Spectrophotometric flow-injection determination of sulphate in soil solutions.
A flow-injection procedure for spectrophotometric determination of sulphate in soil solutions is proposed. Samples are directly soaked from the soils under field conditions, in-line filtered through ceramic plates, and preserved with thymol. The method involves reaction with barium dimethylsulphonazo(III) (DMSA) in the presence of dimethylsulphoxide (DMSO) with further measuring the decrease in absorbance at 668nm. A linear response is observed up to about 5mgl(-1) SO(4), and detection limit (3sigma criterion) is 0.1mgl(-1) SO(4). Only 4.5mug DMSA is consumed per determination. The system is rugged and baseline drift is not observed during extended operation periods. About 60 samples are injected per hour, and the results are precise (r.s.d. <2%) and in agreement with ion chromatography.
Meneses
Silvia R P
SR
Centre for Nuclear Energy in Agriculture, University of S. Paulo, P.O. Box 96, Piracicaba SP 13400-970, Brazil.
Maniasso
Nelson
N
Zagatto
Elias A G
EA