Carmen W. Huie

Peroxyoxalate chemiluminescence detection in capillary electrophoresis

Abstract The feasibility of employing peroxyoxalate chemiluminescence (PO-CL) detection in capillary electrophoresis (CE) was demonstrated using a two- step approach for the CE separation and dynamic elution (elution under pressure) of the analytes. In this approach, potential problems associated with incompatibilities between mixed aqueous-organic solvent and clectrically driven separation systems were avoided by switching off the CE power supply at an appropriate time and connecting the CE capilliary to a syringe pump to effect dynamic elution. The effect of dynamic flow- rate and PO-CL reagent concentration on the CL signal intensity and/or peak width were examined for the measurements of three dansylated amino acids. The average limit of detection for these analytes using this PO-CL method is about 1.2 fmol ( ca. 85 nM) which is approximately 35-fold lower than UV absorption methods.

Speciation of aluminum using capillary zone electrophoresis with indirect UV detection

Abstract Capillary zone electrophoresis was evaluated as a method for the speciation of aluminum in aqueous solution using indirect UV absorption detection. Flu

Salting-out surfactant extraction of porphyrins and metalloporphyrin from aqueous non-ionic surfactant solutions.

A number of cloud point temperature-depressing electrolytes have been investigated for the separation of a non-ionic surfactant (Triton X-100) from aqueous solutions and the corresponding extraction of the organic solutes into the smaller volume surfactant-rich phase using the salting-out method. High extraction efficiencies and preconcentration factors were obtained at room temperature for the extraction of several hydrophilic and hydrophobic metal-free porphyrins (uroporphyrin, coproporphyrin, protoporphyrin and hematoporphyrin) and one metalloporphyrin (iron-protoporphyrin) that were dissolved in the aqueous non-ionic surfactant solutions. Possible mechanisms responsible for the efficient extraction of these important biological molecules into the surfactant-rich layer are discussed.

Spatial Mapping of Analyte Distribution within a Graphite Furnace Atomizer

A versatile diagnostic scheme based on the combination of the unique properties of a laser, such as collimation and monochromaticity, together with absorption spectroscopy and subsequent computer extraction of quantitative information from a video signal has been applied to acquire spatially and temporally resolved information in a graphite tube atomizer. Spatially resolved concentration profiles with a 256 × 240 array of intensities can be obtained in 1/60 second. This capability has been demonstrated in the study of sodium atom distribution within a graphite furnace. Spatially and temporally resolved absorbance profiles taken within the furnace show extreme nonuniformities throughout the lifetime of the sodium atom plume. Early in the absorbance signal, the distributions show absorbances which decrease in going from the bottom, where the sample was initially deposited, to the top of the furnace. A more uniform distribution of the free atoms can be seen after a majority of the analyte has been released from the surface of the graphite tube, i.e., after the absorbance peak.

Separation of porphyrins and porphyrin isomers in capillary electrophoresis using mixed ionic surfactant-bovine serum albumin buffer systems

Abstract The separation of six porphyrins having two to eight carboxylic acid side-chains by capillary electrophoresis using a combination of ionic surfactant and protein as a novel modifier in the run buffer is reported. Using sodium dodecyl sulfate (SDS) together with bovine serum albumin (BSA) as buffer additives, efficient and reproducible separation of mesoporphyrin, coproporphyrin, uroporphyrin, penta-, hexa- and heptacarboxylporphyrins was achieved at pH 7.4 whereas sodium taurodeoxycholate (bile salt) combined with BSA in the run buffer separated type I and III isomers of coproporphyrin as well. The presence of SDS or bile salt appeared to minimize protein-and/or porphyrins-inner capillary wall (untreated silica) interaction and to enhance solubilization and selectivity of porphyrins due to the formation of ionic surfactant-protein complex(es) in the run buffer.

DETECTION OF BILIRUBIN USING SURFACTANT FLUORESCENCE ENHANCEMENT AND VISIBLE LASER FLUOROMETRY

Abstract Improvements on detection limits for the measurement of unconjugated and conjugated bilirubin in aqueous solutions using surfactant fluorescence enhancement and visible laser fluorometry were investigated. To maximize the fluorescence signal, commonly used surfactants were employed to enhance the fluorescence quantum yields of these bilirubin molecules and one of the visible lines of an argon ion laser was used for fluorometric excitation; to minimize optical noise, a unique optical fiber flow-cell was employed. Relative and absolute limits of detection for the micelle-bound unconjugated and conjugated bilirubin were in the sub-micromole per liter and sub-nanogram range, respectively. These capabilities should be important for the potential use of surfactants in flow injection analysis or micellar liquid chromatography for the determination of bilirubin species in biological materials.

Light emission from bilirubin using the peroxyoxalate chemiluminescence reaction

Abstract The observation of light emission from bilirubin in an organic solvent as a result of the peroxyoxalate chemiluminescence reaction is reported for the first time. The results presented herein indicate that bilirubin chemiluminescence can be detected in N,N′ dimethylformamide but not in chloroform, dimethylsulfoxide, or pyridine. To elucidate this phenomenon, the effects of solvent on the chemiluminescence intensity were examined as a function of solvent composition. Furthermore, analytical utilization of the present observation for the determination of bilirubin in biological materials was evaluated. Relative and absolute limits of detection were found to be 8.5 nmol 1 −1 and 5.0 ng, respectively, and the response was found to be linear at least over three orders of magnitude. Selectivity for the detection of bilirubin in the presence of a number of common interference species was also examined. Finally, the visible spectrum of bovine serum in the blue-green region was obtained using the present chemiluminescence method and was briefly compared with those obtained from absorption ad fluorescence methods.

Chronic aluminum fluoride administration: I. Behavioral observations

This study examined the behavioral effects of chronic ingestion of various monofluoroaluminum complexes (AlF3) in drinking water. Forty young adult male Long-Evans rats were divided into four groups of 10 rats each. The groups received different concentrations of AlF3 in the drinking water from three sample solutions having a total Al concentration of 0.5, 5.0, and 50 ppm, respectively, or double-distilled deionized water on an ad lib. basis for 45 weeks. General decline of bodily appearance was observed in the lowest concentration AlF3 group, and animals in this group succumbed in greater numbers during the course of the study than those in any other group. Examinations of performance in an open field, an analysis of walking patterns, and a balance beam test did not find any difficulties indicative of motor disorder. Indeed, on the initial trial on the balance beam, the AlF3-treated animals exhibited superior performance. No group differences were found in behavior assessed by spontaneous alternation or by a modified Morris water maze test. When retested in the Morris maze after a low dose of scopolamine (0.4 mg/kg), the control animals took longer to reach the platform while the AlF3-treated rats were not affected. In an olfactory preference test, the AlF3-treated animals failed to show preferences exhibited by the controls, indicating a possible olfactory impairment. The level of Al in the brains of the AlF3-exposed rats, as determined by direct current plasma analysis, was almost double that of the control animals. There was a similar trend for the Al content found in the kidneys.

The Effect of Internal Gas Flow on the Spatial Distribution of Sodium Atom within a Graphite Furnace Atomizer

A laser-based vidicon imaging system has been used to obtain spatially and temporally resolved absorbance profiles of Na atoms within pyrolytic graphite coated and uncoated polycrystalline electrographite tubes under gas-stop and gas-flow conditions in graphite furnace atomic absorption spectrometry. During the initial period of atomization, the spatial distribution of Na indicates that most of the atoms are localized near the bottom of the furnace under the influence of convective flow. This observation suggests that the free Na atoms, upon collisions with the furnace walls, are interacting strongly with the graphite surface. The strength of interaction appears to be stronger for uncoated graphite tubes. After the peak absorbance, the Na atom density is lower near the furnace wall than in the center of the furnace. The observed gradient is likely a result of the Na atoms undergoing a series of redeposition and revaporization reactions with the graphite surface during the course of atom removal.

Screening of urinary coproporphyrin using cloud point extraction and chemiluminescence detection

A simple screening test was developed for the sensitive and selective measurement of urinary coproporphyrin. In this screening test, efficient and selective extraction/pre-concentration of coproporphyrin from the aqueous medium(urine) into a much smaller volume phase containing a common non-ionic surfactant (Triton X-100) and ethyl acetate was accomplished by the addition of a relatively large amount of a cloud point depressing electrolyte (K(3)PO(4)) into the sample solution to effect cloud point separation. Sensitive and selective detection of coproporphyrin in the mixed Triton X-100 and ethyl acetate phase was performed via chemical excitation using the peroxyoxalate chemiluminescence reaction. The effects of surfactant and cations (from the cloud point depressing electrolyte) on the chemiluminescence intensity of coproporphyrin were briefly investigated. Furthermore, the spectrum of urinary coproporphyrin obtained using the present chemiluminescence method was briefly compared with that obtained from fluorescence method.