John W. Hylin

Problems in water analysis for pesticide residues

Abstract Organic solvents, glassware, plastic ware, cellulose extraction thimbles, filter paper, and silica gels may contribute contaminants to water samples which may interfere with the subsequent gas chromatographic analysis of the samples for pesticides in the parts per billion range. Prior to their use, heat treatment of the glassware and the silica gels is recommended to eliminate contaminants contributed by these materials. Plastic ware and filter paper should not be included in the analytical procedure.

Ergoline Alkaloids in Tropical Wood Roses

Extracts of Argyreia nervosa, a tropical wood rose, contain appreciable quantities of ergoline alkaloids tentatively identified as ergine isoergine, and penniclavine together with related substances.

Analysis for kawa pyrones in extracts of Piper methysticum

Abstract The amounts of kawa pyrones (e.g. I and II) in ether extracts of Piper methysticum were determined using two-dimensional thin-layer chromatography on aluminium oxide. The concentrations of desmethoxyyangonin, yangonin, dihydromethysticin, methysticin, dihydrokawain, and kawain were determined by u.v. spectroscopy after elution of the spots with methanol. Recoveries of known compounds were 80–85 per cent for yangonin and 90–95 per cent for all others.

Total and organic mercury in the pacific blue marlin

Muscle, liver, nerve tissue, and gonads of Pacific Blue Marlin were analyzed for total and organic mercury. The ratios of total to organic mercury in the tissues indicate a partial physiological control over the form in which the mercury exists in the marlin. Total to organic ratios in the muscle, gonad, and central nervous tissue are similar. The liver, however, with a ratio of 35:1 reflects an unusually high proportion of inorganic to organic mercury. A possible explanation involves demethylation in the liver. (JTE)

Biosynthesis of mimosine

Abstract Administration of [2-14C]- dl -lysine to Leucaena glauca results in incorporation of radioactivity into mimosine, pipecolic acid and 5-hydroxypipecolic acid. Degradation of the mimosine reveals that 95% of the radioactivity is present in the pyridone ring.

Thin Layer Chromatography of Dithiocarbamate Fungicides

During the course of studies on the transformation of dithiocarbamate fungicides on leaf surfaces, it became necessary to develop a procedure which would distinguish the residue of the applied substance from its transformation products. Thin layer chromatography proved to be the most effective method for this separation and the following procedure was developed. Absorbent. Silica-gel G was applied to glass plates in layers 250 microns thick using conventional techniques. Sample Preparation. Intact leaves were extracted with chloroform for 30 minutes on a mechanical shaker. The chloroform extract was filtered and concentrated to a small volume on a rotating evaporator. An aliquot of the concentrated extract was applied to the thin layer plate. Highly pigmented extracts were decolorized with a minimum amount of Darco G-60 activated charcoal. Development. Benzene was the solvent used for ascending development of plates containing dimethyldithiocarbamates while benzene-methanol-acetic acid (48:8:4) was used for samples which contained ethylene-bis-dithiocarbamates.

Separation of polychlorobiphenyls from chlorinated pesticides in sediment and oyster samples for analysis by gas chromatography

Polychlorobiphenyls (PCBs) have been separated from DDT and its analogs and from the other common chlorinated pesticides by adsorption chromatography on columns of alumina and charcoal. Elution from alumina columns with increasing fractional amounts of hexane first isolates dieldrin and heptachlor epoxide from a mixture of chlorinated pesticides and PCBs. The remaining fraction, when added to a charcoal column, can be separated into two fractions, one containing the chlorinated pesticides, the other containing the PCBs, by eluting with acetone-diethyl ether (25:75) and benzene, respectively. The PCBs and the pesticides are then determined by gas chromatography on the separate column eluates without cross interference. The method is applicable to sample extracts prepared for gas chromatography. Recoveries of the PCBs (Aroclors) and the chlorinated pesticides are good and the method is applicable to sediment and marine biota samples.

Potential problems with the use of distilled water in pesticide residue analyses

Abstract Precautions should be taken with distilled water that may be included in any scheme of analysis for pesticides, especially in the nanogram-picogram analytical range, to insure that the water has not been contaminated with organic components derived from the water distillation system. Ultimate analysis of the sample by gas chromatography, utilizing an electron capture detector, will record any contaminants present and they may confuse the interpretation of the pesticide analytical data. Preferably, an all-glass still unit which contains no plastic fittings of any type should be used. Some of the potential problems with distilled water that may occur if plastic or resin components are included in the distillation system are discussed in this report.

Pesticide residue analysis of water and sediments: Potential problems and some philosophy

The analysis of water and sediments for residues of pesticides has occupied many research workers throughout the world. This present paper will not attempt to review this voluminous amount of work, but will instead discuss the underlying theoretical and philosophical concepts on how-to and how-not-to analyze water and sediments for pesticide residues. The first point that must be clarified is what is meant by “water.” There are many liquids that are referred to as water: drinking water, rainwater, fresh water, salt water, sea water, and even some beer and rice wine. All of the above are impure forms of water. As I will use the term in this paper, “water” is pure H2O, a substance that is difficult to prepare in the pure state. We think of distilled water as “pure” water but studies have shown that such need not be the case Bevenue et al. 1971 b). When we discuss the analysis of pesticide residues in water it is important to remember to define the quality of water under study since this markedly affects the approach to problem solution.

Potential interferences in certain pesticide residue analyses from organochlorine compounds occurring naturally in plants

Analytical determination of residual amounts of pesticides applied for the protection of livestock or crops is beset with a multitude of problems resulting from interfering substances. Cleanup procedures attempt to separate and concentrate the sought-for-chemical in usually submicrogram amounts from the thousands of other organic compounds present in the sample extractives. Segregation of the pesticide residue is rarely complete and the final analytical sample still usually contains a mixture of components. When a nonspecific analytical procedure is used, naturally occurring substances can grossly interfere in the determination of the applied chemical. This was clearly shown by Gunther et al. ( 1966) in the determination of organochlorine pesticide residues in plants by total combustion followed by direct potentiomet-ric titration of the released chloride ion. The interfering substances were identified as chloride salts of lecithins, a class of phospholipids universally distributed in all living organisms. These lecithin chlorides accompanied the pesticide residues through all the normal organic-solvent extraction and cleanup procedures and were determined as pesticide in the quantitation step. If the same determinations were made by gas chromatography (Gunther and Barkley 1966), the lecithin chlorides did not interfere since they were nonvolatile.