Abstract: A flow injection method is described for the determination of (5 x 10^-7 to 1 x 10^-3 M) ascorbic acid by measurement of the chemiluminescence from direct oxidation with permanganate in an acidic medium. The method is applied to fruit drinks and nutritional supplements and compared satisfactorily with titrimetric and spectrofluorimetric methods. 14 References

Abstract: A stream of 10 mM HCl containing Eu(III) passed through a Zn amalgam reductor column (4 cm x 6 mm i.d.; preparation described), the eluate merged with a carrier stream of 0.1 M phosphate buffer of pH 6 containing 20 µM-flavin mononucleotide and 120 µM-decanal and the combined streams passed through a 15 cm coiled tube adjacent to a photomultiplier tube (detector). The total flow rate was 7.5 ml/min. Portions (85 µL) of ~0.05 µM-luciferase in 0.1 M phosphate buffer of pH 7 containing 149 µM-BSA and 6.5 mM DTT were injected into the carrier stream to facilitate luminescence determination of Eu(III). A calibration graph was established from 0.5 (detection limit) to 100 µM-Eu(III). RSD and recoveries are not stated. Up to 1 mM levels of Sm(III) Yb(III), Nd(III), Y(III), Fe(II), Ca(II) and Mg(II) did not interfere. However, Ti(IV) is detected by the system described above and hence would interfere in Eu(III) determinations (cf. Jewsbury and Zeng, J. Chem. Soc. Chem. Commun., 1993, 1677). The analysis rate was 60/h. Europium(III) is determined in a flow system based on the reduction of flavin mononucleotide, FMN, by Eu(II) followed by bacterial bioluminescence. Using flow injection analysis, Eu(III) is first reduced to Eu(II) in a zinc amalgam mini-column. The Eu(II) then reduces FMN to FMNH(2) and the bioluminescence produced on aerial oxidation of FMNH(2) in the presence of alkanal mono-oxygenase (FMN linked), EC 1.14.14.3, and n-decanal is used to determine the Eu(II). Calibration is achieved for 5 x 10^-7 to 1 x 10^-4 M Eu(III) with a limit of detection (3 s.d.) of 5 x 10^-7 M and an analysis rate of 60 h-1. The effects of possible interferences are reported.