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A new first-derivative photochemically-induced fluorescence (D-PF) method is proposed for the determination of sulfapyridine (SPY) in milk. An 60:40 v/v ethanol-water medium and a 8-min UV irradiation time were selected for D-PF measurements. The method is suitable for SPY concentrations ranging from 0.1 to 0.6 ppm. Limits of detection are comprised between 6 and 21 ppb. Recoveries between 95 and 102% are found. This new D-PF method is remarkably simple, rapid, precise, and it allows one to determine low levels of SPY in milk without prior separation.

In this paper a spectrophotometric method for the Mn(II) determination is proposed. This method is based on the extraction in toluenic Adogen 464 solution of the complex origined between Mn(II) and isophtaldihydroxamic acid. The method permits determination of 50-100 of Mn (II). The error and the molar absorptivity are values of 2.0% and 8.500 1. mol. -1.cm-1 respectively. The interference levels caused by foreign ions are established. Also the standard line by extraction with ethylacetate Adogen 464 solution was studied.

The spectrophotometric study of violet complex isophthaldihydroxamic acid-vanadium extracted into solution of trioctylmethylammonium chloride in ethylacetate was made (max = 380 nm, = 7500 l.mol-1.cm-1; max = 510 nm, = 5510 l.mol-1 .cm-1; stoichiometries, 1:1 and 1:2, V:reagent). A new method for the extract-spectrophotometric determination of V(V) in the range 14–80 g of vanadium is proposed.

A spectrophotometric study has been carried out of the violet complex 3-indole-acetohydroxamic acid-vanadium extracted into a solution of trioctylmethyl-ammonium chloride in toluene [?max 525 nm; e=5381 l mol-1 cm-1; stoichiometry 1:3 (metal:reagent)]. A new method for the extract-spectrophotometric determination of V5+ in the range of 2–7 µg/g is proposed and interferences by foreign ions were investigated. The method has been satisfactorily applied to the determination of vanadium(V) in fuel oil. The relative error is ±2.9%.

A new extract-photometric method is proposed for determining trace amounts of Fe3+ based on the formation of a coloured complex with 2-indolehydroxamic acid (2-IHA), that can be extracted into a solution of trioctylmethylammonium chloride solution in toluene. Beer's law was obeyed between 0.06 µg/g and 1.25 µg/g (minimum error range) of iron in the aqueous phase, with a relative error (p=0.05) of ±0.86%. Molar absortivity at 455 nm was 6500 l mol-1 cm-1. The method was applied to the determination of iron in various samples: commercial pharmaceutical nutritional preparations, wine and standard samples of Portland cement and magnesite.