A rapid method has been developed for the determination of mercury in environmental samples by thermal neutron activation analysis. Radiochemical separation involves the extraction of Hg/II/ with substoichiometric amounts of 2-mercaptobenzothiazole /2-HMBT/ into chloroform1. The time required for radiochemical purification and counting of two samples and a standard is about 2 h. Water, sludge and IAEA standard samples were analyzed for Hg concentration by this method.
The extraction of mercury/II/ with 2-mercaptobenzothiazole /2-HMBT/ into chloroform has been studied. The effect of various parameters on the extraction coefficient value such as effect of pH, time of equilibration, effect of anions and cations have been evaluated. The stoichiometry of the extracted species obtained by the method of substoichiometric extraction and slope ratio method was found to be 12. Decontamination factors for a number of elements in the substoichiometric extraction of Hg/II/ were also obtained.
A rapid method has been developed for the determination of cadmium in environmental samples by thermal neutron activation analysis involving substoichiometric extraction with 1,2,3-benzotriazole /1,2,3-BT/. Cd was radiochemically separated as CdS using 1-amidino-2-thiourea. The time required for radiochemical purification containing two samples and a standard was about 2 h. 4.63 g of Cd can be determined with an accuracy of 6.69% and precision of 6.25%. Mash potatoes, animal bones, raw sludge and cattle manure have been analyzed by this method.
Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and oxo donors with widely varying basicity, viz. diphenyl sulfoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octylphosphine-oxide (TOPO) has been studied at various fixed temperatures. Results indicate that the equilibrium constants in the organic phase for addition reactions (KS) with these donors follow their order of basicity (KH) viz. DPSO (0.033)<TBP (0.16)TOPO (8.9) with log KS values of 3.70, 4.28 and 6.45, respectively. The thermodynamic parameters associated with the formation of these systems have been evaluted by the temperature coefficient method. The results indicate that the complex in the organic phase for DPSO and TBP is stabilized only by enthalpy, whereas both enthalpy and entropy contribute to the stabilization of the TOPO complex. Also, enthalpy contribution is more prominent as compared with the UO
/HTTA/TOPO system, where both enthalpy and entropy contribute almost equally.
The extraction of cadmium/II/ with 1,2,3 benzotriazole /2-BT/ into n-heptanol has been studied. The effect of various parameters such as effect of pH, time of equilibration, effect of anions on the extraction coefficient values have been evaluated. The stoichiometry of the extracted species by the method of substoichiometric extraction and slope ratio method was found to be 12. Decontamination factors for a number of elements in the substoichiometric extraction of Cd/II/ were also obtained.
Synergistic extraction of uranyl ion with 1-phenyl-3-methyl-4-benzoyl pyrazolone-5 (HPMBP) and aliphatic sulfoxides of varying basicities, viz di-isoamyl (DIASO), di-n-hexyl (DHSO), di-n-septyl (DSSO), di-n-octyl (DOSO), di-n-nonyl (DNSO), di-n-decyl (DDSO) or di-n-undecyl (DuDSO) sulfoxide has been studied at 30±0.1°C. Extraction with some of these sulfoxides has been studied at various fixed temperatures also. The organic phase equilibrium constant (log Ks) has been found to increase with the basicity of the sulfoxide up to DOSO beyond which there is a gradual decreasing trend which has been attributed to the effect of possible steric hindrance (spatial) involved in the bonding of the higher sulfoxides (greater than 8 carbon atoms) with UO2 (PMBP)2 chelate. This has been supported by thermodynamic data involved in these systems. The entropy values for sulfoxides with eight or more carbon atoms are much more negative as compared to the lower sulfoxides and are also in contrast to HTTA and BTFA systems with these sulfoxides studied earlier.
Aqueous 1,2,3-benzotriazole has been used for the extraction of In/III/ in alkaline medium. The extraction of In/III/ was found to be better than 99% over the pH range 5.0–10.0 and an equilibration time of 2.0 min. The effect of anions and cations on the extraction coefficient has been studied. The stoichiometry of metal: reagent determined by the slope-ratio method was found to be 13. Separation factors for around 20 elements were better than 103.
Synergistic extraction of uranyl ion with acylpyrazolones such as 1-phenyl-3-methyl-4-trifluoroacetylpyrazolone-5 (HPMTFP, pKa=2.7), 1-phenyl-3-methyl-4-acetylpyrazolone (HPMAP, pKa=3.8) or 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (HPMBP, pKa=4.2) in combination with dicyclohexano-18-crown-6 (DC-18-C6) has been studied at various fixed temperatures. The results indicate that the equilibrium constants of the organic phase addition reaction, log Ks, at 30°C are almost constant, viz., 2.72, 2.69 and 2.84, respectively, for the above three systems. The similarity and low log Ks values with DC-18-C6 as compared with TBP systems with these pyrazolones appears to arise due to the limitation to the approach of the large crown ether molecule in bonding with the uranyl chelate. This is in contrast to the fact that the relative basicities of the two donors (equilibrium constant for nitric acid uptake) are comparable. Thermodynamic data for chelate extraction with HPMTFP evaluated by the temperature coefficient method indicates that a hydrated chelate is extracted into the organic phase. Also, the organic phase addition reaction with DC-18-C6 is stabilized by exothermic enthalpy change, the entropy change counteracting in all the three cases.
Exposure to enriched environment (EE) is known to promote sensory, cognitive, and motor stimulation with intensified levels of novelty and complexity. In this study, we investigated the positive regulatory effect of short-term exposure to EE on establishing functional recovery in monosodium glutamate (MSG)-induced obese rats. Unless treated, MSG rats exhibited peripheral insulin resistance, cognitive deficits, and a reduction in the total hippocampal volume with decreased neuron count in the DG, CA3, and CA1 subfields. These MSG rats were exposed to short-term EE for 15 days for a period of 6 h/day, beginning either at 45 or at 75 days of age. EE exposure has improved insulin sensitivity, yielded a significant increase in total hippocampal volume along with increase in neuron number in the CA1 subfield of the hippocampus in both age groups. However, as assessed by radial arm maze task, which relies upon the positive reinforcement to test spatial memory, and the Barnes maze task, which utilizes an aversive learning strategy, a complete recovery of cognitive function could be achieved in 2-month-old rats only and not among 3-month-old rats, thus highlighting the importance of critical window period for EE interventions in restoring the memory functions. These results suggest the therapeutic potential of EE paradigm in prevention of cognitive disorders.
Authors:R. Veeraraghavan, S. Pai, and M. Subramanian
Synergistic extraction of uranyl ion with 2-thenoyltrifluoroacetone (HTTA) and aliphatic amides with varying basicities, viz. dibutyl hexanamide (DBHA), dibutyloctanamide (DBOA) or dibutyldecanamide (DBDA) has been studied at various fixed temperatures of 20, 30, 40 and 50±0.1°C. Results indicate that the equilibrium constants of the organic phase addition reaction (Ks) with these amides follow their order of basicity (Kh) viz. DBHA (0.09)<0.10) H DBOA (0.13) with log Ks values of 4.91, 4.99 and 5.02, respectively. These values are much higher than those with TBP (3.8) or sulfoxides (4) as donors. This may be attributed to the existence of a resonance form of the amide, which has higher electron density on the carbonyl oxygen. The thermodynamic parameters associated with these systems evaluated by the temperature coefficient method indicate that the organic phase addition reaction with all the three amides is stabilized by both enthalpy and entropy changes as against UO
/HTTA/TBP system, where only the enthalpy change contributes to the stabilization.