Change in Peak Size Possible Cause


Change in detector response Change in the split ratio


Change in the purge activation time Change in injection volume


Change in sample concentration Leak in the syringe Column contamination


Column activity Coelution


Change in injector discrimination Sample flashback


Decomposition from inlet contamination


Loss of Resolution Possible Cause


Decrease in separation Different column temperature


Different column dimensions or phase Coelution with another peak


Increase in peak width Change in carrier gas velocity Column contamination


Change in the injector Change in sample concentration Improper solvent effect, lack of focusing


Solution


Check gas flows, temperatures and settings Check background level or noise


Check split ratio


Check the purge activation line Check the injection technique


Check and verify sample concentration


Use a different syringe Trim the column


Solvent rinse the column Irreversible


Maintain the same injector parameters


Inject less, use a larger liner, reduce the inlet temperature


Clean the injector; replace liner, gold seal


Comments All peaks may not be equally affected


May be caused by system contamination and not the detector


All peaks may not be equally affected For splitless injection


Injection volumes are not linear


Changes may also be caused by degradation, evaporation, or variances in sample temperature or pH


Sample leaks passed the plunger or around the needle; leaks are not often readily visible


Remove 0.5-1 meter from the front of the column Only for bonded and cross-linked phases Only affects active compounds


Change column temperature or stationary phase Decrease column temperature and check for the appearance of a peak shoulder or tail


Most severe for split injections


Less solvent and higher flow rates are most helpful


Only use deactivated liners and glass wool in the inlet


Solution


Check the column temperature Verify column identity


Change column temperature


Check the carrier gas velocity Trim the column


Solvent rinse the column Check the injector settings


Try a different sample concentration


Lower oven temperature, better solvent, sample phase polarity match, use a retention gap


Comments


Differences in other peaks will be visible Differences in other peaks will be visible


Decrease column temperature and check for the appearance of a peak shoulder or tail


A change in the retention time also occurs Remove 0.5-1 meter from the front of the column Only for bonded and cross-linked phases


Typical areas: split ratio, liner, temperature, injection volume


Peak widths increase at higher concentrations For splitless injection


152


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