Toxicological analysis sampling techniques

GC/MS has been employed by Demeter et al. (1978) to quantitatively detect low-ppb levels of a- and P-endosulfan in human serum, urine, and liver. This technique could not separate a- and P-isomers, and limited sensitivity confined its use to toxicological analysis following exposures to high levels of endosulfan. More recently, Le Bel and Williams (1986) and Williams et al. (1988) employed GC/MS to confirm qualitatively the presence of a-endosulfan in adipose tissue previously analyzed quantitatively by GC/ECD. These studies indicate that GC/MS is not as sensitive as GC/ECD. Mariani et al. (1995) have used GC in conjunction with negative ion chemical ionization mass spectrometry to determine alpha- and beta-endosulfan in plasma and brain samples with limits of detection reported to be 5 ppb in each matrix. Details of commonly used analytical methods for several types of biological media are presented in Table 6-1. 

Sodium silicate is somev at more difficult to analyze than many other materials because of the formation of the relatively long lived radionuclide Na whose emissions interfere with the detection of other elements. Nevertheless we were able to determine, in a sample of sodium silicate, that many heavy elements of toxicological concern were undetectable down to the ppm to ppb level in the undiluted silicate (13), An XRF spectrometer can be configured to perform sequential multi-elemental analyses. It is less sensitive to the elements of lower atomic number. Also, since the X-rays penetrate only to a depth of about 10 urn, the sample must be homogeneous. Solid samples must be presented to the X-ray beam with a flat surface. However, the relative ease of sample preparation and the ability to run glasses and solutions with only minor dilution make X-ray fluorescence a useful technique where analysis for a wide range of impurities is required,... 

SPME is a solvent-free sampling technique suitable for analysis of volatile and semivolatile compounds from several matrices. This technique allows rapid sample preparation and simultaneously minimizes its manipulation, which is particularly important with toxic compounds. SPME has been demonstrated equally suitable for quantitative purposes, especially when trace amounts of analytes are to be determined, such as in clinical and toxicological investigations. 

Solid phase microextraction (SPME) was introduced by Arthur and Pawliszyn over 20 years ago [44]. It is a straightforward, solvent-free, and fast sample extraction method. SPME has become a widely used technique in many areas of analytical chemistry, such as food analysis, environmental sampling, forensics/toxicology, and biological analysis. Recent reviews have been published showing the latest development of this versatile extraction method [45 8]. SPME is based on the partition of the analyte between the extraction phase and the matrix. The technique can be used to monitor analytes in liquid samples or in the headspace and is basically compatible with HPLC and CE, but most applications are made by GC. As indicated by its name, it is not an exhaustive extraction technique and only a fraction of the target analyte is actually extracted. The quantity of analyte extracted is proportional to its concentration, as long as the equilibrium between the analyte in the fiber and the sample is reached. It provides linear results for wide concentrations of analytes (typically from levels of parts per million to parts per billion). 

Qiromatographic techniques are a vital component in the field of forensic toxicology. Their ability to separate components of a complex mixture assists in the identification of a wide range of chemical substances. Samples required for analysis are predominantly biological in nature, in particular, whole blood, urine, oral samples, and hair. 

Blood matrices are a field of great development concern regarding sample collection and handling. Within this field, there is growing interest in the analysis of dried blood spots (DBS) and dried matrix spots (DMS). The use of such supports presents numerous advantages over traditional wet plasma sampling techniques they are less invasive and use less blood, which enables juvenile toxicology and pediatric studies... 

Principles and Characteristics The fastest growing area in elemental analysis is in the use of hyphenated techniques for speciation measurement. Elemental spe-ciation analysis, defined as the qualitative identification and quantitative determination of the individual chemical forms that comprise the total concentration of an element in a sample, has become an important field of research in analytical chemistry. Speciation or the process yielding evidence of the molecular form of an analyte, has relevance in the fields of food, the environment, and occupational health analysis, and involves analytical chemists as well as legislators. The environmental and toxicological effects of a metal often depend on its forms. The determination of the total metal content... 

There are three assumptions about sampling which are common to most of the statistical analysis techniques that are used in toxicology. These are that the sample is collected without bias, that each member of a sample is collected independently of the others and that members of a sample are collected with replacements. Precluding bias, both intentional and unintentional, means that at the time of selection of a sample to measure, each portion of the population from which that selection is to be made has an equal chance of being selected. Ways of precluding bias are discussed in detail in the section on experimental design. 

Chemical and biological analyses of trace organic mixtures in aqueous environmental samples typically require that some type of isolation-concentration method be used prior to testing these residues the inclusion of bioassay in a testing scheme often dictates that large sample volumes (20-500 L) be processed. Discrete chemical analysis only requires demonstration that the isolation technique yields the desired compounds with known precision. However, chemical and/or toxicological characterization of the chemical continuum of molecular properties represented by the unknown mixtures of organics in environmental samples adds an extra dimension of the ideal isolation technique ... 

The nutritional, chemical, biological, and toxicological properties of a chemical element are known to be critically dependent on the form in which it occurs in food. The recognition of this fact has spurred the development of species-selective (speciation) analytical methods for food additives and contaminants. According to the IUPAC s dehnition, speciation analysis deals with the analytical activities of identification and/or measurement of the quantities of one or more individual chemical species in a given sample [1], The analytical approach is usually based on the combination of a chromatographic separation technique with an element-specif>c detection technique. The former ensures that the analyte compound leaves the column unaccompanied by other species of the analyte element, whereas the latter enables a sensitive and specil>c detection of the target element. Coupled (also called hyphenated) techniques have become a fundamental tool for speciation analysis and have been discussed in many published reviews [2D6]. 

Ulhaviolet, infra-red, nuclear magnetic resonance, and mass spectrometry all find a role in the analysis of pesticides, but only ultraviolet and mass spectrometry are suitable for screening purposes. Infra-red and nuclear magnetic resonance require extensive clean-up procedures before they can be used and the sample requirement is not consistent with the concentrations usually available in toxicology cases. However, both these techniques are valuable in the differentiation of isomers. 

Analytical toxicology is the use of qualitative and quantitative chemical and physical techniques used in sample preparation, separation, assay calibration, detection and identification, and quantification for the purposes of toxicological research and testing. Examples of the objectives of such analysis include ... 

---