Indirect detection chromatography

Ohta and Tanaka reported a method for the simultaneous analysis of several inorganic anions and the cations Mg + and Ca + in water by ion-exchange chromatography. The mobile phase includes 1,2,4-benzenetricarboxylate, which absorbs strongly at 270 nm. Indirect detection of the analytes is possible because their presence in the detector leads to a decrease in absorbance. Unfortunately, Ca + and Mg +, which are present at high concentrations in many environmental waters, form stable complexes with 1,2,4-benzenetricarboxylate that interfere with the analysis. 

Tran, C. D., Huang, G., and Grishko, V. I., Direct and indirect detection of liquid chromatography by infrared thermal lens spectrometry, Anal. Chim. Acta, 299, 361, 1995. 

Figure 26-8 Indirect spectrophotometric detection of transparent ions. The column was eluted with I mM sodium phthalate plus 1 mM borate buffer, pH 10. The principle of indirect detection is illustrated in Figure 26-30. [Reproduced tram H. Small, Indirect Photometric Chromatography, Anal Chem. 1982,54,462]...

Sanchez-Martinez, M., M. Aguilar-Caballos, S. Eremin, et al. 2006. Long-wavelength fluorimetry as an indirect detection system in immunoaffinity chromatography Application to environmental analysis. Anal. Bioanal.Chem. 386 1489-1495. 

Liquid chromatography separation and indirect detection using iron(II), 1,10-phenanthroline as a mobile phase additive have been used for the separation of carboxylates (and sulphonic acids) [49], Detection limits approach 20ng. 

Forssen, R and Fomstedt, T. General theory of indirect detection in chromatography. J. Chromatogr. A. 2006, 1126, 268-275. 

L. L. M. Glavina and F. F. Cantwell, Origin of indirect detection in the liquid chromatography of a neutral sample with an ionic probe using an ODS bonded phase and aqueous mobile phase. Anal. Chem. 65 (1993), 268-276. 

Fig. 2 Conductivity detection of anions in nonsuppressed (single column) ion chromatography using an eluent of (a) low background conductance (direct detection) and (b) high background conductance (indirect detection). The direction of the arrow indicates the increase of conductivity.

Chen, M.J., Chen, H.S., Lin, C.Y., and Chang, H.T. 1999. Indirect detection of organic acids in non-aqueous capillary electrophoresis. Journal of Chromatography A 853 171-180. 

Various Amines Showing Retention Times and their Detection Limits by Indirect Photometric Chromatography... 

Indirect detection in ion-pair chromatography provides a mechanism for the detection of ions with poor detection properties based on their interactions in the chromatographic system with a mobile-phase ion that possesses favorable detection properties [334-338]. In ion-pair chromatography indirect detection is complicated by the fact that the detection and separation process are coupled and both positive and negative analyte peaks are observed based on the separation mechanism. The detectable ion is added... 

Indirect detection is an alternative to derivatization for the detection of analytes with a weak detector response. It is commonly used in ion exchange (particularly ion chromatography) and ion-pair chromatography with absorbance, fluorescence or amperometric detection [168,254,255]. This requires the selection of an eluent ion with favorable detection properties to regulate the separation process and provide a constant detector signal. Detector transparent analyte ions cause displacement of eluent ions from the eluted band and a decrease in the detector response compared with the steady state signal for the mobile phase. The detected ion concentration is coupled to the retention mechanism, which can result in the appearance of additional system peaks in the chromatogram (section 4.3.3.2). These applications should be... 

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