Neutron activation analysis has become one of the most sensitive and selective analytical technique for the determination of trace elements in a wide variety of matrices. Neutron activation involves the irradiation of the test sample and a standard of the element to be determined with thermal neutrons in a reactor, followed by dissolution of the test sample in the presence of carrier of the element to be determined. The carrier and radioisotopes are separated from the bulk of other induced activities (employing precipitation, solvent extraction, ion exchange etc.) and then the activity induced in the sample is measured on a suitable detector. The standard is treated identically. From the ratios of the activity of the sample and standard and the weight of the standard irradiated, the concentration of element in the test sample is calculated. A rapid, selective and sensitive method of radiochemical separation is subtoichiometric extraction in which the same amount of carrier is added to the irradiated test sample and standard. Exactly the same amount of reagent is added to both the sample and standard but in substoichiometric amounts, followed by the separation of the species formed by extracting it with an organic solvent. The activities of the extracts are measured. The amount of element present in the sample is calculated with help of the ratio of the activities and the weight of the standard taken. The advantages of the method are discussed. Application of substoichiometry in neutron activation has been elucidated with reference to the determination of Au in various samples by substoichiometric neutron activation analysis.
A method based on solvent extraction has been developed for the radiochemical separation of Zn/II/ from other elements employing 1,2,3-benzotriazole as a complexing agent and n-heptanol as an extractant. Optimum conditions for the extraction have been established. The effect of various anions and cations on the extraction coefficient value of Zn/II/ has been studied. The stoichiometry of the metal to reagent determined by the method of substoichiometric extraction and slope-ratio method was found to be 12.
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.
A rapid, selective and simple method have been developed for the determination of palladium in alloys and ores by thermal neutron activation analysis, incorporating substoichiometric solvent extraction of Pd/II/ with 1,2,3-benzotriazole /1,2,3-BT/ into methyl iso-butyl ketone /MIBK/. Two samples and a standard can be processed and counted within two hours.
A procedure is described for the determination of thallium in complex biological matrices by thermal neutron activation analysis employing substoichiometric extraction of thallium(I) with 2-mercaptobenzothiazole (2-HMBT) at a pH of 7.5 into chloroform, and low-level beta-counting.
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.
A novel method has been developed for the extraction of Pd/II/ with 1,2,3-benzotriazole /1,2,3-BT/ into methyl isobutyl ketone /MIBK/ at a pH of 4.0. The effects of pH, time of equilibration, solvent, anions and cations on the extraction coefficient have been evaluated. The stoichiometry of the extracted species of 12 was obtained by the slope ratio method and by the method of substoichiometric extraction. Separation factors and decontamination factors for a number of elements in the extraction of Pd/II/ were also obtained.
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.
A new and rapid method has been developed for the quantitative extraction of Ru/III/ with 1,2,3-benzotriazole /1,2,3-BT/ into 1-pentanol. The extraction coefficient value of Ru/III/ between 1-pentanol and an aqueous 5% solution of 1,2,3-BT in 2M sodium acetate-acetic acid buffer showed a maximum value of E=46 at pH 4.5. The effect of various other parameters on the extraction coefficient of Ru/III/ such as solvents, anions, cations, etc. have also been studied. The stoichiometry of metal:reagent determined by the method of substoichiometric extraction and slope ratio method was found to be 13. Decontamination factors for many elements in the substoichiometric extraction of Ru/III/ were also evaluated.
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.