Chemistry: analytical and immunological testing – Nuclear magnetic resonance – electron spin resonance or other...
Reexamination Certificate
1998-01-29
2004-09-14
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Nuclear magnetic resonance, electron spin resonance or other...
C250S282000, C250S288000, C436S056000, C436S073000, C436S074000, C436S083000, C436S161000, C436S179000
Reexamination Certificate
active
06790673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of employing enriched speciated isotope spikes in the same speciated form as a specie to be measured regardless of incomplete extraction or the presence of conversion, partial destruction, and instability.
2. Description of the Prior Art
The need for making quantitative determinations of a specie of interest occurs in many contexts including environmental, biological, pharmaceutical and industrial samples and in standard reference materials. For example, certain forms of an element or molecular species may exhibit different toxicities or chemical behaviors from others. Existing techniques, with the exception of electrochemical methods, rely predominately on physical separation and time. They are incapable of determining whether the species cross-over (transformation of one specie form into another), are lost, created or are altered or are completely recovered. Such techniques cannot be used to determine transformation of one species into another, destruction or generation during storage, manipulation and sample preparation during the measurement process, or in the separations that are incomplete or variable in measurement processes.
An example of the criticality of such measurements would be to consider chromium. While Cr(III) is a trace element essential for human health, Cr(VI) is poisonous to humans and most other animals and is also a carcinogen. As a result, the difference between these two species, which resides in the oxidation state of the element, may be of critical importance. While chromatography can be used to separate Cr(III) in time resolution from Cr(VI), as each specie can react with its surroundings and even with separating agencies, the chromatographic separation is only a snapshot in time recording the state of affairs at the end of the manipulation. Each specie may have reacted with many other reagents and transformed during the analysis. There is, therefore, with time resolution, no way of determining how much chromium was actually in each specie when the experiment began or when the sample was actually taken.
Specific species are often required for a particular process. For example, barium is toxic in some compound forms, but is also prescribed for medical diagnostic x-ray tests, usually as barium sulfate in liquid slurry form. The conformation and evaluation of a body's processing of barium into another specie can be accomplished with isotopically labeled barium sulfate. These studies have been done, but the use of speciated isotope dilution measurements has not been used for such analysis.
Some isotopic tracking has been done for lead due to terrestrially unique and naturally occurring isotopic composition differences of this element. The isotopic ratios can be matched with a particular source to determine the origin of the lead. These measurements are not speciated measurements, but depend on the isotopic ratio differences of the natural material to be detected. This technique has also been used for lead pottery glazes to determine the origin of art objects, however in this case also, naturally occurring isotopic ratios were determined. Lead is a uniquely feasible non-radioactive element to be evaluated as to origin by the isotopic ratio method, as its isotopic ratios change with the amount of uranium mixed with the lead in the original ore deposits. The decay of uranium into different lead isotopes creates unique isotopic ratios for different lead deposits.
The development of modern analytical instrumentation has focused on the accurate determination of lower and lower concentrations. Techniques have addressed the measurement of major, minor, trace, and ultratrace levels of elements. At each analysis level, these techniques have been concerned primarily with bulk concentrations of the analytes.
My prior U.S. Pat. No. 5,414,259 discloses a method of measuring the elemental species present in a particular sample, not only its bulk elemental concentration. The disclosure of this patent is expressly incorporated herein by reference.
It may be desired to measure a species for a variety of reasons, including characterization and evaluation of systems in environmental science, medicine, biological process monitoring, nutrition, and industry, for example. As the chemistry in these processes is inherently species-specific, the presence of trace elements is measured at the speciated level. For example, Cr(III) is a trace element essential for human health, while Cr(VI) is a poison and carcinogen to both humans and other animals. Each of these forms is a species of chromium, and each has associated with it unique chemical reactions. The difference lies in the elements' oxidized states. Examples of other species of potential interest are combinations of inorganic ions and covalently bound to organic molecules such as mercury and methylmercury. Others are different chelated species with different ligands and still others are different organic molecules entirely. There are many species described in the chemical literature and a general reference method for distinguishing many of them is highly desirable in order to determine if alterations in their concentrations and relevant abundances have changed during chemical processing and measurement.
Methods of elemental speciation have been known. See Allen, H. E.; Huang, C. P.; Bailey, G. W.; Bowers, A. R.
Metal Speciation and Contamination of Soil
; Lewis Publisher: Boca Raton, Fla., 1995; Batley, G. E.
Trace Element Speciation: Analytical Methods and Problems
; CRC Press: Boca Raton, Fla., 1989; Das, A. K.; Chakraborty, R.; Cervera, M. L.; de la Guardia, M.
Mikrochim. Acta
1996, 122, 209-246; Kramer, J. R.; Allen, H. E.
Metal Speciation: Theory, Analysis and Application
; Lewis Publishers: Chelsea, Michigan, 1991; Krull, I. S.
Trace Metal Analysis and Speciation
; Elsevier: Oxford, 1991; Van Loon, J. C.; Barefoot, R. R.
Analyst (London)
1992, 117, 563-570; Vela, N. P.; Olson, L. K.; Caruso, J. A.
Anal. Chem
. 1993, 65, 585a-597a. Several specific problems that cause errors in speciation analysis are identified in this literature. Currently, only bulk measurements of total element concentrations can be made routinely and accurately. Several potential problems may exist with speciation methods. Many species are reactive, and are transformed or converted to other species during the sampling, storage, and measurement steps. Also, species continue to react during these processes and may be altered many times prior to the numerical measurement. Further, these classical methods do not correct for the species' possible reaction with separating agents. As a result, although analysis through these methods may be both precise and replicable, the results of such analysis are not fully reliable. For example, the state of California has enacted legislation relating to the analysis of Cr(VI) in water, soils and contaminated wastes, even though there are no fully accurate methods to make these measurements. For regulatory purposes, environmental solutions thus far frequently have been to analyze samples for total chromium and assume all chromium may be in the +6 oxidation state. This may be safe, but it is an unsophisticated solution and wastes a significant amount of money on unnecessary remediation. Other methods with unknown accuracy have also been applied, such as a pair of US EPA RCRA (United States Environmental Protection Agency's Resource Conservation and Recovery Act) Methods 3060, which is an alkaline extraction for isolating Cr(VI) from soils and solid materials, and 7196, which is an ultraviolet-visible colorimetric method for the quantification of Cr(VI). These methods have biases and are inaccurate in various kinds of sample matrices with no way to evaluate their own accuracy and require another method to validate them. Until now there has been no validation method or way to evaluate bias in these methods. While some methods may be accurate for some matrices and invalid for others there has b
Duquesne University of the Holy Ghost
Silverman Arnold B.
Soderquist Arlen
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