Trace metal residues in finfish from Maryland waters, 1978-1979.

Levels of seven heavy metal residues, arsenic, cadmium, chromium, copper, lead, mercury and zinc were monitored in samples of various species of finfish harvested from the Maryland section of the Chesapeake Bay and its tributaries over a two year period (1978-79). Results of the analysis of the edible portions of these finfish are presented along with the species of finfish, date and location of harvest. A number of samples of finfish gonad and liver tissue were analyzed to study the relative level of preconcentration of heavy metals in these tissues compared to the edible (flesh) portion. Results of this study are consistent with other available data for Atlantic Coast finfish. Gonad tissue, when compared to flesh, show enrichment of copper and zinc and decreased mercury and cadmium levels. Liver tissue shows enrichment in copper, zinc and cadmium and generally lower levels of mercury compared to flesh.

Organochlorine residues in finfish from Maryland waters 1976-1980.

Organochlorine pesticide and herbicide levels were monitored in samples of a variety of edible finfish harvested from the Maryland section of the Chesapeake Bay and its tributaries over a five-year period (1976-80). Qualitative and quantitative information was obtained for the various polychlorinated biphenyls (PCB's), heptachlor, alpha-BHC, chlordane, DDD, DDE, DDT, dieldrin, endrin, heptachlorepoxide, lindane, mirex, methoxychlor, aldrin, toxaphene, hexachlorobenzene, kepone and dacthal. In addition to analyses of the flesh of the animals, organochlorine residue levels were determined in roe or gonad tissue of several samples. Striped bass, white perch and yellow perch samples showed significantly higher concentrations of certain of these substances in roe or gonad tissue, especially PCB's, chlordane, DDD and dieldrin. Significantly higher levels of six organochlorine residues were found in the gonad tissue of striped bass; however, similar studies on gonad tissue of American Shad, harvested from the same region, show no such enhancement. Rather, the reverse is true; levels of certain organochlorine residues are higher in flesh tissue. All mean values, and virtually all individual values of organochlorine concentrations in the edible portion of the fish were within the U.S. Food and Drug Administration guideline, where such guidelines have been established.

Trace metal residues in shellfish from Maryland waters, 1976-1980.

Levels of seven heavy metal residues, arsenic, cadmium, chromium, copper, lead, mercury and zinc were monitored in samples of the American oyster (Crassostrea virginica), the soft shell clam (Mya arenaria), the hard shell clam (Mercinaria mercinaria) and the blue crab (Callinectes sapidus). Samples were taken from the Maryland section of the Chesapeake Bay and its tributaries over a five year period (1976-80). This study was undertaken to provide an estimate of a baseline for values of trace heavy metals. Also, the oyster, being a non-mobile filter feeder, provides information regarding the level of metal residues in its environment (water and sediment), because heavy metal uptake is related to the surrounding metal concentrations. Additionally, this type of monitoring program is essential to ensure that shellfish sold for human consumption are within safe limits established for toxic substances by the United States Food and Drug Administration. Results of the study are consistent with data from previous years and no statistically significant year-to-year trends were observed over the period of the investigation.

Organochlorine residues in shellfish from Maryland waters, 1976-1980.

Shellfish samples, including the American oyster (Craessostrea virginica), the soft shell clam (Mya arenaria), the hard shell clam (Mercenaria mercenaria) and the blue crab (callinectes sapidus), were taken from the Maryland section of the Chesapeake Bay and its tributaries over a five year period (1976-80) and analyzed to determine residue levels of various organochlorine pesticides. Qualitative and quantitative information was obtained for a variety of polychlorinated hydrocarbons. The purpose of this study includes the establishment of baseline values for levels of shellfish contamination, utilization of the data as an indicator of probable levels of water and sediment contamination in the vicinity of the sampling site and ensurance that shellfish harvested for human consumption are within U.S. Food and Drug Administration guidelines for organochlorine contamination. All mean values and virtually all individual values were within FDA guidelines.

Analytical methods for the determination of tungsten.

Methods developed and employed in the recent literature (1969-1975) for the detection and determination of tungsten in a wide variety of matrices are reviewed. This paper is a supplement to the books, monographs and review papers which deal with the earlier literature.

Preconcentration and determination of cadmium in water by reversed-phase column chromatography and atomic absorption.

Studies were made of the solvent extraction of cadmium(II) from hydrochloric acid into a tri-n-octylamine-cyclohexene mixture. Distribution ratios, as a function of amine and acid concentration, were determined and this information was used to establish optimum extraction conditions and the probable nature of the extracted species. This system was used as the basis for the development of a reversed-phase column chromatographic technique for preconcentrating Cd(II). The amine-cyclohexene phase was coated on an inert macroreticular resin (XAD-2) to provide a stable column. With this system, Cd(II) in acidified water samples as large as 31. may be concentrated to 10 ml and determined by conventional atomic absorption. Interferences were studied, and the method was applied to the analysis of fresh-water streams for Cd(II).

Chromatographic separation of vanadium, tungsten and molybdenum with a liquid anion-exchanger.

In acidic solution only molybdenum(VI), tungsten(VI), vanadium(V), niobium(V) and tantalum(V) form stable, anionic complexes with dilute hydrogen peroxide. This fact has been used in developing an analytical method of separating molybdenum(VI), tungsten(VI) and vanadium(V) from other metal ions and from each other. Preliminary investigations using reversed-phase paper chromatography and solvent extraction led to a reversed-phase column Chromatographic separation technique. These metal-peroxy anions are retained by a column containing a liquid anion-exchanger (General Mills Aliquat 336) in a solid support. Then molybdenum(VI), tungsten(VI) and vanadium(V) are selectively eluted with aqueous solutions containing dilute hydrogen peroxide and varying concentrations of sulphuric acid.