The retention of 1-(2-pyridylazo)-2-naphthol (PAN), 1-(2-thiazolylazo)-2-naphthol (TAN), and their chelates with Pd(II), Cu(II), Ni(II), Fe(III), Co(II, III), and Rh(III) on Separon C-18 and Silasorb C-18 in a flow of water-acetonitrile mixtures containing additions of acetate buffer solutions with different values of pH and different salts (NaNO3, NaClO4, NH4CN, tetrabutylammonium bromide (TBAB), and cetyltrimethylammonium bromide) was studied. Possible mechanisms of the influence of different additives on the retention of the chelates of PAN and TAN are discussed. Depending on the nature of the dynamic modifier, a change in the sorption mechanism because of the modification of the surface of the adsorbent (TBAB and cationic and anionic surfactants) or a change in the interaction between the sorbate and the mobile phase (NH4SCN) is possible. Addition of NaNO3 and NaClO4 changes the retention of the chromatographed compounds because of a change in the ionic strength of the mobile phase.

A literature survey on retention models used for the interpretation of the retention mechanism in ion-pair chromatography is given.

The retention of 2-(2-thiazolylazo)-5-diethylaminophenol and its chelates with Co(TT), Ni(II), Cu(II), Pd(II), Rh(III), and Ru(IV) on several stationary phases with different bonded hydrocarbon radicals (C-2, C-8, or C-18) was studied. The effect of mobile phase modifiers (quaternary ammonium bromides) was examined.

The extraction of palladium from chloride solutions in the presence of ethylenediaminetetraacetic acid on a column packed with Teflon impregnated with 1-(2-pyridylazo)-2-naphthol in isopentanol was studied as a function of the pH of the solution, the temperature of the column, and the flow rate of the aqueous phase. The conditions were selected for quantitative (concentration factor 100) and relative (from 10(5)-fold excess of copper, (5 x 10(4))-fold excess of nickel, (1 x 10(3)-5 x 10(3))-fold excesses of lead, iron(III), calcium, magnesium, aluminum, manganese(II), and predominant quantities of other noble metals) extraction. The procedure was used for determining palladium in anode copper, blister copper, regeneration copper, and Zh-3 ore.

A survey of the authors' work on liquid chromatography of platinum metals in the form of chelates with 1-(2-pyridylazo)-2-naphthol (PAN) is given. Extraction chromatography with PAN in isopentanol as a stationary phase was used to achieve a group concentration of these metals (Pd, Pt and Rh, concentration coefficient 100) from large volumes of aqueous solutions and a selective extraction of palladium from solutions containing other platinum, nonferrous and heavy metals on a 85–98° C thermostatted chromatographic column. The prospects for the use of liquid chromatography in the analysis of platinum metals are discussed.