Conductimetric detection

Magnesium, calcium, barium, and strontium can also be deterrnined by ion chromatography with y -phenylenediamine in perchloric acid as the eluent. Ion chromatography by conductimetric detection has been described, and appHcations to environmental waters have been discussed (1,22—23). 

Sjogren. A. and Dasgupta, P. K., Two-dimensional conductimetric detection in ion chromatography. Analyte identification, quantitation of very weak acid anions, and universal calibration, Anal. Chem., 67, 2110, 1995. 

Cassidy, R. M. and Elchuk, S., Dynamic and fixed-site ion-exchange columns with conductimetric detection for the separation of inorganic ions, /. Chrom. Sci., 21, 454, 1983. 

Small, H., Stevens, T. S., and Bauman, W. C., Novel ion exchange chromatographic method using conductimetric detection, Anal. Chem., 47, 1801, 1975. 

The second column is called a suppressor column. Its function is to convert the eluent to a less conductive species while converting sample ions to a common form. This system enables conductimetric detection of the sample ions in a low conductivity background. The ion-exchange suppressor reactions are also shown in Figure 1. In the case of anion analysis, sodium carbonate and/or bicarbonate eluent is converted to a weakly conductive dilute carbonic acid while the sample ions are converted to strong-... 

Non-suppressed conductimetric detection can be applied in direct or indirect modes, according to the chemical properties of the eluent and analytes. 

As more information on the extent of the contamination and the dangerous effects of perchlorate consumption has become available, much concern has arisen over perchlorate contamination in public water systems. Furthermore, the US Environmental Protection Agency (USEPA) has periodically reduced the acceptable limit for safe consumption. Currently, the limit stands at 0.7 pg/kg/day, which corresponds to 24.5 pg/E for a 70 kg human drinking 2 E of water per day. The method described by Eamb et al. [17] provides effective perchlorate determinations (shown in Figure 7) using standard conductimetric detection by combining an... 

Ion chromatography (IC) offers the analytical tool for the determination of each of the inorganic acids in a single sample. The principle of ion chromatography is the separation and measurement of ions in solution using ion exchange resins, background suppression, and conductimetric detection (5). 

The versatility of the sensory amplification approach is expanded considerably by the ease with which it may be adapted to conductimetric detection methods. By way of example, consider sensory polymer 87, which is produced... 

Several papers have reported use of a weak acid/crown ether eluent in ion-exclusion/cation exchange chromatography with conductimetric detection on a weakly acidic cation-exchange column to effect the simultaneous determination of both cations and anions. Resolution was significantly improved when 18-crown-6 was present in the eluent. Detector response was positive for anions and negative for cations. [76-80] A sample chromatogram is shown in Figure 9. 

Polasek et al. [107] used anionic capillary isatachophoresis (ITP) with conductimetric detection for determining selected nonsteroidal antiinflammatory and analgesic drugs of the phenamate group, namely tolfenamic, flufenamic, mefenamic and niflumic acids. Isatachophoresis analyses were carried out with the use of a computer-controlled EA 100 ITP analyzer (VILLA s.r.o.) operated in the single-column mode. The analyzer was equipped with a 30-pL sampling valve, a 160... 

Also, conductimetric detection has been used, by applying two electrodes into the capillary. In this detection mode, the separation of the high voltage part of the capillary (under dc) from the detection zone (under ac) can be accomplished also by electronic filtering. A capillary electropherograph, with a conductimetric detector, is commercially available. 

Kvasnicka, F. Voldrich. M. (2006). Determination of biogenic amines by capillary zone electrophoresis with conductimetric detection. J. Chromatogr. A, 1103, 145-149. 

Organic anions. Carboxylic ions such as formate, acetate and propionate ions, etc. which would normally be difficult to analyse using conventional analytical techniques can be analysed successfully using ion chromatographic exclusion techniques. Using conductimetric detection, sub-ppm detection levels can be achieved. A major advantage of this type of analysis is that a complete series of anions can be analysed simultaneously. 

Applications. An example of practical approach based on polymer-imprinted materials is the development of biosensors for the detection of the herbicides atrazine [87] and 2,4-dichlorophenoxyacetic acid (2,4-D) [88]. The first one is based on conductimetric detection and it uses an atrazine selective polymeric matrix generated from triethylene glycol dimethacrylate... 

H. SmaU, T. S. Stevens and W. G. Bauman, Novel ic -exdiange chromatographic method using conductimetric detection, i4n[Pg.57]

K. Tanaka, K. Ohta, J. S. Fritz, S. Matsushita and A. Miyanaga, Simultaneous ion-exclusion chromatography-cation exchange chromatography with conductimetric detection of anions and cations in acid rain waters,/ Chromatogr. A, 671,239,1994. 

Figure 18.6 Direct and membrane conductimetric detection methods for measuring TOC. Radiation of a high output UV lamp (185 and 254 nm) produce, in water, by different pathways, hydroxyl free radicals (OH), which oxidize the organic compounds to carbon dioxide and water from oxygen dissolved in the water. The difference between types (a) and (b) detectors is that the direct detector is subjected to interference from ionic contamination, acids, bases, and halogenated organics. In the membrane based conductimetric method, the membrane is a protective barrier to interfering ions, enabling the analysis of COj only (reproduced courtesy of GE Analytical Instruments for illustrations).

M.C.H. Silva, J.J.R. Rohwedder, C. Pasquini, Determination of CO2 in gaseous samples using a monosegmented flow system and conductimetric detection, Anal. Chim. Acta 366 (1998) 223. 

Tanaka, K., Mori, M., Xu, Q., Helaleh, M. I. H., Ikedo, M., Taoda, H., Hu, W., Hasebe, K., Fritz, J. S., and Haddad, P. R., Ion-exclusion chromatography with conductimetric detection of aliphatic carboxylic acids on a weakly acidic cation-exchange resin by elution with benzoic acid- 3-cyclodextrin, J. Chromatogr. A, 997, 127-132, 2003. 

Nanosecond laser photolysis and conductimetric detection have been used to show that the photoisomerisation of 4-nitrobenzaldehyde to 4-nitrosobenzoic acid in aqueous solution occurs via the mechanism in Scheme 4 The... 

Lauti, J. R, V. Stankovic, and G. Sinoquet. 2000. Determination of chlormequat in pears by high-performance thin layer chromatography and high-performance liquid chromatography with conductimetric detection. 28 155-158. 

Figure 4.12. Schematic illustration of DNA conductimetric detection enhanced by reporter DNA-Au-NP conjugates [71] (reprinted with permission ofWiley],...

Commercial ion chromatograph instruments have become available since early 1976. Ion chromatography (IC) is a combination of ion exchange chromatography, eluent suppression and conductimetric detection. For anion analysis, a low capacity anion exchange resin is used in the separator column and a strong cation exchange resin in the H+ form is used in the suppressor column. 

The highly conductive anions in a low background conductance of H2CO3 are detected at high sensitivity by the conductivity detector. The nonspecific nature of the conductimetric detection allows several ions to be sequentially determined in the same sample. The conductimetric detection is highly specific and relatively free from interferences. 

Recently, electrochemical detection methods, namely, conductimetry, amperometry, and potentio-metry, have also become accessible. All three variants of electrochemical detection are intrinsically simpler than the optical methods, and their success depends highly on the electrode materials and designs used. Conductivity detection relies on measurement of the differences between the conductivities of the analyte and the separation electrolyte this provides a direct relationship between migration times and response factor, and makes this detector universal. On the contrary, amperometric detection is restricted to electroactive species and potentiometric detection is not possible for certain small ions with multiple charges. Conductimetric detection works better for inorganic compounds since the higher mobility of... 

Increase of sensitivity of conductimetric detection as the basic detection method... 

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