Online detection, flow-through methods with

Flow-through methods with online detection 508... 

LC-ARC is a novel online RAD method that is 10-20 times more sensitive than the conventional flow-through radioactivity detectors [219] and manufactured by Aim Research Company. It is a powerful technique to detect compounds with low... 

Detection can be carried out either with an online detector coupled to the eluent flow, or by collection and subsequent analysis of discrete fractions. For collected fractions, a range of analytical methods can be used, both quantitative (e.g., radioactive isotope labeling and metal analysis) and more qualitative (e.g., microscopic techniques). Online detectors suitable for coupling to the FFF channels include both non-destructive flow through cell systems and destructive analysis systems. It is often desirable to use online detection if possible since the total analysis time is much less than for discrete fraction analysis. Regardless of detector type, the dead volumes and flows in the system between the FFF channel and detector or fraction collector must be accurately determined and corrected for. 

A hybrid SIA-FIA spectrophotometric method for the determination of total sulfite in white and red wines has been reported (Tzanavaras et al., 2009). The assay was based on the reaction of sulfite with o-phthalaldehyde (OPA) and ammonium chloride. Upon online alkalization with NaOH, a blue product was formed having an absorption maximum at 630 nm. Sulfite was separated from the wine matrix through an online gas-diffusion process incorporated in the SI manifold, followed by reaction with OPA in the presence of ammonia. The reaction mixture merged online with a continuously flowing of NaOH prior to detection. The SIA-FIA manifold is illustrated in Figure 2.8. 

The solvent technique for concentrating surfactants is not discussed here. See Ref. [40] for details. Morales-Munoz et al. discuss a screening method for LAS in sediments. It is based on water Soxhlet extraction assisted by focused microwaves. The extractor is coupled with an online preconcentrator/derivatization/detection manifold through a flow injection interface [107]. 

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