Elution leakage

In runs from 2-1 to 2-4, the adsorption of phosphate was carried out by supplying the feeding solutions at SV 10 h 1. Leakage of phosphate from the column up to 100 BV of the feed is markedly depressed by repeating the adsorption-elution-regeneration cycle of the method (ii). In the runs from 2-2 to 2-4, the uptake until 100 BV of the feed is almost quantitative, and then the flow rate of the feed increased to SV 20 h1. Even at the higher flow rate of SV 20 h 1 (runs from 3-1 to 3-7), the column took up phosphate almost quantitatively up to 100 bed volumes of the feed. 

Fig. 15.4 A dual-jet cryogenic modulator, a Right-hand-side jet traps analytes eluted from the first column b right-hand-side jet switched off, cold spot heats up rapidly and analyte pulse is released into the second column simultaneously, left-hand-side jet switched on to prevent leakage of first-column material c next modulation cycle is started (adapted from [32])...

Procedure Carefully add the Sample Preparation to the prepared column. Open the stopcock, and adjust the flow rate to about 2 mL/min, discarding the eluate. Rinse the sample beaker with 5 mL of chloroform, and add the rinsing to the column when the level drops to 2 cm above the silica gel. Never allow the column to become dry on top, and maintain a flow rate of 2 mL/min throughout the elution. Avoid interruptions during elution as they may cause pressure buildup and result in leakage through the stopcock or cracks in the silica gel packing. 

In both techniques, leakage of the chiral selector into the elute can be completely eliminated by filling the outlet of the column with a proper amount of the CS-free stationary phase so as to absorb the chiral selector leaking into the flowing mobile phase. 

The nonsynchronous flow-through CPC is a particular type of planetary centrifuge which allows adjustment of the rotational rate of the coiled separation column at a given revolution speed. The first prototype was equipped with a dual rotary seal for continuous elution. Later, an improved model " was designed to eliminate the rotary seal which had become a source of complications such as leakage, contamination, and clogging. 

Leakage of metals from the column during elution can be the most significant problem due to their toxicity, but there are several ways to avoid this pitfall. Some references suggest the precaution of underloading IMAC columns (by as much as 20%) with the metal ion to begin with [8]. Another precaution is to add EDTA with imidazole, histidine, or histamine to the column fractions. EDTA competitively blocks formation of coordination complexes between protein... 

Leakage from a damaged septum can be detected by inaccuracies in quantitation, problems with the chromatography such as a change in retention time, or the deterioration of the column from the entry of air. The septa can bleed substances into the gas flow and also can become brittle with use. Shreds from the penetrated septa can break loose and block wide-bore columns and block gas flow. Tailing can be caused by septum bleed and can be checked for as follows the noise level increases, the early eluters show decreased response, and the baseline drifts if programmed temperature is used. 

Valve leakage A leak of one valve, for example in the gradient module, could disturb the elution profile. 

It is very important to keep valve (26) in Figure 12 tightly closed during the whole elution. Otherwise the acidic or basic electrode solution will leak out of the electrode compartment. This will destroy the possibility of accurate pH measurements of the fractions which come out of the column. To prevent the leakage of electrode solution out of the central tube (19), the contents should be sucked out of the tube with the aid of a syringe and a capillary tube in order to achieve a pressure slightly under atmospheric in the tube. 

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