Ramon M. Barnes

How much soil do young children ingest: An epidemiologic study

Sixty-four children aged 1-4 years were evaluated for the extent to which they ingest soil. The study followed the soil tracer methodology of S. Binder, D. Sokal, and D. Maughan (1986, Arch. Environ. Health, 41, 341-345). However, the present study included a number of modifications from the Binder et al. study. The principal new features were (1) increasing the tracer elements from three to eight; (2) using a mass-balance approach so that the contribution of food and medicine ingestion would be considered; (3) extending the period of observation from 3 days to 8 days; and (4) validating the methodology by having adult volunteers ingest known amounts of soil in a mass-balance validation study. The principal findings reveal the following. (1) The adult study confirmed the validity of the tracer methodology to estimate soil ingestion. (2) Of the eight tracers employed in the adult study, only Al, Si, and Y provided sufficient recovery data that was directly acceptably stable and reliable. (3) If food ingestion determinations were taken into consideration, the median estimates of soil ingestion from the eight tracers ranged from a low of 9 mg/day (Y) to a high of 96 mg/day (V); the median values of Al, Si, and Y, the three most reliable tracers, ranged from 9 mg/day to 40 mg/day. (4) One child had soil ingestion values ranging from 5 to 8 g/day, depending on the tracer. (5) If food ingestion had not been considered, the estimates of soil ingestion would have increased about two- to sixfold, depending on the tracer with Ti and Y being most affected by food intake. (6) Since soil and dust samples did not significantly differ in their levels of tracer elements, no reliable differentiation between the contribution of ingestion of dust and soil could be made. (7) These findings are generally consistent with the previously reported findings of Binder et al. (1986) and P. Clausing, B. Brunekreff, and J.H. van Wijnen (1987, Int. Arch. Occup. Med., 59, 73) if these latter studies are corrected for ingestion of tracers in food and medicine. The findings also account for the apparent discrepancy between the estimates from Al and Si and estimates based on Ti in previous studies. Thus the elevated estimates of soil ingestion by Ti were substantially reduced when food ingestion is considered.

Direct Determination of Major and Trace Elements in Milk by Inductively Coupled Plasma Atomic Emission and Mass Spectrometry

The direct determination of major elements (Ca, K, Mg, Na and P) and Zn by inductively coupled plasma atomic emission spectrometry (ICP-AES) and trace elements (Al, Ba, Cu, I, Mn, Mo, Pb, Rb, Se, Sr and Zn) by inductively coupled plasma mass spectrometry (ICP-MS) in powdered, skimmed and whole milk was developed. Samples were diluted with a 5 or 10% v/v water-soluble, mixed tertiary amine reagent at pH 8. This reagent mixture dissociated casein micelles and stabilized liquid phase cations. Analyte emission or mass intensities losses were not observed. Reference solutions were prepared in 10% v/v mixed amine solution, and no internal reference element was needed for ICP-AES. The quantitative ICP-MS procedure applied the standard additions method with an yttrium internal reference. Except for Se in whole milk powder, all determined values in NIST Standard Reference Material (SRM) Non-Fat Milk (SRM 1549) and Whole Milk (SRM 8435) Powders agreed with certified values at the 95% confidence level. This direct technique is as fast as slurry approaches without particle size effects and sensitivity losses.

Computer simulation of RF induction-heated argon plasma discharges at atmospheric pressure for spectrochemical analysis-I. preliminary investigations

Abstract Models of induction coupled plasma (ICP) discharges are developed for arrangements important in spectrochemical analysis. These models account for the spatial distribution of gas properties and major energy losses found in high temperature discharges. Realistic gas flows, and sample particle motion and decomposition are incorporated into the models. Computer simulations based on these models provide spatial temperature, gas velocity, sample concentration, and radiation distributions for a number of experimental ICP discharge configurations. The alteration of these distributions for various operational parameters permits evaluation of some important factors in developing spectroohemical analysis with the ICP source. Recognized differences between theory and experiment are discussed.

Identification of potential environmental sources of childhood lead poisoning by inductively coupled plasma mass spectrometry. Verification and case studies

The isotopic determination of lead in blood and environmental materials by inductively coupled plasma mass spectrometry was used for the identification of potential sources of childhood lead poisoning. Sample preparation methods for blood, dust, paint, sediment and soil were evaluated and the recovery of total lead and the lead isotope composition of samples were determined. Verification of the measurement accuracy and precision was obtained for standard reference materials and a number of practical cases of childhood lead poisoning from an unknown source were studied.

Interfaced d.c. argon-plasma emission spectroscopic detection for high-pressure liquid chromatography of metal compounds

Abstract A d.c. argon-plasma emission spectroscopic system is described for directly interfaced metal-specific detection of eIuates in high-pressure liquid chromatography. Differing approaches are needed with regard to solvent systems used in normal-phase or reversephase chromatography. A simple nebulization system is adequate for reverse-phase applications of polar solvents. However, a novel design of an impact nebulizer-interface is required to accommodate the hydrocarbon and halocarbon solvents typically encountered in normal-phase and adsorption chromatography. The d.c. plasma detection system has been applied to the h.p.l.c. of a range of transition metal β-diketonate, β-ketoamine and diethyldithiocarbamate complexes, with good linear ranges for metalspecific detection and with detection limits in the sub ng s -1 range of metal eluted in the complexes.

A Study of Inductively Coupled Plasma Torch Configurations

Plasma torch design and shapes were studied to facilitate ignition, to concentrate the sample into a narrow central channel, to raise the sample to excitation temperatures with optimized efficiency, and to avoid clogging by organic samples such as residual oil. Observation of the influence of the torch configuration on ignition emphasized the importance of the shape and rate of the gas flows. Operating conditions of torches with diameters from 7 to 18 mm were calculated using a computer model, and predicted operation of small diameter torches requires high magnetic flux density. Experimental verification of an improved torch design demonstrated a higher efficiency, a lower gas consumption, and an easier ignition than conventional configurations.

Elimination of boron memory effect in inductively coupled plasma-mass spectrometry by ammonia gas injection into the spray chamber during analysis

Abstract Injection of 10–20 ml/min of ammonia gas into an inductively coupled plasma-mass spectrometry (ICP-MS) spray chamber during boron determination eliminates the memory effect of a 1 μg/ml B solution within a 2-min washing time. Ammonia gas injection also reduces the boron blank by a factor of four and enhances the sensitivity by 33–90%. Boron detection limits are improved from 12 and 14 to 3 and 4 ng/ml, respectively, for two ICP-MS instruments. Trace boron concentrations in certified reference materials agree well using ammonia gas injection.

Computer Simulation of Inductively Coupled Plasma Discharge for Spectrochemical Analysis. II. Comparison of Temperature and Velocity Profiles, and Particle Decomposition for Inductively Coupled Plasma Discharges in Argon and Nitrogen:

Using a recently developed numerical procedure for the solution of energy and magnetic flux density equations for inductively coupled plasma (ICP) discharges with diatomic gases, we made a theoretical comparison of ICP discharges in argon and nitrogen with the objective of evaluating their relative spectrochemical usefulness. Nitrogen discharges operating at powers between 3 and 7 kW and argon discharges of powers between 0.6 and 6 kW are investigated for a three-concentric gas flow arrangement now popular in spectrochemical analysis. Although the argon discharge temperatures are higher and the linear velocity of the central gas stream lower, nitrogen provides a more effective discharge for decomposition of A12O3 particles. Two-dimensional temperature distributions, velocity profiles, and power loss relationships are described.

Decomposition of biological samples for inductively coupled plasma atomic emission spectrometry using an open focused microwave digestion system

A focused microwave digestion system operated at atmospheric pressure was applied to the preparation of milk, total parenteral nutrition, tissues (mussel, kidney, oyster and bovine liver) and urine. Reagent combinations (HNO3, H2SO4 and H2O2) and power–time programmes were examined with respect to the residual carbon content (RCC) and element recovery. Inductively coupled plasma atomic emission spectrometry was used to determine the residual carbon and analytes (As, Ba, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, Pb, Sr and Zn). Different reagents (HNO3, HCl and ethylenediaminetetraacetic acid) were investigated for the final digestion step in order to improve the accuracy in the determination of elements forming low-solubility sulfates. The RCC obtained with an open-focused microwave system was similar to that obtained with high-pressure digestion, but lower than with a closed, medium-pressure microwave system.

Temperature and velocity profiles and energy balances for an inductively coupled plasma discharge in nitrogen

Modification of a mathematical model described originally by Miller and Ayen to predict radial and axial temperature profiles in an inductively coupled plasma discharge was developed and applied to nitrogen. The modified model incorporates an updated description of three‐concentric gas‐flow patterns now common in spectrochemical applications. Temperature and velocity profiles and energy‐balance distributions were demonstrated for a variety of input power levels and central flow rates. These results parallel similar results for well‐characterized argon discharges. The modified plasma model depends upon the application of a weighted average of previous and current computed temperature values in achieving a stable numerical solution.