Column performance degradation

Lewisite is too reactive to be analyzed by LC. Even with GC, it leads to a rapid degradation of column performance. Lewisites 1 and 2 initially hydrolyze to 2-chlorovinylarsonous acid (CVAA) (26) and bis(2-chlorovinyl)arsenous acid (28), respectively. LC/MS analysis of these trivalent acids is problematic, giving very poor signal-to-noise ratios in both... 

The use of carbon dioxide as the mobile phase also means that it is possible to carry out assays considerably below subambient temperatures. At -50°C, Gasparrini et al. used a DACH-DNB column to resolve the enantiomers of the thermally enantiolabile 2-methyl-l-(2,2-dimethylpropanoyl) naphthalene, which can undergo rotation around the CO-CAr bond [54]. Reducing the temperature resulted in negligible degradation in column performance. 

The most accurate assays require good separation of the peak under examination. This may not always be possible with the equipment at hand, and usually it is necessary to invest time to develop good analytical methods. Although software is available to integrate peaks that appear as shoulders, analyses may no longer be accurate if the peaks become closer as the analytical system degrades. (For instance, HPLC column performance may deteriorate as more samples are applied.)... 

Haginaka, J. Yasuda, H. Uno, T. Nakagawa, T. Alkaline degradation of clavulanic acid and high performance liquid chromatographic determination by post-column alkaline degradation. Chem. Pharm.Bull., 1983, 31, 4436-4447... 

If standards deviate from the optimal profiles, it is possible that the column requires a reverse column hot wash with Solution D, as with increasing numbers of injections the column will gradually lose resolution (however, with proper maintenance columns should reach more than 10,000 injections). A reverse column hot wash removes contaminants off of the front side of the column beads. Because the flow direction is reversed, the buildup of contaminants is now washed off the backside of the column. Another possibility of decreased column performance is that the reagents may have degraded and need to be changed. 

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