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Chromatografy Methods for Environmental - Ando D.J.

Ando D.J. Chromatografy Methods for Environmental - Wiley publishing , 2003. - 265 p.
Download (direct link): chromatography2003.pdf
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Chromium(VI). This inorganic pollutant can be determined by a whole range of analytical techniques, e.g. FAAS, ICP-AES/MS or XRF. However, in this situation the requirement is to determine a particular oxidation state of chromium. While not mentioned specifically in the list of analytical techniques above, a method does exist for the spectrophotometric determination of hexavalent chromium based on extraction with a chelating agent (see Chapter 5 for details).
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Alternative analytical techniques could also be employed. For example, ion chromatography could be used for separation, followed by either spectropho-tometric detection after post-column chelation, or ICP-AES/MS detection.
Benzene-toluene-ethylbenzene-xylene(s) (BTEX). In this situation, the method of choice would be GC-FID. However, as discussed previously, the optional benefits of an mass-selective detection (see PAHs) may be advantageous.
Total petroleum hydrocarbons (TPHs). A method for the determination of TPHs could be GC-FID. As before, the optional benefits of MSD (see PAHs) may be advantageous. However, as information is only required on total petroleum hydrocarbons, an alternative analytical technique is possible, i.e. FTIR spectroscopy. In this situation, C-H bands are observed in the region 2800-3000 cm-1. Care, however, must be taken in the choice of the solvent used for the preparation of standards and samples. The solvent must not contain carbon and hydrogen. A typical solvent to use, therefore, would be tetrachloroethylene.
Nitrate. In this case, the method of choice would be IC, with conductivity detection. The use of a dedicated ion chromatograph with an anion-exchange column allows the separation of nitrate (plus fluoride, chloride, bromide, nitrite, sulfate, etc.).
Sodium. In this situation, the method of choice would be FP.
Methods for Environmental Trace Analysis. John R. Dean
Copyright 2003 John Wiley & Sons, Ltd.
ISBNs: 0-470-84421-3 (HB); 0-470-84422-1 (PB)
Glossary of Terms
This section contains a glossary of terms, all of which are used in the text. It is not intended to be exhaustive, but to explain briefly those terms which often cause difficulties or may be confusing to the inexperienced reader.
Absorbance A measurement of the absorption of light; absorbance = log I0/I, where I0 and I are the intensities of the incident and transmitted radiation, respectively.
Accelerated solvent extraction (ASE) Method of extracting analytes from matrices using a solvent at elevated pressures and temperatures (see also Pressurized fluid extraction).
Accuracy A quantity referring to the difference between the mean of a set of results or an individual result and the value which is accepted as the true or correct value for the quantity measured.
Acid digestion Use of acid (and often heat) to destroy the organic matrix of a sample to liberate the metal content.
Aliquot A known amount of a homogenous material assumed to be taken with negligible sampling error.
Analyte The component of a sample which is ultimately determined directly or indirectly.
Anion Ion having a negative charge; an atom with extra electrons. Atoms of non-metals, in solution, become anions.
Bias Characterizes the systematic error in a given analytical procedure and is the (positive or negative) deviation of the mean analytical result from the (known or assumed) true value.
Blow-down Removal of liquids and/or solids from a vessel by the use of pressure; often used to remove solvents to pre-concentrate the analyte.
BTEX Acronym used to describe a mixture of the following volatile organic compounds: benzene, toluene, ethylbenzene and ortho-, meta- and para-xylenes.
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Calibration The set of operations which establish, under specified conditions, the relationship between values indicated by a measuring instrument or measuring system and the corresponding known values of the measurand.
Calibration curve Graphical representation of the measuring signal (response) as a function of the quantity of analyte.
Cation Ion having a positive charge. Atoms of metals, in solution, become cations.
Certified Reference Material (CRM) Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realization of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence.
Complexing agent The chemical species (an ion or a compound) which will bond to a metal ion using lone pairs of electrons.
Confidence interval Range of values which contains the true value at a given level of probability. The level of probability is called the confidence level.
Confidence limit The extreme values or end values in a confidence interval.
Contamination In trace analysis, this is the unintentional introduction of ana-lyte(s) or other species which are not present in the original sample and which may cause an error in the determination. It can occur at any stage in the analysis. Quality assurance procedures, such as the analyses of blanks or reference materials, are used to check for contamination problems.
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