Liquid chromatography of lanthanide chelates of 1-(p-nitrophenyl)ethylenediamine-N,N,N',N' -tetra-acetic acid.

Preparation of the chelating agent, 1-(p-nitrophenyl)ethylenediamine-N,N,N',N'-tetra-acetic acid (p-nitrophenylEDTA), is described in detail. Separation of p-nitrophenylEDTA chelates of ytterbium(III), erbium(III), dysprosium(III) and europium(III) has been achieved by reversed-phase ion-pair liquid chromatography. With spectrophotometric detection at 254 nm, linear responses over about four orders of magnitude were achieved with detection limits (S/N = 2) of about 0.5 pmole.

Determination of tert-butylhydroquinone in edible oils by differential-pulse polarography.

A differential-pulse polarographic method for the determination of tert-butylhydroquinone (TBHQ) in vegetable oils has been developed and tested with a variety of oil samples. No prior extraction or other separation of TBHQ from the sample matrix is required. An oil sample is dissolved in a 1:5 v/v toluene/ethanol mixed solvent containing an acetate buffer, and polarograms are obtained directly for this solution. Recovery studies indicate that this method is suitable for routine determination of TBHQ at the concentrations normally used in edible oils.

Spectrophotometric determination of tetrafluoroborate with ferroin.

A spectrophotometric method for determination of the tetrafluoroborate anion with ferroin is described. The ferroin tetrafluoroborate is selectively extracted in the presence of excess of ferroin into n-butyronitrile, and the absorbance of the organic extract is measured at 520 mmicro. Beer's law is followed over a wide range of tetrafluoroborate concentrations when a single extraction procedure is used. Exhaustive extractions indicate that 74 % of the tetrafluoroborate is removed in a single extraction.

Gravimetric and spectrophotometric determination of hexafluoroantimonate with tetraphenylarsonium chloride, nitron and ferroin.

Two methods are described for the gravimetric determination of the hexafluoroantimonate anion with tetraphenylarsonium chloride and nitron as precipitants. In addition, a spectrophotometric method for this anion with ferroin as reagent is described. Hydrolysis of the anion is avoided by using stock solutions of KSbF(6) in N,N-dimethylformanude and adding these directly to concentrated aqueous solutions of the analytical reagent. Interference studies are included on a number of anions.

Spectrophotometric determination of hexafluoroarsenate with ferroin.

A spectrophotometric method for the hexafluoroarsenate anion is described. The determination involves selective extraction of the tris(1,10-phenanthroline)iron(II) salt of the anion into n-butyronitrile, followed by measurement of the absorbance of the organic layer. The extracts give good Beer's law plots over a wide range of concentrations and more than 98% of the hexafluoroarsenate is removed in a single extraction. Interference studies were made on a number of anions.