H. M. Kingston

On-line solid-phase chelation for the determination of eight metals in environmental waters by inductively coupled plasma mass spectrometry

A low-pressure method for the on-line preconcentration of analytes and elimination of matrix elements prior to determination by inductively coupled plasma mass spectrometry (ICP-MS) is described. The method reduces the concentrations of matrix elements in samples to levels that do not interfere with the determination of the first row transition elements at trace levels. The method also reduces biases caused by differences between samples and standards by delivering the analytes to the ICP-MS instrument in a consistent nitric acid matrix. A commercially available low-pressure sample manipulation system was used to perform solid-phase chelation on an iminodiacetate column. The effectiveness of the method is demonstrated for the determination of Cd, Co, Cu, Mn, Ni, Pb, U and Zn in the certified reference materials CASS-2, Near Shore Sea-water; NASS-4, Open Ocean Sea-water; and the Standard Reference Material 1643b, Trace Elements in Water. The volume of sample preconcentrated was varied in order to optimize the analyte signal. The detection limits for 10 ml samples ranged from 0.8 ng l–1 for Co to 40 ng l—1 for Cu and Zn.

Dissolution problems with botanical reference materials

SummaryAs part of the analytical research leading to the certification of the new Apple and Peach Leaves Standard Reference Materials (SRMs), a study was undertaken to evaluate different sample dissolution techniques for losses of analyte species. Possible loss mechanisms include absorption or adsorption of analyte elements at the walls of the sample decomposition vessels, and the formation or persistence of insoluble particulate material during sample dissolution. Results of this study indicated that significant fractions of some elements were present on particles after acid dissolution, despite visual indications that dissolution was complete. In addition, large amounts of some elements remained in the platinum crucibles used to fuse samples with lithium metaborate.

The use of isotope dilution mass spectrometry for the certification of standard reference materials

Abstract Isotope dilution mass spectrometry (IDMS) has been used extensively at the U.S. National Bureau of Standards as an accurate method to determine trace element concentrations in natural materials. Thermal ionization mass spectrometry is a single element technique capable of high accuracy and precision, and has been used for “definitive” measurements of trace elements in sera with 95% confidence limits less than 0.25%. Spark source mass spectrometry is a complementary multielement, high-sensitivity technique that has been used to determine up to 20 elements in a sample, with typical accuracies of 2%–5%. Together with appropriate chemical separations, such as anion and cation exchange, chelate resins, electrodeposition, and chemical extraction, IDMS has been applied to elemental concentration measurements ranging over eight orders of magnitude, from decigrams/gram to picograms/gram. Many of these applications have been used for the certification of a broad spectrum of biological and environmental Standard Reference Materials, including lead in Trace Elements in Water (SRM 1643), 15 elements in Coal Fly Ash (SRM 1633a), uranium in Bovine Liver (SRM 1577a), and mercury in water (SRM 1642).

An expert-database system for sample preparation by microwave dissolution. 2. Electronic transfer and implementation of standard methods

Currently, implementation of standard methods for chemical analysis relies upon the expertise of an analyst for conversion of the methods into usable procedures and for reproducible execution of these procedures. One can now encapsulate standard methods in a database format which can be transferred among laboratories. These methods can then be converted automatically to reproducible procedures for specific samples types. This paper describes the application of these software techniques to standard methods for microwave sample dissolution.

Neutron activation analysis of the NIST Bovine Serum Standard Reference Material using chemical separations

SummaryThe US National Institute of Standards and Technology is currently in the process of certifying a Bovine Serum Standard Reference Material. In addition to elements normally considered to be of clinical interest, a number of other elements, which are analytically more difficult to determine yet are of importance from either a nutritional or toxicological viewpoint, are being determined by a variety of analytical techniques. Neutron activation analysis in combination with appropriate pre- or post-irradiation chemical separations, has been used to determine many of these difficult elements.

A journey through quality control

The Euroanalysis VII conference in Vienna included a two-day session: Quality Assurance in Analytical Chemistry. The contributions comprised 15 lectures devoted to: intra-laboratory quality measures, inter-laboratory control, formal aspects and accreditation and implementation. The paper presents an overview of the main items developed by the contributors.

An elemental rationing technique for assessing concentration data from a complex water system

Abstract Water samples have been collected at the surface and bottom layers at 51 locations throughout Chesapeake Bay. The suspended particulate and dissolved fractions of these samples have been analyzed for Cd, Ce, Co, Cu, Fe, Mn, Mo, Ni, Pb, Sc, Sn, Th, U, and Zn using neutron activation analysis and atomic absorption spectrometry. Special chemical procedures were used to preconcentrate the elements of interest in the dissolved samples and separate them from the salt water matrix. The elemental concentrations observed in the dissolved samples were evaluated by direct comparison to those found in coastal seawater; however, the elemental concentrations in the particulate samples (mass per volume of water) were strongly influenced by the total amount of particulate material suspended in the water at time of collection. A double normalization procedure was used to calculate crustal enrichment factors for each sample, and these enrichment factors provided both a means to observe sample-to-sample variations, and also allowed a crude comparison with the natural levels occurring in the earths crust.

Investigation of a precise static leach test for the testing of simulated nuclear waste materials

Abstract The precision of the nuclear waste static leach test was evaluated using controlled experimental conditions and homogeneous glass materials. The majority of the leachate components were subjected to simultaneous multielement DCP analysis. The overall precision of the static leach test is determined by the summation of random effects caused by: 1. variance in the experimental conditions of the leaching procedure; 2. inhomogeneity of the material to be leached; and 3. variance of the analytical techniques used to determine elemental concentrations in the leachate. In this study, strict control of key experimental parameters was employed to reduce the first source of variance. In addition, special attention to the preparation of glass samples to be tested assured a high degree of homogeneity. Described here are the details of the reduction of these two sources of variance to a point where the overall test precision is limited by that of the analysis step. Of the elements determined-B, Ba, Ca, Cs, Mo, Na, Si, Sr, and Zn-only Ca and Zn exhibited replicate imprecision significantly greater than that observed in the analysis of the leachate solutions. The imprecision in the Zn was partially attributed to the nonreproducible adsorption onto the leach vessel walls during the 28 day test period. None of the other elements exhibited this behavior.

Neutron Activation Analysis of Biological Samples with a Preirradiation Chemical Separation

A preirradiation separation procedure has been developed to separate Al, Cu, Mn, and V from biological materials. Chelex-100 resin is used as the separation medium, and the resin is irradiated directly. Three NIST biological Standard Reference Materials and five samples of human blood serum, obtained under carefully controlled conditions, have been analyzed by NAA following this separation.

Adsorption and stability prior to analysis of simulated nuclear waste leachate

Before analytical compositional analysis can be applied to the evaluation of the nuclear waste leachates, the credibility of the sample must be demonstrated. During the leaching in neutral to basic aqueous conditions the adsorption of metal ions onto the walls of the Teflon leach vessels was demonstrated. The adsorption was found to be variable for both zinc and neodymium. The resolubilization of zinc and neodymium using dilute nitric acid proved effective prior to analysis. Certain elemental groups represented by cesium, barium, and strontium demonstrated resistance to container adsorption during leaching under these conditions. The maintenance of a dissolved analytical sample was followed and demonstrated for at least seven weeks following the postleaching procedure.