Joseph Sneddon

QUANTITATIVE SIMULTANEOUS ELEMENTAL DETERMINATIONS IN ALLOYS USING LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) IN AN ULTRA-HIGH VACUUM

Laser-induced breakdown spectroscopy (LIBS) in an ultra-high vacuum is used in simultaneous quantitative elemental analysis of NIST transition metal alloy samples. A plasma is formed by focusing a Nd:YAG laser onto the samples surface inside a vacuum chamber. UV-visible emission from excited species is monitored with the use of an optical multichannel analyzer (OMA). Linear calibration curves are shown for the elements (percent composition) Al (0.2–1.2%), Cu (0.021–0.49%), Fe (4.5–51.0%), Ni (30.8–80.3%), and Zn (6–12.8%) with the use of nonresonant lines. Detection limits (signal-to-noise = 3) vary with sample composition complexity from 0.0001% for Ni in a simple copper alloy (SRM 1111) to 0.16% for Al in a complex granular sample (SRM 349a). Absolute detection limits are estimated to be in the 20–200 μg/g range for the elements of interest. Simultaneous mass spectra were taken by sweeping the magnetic field of a mass spectrometer. Preliminary results showed the magnet could not be swept fast enough for multielement analysis. The use of a position-sensitive ion detection system is proposed.

Lasers in atomic spectroscopy : selected applications

Abstract The use and results of the laser in selected areas of atomic spectroscopy are discussed, in particular as a light source in atomic absorption and fluorescence spectrometry, as a sample introduction system, as an atomizer, and in laser-enhanced ionization spectrometry.

An atomic-emission study of the removal and recovery of chromium from solution by an algal biomass (Chlorella vulgaris)☆

Inductively coupled plasma atomic-emission spectrometry has been used to study the removal of chromium, principally in the sexivalent oxidation state, from solution by an algal biomass, Chlorella vulgaris, and its subsequent recovery. Binding of the chromium at the 5-100 mug/ml level was maximal (75%) at pH 3 within 3 min, with 5 mg of algae. Quantitative recovery of chromium was achieved by lowering the pH. The algae could be used four times in removal/recovery cycles before losing their 75% removal efficiency.

Direct and near-real-time determination of lead, manganese and mercury in laboratory air by electrostatic precipitation-atomic absorption spectrometry

Abstract The direct and near-real-time determination of lead, manganese and mercury in laboratory air by electrostatic precipitation-atomic absorption spectrometry is reported. Background levels in the low-to-sub ng m −3 range were found, which increased by up to two orders of magnitude if the air was disturbed. Detection limits were sub-ng m −3 and a linear relationship between sampling time and atomic absorption signal was obtained if the laboratory air sampled was undisturbed or homogeneous.

Binding and Removal of Aluminum Ions in Waters by an Algal Biomass

Abstract A preliminary study on the binding and removal of trace concentrations of aluminum ions in waters by two species of algae, Chlorella Pyrenoidosa and Chlorella Vulgaaris, were investigated. Binding by the former was minimal over all pH ranges, but binding by the latter was effective with a maximum binding of 68% occurring at pH 5. Binding was lowered drastically below pH 2, and this may be used to remove aluminum from the algae. Optimum binding occurred after 20 minutes exposure time of algae to aluminum solution and 450 mg algae mass to 100 mL solution. Binding was reproducible and more efficient in waters with low suspended solids. High salt concentrations interfere with binding, and the Chlorella Vulgaris could be reused 7 times with washings between each binding before a noticeable decrease in binding efficiency was found.

Electrostatic Precipitation Atomic Absorption Spectrometry

The theory and principles, design, construction, and preliminary evaluation of a system based on the electrostatic precipitation of metals in aerosols on a tungsten collecting electrode, followed by injection of this rod into an electrothermal atomizer for atomic absorption spectrometric determination of the metal, is described. With the use of a manganese aerosol generated by an electrothermal vaporizer, the highest atomic absorption signals—and therefore the optimum charging and collecting efficiency for the geometry of the system as described—were achieved with a negative corona of 15 kV and low aerosol velocity. The system determined copper in the laboratory atmosphere on a near-real-time basis.

Collection Efficiency of an Impaction-Electrothermal Atomization Atomic Absorption Spectrometric System for the Direct and Near-Real-Time Determination of Metals in Aerosols: Some Preliminary Results

Recent results have shown the potential for the direct and near real-time determination of metals in aerosols (a solid or liquid particle in a gas, e.g., an air or atmospheric sample) using a single-stage impactor connected to an electrothermal atomization atomic absorption spectrometer. The basic principle involves the drawing of an aerosol by vacuum through a jet, with the output stream directed against the electrothermal atomizer surface (impaction plate surface) opposite the injection port. The impaction plate deflects the flow rate to form an abrupt bend in the streamline, and particles in the aerosol with sufficient inertia are unable to follow the streamline and collide or impact with the electrothermal atomizer surface. The solid sample is then determined for metal content by conventional electrothermal atomization atomic absorption spectrometry. Detection limits were in the low ng/m3, the system was capable of detecting approximately 60 different metals on a sequential basis, moving mechanical parts were minimal, and the system was shown to directly determine mercury, cadmium, copper, and lead in the laboratory atmosphere.

Direct determination of metals in milligram masses and microlitre volumes by direct-current argon-plasma emission spectrometry with sample introduction by electrothermal vaporization

The development of an electrothermal vaporization and direct-current argon-plasma emission spectrometric system which allowed the determination of metals in microlitre volumes and milligram masses is described. For the five metals investigated, the concentration detection limits were comparable to those for conventional pneumatic nebulization of solutions, and the mass detection limits were superior. The use of an ashing stage was found to reduce enhancement by sodium in the determination of copper and manganese by the plasma method. The system was shown to give accurate results for complex biological, nutritional, water and geological samples.

A simultaneous multielement flame atomic absorption study for the removal of lead, zinc, and copper by an algal biomass

Abstract The effects of parameters such as pH, concentration of metals in solution, mass of algae, and residence time of algae were investigated as they relate to the uptake and removal of Pb, Zn, and Cu simultaneously from aqueous solutions by an algae biomass, Chlorella Vulgaris. This is the first detailed study of the binding of three metals simultaneously to Chlorella Vulgaris. The aforementioned parameters were found to have varying degrees of influence on the adsorption of metals to Chlorella Vulgaris. Analysis was performed using a Simultaneous Multi‐element Flame Atomic Absorption Spectrometer.

A modified torch system for direct solid analysis by laser ablation-inductively coupled plasma-atomic emission spectrometry

Abstract A modified torch for use as a solid sampling system for laser ablation inductively coupled plasma-atomic emission spectrometry (ICP-AES) is described. The torch system could replace the conventional torch used for solution analysis. Preliminary results based on copper determination in standard steel samples in terms of precision (±10%) and accuracy (±20%) were considered acceptable though poorer than conventional solution ICP-AES.