Gradient elution liquid detection

Micellar gradient elution liquid chromatography with electrochemical detection with sodium dodecyl sulfate has been used to separate phenols [186]. 

Typically, in gradient elution liquid chromatography, electrochemical detection has been difficult due to base-line shifts that result as a consequence of the altered mobile phase composition. However, a unique property of micelles allows for much improved compatibility of gradients (i.e. gradient in terms of micellar concentration or variation of small amount of additive such as pentanol) with electrochemical detectors. This has been demonstrated by the separation and electrochemical detection of phenols using micellar gradient LC (488). A surfactant (apparently non-micellar) gradient elution with electrochemical detection has also been successfully applied for the assay of some thyroid hormones by LC (491). 

Khaledi MG, Dorsey JG (1985) Hydro-organic and micellar gradient elution liquid chromatography with electrochemical detection. Anal Chem 57 2190-2196 Kissinger PT (1989) Biomedical applications of liquid chromatography-electrochemistry. J Chromatogr 488 31-52... 

Sulphonated azo dyes were separated and quantitated in various food products by ion-pair liquid chromatography with DAD and electrospray MS detection. The chemical structure of sulphonated azo dyes included in the investigation are shown in Fig. 3.36. Dyes were separated in an ODS column (125 X 2.0 mm i.d. particle size 5 pm) using gradient elution. An aqueous solution of 3 mM triethylamine (pH adjusted to 6.2 with acetic acid) and methanol... 

Reverse-phase columns with a gradient elution in combination with UV-Vis spectrophotometers using photodiode-array (PDA) (Fig. 1.6) and spectrofiuorimeters are common devices employed in this technique. In a lesser extent, MS, tandem mass spectrometry (MS-MS), and nano liquid chromatography-electrospray ionization-quadrupole time-of-flight tandem mass spectrometry (nanoLC-nanoESI-Q-qTOF-MS-MS) has been used as detection system. This instrumentation has been mainly used in the analysis of dyes and proteinaceous media, and in some extent, in the analysis of drying oils and terpenoid varnishes [47,48],... 

T Takeuchi, T. Miwa. Signal enhancement by on-column fluorimetric detection in gradient elution of danysl amino acids in liquid chromatography. Chromatographia 41 148-152, 1995. 

Liquid-liquid partition chromatography. The stationary phase consists of 1% tris(2-cyanoethoxy)propane (TCEP) on Zipax support. The mobile phase, hexane, is saturated with TCEP prior to use. A pre-column consisting of 30% TCEP on Gas-Chrom Q is used in order to prevent stripping of the liquid phase from the analytical column. The detector is set at 254 nm for monitoring the column effluent. The retention times of a number of 2,4-dinitrophenylhydrazones obtained with this system are given in Table 4.12. Gradient elution may be made with Permaphase ETH as stationary material and a gradient of hexane-chloroform. The limit of detection is ca. 5 ng per injection. 

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