Columns loading

With a defined loading period, the amount of analyte retained on the column, reflected in the analytical response of the eluate, always reaches a maximum with an increase in sample loading rate in time-based sampling, beyond which an increase in sample volume leads to decrease in signal due to insufficient contact time. Although complete retention of the analyte is not a prerequisite for FI procedures, systems with excessively low P values are more vulnerable to interferences. The optimized sample loading rate should therefore be based on an overall consideration for sensitivity and 

Carry-over and Cross Contamination in Column Loading 

---

Reduce the tendency of pipe acting as a column loaded by friction at supports to buckle sideways off supports. 

An expression for the maximum charge that can be placed on a column without impairing resolution has already been derived, but the approach, when dealing with an overloaded column for preparative purpose, will be quite different. For preparative purposes the phase system is chosen to provide the maximum separation of the solute of interest from its nearest neighbor. It should be pointed out that the separation may, but probably will not, involve the closest eluting pair in the mixture. Consequently, the maximum resolving power of the column will not be required for the purpose of separation and the excess resolution of the solute of interest from its nearest neighbor can be used to increase the column load. 

Sada, E., Kumazawa, H. and Lee, C.H., 1983. Chemical absorption in a bubble column loading concentrated slurry. Chemical Engineering Science, 38, 2047-2051. 

Table 8-6. Single column elution of a 3.9 g ChiraLig column using an H O elution at 0.2 ml min following column loading (25 mM D-methyl ester valine versus 25 mM L-methyl ester valine) and washing.

Mazsaroff, I., Bischoff, R., Tice, P. A., and Regnier, F. E., Influence of mobile phase pH on high-performance liquid chromatographic column loading capacity, /. Chromatogr., 437, 429, 1988. 

For samples that meet the solubility requirements of the SEC approach, analyses were also reported for additives in polymers such as PVC and PS [28,29]. Direct SEC analysis of PVC additives such as plasticisers and thermal stabilisers in dissolution mode has been described [28,30,31 ]. In the analysis of a dissolved PS sample using a SEC column of narrow pore size, the group of additives was separated on a normal-phase column after elution of the polymer peak [21]. Column-loading capacity of HPSEC for the analysis of additives, their degradation products and any other low-MW compounds present in plastics has been evaluated for PS/HMBT, PVC/TNPP and PVC/TETO (glyceryl tri[l-14C] epoxyoleate) [31]. It was shown that HPSEC can be used to separate low-MW compounds from relatively large amounts of polymers without serious loss of resolution of the additives the technique has also been used for the group analysis of chlorohydrin transformation products of the TETO model compound [32]. 

The Fur protein from E. coli was isolated in one step due to its high affinity for metal-chelate columns loaded with zinc. In DNase footprinting experiments, the Fur protein was shown to bind DNA in the promoter region of several iron-regulated genes. The consensus sequence, called the Fur box, is GATAATGATAATCATT ATC. In vitro binding is dependent on the divalent cations Co2+ Mn2+ /s Cd2+ Cu2+ at 150 iM, while Fe2+ seemed to be less active at this concentration, probably due to oxidation to Fe3+ (De Lorenzo et al., 1987). The unspecificity for divalent metals observed in vitro shows that the cells have to select the ions transported carefully and have to balance their active concentrations. In addition, it is a caveat for the experimenter to test a hypothesis on metal-ion specificity not only in vitro, but also in vivo. 

A Cis column loaded with sodium diethyldithiocarbamate has been used to extract copper and cadmium from seawater. Detection limits for analysis by graphite furnace atomic absorption spectrometry were 0.024 pg/1 and 0.004 xg/l, respectively [283]. 

Figure 7 Regeneration of ODA-clinoptilolite columns loaded with chromate by means of 2% NaCI and 2% Na2S04 aqueous solutions and breakthrough curves for ODA- clinoptilolite in 0.5 mM/L chromate solution by 30 BV/hr and 15 BV/hr in downflow mode (from the left)...

Figure 8. Regeneration of ODA-clinoptilolite column loaded with arsenate by means of 2% NaCl aqueous solution and breakthrough curves for ODA-clinoptilolite in arsenate solution of co = 25 mg/L repeated cycle after regeneration, first cycle breakthrough curve on Pb-clinoptilolite (from the left).

IEC was applied to determine biogenic polyamines such as putrescine (4a), cadaverine (4b), tyramine (5), histamine (6), spermidine (38), agmatine (39) and tryptamine (40), contained in aqueous trichloroacetic extracts of leafy vegetables, such as cabbage and lettuce. A cation exchange column loaded with potassium ions and a special buffer were used. Spermidine (38) was the major amine detected in this group (7-15 Xg/g fresh weight)144. 

Analytical HPLC columns loaded with small samples gave the best separations and useful information (9). Screening the resulting column fractions with a series of enzyme substrates indicated the minimum number of different enzymes present, the salt concentrations at which enzymes tended to elute, where multiple enzymes were likely to be co-eluting (thus requiring further separation), and the substrates most useful to distinguish between the different enzymes present (Figures 2,3 and 4). 

However, issues remain with sample loading capacity, and CapLC-NMR may be best suited to mass-limited samples where the component of interest is present at a sufficient concentration such that column loading does not become an issue [88]. Capillary probes have therefore been used most effectively where... 

Tc meets all these requirements. A widely available generator system is the source of Tc for nuclear medicine and consists of an alumina column loaded with Mo in the form of [ Mo04] ... 

Loading of supports can be done in two ways batch loading and column loading. 

---