Sample preservation absorption

Single-component methods are valid for that parameter cited in the seope of the standard, only. Generally, a single-component method requires parameter specific descriptions like sampling procedure, sample preservation and preparation, chemical reaction procedures, and measurement steps. Examples for typieal singlecomponent procedures are photometric, electrometric, or atomic absorption spectro-metric (AAS) methods. The capital cost for the apparatus is relatively low. However, the obligatory procedural steps m be time consuming and labour intensive. 

It was obvious that contamination had been occurring during the analytical procedure. In addition, adequate pretesting of the polyethylene vessels revealed that contamination of the sample preserved with 1% v/v cone. H2SO4 could occur both by desorption of mercury from the walls of the vessel (despite previous concentrated acid washes) and by absorption through the walls of the vessel (5). 

Speciation Overview Waters, Sediments, and Soils. Environmental Analysis. Extraction Solid-Phase Extraction. Food and Nutritional Analysis Overview. Geochemistry Soil, Minor Inorganic Components. Ion Exchange Overview. Isotope Dilution Analysis. Liquid Chromatography Overview. Polarography Overview. Sample Handling Sample Preservation. Voltammetry Overview. Water Analysis Industrial Effluents. X-Ray Absorption and Diffraction X-Ray Absorption. 

Spectrometry Overview. Mercury. Microscopy Techniques Scanning Electron Microscopy X-Ray Microscopy. Particle Size Analysis. Polychlorinated Biphenyls. Polycyclic Aromatic Hydrocarbons Environmental Aj li-cations. Radiochemical Methods Overview. Sample Handling Sample Preservation. Sampling Theory. Surface Analysis Auger Electron Spectroscopy. Tin. X-Ray Absorption and Diffraction Overview. X-Ray Fluorescence and Emission Energy Dispersive X-Ray Ruores-cence Particle-Induced X-Ray Emission. 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Chemiluminescence Overview. Chromatography Overview. Flow Injection Analysis Principles Instrumentation. Ion-Selective Electrodes Overview. Quality Assurance Quality Control Reference Materials. Sample Handling Sample Preservation. Sampling Theory. Water Analysis Overview Organic Compounds. Water Determination. 

With respect to sampling, sufficient numbers of environmental samples should be obtained to permit reliable statistical and biologic Interpretation of results. At the same time, the samples collected should be from environmental locations where human exposure Is most likely to occur (or did occur. If questions of past exposures require assessment). They should also be targeted for those environmental media which can be expected to have the greatest potential for human exposure and absorption. Finally, the samples must be obtained and preserved so that the chemicals which pose the greatest threat for human health In terms of toxicity and tissue persistence can be accurately measured. 

Absorption of atmospheric gases Chemical oxidation due to exposure to oxygen in air Change in pH and conductivity due to carbon dioxide absorption Prompt and proper preservation Measurements of field parameters during sampling... 

The analysis of corrosion scale or product may be done by wet chemical methods such as spectrophotometry or atomic absorption spectrophotometry in cases where the removal of corrosion scale is permitted, or by surface analytical techniques such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, electron microprobe analysis, by energy dispersive X-ray analysis in the case of samples which need to be preserved. 

Losses of metals from dilute aqueous solution on storage are well documented. To prevent this it is usually necessary to acidify the sample after collection and filtration to pH 1. If the sample is to be analysed subsequently by flame AAS hydrochloric acid should be used (Section III.C.2) alternatively, prior to flameless electrothermal atomic absorption analysis, nitric acid should be added to preserve the sample (IV.B). The type of storage container is also important and high-density polyethylene is the preferred material for sample bottles. Here the adsorptive losses of metals appear to be lower than on glass. To avoid container contamination of the sample the container should be leached with dilute nitric acid for several days prior to use. This will remove surface contamination from the container material. Subsequent to the acid-leach, containers are washed in distilled-deionised water and then with a portion of the sample. Storage of samples for mercury analysis requires special conditions and these will be discussed later. 

The majority of flame analyses in water and effluents presents few problems. A pretreatment on the sample is performed only when necessary, as described earlier. Standards are prepared in the linear range of the analytical curve and blank solutions are also made up. It is preferable to acidify blanks, standards and samples to 1% with hydrochloric acid. Apart from acting as a preservative, it promotes atomisation of the analyte by forming volatile metal chlorides. The atomic absorption instrument is then set up and flame conditions and absorbances are optimised for the analyte. Following this, blanks, standards and samples are aspirated into the flame absorbances are recorded and results calculated. 

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