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Solid-phase microextraction (SPME) A sample preparation technique that uses a fused silica fibre coated with a polymeric phase to sample either an aqueous solution or the headspace above a sample. Analytes are absorbed by the polymer coating and the SPME fibre is directly transferred to a GC injector or special HPLC injector for desorption and analysis.
Solvent extraction The removal of a soluble material from a solid mixture by means of a solvent, or the removal of one or more components from a liquid mixture by use of a solvent with which the liquid is immiscible or nearly so.
Soxhlet extraction Equipment used for the continuous extraction of a solid by a solvent. The material to be extracted is placed in a porous cellulose thimble, and continually condensing solvent is then allowed to percolate through it, and return to the boiling vessel, either continuously or intermittently.
Speciation The process of identifying and quantifying the different defined species, forms or phases present in a material, or the description of the amounts and types of these species, forms or phases present.
Specificity The ability of a method to measure only what it is intended to measure - the ability to assess unequivocally the analyte in the presence of components which may be expected to be present. Typically, these might include impurities, degradants, matrices, etc.
Spiked sample ‘Spiking a sample’ is a widely used term taken to mean the addition of a known quantity of analyte to a matrix which is close to or identical with that of the sample(s) of interest.
Standard (general) An entity established by consensus and approved by a recognized body. It may refer to a material or solution (e.g. an organic compound of known purity or an aqueous solution of a metal of agreed concentration), or a document (e.g. a methodology for an analysis or a quality system). The relevant terms are:
Glossary of Terms
Analytical standard (also known as Standard solution) A solution or matrix containing the analyte which will be used to check the performance of the method/instrument.
Calibration standard The solution or matrix containing the analyte (mea-surand) at a known value with which to establish a corresponding response from the method/instrument.
Internal standard A measurand, similar to but not identical with the analyte, which is combined with the sample.
External standard A measurand, usually identical with the analyte, which is analysed separately from the sample.
Standard method A procedure for carrying out a chemical analysis which has been documented and approved by a recognized body.
Standard addition The addition of a known amount of analyte to the sample in order to determine the relative response of the detector to the analyte within the sample matrix. The relative response is then used to assess the sample analyte concentration.
Stock solution This is generally a standard or reagent solution of known accepted stability, which has been prepared in relatively large amounts, of which portions are used as required. Frequently, such portions are used following further dilution.
Sub-sample This may be (i) a portion of the sample obtained by selection or division, (ii) an individual unit of the lot taken as part of the sample, or (iii) the final unit of multi-stage sampling.
Supercritical fluid extraction (SFE) A method of extracting analytes from matrices using a supercritical fluid at elevated pressures and temperatures. The term supercritical fluid is used to describe any substance above its critical temperature and critical pressure.
True value A value consistent with the definition of a given particular quantity.
Ultrasonic extraction A method of extracting analytes from matrices with solvent, using either an ultrasonic bath or probe.
Uncertainty Parameter associated with the result of a measurement, which characterizes the dispersion of the values that could reasonably be attributed to the measurand.
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)
SI Units and Physical Constants
The SI system of units is generally used throughout this book. It should be noted, however, that according to present practice, there are some exceptions to this, for example, wavenumber (cm-1) and ionization energy (eV).
Base SI units and physical quantities
Quantity Symbol SI Unit Symbol
length l metre m
mass m kilogram kg
time t second s
electric current I ampere A
thermodynamic temperature T kelvin K
amount of substance n mole mol
luminous intensity /v candela cd
Prefixes used for SI units
Factor Prefix Symbol
1021 zetta Z
1018 exa E
1015 peta P
1012 tera T
109 giga G
106 mega M
103 kilo k
(continued overleaf )
252 Methods for Environmental Trace Analysis
Prefixes used for SI units (continued )
Factor Prefix Symbol
102 hecto h
10 deca da
10-1 deci d
10-2 centi c
10-3 milli m
10-6 micro fi