Biomedical subjects

M Sepaniak

Publications and source records attributed to M Sepaniak.

4 recordsLinked to original sources

PubMed2000

Chelating scintillation fibers for measurements of 137Cs

Solid scintillating fibers, coated with a dual-mechanism bifunctional polymer shown to bind Cs(I) in alkaline solutions, were developed for measurement of 137Cs. The effect of the epoxy-polymer coating thickness on attenuation of the signal from 137Cs was evaluated. After optimal coating conditions were determined, both scintillation fiber and resin functions were retained, producing stable field-ready fibers. Temporal studies were performed to examine the kinetics of 137Cs uptake into the resin. Calibration curves of the fiber response were generated by beta-emission from solutions of 137Cs dissolved in 1 M sodium hydroxide. The plots exhibited a linear response over a range of 4-3200 nCi/mL (3.4 x 10(-10)-2.7 x 10(-7) M 137Cs), with a limit of detection of 3.65 nCi/mL (approximately 42 parts per trillion 137Cs). The distribution coefficient of Cs was determined to be 490 +/- 50 mL/g from these measurements. Selectivity studies of the resin were performed in the presence of 100 fold excess of Sr(II), Al(III), and nonradioactive Cs(I). Linear calibration plots were obtained in the presence of these potential interferences, but at a reduced sensitivity. The fibers were also used to evaluate the 137Cs content of a mock tank waste sample to show the potential of the fibers in complicated matrixes.

Journal Article↗

PubMed2000

Selectivity in capillary electrochromatography using native and single isomer anionic cyclodextrin reagents.

Separations of naphthalene compounds that differ in position of substitution and type of substituent were accomplished using cyclodextrin distribution capillary electrochromatography. Separation systems composed of running buffers containing mixtures of native neutral and single isomer anionic cyclodextrins (CDs) were employed yielding efficiencies of approximately 200,000 plates/meter. Solute migration rates and relative orders can be readily modified by changing CD types and concentrations. Experiments were performed to determine distribution coefficients between each of the CDs used in these studies and an aqueous running buffer. For this work, naphthalene-CD cavity inclusion is assumed to be the principal mode of interaction. The distribution coefficients for carboxymethyl-beta-cyclodextrin (CM-beta-CD), degree of substitution 1, were 10-70% larger than those for native beta-CD and 75-1800% large than those for gamma-CD. The CM-beta-CD was singly charged and yielded a narrow elution window. Nevertheless, baseline resolution was achieved for several substituted naphthalene compounds using CM-beta-CD in conjunction with beta-CD or gamma-CD. Under certain conditions, the gamma-CD system yielded an elution order that differed from that of the beta-CD system. Heptakis-(2,3-dimethyl-6-sulfato)-beta-CD with its -7 charge produced a much larger elution window. The extensive substitution with sulfonic groups at the truncated bottom of the CD seemed to inhibit inclusion as the distribution coefficients for the naphthalene compounds were generally more than an order of magnitude smaller than those for CM-beta-CD. Moreover, there was evidence that this sulfato-CD interacted with both the capillary wall and neutral beta-CD. This work differs from prior uses of CDs in that relatively complicated mixtures of neutral, achiral compounds are separated using combinations of recently developed single-isomer CDs as running-buffer additives. The single-isomer CDs, as opposed to most highly complex derivatized CD products, facilitate predictions of separation performance for multicomponent samples. In this manner, the ability to use knowledge of distribution coefficients to predict elution characteristics for a ternary CD system is demonstrated.

Anions↗

PubMed2000

Modular separation-based fiber-optic sensors for remote in situ monitoring.

A modular separation-based fiber-optic sensor (SBFOS) with an integrated electronically controlled injection device is described for potential use in remote environmental monitoring. An SBFOS is a chemical monitor that integrates the separation selectivity and versatility afforded by capillary electrophoresis with the remote and high sensitivity capabilities of fiber-optic-based laser-induced fluorescence sensing. The detection module of the SBFOS accommodates all essential sensing components for dual-optical fiber, on-capillary fluorescence detection. An injection module, similar to injection platforms on micro-analysis chips, is also integrated to the SBFOS. The injection module allows for electronically controlled injection of the sample onto the separation capillary. The design and operational characteristics of the modular SBFOS are discussed in this paper. A micellar electrokinetic capillary chromatography mode of separation is employed to evaluate the potential of the sensor for in situ monitoring of neutral toxins (aflatoxins). The analytical figures of merit for the modular SBFOS include analysis times of between 5 and 10 min, separation efficiencies of approximately 10(4) theoretical plates, detection limits for aflatoxins in the mid-to-low nanomolar range, and controllable operation that results in sensor performance that is largely immune to sample matrix effects.

Chromatography↗

PubMedDate not supplied

Capillary electrophoresis as a method to study DNA reassociation.

To develop analytical methodology to assess the genetic complexity of a DNA sample, capillary electrophoresis with laser-induced fluorescence detection is used to monitor the annealing process of DNA samples. Coated columns are filled with an entangled polymer solution shown to optimally separate DNA through size-selective capillary electrophoresis. DNA samples are denatured by heating in a boiling water bath for approximately 10 min and then cooled to approximately 25 degrees C below the melting point of the DNA sample to initiate the reassociation process. The DNA is detected by means of the laser-induced fluorescence of intercalated ethidium bromide, which produces a substantially greater signal for double- versus single-stranded DNA. The rate of reassociation is dependent upon the rate at which complimentary strands of DNA encounter each other and the degree of repeating base sequences in the sample (hence, the diversity of the DNA). Experimental parameters also influence the reassociation rate. The effects of salt concentration and incubation temperature are presented. Traditional plots of C(o)t (C(o) = DNA concentration and t = reassociation time) versus % recovery of double-stranded DNA signal are generated for PhiX 174 Hae III digest and 50 bp stepladder DNA, individually and combined, to calculate the reassociation rate constants for these samples. Because reassociation of individual fragments is observed by the CE-LIF method, more information about the samples is available than with less specific and time-consuming traditional methods of investigating DNA reassociation.

DNA↗