Ion chromatography see Section

Waters and wastewaters may contain orthophosphates, condensed phosphates (poly- and metaphosphates) and organic phosphorus compounds. Under natural conditions free from human influence, concentrations of phosphorus 

The water samples may be taken in plastic bottles or glass receptacles, but on no account must these have been treated with cleaning agents containing phosphate (not even if they have been thoroughly rinsed ). 

The ion POz/l does not occur in natural waters. In the pH range of ground-water and surface waters, it is almost always mixtures of HPOz 2- d H2PO/ that are encountered. In conventional water analysis, therefore, the 

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The conductance detector is a universal detector for ionic species and is widely used in ion chromatography (see Section 7.4). 

Ion chromatography (see Section 7.4). Conductivity cells can be coupled to ion chromatographic systems to provide a sensitive method for measuring ionic concentrations in the eluate. To achieve this end, special micro-conductivity cells have been developed of a flow-through pattern and placed in a thermostatted enclosure a typical cell may contain a volume of about 1.5 /iL and have a cell constant of approximately 15 cm-1. It is claimed15 that sensitivity is improved by use of a bipolar square-wave pulsed current which reduces polarisation and capacitance effects, and the changes in conductivity caused by the heating effect of the current (see Refs 16, 17). 

Other fluorinated derivatives of acetylacetone are trifluoroacetylacetone (CF3COCH2COCH3) and hexafluoroacetylacetone (CF3COCH2COCF3), which form stable volatile chelates with aluminium, beryllium, chromium(III) and a number of other metal ions. These reagents have consequently been used for the solvent extraction of such metal ions, with subsequent separation and analysis by gas chromatography [see Section 9.2(2)]. 

Whilst many functionalities may be reduced, reductive HPLC detectors are less commonly used. Another form of electrochemical detection is conductivity, which is useful when an analyte is ionic. Hence, it is often used in conjunction with ion-exchange chromatography (see Section 4.5.1.4). 

The ion-exchange constant does vary from one pair of ions to another therefore selectivity can be controlled by appropriate choice of the counter ion. However, selectivity is more conveniently manipulated by controlling the pH of the mobile phase and taking advantage of differences in the values of the analytes to be separated. In contrast with reversed-phase liquid chromatography (see section 3.6.2.1) the retention of weak acids and weak bases will reach a maximum when the compounds are in their ionized forms. Zwitterionic compounds such as amino acids, peptides and proteins can be separated on anion exchangers or cation exchangers. 

For the tris[( )-propylenediamine]cobalt(III) ion, there are 24 possible isomers (Table 3.1, where symbols A and A refer to the absolute configurations of the complex ion, lei and ob to the conformations of the chelate ring, and fac and mer to the isomerism with respect to the methyl groups of the chelated pn molecules). Dwyer et al. studied this system by column chromatography with cellulose powder and paper chromatography (see Section 3.4). MacDermott separated the fac isomer... 

Commercially, SEC has been used for desalting proteins and as one step in protein purification procedures.The equipment for desalting is similar to LC equipment and is described in detail elsewhere. The SEC desalting and buffer exchange of human blood plasma is shown in Fig. 14.2-5.Repeated injections of the feed are illustrated. Size exclusion chromatography is used in blood banks for purification of various factors from human plasma either in conjunction with ion-exchange chromatography (see Section... 

Another important application for the lonPac CSIO is the separation of biologically relevant amines such as choline and acetylcholine, which previously have been used to be separated by ion-pair chromatography (see Section 6.4). 

A micromembrane suppressor for ion-exclusion chromatography has been introduced under the trade name AMMS-ICE. Its structure corresponds to the systems developed for anion and cation exchange chromatography (see Sections 3.6.3 and 4.3.3). However, in its mode of operation, it corresponds to the AFS-2 hollow fiber suppressor. An AMMS-ICE micromembrane suppressor also contains membranes that are compatible with water-miscible organic solvents. Therefore, it is used for the analysis of long-chain fatty acids, which are separated on a non polar stationary phase in a weakly acidic medium with methanol or acetonitrile as mobile phase components. In this case, a dilute potassium hydroxide solution is used as the regenerant. With respect to the ion-exchange... 

Stahlberg has presented models for ion-exchange chromatography combining the Gouy-Chapman theory for the electrical double layer (see Section V-2) with the Langmuir isotherm (. XI-4) [193] and with a specific adsorption model [194]. 

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