The effect of solvent injection on the area and peak-height responses
of some drugs (ergotamine tartrate, astemizole, terfenadine, bromhexin
e hydrochloride, caffeine, ambroxol hydrochloride, phenylephrine hydro
chloride, enalapril maleate and betamethasone) was evaluated. Reversed
-phase chromatographic systems were employed and loops of different si
zes and various overfill volumes were assayed. When injection solvents
weaker than the mobile phases were used, significant variation in the
area responses was observed for astemizole, bromhexine, ergotamine an
d terfenadine. Adsorption on the internal surface of the injection loo
ps produced this anomalous behaviour depending on the chemical nature
of the analyte injected.