High performance liquid coupling problems

Harrington, C.F. and Catterick, T. (1997) Problems encountered during the development of a method for the speciation of mercury and methylmercury by high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry. /. Anal. At. Spectrom., 12, 1053-1056. 

A limitation of the application of luminescence spectroscopy to the analysis of real samples is its lack of specificity owing to similarities in spectral bandshapes and spectral positions of the luminescence spectra of many compounds. An obvious solution to this problem is the separation of the analytical sample s interfering constituents from each other before quantitation by fluorescence. High-performance liquid chromatography (HPLC) and related separation methods can be coupled to fluorescence spectroscopy to take advantage of the sensitivity of the spectroscopic method and the specificity of the separation method. 

More recently for ultratrace determination and speciation of antimony compounds the so-called hyphenated instrumental techniques have been applied which combine adequate separation devices with suitable element-specific detectors. They include high-performance liquid chromatography (HPLC) connected on-line with heated graphite furnace (HGF) AAS (HPLC-HGF-AAS), hydride-generation atomic fluorescence spectrometry (HPLC-HG-AFS) or inductively coupled plasma (ICP) mass spectrometry (MS) (HPLC-ICP-MS) capillary electrophoresis (CE) connected to inductively coupled plasma mass spectrometry (CE-ICP-MS) and gas chromatography (GC) coupled with the same detectors as with HPLC. Reliable speciation of antimony compounds is still hampered by such problems as extractability of the element, preservation of its species information, and availability of Sb standard compounds (Nash et al. 2000, Krachler etal. 2001). Variants of anodic stripping voltammetry for speciation of antimony have also been applied (Quentel and Eilella 2002). 

Direct introduction of a sample into an ICP produces information only on the total element content. It is now recognised that information on the form of the element present, or trace element speciation, is important in a variety of applications. One way of obtaining quantitative measurement of trace element speciation is to couple the separation power of chromatography to the ICP as a detector. Since the majority of interesting trace metal speciation problems concern either nonvolatile or thermally unstable species, high-performance liquid chromatography (HPLC) becomes the separation method of choice. The use of HPLC as the separation technique requires the introduction of a liquid sample into the ICP with the attendant sample introduction problem. 

Among the proposed methods for quantification of LA, high-performance liquid chromatography (HPLC) coupled with UV detection has been the technique most applied to analysis of fermented dairy and beverage products [22-24]. With this strategy, it is possible to quantify LA in the presence of other organic acids with a similar structure however, there are some limitations and drawbacks, including problems associated with matrix color, excessive sample preparation and analysis time, separation efficiency, complexity, and cost. Some improvements in resolution and simplicity, reduction of consumption of chemicals, and reduction of sample preparation have been reported... 

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