Removal of an Iron Matrix with Polyoxyethylene-Type Surfactant-Coated Amberlite XAD-4 for the Determination of Trace Impurities in High-Purity Iron

Abstract

Admicellar sorbents for the removal of an iron matrix were prepared for the determination of trace impurities in high-purity iron. A 1.0-g amount of Amberlite XAD-4 (macroreticular styrene-divinylbenzene copolymer) was coated with 0.14-1.3 mmol of polyoxyethylene-type surfactants, including polyoxyethylene-4-tert-octylphenoxy ethers (Triton X series) and polyoxyethylene-4-isononylphenoxy ethers (PONPEs). The surfactant-coated XAD-4 was packed into a polypropylene column (7 mm i.d. x 50 mm high). A 5.0-cm(3) volume of sample solution was passed through the column at a flow rate of 0.5 cm(3) min(-1). Milligram amounts of iron(III) were effectively sorbed on the column from 8 mol dm(-3) hydrochloric acid solutions. Among the surfactants tested, polyoxyethylene(20)-4-isononylphenoxy ether (PONPE-20) showed the best performance: the iron leaked from the PONPE-20 column was 4 microg when 25 mg of iron(III) was introduced onto the column. Trace elements, such as Ti(IV), Cr(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Cd(II), Pb(II), and Bi(III), were not retained on the column and thus quantitatively recovered in the column effluent. The effective separation of trace elements from an iron matrix allowed their accurate determinations by inductively coupled plasma-mass spectrometry or graphite furnace atomic absorption spectrometry. The detection limits (3sigma blank) were in the nanogram per gram range. The proposed method was successfully applied to the determination of trace impurities in high-purity iron samples.

Solid-Phase Extraction Followed by HPLC for the Determination of Phosphorus(V) and Arsenic(V)

“…As described in our previous report, 12 the sorption of Fe(III) onto the PONPE-admicelles was quantitative in 6 -8 M HCl, while it became negligible in <2 M HCl. The separation of P(V) and As(V) from an Fe(III) matrix was thus carried out at pH 1.5, which was the optimal pH for the formation and sorption of the heteropoly acids.…”

“…Compared with the previous study, 12 only a 1/10-amount of XAD-4 was used because the resulting admicelles were employed for trace analytes, not for the iron matrix. The adsorption mechanism of polyoxyethylene-type nonionic surfactants onto polystyrene surfaces has been discussed in the field of surface and colloid chemistry.…”

“…[10][11][12] For example, the combination of polyoxyethylene(20)-4-isononylphenoxy ether (PONPE) and an Amberlite XAD-4 resin provided a unique sorbent for SPE, where the ethylene oxide chains of the surfactant interacted with Fe(III) in 6 -8 M HCl similarly to diethyl ether in solvent extraction. 12 The selective sorption of Fe(III) allowed the matrix-removal for the multielement analysis of iron metals by ICP-MS. However, the determination of P and As was not attempted because of the low sensitivity of ICP-MS for these elements.…”

Matrix-precipitation for the Determination of Trace Impurities in High-purity Iron

“…Many separation techniques, including sorption, [5][6][7][8][9][10][11][12] liquidliquid extraction, [13][14][15][16][17][18] coprecipitation, [18][19][20][21][22] electrolysis, 14,23,24) and volatilization, 25,26) have been employed to determine impurities at ultratrace levels in iron and steels. However, these techniques are often tedious and time-consuming and they sometimes require volatile, flammable, and ill-smelling organic solvents or corrosive and hazardous acids.…”

Ionic Liquid-based Extraction of Heteropoly Molybdic Acids for the Sensitive Determination of Si, P, and As in High-purity Iron

“…During the course of our study on the separation techniques for the analysis of iron metals, [10][11][12][13] we found that a polyoxyethylene-type nonionic surfactant-coated resin provided the quantitative extraction of heteropoly molybdic acids. 13) The desorption was made by decomposing them with an alkaline reagent and the obtained solution was acidified again to form heteropoly molybdic acids for the determination by high-performance liquid chromatography (HPLC).…”