Ravi K. Puri

Supercritical fluid extraction and cleanup procedures for determination of xenobiotics in biological samples.

Abstract Application of supercritical carbon dioxide for rapid extraction of various xenobiotics from biological tissue and fluid samples was investigated. The results obtained indicate that good recoveries (≥ 80%) can be readily obtained for all but polar solutes (k OW ≤ 2.5)

Studies on the transport and transformation of PCBs in plants

Abstract The uptake of polychlorinated biphenyls (PCBs) from soil by terrestrial plants was investigated. The results revealed a lack of active transport of these compounds through the plant xylem system. No measurable evidence of metabolism of PCBs in plants was observed.

Persistence of Chlorinated Dioxins and Furans in the Soil Environment

Abstract The persistence of di- to octachloro dioxins and furans has been investigated in various soil environments. Over a 15-month period, measurable degradation — i.e., that leading to loss greater than the precision level of the analytical methodology — was found to occur only in the case of di- and trichloro congeners. The degradation of tetra through octachloro congeners was minimal. In the absence of a carrier co-pollutant, the mobility rates of chlorinated dioxins and furans are not significantly affected by the presence of co-pollutants such as pentachlorophenol and creosote components which are commonly present at wood treatment sites.

On Translocation of 2,3,7,8-tetrachlorodibenzo-p-dioxin: Time Dependent Analysis at the Times Beach Experimental Site

Abstract The rate of migration and loss of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in contaminated soil has been studied under natural conditions in experimental plots at the Dioxin Research Facility, Times Beach, Missouri. The TCDD concentration profiles of sample cores taken at Times Beach in 1988 are virtually the same as those in cores taken in 1984. The data confirm our earlier work with soil columns exposed to simulated environmental conditions in the laboratory, and lead us to conclude that little movement and essentially no loss of TCDD has occurred in the experimental plots in the four years since the Dioxin Research Facility was established.

A multiple sample extraction and on-line system for the analysis of chlorinated compounds

Abstract A multiple sample extraction and on-line analysis for rapid determination of polychlorinated organics in complex matrices has been developed. The system is based on the direct coupling of supercritical fluid extraction with tandem supercritical fluid chromatography and gas chromatography. The on-line system permits the simultaneous extraction and analysis with high reproducibility and accuracy, while the overall methodology is considerably faster and less laborious than the conventional liquid extraction-based analytical procedures.

Studies on uptake of PCBs by Hordeum vulgare (barley) and Lycopersicon esculentum (tomato)

Abstract The uptake of polychlorinated biphenyls (PCBs) from soil by barley and tomato plants was investigated. The results indicate a lack of active transport of these compounds. However, plants readily trap airborne PCBs escaping from soil, and a good correlation between vapor pressure of PCBs and their concentration in plant tissue was observed.

Promises and pitfalls of supercritical fluid extraction in polychlorinated compound analyses

Abstract The application of supercritical fluid extraction (SFE) for the determination of organochlorine compounds in a variety of environmental matrices was explored. The results obtained show that SFE holds a clear advantage in the case of complex matrices such as biological tissues. The limiting factors for the applicability of this technique are the initial instrumentation costs and impurities in commercially available supercritical fluids such as CO 2 and N 2 O.

Effect of Co-contaminants on the Disposition of Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans in Saturated Soils

Abstract The effect of such co-contaminants as chlorinated phenols, naphthalenes and petroleum oil on the partition behaviors of polychlorinated dibenzo-p-dioxins (PCDDs) was investigated. The results obtained indicate that the transport of PCDDs in a saturated environment can be directly attributed to colloidal suspensions of the co-contaminants.

Field and laboratory studies on sources and persistence of chlordane contamination in the Missouri aquatic environment.

Abstract Field and laboratory studies were conducted to investigate the persistence of chlordane in the aquatic and terrestrial environment. The laboratory data show that the transformation and loss of the chlordane constituents is dependent on soil characteristics. The overall rate of loss is also dependent on the depth of application, being significantly lower at greater depths. The field data show a strong correlation between urban development and residue concentration levels.

Evaluation of carbon for removal and destruction of polychlorinated biphenyls (PCBs) from transformer mineral oils

Abstract Adsorptive removal of PCBs by carbon followed by destruction through an oxidative carbon regeneration process were evaluated. The combined processes performed well for PCBs with lower chlorine content. Adsorption efficiencies of ≥95% were achieved for lower chlorinated PCB formulations such as Aroclor 1240; adsorption efficiencies for higher chlorinated PCBs were considerably lower. The regeneration process was highly effective and ≥99.7% of the adsorbed PCBs were mineralized or converted to unrecoverable forms.