On-line Filtration Systems Without Precipitate Dissolution

1 On-line Filtration Systems Without Precipitate Dissolution 

This is the simplest type of FI manifold used for on-line precipitation, used principally with stainless-steel filters [13,16], the variations of which are shown in Fig 7.2 a-c. In the normal FIA or hFIA mode, the sample may be either injected directly into the precipitant J (Fig. 7.2 a) or injected into a water carrier and later meiged with the precipitant (Fig. 

With this type of manifold, obviously no components can be determined in the precipitate. They may be used either to separate an interfering species from the analyte which is transported to the detector after the separation, or for indirect determination of the analyte. In the latter case, the analyte forms a precipitate with a species in the reagent which could be readily detected by the detector, either directly or after a reaction. The decrease in concentration of the detectable species (in flame AAS often a metallic ion) was then evaluated to determine the analyte concentration..  

Since the analytical results are based on a difference of two measurements (i.e. a blank with high response, and the sample with lower response) (see recordings in Fig. 

and the noise level is higher with larger signals which serves as the real baseline, the errors in the measurements may be amplified, especially with low analyte concentrations. 

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Fig 7 2 FI on-line filtration systems without precipitate dissolution, a, normal FIA (nFlA) mode with sample injected into precipitant b, nFlA mode with sample injected into water carrier before merging with precipitant and c, reversed FIA (rFlA) mode with precipitant injected into sample or blank. S, sample PR, precipitant P, pump F, filter, D, detector, W, waste R, reagent (optional) BLK, blank [13,16]. 

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