Flow-injection analysis peak effects

Because of its advantages (high sensitivity and selectivity, low cost and miniaturization) amperometric detection has been frequently used in flow injection analysis (FIA) and RP-HPLC. However, it has been established that the peak area (detector response) considerably depends on the flow rate. A general approach has been proposed to predict the effect of flow rate on the peak area in FIA and RP-HPLC. The general form of the correlation describing the flow in a parallel plate cell with short rectangular electrodes is... 

The length of the analytical path plays an important role in the extent of sample dispersion in flow injection analysis. Increasing this length decreases the recorded peak height and increases sample broadening, with these effects being more evident for lower path lengths (Fig. 5.13). 

The coupling of sensors with flow injection analysis (FIA) is already a very popular option. The flow regime offers important advantages over discrete manual measurements that include (1) Sample preparation processes such as reagent mixing, selectivity enhancement (e.g., removal of large molecular mass interferents such as protein by dialysis in clinical assays), and solvent extraction can all be carried out online. The improved sample preparation and more reproducible sample delivery result in improved measurement precision and accuracy. Drift is less of a problem as measurements are made of peak heights relative to a baseline. (2) Improved sensor lifetime in flow analysis, the sensor may be exposed to the sample for only a short period of time, and maintained in a friendlier matrix between measurements that can help counteract or delay the deleterious effects of the sample. (3) Automation the entire analysis can be... 

A pentaerythritol-based dendrimer modified with bis-terpyridyl Ru(II) was shown to be effective as a catalyst for the electrochemical oxidation of methionine (L-Met) and cystine (L-Cys) in aqueous solution or the mixed solvent AN-water (12% AN) [100]. In this case, the dendrimer was mixed with carhon powder and, using a sol-gel hinder, the carhon electrode doped with the [Ru(tpy)2] " -functionalized dendrimer was prepared. The oxidation peak of [Ru(tpy)2] was enhanced by the addition of L-Met, indicating the electro-catalytic effect of the dendrimer. Using the composite electrode doped with the dendrimer as an amperometric detector for flow-injection analysis, a linear calibration curve was obtained over the range 1-lOpM of L-Met in phosphate buffer (pH 7.0). A similar cahbration curve was obtained for L-Cys over the range 1-10 pM in phosphate buffer (pH 2.3). 

Yamane, T. and Saito, M., Simple approach for elimination of blank peak effects in flow injection analysis of samples containing trace analyte and an excess of another solute, Talanta 39, 215,1992. 

Quantitative analysis using the internal standard method. The height and area of chromatographic peaks are affected not only by the amount of sample but also by fluctuations of the carrier gas flow rate, the column and detector temperatures, etc., i.e. by variations of those factors which influence the sensitivity and response of the detector. The effect of such variations can be eliminated by use of the internal standard method in which a known amount of a reference substance is added to the sample to be analysed before injection into the column. The requirements for an effective internal standard (Section 4.5) may be summarised as follows ... 

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