Warren B. Crummett

Thermolytic surface-reaction of benzene and iron (III) chloride to form chlorinated dibenzo-p-dioxins and dibenzofurans

The investigation of a potential “denovo” synthesis for chlorinated dibenzo-p-dioxins and dibenzofurans (CDDs/CDFs) from simple compounds that can be formed during the combustion of natural fuels is presented. The interaction of benzene in the gas phase with FeCl3 on a supporting-surface is demonstrated to produce trace quantities of CDDs/CDFs over a wide range of precursor composition and thermolytic conditions. Molar yields of 0.00004% for CDDs and 0.013% for CDFs are typical for this reaction under laboratory conditions. Additional species produced in significantly greater yield include: chlorobenzenes, chlorobiphenyls and chlorodiphenyl ethers Benzene is demonstrated to be a definitive precursor for CDD/CDF products via use of [13C6]-benzene.

Industrial analytical applications of rapid ion-exchange separations of weak organic acids

Abstract Rapid ion-exchange chromatography has been adapted to the separation of industrial mixtures of weak organic acids. Minor impurities can be determined with a sensitivity of 0.1%. A methanol solution of the sample is injected directly into a 2.8 × 500 mm acetate form ion-exchange column. Using a specially designed gradient elution apparatus separation is achieved with an acetic acid-methanol gradient. The eluate proceeds through a flow cell mounted in an ultraviolet spectrophotometer. Response of the spectrophotometer is monitored on a strip-chart recorder. Concentrations are calculated by comparing peak areas with those of standards. Separations are generally produced in thirty to sixty minutes. Products analyzed by this technique include: 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,2′,6,6′-tetrabromobisphenol A, 2,6-dimethyl-4-pyridinol, 3,4′,5-tribromosalicylanilide, and 3,5,6-trichloro-2-pyridinol.

Determination of 18 to 22 mole ethoxymers in nine mole ethylene oxide adduct of p-nonylphenol.

Abstract The 18 to 22 mole ethoxymers of p -nonylphenol were separated from a nine mole adduct by preparative thin-layer chromatography on alumina. Concentration determination was made by ultraviolet spectrophotometry and found to be in the 1.0 to 1.5% range. This is moderately higher than that calculated by Poisson distribution.

Fundamental problems related to validation of analytical data elaborated on the example of TCDD

Abstract Problems of sample selection, contamination, and degradation, background noise, interferences, signal detection and measurement, identification, confirmation, and corroboration are highlighted in a review of efforts to determine 2, 3, 7, S‐tetrachloro‐dibenzo‐p‐dioxin (2, 3, 7, 8‐TCDD) at the limit of detection in a variety of matrices. Recently developed methods using lengthy and painstaking procedures can separate, isolate, detect, and measure this material without interference from its isomers at parts per trillion levels. This particular achievement is helpful in putting earlier work in perspective and illustrates the general nature of difficulties encountered when using modern analytical methods and generating data close to the measurable limits of the method. A need for simple criteria for assuring the soundness of data obtained near the limit of detection is made clear. These criteria are currently being developed by an ACS subcommittee on Environmental Analytical Chemistry.

THE PROBLEM OF MEASUREMENTS NEAR THE LIMIT OF DETECTION

Problems arise because the results obtained in these analyses are very uncertain because of difficulties in validating methods near the limit of detection, which is often at 1 part per billion or lower. The limit of detection itself is defined and determined by a wide variety of approaches,’ which are generally subjective and often designed to serve the investigators purpose. The interpretation of the data is further hindered because the amount of uncertainty is very seldom known. Abuse of analytic systems and data in these situations is widespread among those who are relatively inexperienced in the application of analytic chemistry. However, even highly trained experienced professional chemists can be misled by results, either positive or negative, generated near the “limit of detection.” The examples that follow were generated by “state-of-the-art” technology. The measurement of trace impurities in products is the most important of the various industrial analyses because it provides data from which processes can be changed or modified to minimize the presence of an impurity and thus eliminate it in

Analytical Methodology for the Determination of PCDDs and PCDFs in Products and Environmental Samples: An Overview and Critique

Progress in the development of analytical methodology for the determination of chlorinated dibenzodioxins (CDDs) and dibenzofurans (CDFs) in products and environmental samples has been extensive and dramatic during the last decade. Thus, the limit of detection for the tetrachlorodibenzo-p-dioxins (TCDD) in products has been lowered from one part per million in 1969 to 1 part per billion in 1980. Similarly the limit of detection for 2,3,7,8-TCDD in environmental samples has developed to a part per trillion in 1978 from 50 parts per billion in 1970. Furthermore, the ability to separate a specific isomer in a particular isomer group from all of its isomers and other congeners has advanced from the ability to separate 2,3,7,8-TCDD from only two of its isomers in 1974 to an ability to separate all of the 22 TCDD isomers in 1978. Likewise all 10 isomers of HP6CDD have been separated as have the two isomers of H7CDD.

Review and trends in the analysis for PCDD/PCDF

The analytical process for the detection and measurement of chlorinated dioxins in environmental samples has advanced in a dramatic way with respect to sensitivity, selectivity, and scope (Crummett et al., 1985). It should now be possible to generate data having a specified degree of certainty down to sub parts per trillion levels.

ADVANCED/GOOD ANALYTICAL TECHNIQUES ELABORATED ON THE DETECTION OF POLYCHLORINATED DIBENZODIOXINS IN ENVIRONMENTAL SAMPLES

The determination of individual isomers of the chlorinated dibenzo-p-dioxins in environmental samples is so time-consuming that judgments must be made based on the analysis of a limited number of samples. The certainty of the data taken must be controlled and measured on each sample analyzed. The analysis thus sets new standards for quality assurance and becomes a model for trace analysis in general. Special newly developed techniques which make quality assurance on individual samples possible include: the use of isotopes as internal standards, special performance chromatographic separation systems designed and monitored to remove interferences and separate isomers, criteria placed on recovery data, and rigorous criteria for detection and determination of the compound of interest. Details of these are presented together with some typical data which demonstrate the power of the approach. Not only is the philosophical model useful for the determination of specific compounds by means of difficult residue analysis but it is necessary for maximum certainty in any research on the behavior of trace materials in the environment.