely or partly not identical with the matrix to be analyzed Ber-mejo-Barrera et al. (1999) studied enzymatic hydrolysis procedures using pronase E as sample pretreatment for multi-element - Cu, Fe, Mg, Zn, Ag, As, Cd, and Pb -determination in biological materials, mussel samples and human hair. 

Bermejo-Barrera P, I Ernanuez-Nocelo S, Moreda-PiSeiro A and Bekmejo-Barrera A (1999) Useftilness of enzymatic hydrolysis procedures based on the use of pronase E as sample pre-treatment for multi-element determination in biological materials. J Anal At Spcctrom 14 1893-1900. 

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