Flame Spectrophotometric Determination of Copper in Ferrous Alloys

Abstract

Organic solvent extraction can be applied to the flame spectrophotometric determination of copper in ferrous alloys. Copper, in the form of the salicylaldoxime complex, is selectively extracted from the aqueous solution of the sample with either chloroform or n-amyl acetate.Citrate was employed to buffer the solution at pH 3 and mask the iron, thereby preventing its coextraction.The organic extract is aspirated directly into an oxyacetylene flame. This procedure circumvents interferences encountered when aspirating the bulk sample containing varying amounts of diverse elements and increases the spectral emission of the copper 324.7-mg line tenfold as compared with an aqueous solution of copper.No interferences were found when the method was applied to a wide variety of ferrous alloys. Accurate measurements can be made on as little as 0.5 y of copper per ml.THE application of organic solvent extraction to flame spectrophotometry offers a number of advantages (2). Compared with an aqueous solution, the spectral emission of the element present in the organic extract is generally enhanced severalfold. A selective extraction avoids the introduction of high concentrations of diverse ions into the flame, thus eliminating errors that might arise due to their presence. Also minimized are variations of the physical properties of the aspirated solution, such as viscosity, droplet size, and volatility. The introduction of solutions containing high salt concentration into a flame produces considerable amounts of incandescence, apparently as a result of minute solid particle formation. Solvent extraction also affords a means for concentrating the test element. The authors have previously applied solvent extraction to the flame spectrophotometric determination of iron (3).Copper exhibits two rather sensitive emission lines in the ultraviolet portion of the spectrum at 324.7 and 327.4 µ. In addition, copper possesses a series of weak emission bands in the visible region (11). Lundegárdh (9) observed that the radiant power of copper was strongly dependent upon operating conditions, and that both lines were prone to suffer strong self-absorption.Dean (1) has reported an extensive flame spectrophotometric study of copper and has developed methods for copper applicable to nonferrous alloys. However, interferences from unknown sources prevented the extension of the method to ferrous alloys.Prior to this, several investigators had employed the two emission lines mentioned to determine copper in biological materials (7) and other substances (4). Dean (1) found that the utility of the 324.7-mg line was hindered by self-absorption, and, while not as serious in the case of the 327.4-mg line, the latter line is about one half the radiant power of the former. It seemed desirable to develop a method for copper applicable to ferrous alloys and with sufficient sensitivity to facilitate the analysis of micro amounts of copper.Feigl's general discussion on the behavior of o-hydroxyaldoximes ( ) suggested the utilization of this class of reagents...

Flame Photometric Determination of Copper in Mineral Mixes. Ion Exchange Technique for Sample Preparation

“…They also reported some depressing effects due to Al, Fe, Mg, Ca, Pb, K, and Ni cations. Dean and Lady (6) reported that interferences from unknown sources caused difficulty with the determinations of Cu in ferrous alloys.…”

“…Extractions. It has been shown by Wise and Brandt (9) and Meloan and Brandt (6) that strong oxidizing and reducing agents will destroy the chelates of benzohydroxamic acid. To minimize this, the hydrogen peroxide is extracted from the organic material with water.…”

Flame Spectrophotometric Determination of Microgram Quantities of Magnesium

“…Different solvents were tested at varying concentrations to determine their effect on the radiant power of 4 7 of magnesium per ml. The data presented in Table I agree with the results reported by Ikeda (9) for 50% methanol solutions.…”

Emission Spectroscopy

“…Improvement in sensitivity by use of a highly reducing oxyacetylene flame in determining magnesium is reported by Knutson (ISO), Increased sensitivity is observed fo'• the use of alcoholic solutions in determining calcium and magnesium by Fink (80), and in determining copper by Manna, Strunk, and Adams (151). .Reaction of the sample with organic reagents followed by extraction is applied to the determination of copper in plant materials (155), for copper in ferrous alloys (66), for copper, nickel, and manganese in aluminum (56), and for ch minium (38).…”