Poly column selectivity

As stated in Section I, columns should be selected so the low molar mass portions of the samples in question can be sufficiently separated from the elution interval of the system peaks. This task cannot always be accomplished, e.g., dimethylacetamide often replaces dimethylformamide as a GPC eluent the analyzed, mostly polar, samples require a neutral salt (e.g., FiBr) (7). The calibration is usually carried out with poly(methylmethacrylate) standards... 

Another application of SFC-GC was for the isolation of chrysene, a poly aromatic hydrocarbon, from a complex liquid hydrocarbon industrial sample (24). A 5 p.m octadecyl column (200 cm X 4.6 mm i.d.) was used for the preseparation, followed by GC analysis on an SE-54 column (25 m X 0.2 mm i.d., 0.33 p.m film thickness). The direct analysis of whole samples transferred from the supercritical fluid chromatograph and selective and multi-heart-cutting of a particular region as it elutes from the SFC system was demonstrated. The heart-cutting technique allows the possibility of separating a trace component from a complex mixture (Figure 12.21). 

Protein mixtures were well resolved on poly(aspartic acid)-silica columns using 0.05 mol/1 phosphate buffer, pH 6.0 and a gradient of sodium chloride from 0 to 0.6 mol/1. The columns displayed a high capacity and selectivity. Figure 3 shows the separation of several standard proteins with isoelectric points ranging from 4.7 to over 11. Peaks are sharp and show minimal tailing. The poly(aspartic acid) coating was quite stable the columns lasted for hundreds of hours of use without decrease in efficiency and capacity. 

Joseph, J.M., Selectivity of poly(styrene-divinylbenzene) columns, ACS Symp. Ser., 297, 83, 1986. 

The advantage of the selective adsorption of a particular element oxidation state has been exploited for on-line element preconcentration and speciation analysis of Cr by FAAS. Cespon Romero et al. [21] described an FIA system employing a minicolumn made of a chelating resin containing poly(aminopho-sphonic) acid groups, able to selectively retain Cr(III) ions. An FIA manifold was employed for efficient preconcentration and subsequent elution of Cr(III) with a small volume of 0.5 M HC1. The original sample was also treated with ascorbic acid to reduce Cr(VI) to Cr(III) and total Cr is determined as Cr(III) after appropriate retention and elution. Eluates are introduced into an N20-acetylene flame connected to the column outlet. The concentration of Cr (VI) is obtained by difference. Employing a sample volume of 6.6 mL, LoD for total Cr is 0.2 pg l-1. A study of FI operational variables, interferences, and precision is reported for the analysis of tap, mineral, and river waters. 

Figure 17.14a shows the separation of racemic propranolol by CEC on a capillary column filled with poly(methacrylic acid-co-TRIM), polymerised in situ using (i )-propranolol as the print molecule [61]. Several attractive features make this system look promising for the future very low consumption of the print molecule (in this case only 10 pg), fast preparation of the capillaries (3 h) and fast separation (less than 2 min). In Fig. 17.14b, MIP particles selective for (5)-propranolol were added to the mobile phase in a CE separation [62]. The application of MIPs in CE and CEC is described in more detailed in Chapter 16.

The role of subducted sediment is particularly well documented for selected, high quality data on arc basalts in which the high Th/La component has Th/La identical to that in the subducting sediment column (Plank, 2003). Very efficient recycling of subducted thorium, together with subducted °Be (present only in surficial sediments), has also been taken as evidence for transport of sediment-derived thorium and beryllium in a partial melt, rather than an aqueous fluid (e.g., Johnson and Plank (1999), Kelemen et al. (1995a) but apparently in disagreement with Morris (see Chapter 2.11) and Schmidt and Poli (see Chapter 3.17). 

Fig.l Gas chromatographic analysis of white wine sample by fused-silica column poly(ethylene glycol) type (15.00 m X 0.53 mm X 1.00 pm). Chromatographic conditions carrier gas hydrogen (3.6 mL/min) column temperature 40°C (4 min) —> 8°C/min 270°C injector port temperature 250°C detector temperature 300°C. Identity of the selected peaks (1) acetaldehyde, (2) acetone, (3) ethyl acetate, (4) ethanol, (5) ethanol,... 

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