Single-Column IC

The use of anions such as phthalate in single-column IC enables another form of detection. Many small anions will have no UV absorption in the range where the aromatic phthalate... 

The determination of SeOs and Se04 in water with graphite furnace atomic absorption detection was investigated by Chakraborti et al. [21]. Some interference by cr and F was reported. DCPAE detection was used by Urasa and Ferede [22]. Results were 1000 times more sensitive than conductivity detection. One of the advantages of atomic emission detection was described in this work. Identical molar sensitivity was obtained for both species. Mehra et al. [23] developed a novel single-column IC method to determine selenium species in seleniferous soil samples. The separation took about 14 min and there were no reported interferences. 

Wigman, L. S., M. L. Thomson, R. S. Wayne, Single column IC determination of anions in agriculturally useful quaternary compounds u.sing indirect UV detection, J. Liq. Chromatogr., 1989,12, 3219-3229. 

Many IC techniques are now available using single column or dual-column systems with various detection modes. Detection methods in IC are subdivided as follows [838] (i) electrochemical (conductometry, amper-ometry or potentiometry) (ii) spectroscopic (tJV/VIS, RI, AAS, AES, ICP) (iii) mass spectrometric and (iv) postcolumn reaction detection (AFS, CL). The mainstay of routine IC is still the nonspecific conductometric detector. A significant disadvantage of suppressed conductivity detection is the fact that weak to very weak acid anions (e.g. silicate, cyanide) yield poor sensitivity. IC combined with potentiometric detection techniques using ISEs allows quantification of selected analytes even in complex matrices. The main drawback... 

Figure 12.5 Separation of a seven-anion standard with single-column ion chromatography. Column [Chromatographic conditions IC-Pak Anion HR, 4.6 mmx7S mm. Waters Corp. Eluent borate/gluconate. Sample seven-anion standard (1) fluoride (2) bicarbonate (3) chloride (4) nitrite (S) bromide (6) nitrate (7) phosplmt (8) suUite. Detection conductivity. (Qiromatogram courtesy of Waters Corp.)...

In 1984, advances in electronics made it possible to develop a highly sensitive thermostated conductivity detector for the single-column technique, and finally help the suppressorless IC technique to come to fruition. Fig. 63 is a schematic representation of the structure of an ion chromatograph without suppressor. 

The determination of transition elements (i.e., Cu, Zn, Mn, and Fe) is usually performed by single-column [278-281] rather than suppressed IC [263]. Spectrophotometric detectors are the most frequently used [67,73,282], even other type of detectors (i.e., conductometric [283,284], electrochemical [285], coulometric [286,287], among others) are also applied to these analysis. 

Procedures based on separation techniques such as HPLC and IC have been developed for single element analysis for the following two reasons. The first reason is to remove interferents in complicated sample matrices that can give rise to incorrect results, in particular for trace analysis in samples with a high organic content, such as the determination of total iodine in egg products. The second reason is to differentiate the total and free forms of a specific element, such as the determination of the free iodide ion and bounded iodine in food additives. The free iodide ion is determined by direct sample injection into the IC column, whereas the total iodine content is determined after oxygen flask combustion. Thus, both the free and bounded forms of iodine in food samples can be determined. 

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