TIME-RESOLVED LUMINESCENCE AS A NOVEL DETECTION MODE FOR THE SIMULTANEOUS HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF GADOLINIUM-DOTA AND GD3+

The simultaneous determination in aqueous media of the gadolinium ion (Gd3+) and the macrocyclic chelate Gd-DOTA (DOTA = 1, 4, 7, 10-tetraaz acyclododecane-1, 1, 4, 7, 10-tetraacetic acid) used in magnetic reson ance imaging (MRI) is described, The proposed approach combines a reve rsed-phase high-performance liquid chromatographic (RP-HPLC) separatio n and time-resolved luminescence detection (TRL). The spectroscopic pr operties of Gd-DOTA and various other Gd chelates (Gd-CDTA, Gd-TETA, G d-EDTA, Gd-DTPA and Gd-TTHA) (CDTA = cyclohexanediaminetetraacetic aci d; TETA = 1, 4, 8, 11-tetraazacyclotetradecane-1, 4, 8, 11-tetraacetic acid; EDTA = ethylenediaminetetraacetic acid; DTPA = diethylenetriami nepentaacetic acid; TTHA = triethylenetetraaminehexaacetic acid) were established in order to optimize TRL detection (lambda(exc) = 274 nm, lambda(em) = 313 nm, delay time 0.1 ms, gate time 10 ms), The Gd3+ ion possibly present in the matrix was detected as a Gd-CDTA chelate afte r dilution of the sample by a pH 7.6-buffered 1 x 10(-2) M aqueous CDT A solution, Then, Gd-DOTA and Gd3+ ion (as Gd-CDTA chelate) were chrom atographed on an RP C-8 HPLC column, The eluent consisted of pH 7.6 TR IS-HCl buffer + acetonitrile (98 + 2 v/v), The analytical figures of m erit obtained for Gd-DOTA in aqueous solution were as follows: lineari ty was assumed from 10 to 5000 mu mol l(-1); the limit of detection (L OD, S/N = 3) was 21 mu mol l(-1), which corresponds to 235 ng of Gd-DO TA injected, The repeatability (RSD = 10%, n = 15) and the intra-assay reproducibility(RSD = 12%, n = 6) were studied for a 50 mu mol l(-1) solution, With this method, 130 ng of Gd3+ ion (as Gd-CDTA) injected c an be detected, which corresponds to an LOD of 42 mu mol l(-1), The LO Q fur Gd3+ ion was 140 mu mol l(-1). Consequently, Gd3+ ion can be dis tinguished from chelated Gd-DOTA in aqueous solution (at the 0.2% leve l).