Sorption manifolds

Both Cr111 and Cr concentrations in natural water samples were measured by flame AAS after pre-concentrations of the chromium species on microcolumns packed with activated alumina (acidic form) (Sperling et al., 1992). An FI manifold was used in this work to obtain conditions for species-selective sorption and subsequent elution of the chromium species directly to the nebuliser of the spectrometer. In this procedure, water samples were maintained at a safe pH of 4 prior to analysis. Analytical conditions of pH 2 and 7 were attained by adding buffers on-line only fractions of a second before the corresponding chromium species was sorbed into the column. In this manner, any risk of losses of analytes and/or shifts in equilibria between the species at pH 2 and 7 were minimised. The detection limits were 1.0 and O.Smgdm 3 for Cr111 and Cr, respectively. 

Fig. 2. Schematic representation of the Michelson-interferometer for gas pressure monitoring attached to a manifold (e.g. a volumetric sorption unit).

We have built a prototype of an interferometric pressure transducer that was designed to be attached to a non-commercial room temperature sorption instrument [3] equipped with a differential membrane sensor (MKS, Baratron 220CD, full range 10 mbar, pressure resolution 0,15 % of full range value). An additional absolute pressure sensor (MKS, Baratron 220 CA) integrated into the set-up provides the average pressure in the manifold and... 

A systematic study, to elucidate this effect, indicates that it probably arises from reversible sorption on the manifold. Therefore a number of determinations were carried out with the MHS-10, which has a more simplified manifold. As illustrated in Fig. 2. memory effects for tin completely disappeared. Therefore, the MHS-10 system was used for all tin-analyses. 

The mini-column can be placed between the injection port and the detection unit (Fig. 8.19), and the solutions involved (sample, wash, eluent and conditioning) are sequentially passed through the column. The flow system can be manual or computer-controlled. This manifold geometry is exemplified by the flow injection chemiluminometric determination of zinc and cadmium [207], After sorption of the analytes as chloro-complexes, two different eluting solutions were injected, allowing sequential determinations the resin was reconditioned by the water carrier stream. This geometry can also be implemented in sequential injection analysis and bead injection analysis, as demonstrated in the... 

Integrated sorption-detection units are based on the placement of an inert or active support in the flow cell of a nondestructive spectroscopic detector where the analytes or their reaction products are retained temporarily for sensing immediately after their elution. The equipment required to develop this type of sorption methodology is very simple and closely resembles that used in ordinary flow injection analysis (FIA) manifolds. The only difference lies in the replacement of the packed reactor located in the transport-reaction zone with a packed flow cell (usually photometric or fluorimetric) situated in the detector. 

Fip.4.5 Schemaiic figure ol a single-channel FI manifold for on-line preconceniraiion with flame AAS detection. S. sample injection valve E. eluent injection valve C. packed sorption column D. flame AAS detector W. waste CR. carrier 3. ... 

Fig.4il Schematic diagram of a dual column FI on-line preconcentration manifold for flame AA or ICP emission spectrometiy with alternating column loading and elution, a, load C2, elute Cl b. load Cl, elute C2. SI, S2, samples B, buffer, E, eluent V, 8-channel multifunctional valve Cl, C2, sorption columns D, detector, W, waste.

The mechanism of complex formation of metals with chitosan is manifold and is probably dominated by different processes such as adsorption, ion exchange, and chelation under different conditions. In Fig. 15.6, it can be seen that the sorption capacity of chromium and cadmium is similar, while zinc has approximately double the affinity of these two metal ions for chitosan. Chitosan has almost three times the removal capacity for copper sorption than that for cadmium or chromium. These effects have proved complex to interpret but are a function of a number of parameters ionic radii ionic charge electron structure and possibly some hydration capacity of the metal ions solution pH and nature and availability of sites for chitosan. 

Oil-Sealed Rotary Pumps Turbomolecular Pumps Diffusion Pumps Cold Traps Sorption Pumps Ion Pumps Manifolds... 

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