Sonochemical degradation of perchloroethylene: the influence of ultrasonic variables, and the identification of products.

Sonochemistry is a technique that offers promise for pollutant degradation, but earlier studies on various chlorinated substrates do not give a definitive view of the effectiveness of this methodology. We now report a thorough study of ultrasonic operational variables upon perchloroethylene (PCE) degradation in water (variables include ultrasonic frequency, power and system geometry as well as substrate concentration) and we attempt to close the mass balance where feasible. We obtained fractional conversions of >97% showing very effective loss of pollutant starting material, and give mechanistic proposals for the reaction pathway based on cavitational phenomena inducing pyrolytic and free radical processes. We note major products of Cl(-) and CO(2)/CO, and also trichloroethylene (TCE) and dichloroethylene (DCE) at ppm concentrations as reported earlier. The formation at very low (ppb) concentration of small halocompounds (CHCl(3), CCl(4)) and also of higher-mass species, such as pentachloropropene, hexachloroethane, is noteworthy. But of particular importance in our work is the discovery of significant quantities of chloroacetate derivatives at ppm concentrations. Although these compounds have been described as by-products with other techniques such as radiolysis or photochemistry, this is the first time that these products have been identified in the sonochemical treatment of PCE; this allows a much more effective account of the mass balance and may explain earlier inconsistencies. This reaction system is now better identified, but a corollary is that, because these haloacetates are themselves species of some toxicity, the use of ultrasound here may not sufficiently diminish wastewater toxicity.

Sonochemical substrate selectivity and reaction pathway of systematically substituted azo compounds.

The sonochemical degradation of the systematically substituted azo compound 2,7-dihydroxy-1-phenylazonaphthaline-3,6-disulfonic acid was investigated using a frequency of 850 kHz and an acoustic input power of 61 W. All derivatives were degraded completely within 6h by the ultrasonic treatment. Trifluoromethyl substituted azo compounds exhibited 2-3-fold higher degradation rates in comparison to the reference hydrogen substituted azo compound (k=0.54 h(-1)). In contrast to enzymatic processes (azoreductase or laccase), the ultrasonic treatment for these ortho-, meta-, and para-substituted azo compound showed 1.5-50-fold higher degradation rates. Additionally the ultrasound treatment was characterized by shorter reaction times. As a result of the detection and identification of specific intermediates using LC-MS a reaction pathway of the sonochemical degradation of the analysed azo compound is proposed indicating the formation of cyclohexadienone and naphthalene quinone derivatives.

High-performance liquid chromatographic determination of penicillins by means of automated solid-phase extraction and photochemical degradation with electrochemical detection.

An automated precolumn exchange system for on-line solid-phase extraction (OPS-2) coupled to liquid chromatography with photochemical degradation and electrochemical detection was used for the determination of residual amounts of penicillin G, penicillin V, oxacillin, cloxacillin and dicloxacillin. A 5-10-fold increase in sensitivity was obtained when compared with direct UV detection of penicillins at 225 nm. The system is recommended for samples that have received an immunoaffinity clean-up. Analysis of bovine muscle tissue indicated, however, that this procedure could also be suitable for the determination of penicillin G at its maximum residue limit of 50 micrograms/kg even with conventional solvent partitioning for the first clean-up steps.

Stimulation of catecholaminergic neurons in the ventral medulla by various stressors monitored with in vivo electrochemistry.

Catecholaminergic metabolism in the A1 cell group of the ventrolateral medulla oblongata was followed after application of 3 interoceptive stressful stimuli by monitoring the extracellular concentration of 3,4-dihydroxyphenylacetic acid (DOPAC) with an in vivo voltammetric approach. These stimuli provoked an increase of the DOPAC signal with different time course and amplitude. Histamine led to a maximal 200% increase that vanished within two hours. Insulin induced a long-lasting increase of up to 350% that could be reversed by glucose infusion. Electrical stimulation of the sciatic nerve triggered an immediate increase of up to 140% which stopped with the ending of the stimulation. The time-course of this activation is compatible with a possible involvement of catecholaminergic afferents from the A1 group projecting to the paraventricular nucleus in the stimulation of the hypothalamic neurosecretory cells elicited by the stressors.

Assessment of cold induced alterations in catecholamine turnover of lean and glutamate-treated obese rats.

Excretion of norepinephrine (NE) and vanillylmandelic acid (VMA) in urine as well as NE-turnover in tissues from lean and glutamate-treated obese rats were determined in warm and cold environment. NE-and VMA-excretion in urine was elevated by cold exposure, indicating an activation of the sympathetic nervous system in animals of both groups. Organspecific NE-turnover responds with higher sensitivity to cold in obese rats but without complete compensation in brown adipose tissue. Urinary NE- and VMA- excretion as well as NE-turnover in organs confirmed that cold exposure activates the sympathetic nervous system. Measurement of NE-turnover in tissues gives organspecific information regarding alterations in sympathetic activity during cold exposure, whereas excretion of NE and VMA in urine is a summarizing measure for the whole body turnover only.

Changes of ATPase activities in erythrocytes of rats with hypothalamic obesity.

Na,K- and Ca,Mg-ATPase activities in the membrane of red blood cells (RBC) were determined in glutamate treated obese rats (GOR). Both activities are related oppositely. In the obese rats the Na,K-ATPase is higher but the efficiency in maintenance of Na/K-ion concentration gradients is diminished. Ca,Mg-ATPase is decreased in GOR. Under the hypermetabolic condition of cold adaption the Na,K-ATPase activity decreases and the Ca,Mg-ATPase activity rises in both animal groups. The Na,K-ATPase activity in RBC-membranes is positively related to fat accumulation and age.

[Development of a rational monitoring strategy for workers exposed to tetrachloroethylene]. / Gestaltung einer rationellen Uberwachungsstrategie exponierter Werktätiger gegenüber Tetrachlorethen.

A 5 year follow-up of 130 workers exposed to tetrachlorethylene (dry cleaning) was performed, including measuring of exposure conditions (personal dosimetry, exposure tests) and clinical investigations. No signs of hepatoxicity of tetrachlorethylene could be detected, but slight derangements of nerval functions may develop in long-term exposed workers. Nerve motor and sensory conduction velocity shows a tendency to diminution. Recommendations are derived for biological monitoring and health surveillance of workers exposed to tetrachlorethylene.

[Animal experiment studies of the effect of the hazardous substance carbon tetrachloride on peripheral nerves]. / Tierexperimentelle Untersuchungen zur Schadstoffwirkung von Tetrachlorethen auf den peripheren Nerven.

The deleterious effects of Carbon Tetrachloride, widely used industrially, on the peripheral nervous system was investigated by experimentation on rabbits. Long-term infusion simulated various conditions of exposure to obtain pharmacological and electroneurographic data. Tetrachlorethen is shown to induce reversible dysfunctions of the peripheral nervous system depending on the degree of concentration. The mode of molecular action remains open. Our results are compared with references in existing literature.

Measurements of membrane potential of human sperm using electrode sensitive to tetraphenyl phosphonium cations.

For the first time, an attempt was made to measure the transmembrane potential of human spermatozoa by an electrode sensitive to the lipophilic cation tetraphenyl phosphonium (TPP+). However, the assumption of a single correlation between the decrease of the TPP+ concentration in the medium and metabolism-dependent membrane potential cannot be confirmed. The participation of different processes is very likely. Artificially damaged spermatozoa showed an enhanced affinity to TPP+ (the stronger the damage, the stronger the affinity of the spermatozoa to TPP+), but there were no significant differences of the cellular affinity to TPP+ between fresh and cryopreserved spermatozoa.

Measurement of tissue catecholamines of obese rats by liquid chromatography and electrochemical detection.

The content and turnover of norepinephrine was measured in the interscapular brown adipose tissue (BAT), white adipose tissue (WAT) and heart of lean and monosodium glutamate treated obese rats (GOR). An HPLC-ECD method was used for efficient separation and sensitive detection of catecholamines with an appropriate sample preparation, especially for lipid rich tissues. The lower basal norepinephrine level and the slower norepinephrine turnover in organs of the glutamate obese rats indicate a diminished activity of the sympathetic nervous system which may be a reason for a reduced thermogenic response and in this way contributes to the development of obesity.