Chapter 7 - On-Line Sample Pretreatment: Extraction and Preconcentration
Section snippets
INTRODUCTION
This chapter focuses on on-line sample pretreatment for chemical analysis prior to measurement, which is based on flow injection, sequential injection, and other related techniques.
In chemical analyses, various kinds of detection method have been used; they are spectrophotometry, fluorophotometry, chemiluminescence (CL) detection, spectroscopy (AAS, ICP-MS, ICP-AES), electrochemical detection, etc. In most cases, some pretreatment procedures prior to the measurement are requisite for improving
LIQUID–LIQUID EXTRACTION (SOLVENT EXTRACTION, SE) WITHOUT MEMBRANE
Liquid–liquid extraction or solvent extraction (SE) is frequently used for sample pretreatment in order to separate an analyte from interfering substances in the sample matrix, to preconcentrate the analyte for enhancing sensitivity, or to improve the limit of detection. This technology is very useful, and has been widely used in pharmaceutical, environmental, agricultural, and industrial analyses. Batchwise SE, however, is very tedious and time-consuming and needs a large amount of organic
LIQUID–SOLID EXTRACTION (SOLID PHASE EXTRACTION, SPE) OF ORGANIC AND INORGANIC SUBSTANCES
Olsen et al. first reported the use of on-line solid phase extraction (SPE) in FIA [27], and subsequently similar technologies have often been applied to the enrichment of analytes and the removal of the matrix. On-line SPE techniques in FIA, SIA, SIA-LAV, and SIA-LOV (lab-on-valve) are clearly advantageous in performing sample-pretreatment processes such as sample clean-up, analyte preconcentration, and removal of matrices and/or interfering substances. Use of on-line SPE-FIA methods has
GAS–LIQUID EXTRACTION BASED ON MASS TRANSFER
The mass transfer of analytes from a gaseous phase to a liquid phase has traditionally been performed by bubbling the gas phase into a liquid phase. This classical approach is very simple and the collection efficiency can often reach almost 100%, although it needs a long time to achieve a high enrichment factor, and is difficult to miniaturize and incorporate a bubbling system in a flow analysis system. To overcome the disadvantages of the gas bubbling methods, several gas–liquid extraction
ON-LINE PRETREATMENT SYSTEM, INCLUDING COMPUTER-CONTROLLED AUTOMATED SYSTEMS
Various kinds of on-line sample-pretreatment devices for preconcentration have been applied to FIA and SIA. In general, the preconcentration process needs tedious and time-consuming procedures. If the preconcentration process is carried out on-line by conventional FIA, the system will become very complicated, several pumping systems and switching valves are necessary to assemble the system, and large volumes of a carrier and reagents are necessary. As a result, large amounts of waste are
Abbreviations
- 4-AAP
4-aminoantipyrine
- ANS
anilinonaphthalenesulfonate
- CL
chemiluminescence
- CMC
chromatomembrane cell
- CTAB
cetyltrimethylammonium bromide
- CTFE
poly(chlorotrifluoroethylene)
- CVAAS
cold vapor atomic absorption spectrophotometry
- CXA
N-cinnamoyl-N-(2,3-xylyl)hydroxylamine
- DDAP
ammonium diethyl dithiophosphate
- DHN
2,3-Dihydroxynaphthalene
- DHNS
1,8-Dihydroxy-3,6-naphthalenedisulphonic acid
- DN
denuder
- EDDP
ethylenediamine-N,N′-dipropionic acid, dihydrochloride
- FAAS
Flame atomic absorption spectrometry
- GDS
Gas diffusion scrubber
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