Sample matrix biota

SPE employing either GCB [6,25,73-75,80,81], C8 [77], C18 [82-87] or a combination of Cis- - SAX [88-91] cartridges is the most used method to determine SPC in environmental samples accompanied by detection with HPLC-FL [6,25,90], LC-MS [73-75,82,83,86], GC-MS with derivatisation [77,80,92] or capillary electrophoresis [81]. For biota samples, matrix SPE [85] or Soxhlet [91] followed by clean-up with SPE have been used to determine SPC. SPE employing GCB cartridges and further analysis by LC-MS has been used for the determination of SPDCs [73,74],... 

Characterisation of the Sample Matrix for Determinations in Biota (AU Types of Chemical)... 

CHARACTERISATION OF THE SAMPLE MATRIX FOR DETERMINATIONS IN BIOTA (ALL TYPES OF CHEMICAL)... 

PFAAs differ from more traditional lipophillic POPs (i.e., PAHs, PCBs, and chlorinated pesticides) in that bioconcentration occurs through association with proteins rather than adipose tissue [183]. As a consequence, higher PFAA levels are expected for protein-rich tissues, such as blood and liver [184]. As with other POPs, bioconcentration is more significant for organisms that are elevated in the food web. Analysis of biota is somewhat more challenging than for aqueous samples, due to increased sample matrix complexity. The development of methods for sample cleanup and PFAA concentration remains a topic of active study. 

The sampling sites are distributed along the entire basin but focusing the areas potentially polluted because of the emission of contaminant substances. Starting from 1992, the sampling sites have been extended, the list of compounds and the studied matrixes included in the network have been enlarged. Nowadays, the RCSP consists of the analysis of different compounds in water, sediments and biota from... 

Ylinen et al. [53] developed an ion-pair extraction procedure employing tetrabutylamonium (TBA) counter ions for determination of PFOA in plasma and urine in combination with gas chromatography (GC) and flame ionisation detection (FID). Later on, Hansen et al. [35] improved the sensitivity of the ion-pair extraction approach using methyl tertiary butyl ether (MTBE) and by the inclusion of a filtration step to remove solids from the extract making it amenable to liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination. Ion-pair extraction procedure has been the basis of several procedures for biota [49,54-58] and food samples [50,59,60]. However, this method has shown to have some limitations, such as (1) co-extraction of lipids and other matrix constituents and the absence of a clean-up step to overcome the effects of matrix compounds and (2) the wide variety of recoveries observed, typically ranging. 

It is not always necessary or required to digest the entire sample in order to free the metals for analysis. In some cases it is not even desirable. In studies of contaminated soils, for instance, the analyte of interest may be present as a soluble salt from a pollution source, as well as also being present in the structure of the mineral crystals. The soluble form is of concern, as it is available to biota and may eventually contaminate groundwater. That in the insoluble particles is not of interest. In such cases, where the analyte is much more soluble than the matrix or where the metals included in the matrix are not of interest, an extraction process rather than complete solubilization is preferred. This is treated further in Section 5.10. 

GAU-Radioanalytical has participated in several intercomparison exercises for H-3 and C-14 activities in aqueous and biota samples. These results are in good agreement with the reference values (Table 4). Currently there are no commercially available natural matrix reference materials for total H-3 and therefore the analysis of spiked samples with known certified activities of H-3 is the best possible way of showing that the method is working. 

Sometimes the sample parameters simply do not mesh with the constraints of a given method. Attempted analysis of a sample in which one or more constituents exceed the amounts in the matrix for which the method was reported to be applicable can result in failure. As discussed in Section 12.2.2, sample matrices such as water, soil, and biota can be so variable that a procedure developed for one set of samples may not be able to control interference from the different constituents of the samples under consideration. In response, analyses can be performed with smaller samples or more reagents. 

The exceptionally sharp, quasilinear spectra provided by PAHs under cryogenic sampling have aroused special interest in low-temperature fluorescence measurements on this type of pollutant. It has become apparent that low-temperature fluorimetry can be used to fingerprint specific compounds present at very low levels in PAH mixtures in various environmental matrices (e.g., sediments and biota) without the need for extensive prior cleanup. Low-temperature fluorimetric methods used for the analysis of PAH mixtures rely largely on the Shpol skii effect (in the frozen-solution or matrix-isolation mode). 

The use of supercritical fluid extraction (SEE) as an extraction technique is related to the unique properties of the supercritical fluid. These fluids have a low viscosity, high diffusion coefficients, low toxicity, and low flammability, all clearly superior to the organic solvents used in SPE extraction. The most common fluid used is carbon dioxide. SEE extractions of sediment samples have shown recoveries of >95% for all the individual PCBs. The separation of PCDDs from PCBs and chlorinated benzenes is difficult because of their similar solubility. An interesting development is the use of fat retainers. Samples, mixed in different weight ratios with, e.g., silica/silver nitrate 10% or basic alumina, can be placed in 7 ml extraction cells. The analytes are recovered by elution with 1.5-1.8 ml of hexane. With the correct fat-silica ratios and SEE conditions, no additional cleanup procedure is necessary for GC with an electron-capture detector (ECD). One drawback of SEE may be that the methods developed are valid for a specific matrix, but as soon as, e.g., the fat content of a biota sample or the type of lipids changes, the method has to be adapted. SEE is relatively complicated compared to other extraction techniques. In addition, the cell volumes are small, which limits the sample intake, and, with that, the detection limits. Einally, some reliable types of SEE equipment have recently been withdrawn from the market. This will have a substantial negative effect on the use of SEE in the near future. 

For the extraction of complex matrices, such as food, procedures based on ion-pair extraction using a tetrabutylammonium (TBA) hydroxide solution are widely employed [64,65]. However, this method has some disadvantages, such as (a) coextraction of lipids and other matrix constituents and (b) the wide variety of recoveries observed, which are related to the matrix effects mentioned previously. Liquid-solid extraction (LSE) is also applied to the analysis of biota and food samples [66]. During recent years, KOH digestion, to release covalently-bound fluoride ions followed by extraction using solid-phase extraction has been used. This method was initially reported by Yamashita et al. [67] and later applied in different studies [68]. For liquid samples, analysis protocols based on filtration followed by SPE are widely used. 

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