Sample collection and storage

For air sampling in industrial settings, personnel mercury vapor samplers rely on a hopcalite filter absorber, followed by chemical treatment and atomic absorption spectrometry (AAS) analysis. This method requires field and reagent blanks, but has a reported detection limit in the pg m range (Turner and Boggle 1993). A passive diffusion sampler has also been developed as a useful technique for mercury vapor monitoring in the atmosphere and as a personal mercury dosimeter (Kvietkus and Sakalys 1994). 

Main mercury species in ambient air are elemental mercury (Hg°), reactive gaseous mercury (Hg(II)), mercury bound to aerosols, and methylmercury. Though dimethyl-mercury is together with Hg° the most volatile form of Hg, it has not been detected unequivocally in the atmosphere. Elemental mercury represents 95% of Hg in the atmosphere with ambient concentrations at the order of 1-5 ng m whereas MeHg in air was found to be in the range of 1 to 20 pg m (Pirrone et al. 2001). For this reason, in most cases mercury is pre-con-centrated on solid absorbers (gold, silver, activated carbon traps, etc.) prior to analysis (Drabaeck and Iverfeldt 1992, Horvat 1996). 

There are, however, some new instruments that do not require pre-concentration for elemental mercury in air, such as AAS with Zeeman background correction (Pogarev etal. 2002) and mobile laser systems for remote measurements (Edner etal. 1992). In general, total gaseous Hg in air can be determined with high precision and accuracy. 

Of particular concern is mono-methyl-mercury (MeHg) due to the high capacity of this species to bioaccumulate in aquatic systems and the need to be considered in risk assessment. The presence of MeHg in the atmosphere and its contribution to water bodies has been demonstrated, for example, by Bloom and Watras (1988), Hult-berg et al. (1995) and Brosset and Lord (1995). Since the concentration of MeHg in 

The collection, storage, and transport of samples for mercury analysis may present problems, since glass and plastic risk being contaminated with mercury therefore, it is advisable to check each batch used for sample collection and storage scrupulously for possible contamination. Older data in the literature should be checked for their accuracy, as reported data were often too high due to possible contamination. 

In the measurement of cytokines in body fluids, samples must be collected and stored in the proper manner. The main problems encountered in the collection process include (1) cytokines can continue to be produced after sample collection by the various cells present in the biological fluid (2) collection tubes can become contaminated by microorganisms, which are a potent stimulus of cytokine production (3) cytokines can be degraded in the collection container and (4) cytokines can bind to cell receptors during storage. 

For bioassays, serum collected in pyrogen-free tubes is required. After rapid centrifugation, freezing of the plasma (or serum) at 80 °C is recommended for storage. Freezingthawing cycles must be prevented. 

For immunoassays in biological fluids, ethylenedi-aminetetraacetic acid (EDTA) plasma is the most suitable 

For intracellular cytokine detection by flow cytometry, PBMCs are often used, but to have a more specific analysis, it may be necessary to use cells from other biological fluids (e.g., synovial fluid, cerebrospinal fluid, and bronchoalveo-lar lavage fluid) or to separate cells according to functional characteristics or expression of membrane antigens (e.g., CD3, CD4, CDS, and CD56). 

In practice, all analyses for cytokines must be performed within a narrow interval of time (not more than 5 hours) after sample collection to prevent cellular interactions and possible cytokine release. Blood samples must be collected with endotoxin-free heparin. The same is true for immunoassays deafing with cytokine production by blood cells. 

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MacKinnon [92] carried out a very detailed study in which sample collection and storage, sample preparation, the dry oxidation procedure, water corrections, adsorption effects, and precision and accuracy are all discussed in detail. 

The overall method includes sample collection and storage, extraction, and analysis steps. Sampling strategy is an important step in the overall process. Care must be taken to assure that the samples collected are representative of the environmental medium and that they are collected without contamination. There is an extensive list of test methods for water analysis (Tables 8.2, 8.3, and 8.4), which includes numerous modifications of the original methods, but most involve alternative extraction methods developed to improve overall method performance for the analysis. Solvent extraction methods with hexane are also in use. 

BH4 in CSF is sensitive to auto-oxidation, and correct sample collection and storage are essential for the performance of the method. CSF (1 ml) should be collected in tubes containing 1 mg DTE and 1 mg diethylenetriaminepentaacetic acid (DTPA). Samples should be immediately stored at -70°C [14]. 

The chemical properties of HVA, 5HIAA and 3-MD make them amenable to reverse-phase high-performance liquid chromatography (HPLC) with electrochemical detection. Furthermore, the composition of CSF means that little, if any, sample preparation is required prior to analysis. However, the susceptibility of these metabolites to oxidation means that careful sample collection and storage is required in order to minimise analyte degradation. 

In addition, the reliability of the stripping data strongly depends on the degree to which contamination can be minimized. Hence, as in other trace analytical methods, all principles of good laboratory practice (glassware cleanliness, sample collection and storage, etc.) must be observed to obtain high accuracy and low detection limits. 

In this section a concise overview of the most widely used analytical procedures for the determination of PCBs in environmental matrices (namely, air, sea water, snow/firn/ice, sediment/soil and biota) is given. Regardless of the nature of the sample, the following steps are generally included in an analytical procedure i) sample collection and storage ii) sample preparation (extraction of the analytes and cleanup of the extract) iii) instrumental analysis iv) data evaluation, including analytical quality control. 

T8.5 If you really want to cover all challenges related to the two analyses, you should also consider the issues related to the sample collection and storage. On the question of specific samples (volcano vs. sediment), consider the phases of the sample, amounts of substances of interest, and potential toxicities. 

Special precautions may be needed to prevent loss of certain volatile organic compounds during sample collection and storage. 

Defining the scope of the method Support for PK/PD/other studies Desired sensitivity Matrix of study samples Sample collection and storage conditions Assay format/technology platform... 

A pure, stable, and well-characterized reference standard is a vital component of a validated PK assay. When accompanied by appropriate sample collection and storage procedures, such a validated assay is the only means to accurate quantitation of protein therapeutics in biological samples. 

Various aspects on sources of error in sample collection and storage for trace element analysis have been reviewed (Aitio, 1981 Aitio and Jarvisalo, 1984 Anand et al., 1975, Angerer et al., 1983 Behne, 1981 Gills et al., 1974 Hops, 1977 Iyengar and Sansoni, 1988 Kosta, 1982 Kumpulainen, 1984 Sansoni and Iyengar, 1980 Stoeppler, 1980, 1983 Sunderman, 1980 Valkovic, 1977 Versieck et al. 1982). 

Wagner, G 1995. Basic approaches and methods for quality assurance and quality control in sample collection and storage for environmental monitoring. Sci. Total Environ. 176, 63-71. 

Sample Collection and Storage. This step in an analytical study offers many opportunities for loss of integrity of samples, and must be described in full detail. Precisely what tools will be used to acquire the samples Disposable scalpels, for example, are coated with an oil that can contaminate tissues. Metal tools obviously should not be used to take samples for trace metal determination. Good judgement can not be assumed details must be provided. 

The chemical analysis consists of the following steps (i) Sample collection and storage (ii) Pretreatment and sample preparation (iii) Measurement (iv) Data processing and validation. Sample collection and storage are very critical steps in the whole procedure. Faults made during these steps cannot be corrected afterwards. Sample preparation must be taken into account in the calibration. The risk of contamination will increase with decreasing concentration of the analyte. Attention must be paid especially to contamination in the determination of ultra small amounts (p.p.b.-level). 

It is critical to ensure ex vivo stability of the targeted analytes in the biological matrices during sample collection and storage in order to accurately measure the concentrations at the time of collection. Instability of a drug or metabolite can be caused by chemical reaction. 

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