Spectrophotometric determination of silicon in soil solutions by flow injection analysis: Reduction of phosphate interference

The molybdenum blue reaction for the determination of orthophosphate revisited: Opening the black box

“…Formic and maleic acids do not appear to interfere with orthophosphate determination [165]; these species lack the necessary atom(s) on an acarbon to create a 5-or 6-membered coordination ring with Mo(VI), and thus coordinate too weakly to be problematic. In fact, organic acids are sometimes used in MB methods to prevent the reduction of excess Mo(VI), particularly in silicate methods where the requisite acidity is lower than for orthophosphate [166,167]. By the same token, interference from organic ligands in PMB methods can be eliminated by complexing these species with excess Mo(VI) [147].…”

Flow injection systems for elemental soil analysis determinations

“…Ultraviolet/visible (UV/Vis) and atomic absorption spectrophotometry (AAS) are the most widely used detection systems (Figure 1), thereby employing existing analytical methodology and detection techniques already in use in manual analytical procedures. For easy adaptation of these detectors to the flow systems, Jacintho et al, 1981Zhang et al, 1984Krug et al, 1987Ferreira et al, 1995aFerreira et al, 1995aFang et al, 1985Cardwell et al, 1988Ferreira et al, 1995bFerreira et al, 1995bNogueira et al, 1996Jorgensen and Regitano, 1980Hongbo and Junyan, 1991Ferreira et al, 1996aZhang et al, 1984Maetal., 1994Cui and Fang, 1984 Garcia et al, 1991Nakajima and Yanagibara, 1993Ruzicka et al, 1977Zhang et al, 1984Krug et al, 1987Cui and Zhang, 1988Hongbo and Junyan, 1991Liu et al, 1992Ferreira et al, 1995aFerreira et al, 1995aFerreira et al, 1995bWang and Fang, 1986Xu et al, 1989Borggaard and Jorgensen, 1985Raben-Lange et al, 1994Narinesingh et al,1994 Zhang et al, 1984Kiugetal., 1987Hongbo and Junyan, 1991FetTeira et al, 1995aFerreira et al, 1995aZhietal., 1994Hollenbach et al, 1994Lukaszewski and Zembizuski, 1992Hollenbach et al, 1...…”

“…All extracts had to be diluted before injection. Arateof35 determinations per hour was obtained with a detection limit of 30 ng Si mL' 1 and a linear limit of 1.0 mg Si IA A similar system, based on the same colorimetric reaction was optimized by Raben-Lange et al (1994) for the determination of water-soluble Si, but with reduction of PO 4 interference. Detection took place at 790 nm.…”