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The utilization of an inductively coupled plasma emission spectrometer as an element and species specific detector in transition metal chromatography

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Description: The utilization of atomic spectrometric detection for chromatography is rapidly gaining acceptance as an important tool for obtaining species specific analytical data. In order to examine the potential of the technique, an ion chromatography -inductively coupled plasma instrument system (hereafter called IC-ICP), was developed. A major objective of the project was to interface the instruments in such a fashion as to allow quick and simple changeover from the IC-ICP operating mode to standard continuous nebulization operation. Controlling software for the hybrid instrument was written in Object Oriented Turbo Pascal, which was chosen because of its flexibility, speed, and modular programming approach. The entire package consists of a small "driver" program, which initializes the system, and several self-contained modules, each containing all of the functions and procedures related to a specific task (i.e. acquisition, deconvolution, file I/O). Iron speciation studies were carried out on a polystyrene/divinylbenzene cation exchange column, using a 10 mM oxalic/7.5 mM citric acid eluent adjusted to pH 4.3 with LiOH. Under these conditions, Fe (III) formed a triply charged anionic complex, and was unretained by the resin. Fe (II), however, was not strongly complexed, and eluted much later, at 11.5 minutes. Chromium speciation studies were carried out on a polystyrene/divinylbenzene mixed functionality ion exchange separator column, using a 20 mM 2,6-pyridine dicarboxylic acid (PDCA) solution adjusted to pH 6.7 with an ammonium acetate/sodium phosphate buffer. In order to effect the separation, Cr (III) in the sample was complexed with excess PDCA before injection. This reaction was accomplished by heating a 10 mL aliquot of the sample for 1 minute with 10 mL of 10X concentrated eluent, and diluting to 100 mL. Under these conditions, Cr (III) formed a singly charged anionic complex, and was only slightly retained by the resin. Cr (VI), however, was not complexed, and eluted as the dinegative chromate anion. Chromium soil extraction studies were carried out by soaking soil obtained on campus with Cr (III) and Cr (VI) solutions, drying, and homogenizing the dried material. Aliquots were subjected to a nitric acid/hydrogen peroxide digestion to determine the total chromium concentration. Separate aliquots were then extracted with concentrated PDCA eluent, and the results compared to the acid digested total chromium results. Several samples of spent chromium ore were also analyzed as above. The PDCA extraction results obtained by IC-ICP and standard ICP emission spectroscopy (ICPAES) compared favorably. The IC-ICP chromatograms indicate that the PDCA extracted only Cr (III).
Language: English
Format: Degree Work