Optimum Detection Limits Research Articles

Constant-temperature atomiser-computer controlled échelle spectrometer system for graphite furnace atomic emission spectrometry

A constant-temperature atomiser (CTA) was combined with an echelle spectrometer for graphite furnace atomic emission spectrometry (GFAES). The spectrometer incorporated a quartz refractor plate, which provided wavelength modulation background correction, under computer control. In order to investigate various parameters for GFAES measurements we developed a versatile computer program (for data acquisition and waveform generation) and a CTA in which tube dimensions and heating modes could be varied. Optimum detection limits and dynamic calibration ranges were obtained for tubes of medium length having spatial and temporal isothermality. A three-step square waveform in combination with appropriate data acquisition parameters was used, which also rendered good background correction capability. Detection limits for 16 elements and analytical results for five elements in two NBS reference materials are presented.

Speciation of Arsenic and Cadmium Compounds by Reversed-Phase Ion-Pair LC with Single-Wavelength Inductively Coupled Plasma Detection

Inductively coupled plasma (ICP) is one of the most popular plasma sources for spectrochemical analysis involving both single-element and multielement determinations. The occurrence of spectral overlap interferences has been a problem with some samples in complex matrices. The selection of appropriate analytical lines may require some compromise between optimum detection limits and the least spectral interference from major concomitants. However, if potential interfering substances are separated in time, their determination within a single-wavelength window (channel) should be possible. The applicability of ICP detection combined with high pressure liquid chromatography (HPLC) for speciation plus time resolution appears to be an attractive and potentially valuable analytical tool. The use of single-channel detection with reversed-phase ion-pair LC to separate Cd and As compounds has been investigated in this work. Complex samples containing sodium arsenite, sodium arsenate, cadmium ethylenediaminetetraacetate, and cadmium nitrilotriacetate were separated by reversed-phase ion-pair LC and detected in the single-channel mode at 228.812 nm, one of the useful “arsenic” emission wavelengths. This enables Cd (228.802 nm) and As speciation and detection at one wavelength setting because, within this bandpass, emission from both Cd and As can be detected. The separation efficiency has been improved through development of suitable column materials and mobile phases. The present experiment also shows the advantage of the ICP as an element-specific and -selective detector when compared to a conventional UV detector. Discussion of the advantages and applicability of this single-channel technique is given in terms of simplicity, sensitivity, precision, and detection limits.

The influence of a high-bran diet on trace element retention in primates (PIXE application)

Proton-induced X-ray emission (PIXE) has become an established analytical method for the determination of trace elements in biomedical samples. The standard PIXE technique has been modified, resulting in a considerable improvement in detection limits. Refinements include the use of an external proton beam, the incorporation of a triggered beam-pulsing system, and the backward angle location (135 degrees to the incident ions) of the Si(Li) X-ray detector. The technique is now clearly capable of rapid, multielemental investigations, and requires a minimum of target preparation. Samples of liver and oesophagus tissue were obtained from 26 baboons at autopsy. Of these, 13 had been maintained on a semi-synthetic (high-bran) diet, with the remaining 13 forming the control group. Some 15 elements were analysed quantitatively; optimum detection limits were in the range 10-20 PPB (1 billion=10 degrees ). Clear differences were obtained: the high-bran diet is shown to produce imbalances in biologically active elements such as S, K, Ca, Ni, Cu and Zn. These results are discussed on the basis of the phytate hypothesis in terms which trace elements in the diet are rendered physiologically unavailable to the subject.

Multi-Elemental X-Ray Analysis of Rat Liver by Proton Excitation of Thick Samples in Air

Abstract Rat liver samples were irradiated in air by 4 MeV protons for elemental analysis by X-ray emission spectroscopy. The standard instrumental procedure was modified in our study, resulting in optimum detection limits being attained. The analytical system was accurately calibrated with standard biological reference materials, compressed into 2 mm thick disks. Ten macro and trace elements were quantitatively determined in the tissue specimens : eight essential elements (S, CI, K, Ca, Mn, Fe, Cu, and Zn) and two with undefined biological roles (Br and Kb). Detection limits in the dry tissue samples were estimated to be 0.1 ppm for Mn, Fe, Cu and Zn. The method was employed to examine the effects of a low level of phytate supplementation on the trace element status of the rat liver, since phytate feeding potentiated tumor yields when carcinogens were administered. The results are discussed in terms of current hypotheses.

Evaluation of a rapid, sensitive and specific assay for the determination of collagenolytic activity in biological samples

Several methods for the determination of collagenolytic activity were compared from the point of view of sensitivity, selectivity, simplicity and practical value for large numbers of biological samples. A labelled collagen substrate was prepared using [ 3H] acetic anhydride. The specificity of the assay as well as conditions allowing an optimum detection limit were investigated. The influence of low temperatures, lyophilisation and salt concentration on Clostridium histolyticum collagenase have been investigated.

Specimen preparation in PIXE analysis

Abstract A review is presented of target backings and specimen preparation techniques for proton-induced X-ray emission analysis. The main emphasis is on techniques that afford the optimum detection limits in trace metal analysis of biological specimens.