Application of time-resolved luminescence to dry reagent chemical technology Original Research Article

A time-resolved luminescence method describing the use of terbium(III) in the dry reagent format is presented for the first time. Paper strips previously treated with sucrose are used as solid substrates where terbium(III) is immobilised by adsorption. The strips are stable for at least 6 months and they can be easily stored under a desiccant medium. Only the addition of the buffered sample is required for the analysis. This methodology has been applied to the determination of two local anaesthetics, namely benzocaine and procaine. These compounds release p-aminobenzoic acid after a hydrolysis step in alkaline medium, which reacts to terbium(III) giving a luminescent chelate. The luminescence intensity measurements are obtained at λex 286 and λem 545 nm by using the time-resolved mode of the instrument. The method presents a linear range from 1.1 to 21.9 μM and the calculated LOD is 0.4 μM. It has been satisfactorily applied to the analysis of pharmaceutical samples and the recoveries obtained are in the range 88–108%.