ASSESSMENT OF INJECTION VOLUME LIMITS WHEN USING ON-COLUMN FOCUSING WITH MICROBORE LIQUID-CHROMATOGRAPHY

It had been ascertained that in the use of microbore liquid chromatogr aphy (LC) and on-column focusing (peak compression), there were advant ages to be had in using the strongest eluting injection solvent that w ould still bring about on-column focusing. Tn such cases, it was found that the scope for the use of on-column focusing with microbore LC wa s greater than previously imagined. It has been possible to explain th ese results by considering on-column focusing to take place in two dis tinct phases, i.e. focusing of the sample band due to the injection so lvent, followed by further focusing of the sample band by the sample s olvent/mobile phase step gradient. In this context, an equation has be en developed which provides a much more accurate estimate of the maxim um allowable injection volume for a given injection solvent and mobile phase than has been possible until now.