Anal. Chem. 1988, 58,2583-2585
occurs through proton addition, and donation of an extra proton to these stronger acids may be difficult. These acids may be detectable with negative ionization monitoring. This work demonstrates the feasibility of using an IEPC/MS system to obtain mass spectral data which provide valuable molecular weight information for unknown components of a monoprotic organic acid mixture. Ongoing and future work involve studying a wider variety of monoprotic and diprotic acids to determine the molecular parameters necessary for successful application of IEPC/MS, and optimization of mobile phase, column type, and thermospray and
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mass spectral operating conditions for various acids. Registry No. Glycloic acid, 79-14-1; acetic acid, 64-19-7; propionic acid, 79-09-4; butyric acid, 107-92-6. LITERATURE CITED (1) Garteiz, D. A.: Vestal, M. L. LC Mag. 1085, 3 , 334-348. (2) Arpino, P. J. J. Chromatogr. 1085, 323,3-11. (3) Schubert, R. GITFachz. Lab. 1084, 28,323-325. (4) Fritz: J. S.; Gjerde, D. 7.; Pohlandt, C. Ion Chromatography; Dr. Alfred Huthig Veriag: New York, 1982; pp 185-199.
RECEIVED for review March 10,1986. Accepted June 6, 1986.
Quantitative Determination of Aluminum-27 by High-Resolution Nuclear Magnetic Resonance Spectrometry P. M. Bertsch,*' R. I. Barnhisel, and G. W. Thomas
Department of Agronomy, University of Kentucky, Lexington, Kentucky 40546
W. J. Layton and S. L. Smith Department of Chemistry, University of Kentucky, Lexington, Kentucky 40546 Quantitative determination of A1 in aqueous solution not containing interfering substances can be made by a variety of spectroscopic and potentiometric methods reliably and with relative ease ( I ) . Aluminum is, however, an element that is frequently analyzed in the study of geologic materials, sediments, sludges, and plant and/or animal tissues and in many industrial processes. For most of these analytical applications, the presence of interfering substances is ubiquitous, often resulting in the introduction of tedious, error-inducing pretreatments that can complicate the analysis. In addition, the reagents commonly used to solubilize and/or extract A1 in many of the aforementioned applications often cause matrix effects which make the analysis even more cumbersome. Many of the methods utilized for the quantitative determination of soluble A1 in different matrix solutions attempt to eliminate the various interferences encountered ( I ) . Although many of these methods are quite good, there still does not exist a rapid method for the routine determination of A1 overa wide m m mrange %is freefrom intmfermce of other elements or matrix complications. In this communication, we describe the use of high-resolution 27AlNMR spectrometry as a rapid, nondestructive analytical tool for the quantitative determination of aluminum over a wide linear dynamic analytical range. The method is useful not only when total A1 determinations are needed but also when the concentration of a particular soluble A1 complex is desired. EXPERIMENTAL SECTION Reagents. Standard aqueous A1 solutions were prepared by serial dilution of a Fisher Scientific 1000 wg/mL certified atomic absorption standard solution with COz-freedouble-deionized H,O. Standard solutions with A1 concentrations ranging from 1.00 to 1000.O g / m L were prepared in this manner and used to construct the calibration curves. During the course of this investigation it became apparent that acidification of certain solutions containing relatively low concentrations of the A~(HQO),~+ cation (ca. 1-10 pg/mL) resulted in significant decrease in the line widths of the "A1 signals. The Fisher standard A1 solution contains a dilute hydrochloric acid media with a pH of
