Analysis of hydroformylated vegetable oils and their methyl esters for rhodium

Two procedures for the determination of fatsolubilized rhodium were investigated. Analysis in aqueous media involves a sulfuric acid digestion which previously was carried out in 20–30 hr. Digestion now takes only 1 to 2 hr. The acid concentration in samples and standards is very critical. For analysis in nonaqueous media the sample is weighed, dissolved in methyl isobutyl ketone containing hydrogen chloride, and analyzed directly by atomic absorption spectrophotometry. Absorbance in both procedures follows Beer’ s law. Results varied when hydrogen chloride was omitted or replaced with phosphoric acid. The results agreed closely with results obtained by published colorimetric procedures.