Determination of arsenic in germanium by the combination of isotope dilution and activation analysis

The determination of arsenic by activation analysis in germanium may be disturbed by arsenic isotopes formed in the irradiation of the germanium matrix itself. The isotopic dilution technique will eliminate such interferences, but it requires weighing of very small masses of arsenic, after appropriate chemical separation. This weighing procedure can be avoided if the mass of the recovered arsenic is determined by activation analysis. In order to apply such a procedure, a known amount of arsenic labelled with⁷⁶As, whose specific activity is also known, is added to the germanium sample to be analysed. The sample is processed, the arsenic separated, and the chemical yield established. The recovered mass of arsenic is then determined by activation analysis applying the classical isotopic dilution analysis formula. The accuracy precision and linearity of the method are discussed.     

Speciation and instrumental neutron activation analysis for arsenic in water samples

Ground water samples obtained from West Bengal, India were analyzed for total arsenic and its inorganic species contents by instrumental neutron activation analysis (INAA). Two anion exchange separation methods using Dowex 1X8 in chloride and acetate forms were standardized for the speciation of As(III) and As(V) using radiotracers. The method by Dowex 1X8 in the acetate form was validated using synthetic mixtures of As(III) and As(V), and applied to water samples; the species concentrations were determined by INAA. The accuracy of the INAA method was evaluated by analyzing the NRCC CRM DORM-2 for total arsenic.     

Determination of arsenic in some Lake Michigan fish using neutron activation analysis

The level of arsenic in six different species of fish collected from Lake Michigan near Saugatuck, Michigan has been measured using radiochemical neutron activation analysis. The arsenic concentration was found to vary from 0.05 μg/g (wet weight) for yellow perch fillet to 1.4 μg/g (wet weight) for eviscerated bloater chubs. A significant correlation was observed between arsenic concentrations and number of years in the lake for lake trout; correlations were also observed between arsenic concentrations and length of lake trout and smelt. No such correlations were found for alewife or yellow perch.     

Measurement of arsenic in sectioned hair samples by instrumental neutron activation analysis

In a recent Texas murder case, bundles of head hair from the female victim (aligned with all root ends together) were washed, cut into 7 mm sections, air-dried and weighed, activated in a nuclear reactor neutron flux, and then counted with a Ge(Li) detector/4096-channel gamma-ray spectrometer. In each of the 15 samples, the 559 keV gamma-ray peak of 26.3 hour⁷⁶As was measured. In the section closest to the scalp, an arsenic concentration of 107 ppm was found (cf. a normal level of about 1 ppm As). Barium ingestion was also possible so Ba was looked for, but not found. The victim's husband was found guilty of murder by chronic arsenic poisoning.     

The determination of inorganic arsenic in water by thermal neutron activation analysis

A simple method is presented for the determination of inorganic arsenic in water samples. The lower limit of determination is 0.01 μg·1⁻¹. Penta-and trivalent arsenic ions as well as arsenic acid substituted with aromatic ligands are collected by coprecipitation with Fe(OH)₃. After irradiation the arsenic is separated from the iron by adsorption to Al₂O₃. The overall efficiency is (97∓1)%. The procedure takes one day per ∼20 samples. It has been checked by standard addition. Data for sea- and surface-water are given. As the concentration of aromatic arsenic-compounds is very small in comparison to that of the inorganic species, it does not affect the result of the determination.     

Determination of arsenic in some Myanmar indigenous medicines by neutron activation analysis

Am(Be) neutron source was used for activation of samples and⁷⁶As radioactivity measured by both ^– and -counting techniques. The samples analyzed were raw materials traditionally used in formulating Myanmar indigenous medicines. The results were compared with those obtained by volumetric analysis and those reported in the literature.     

Redox substoichiometric determination of arsenic in biological materials by neutron activation analysis

A redox substoichiometry is proposed for an accurate and precise determination of arsenic. This method is based on the substoichiometric oxidation of trivalent arsenic to pentavalent with potassium bromate or ceric sulfate followed by the separation of these species by thionalide extraction of trivalent arsenic. It was applied to neutron activation analysis of arsenic in the NBS SRM Orchard Leaves and the Shark Powder. The results were obtained with an excellent accuracy and precision.     

Determination of mercury and arsenic in fresh water by neutron activation analysis

Neutron activation analysis has been applied for the determination of Hg and As in freshwater samples. Preconcentration of Hg and As from the samples before irradiation by using active carbon for scavenging the chelate complex of Hg with dithizone at pH 1 and Fe(OH)₃ for co-precipitating arsenic was used. After irridiation, mercury was determined by direct counting of the irradiated active carbon. Arsenic was separated from Fe(OH)₃ by precipitating arsenic in the metal form after removing¹²²Sb by extraction in 2N HCl with Ni-diethyldithiophosphoric acid in carbon tetrachloride. The method is simple and reliable.     

Radiochemical neutron activation determination of phosphorus in high pure germanium

A radiochemical procedure for determination of ultra low concentrations of phosphorus in germanium has been developed. The method involves application of multicells autoclaves for matrix distillation and extraction chromatography with dioctyltin diacetate for final phosphorus purification. The detection limit is 40 ppt for a 1-g sample.     

Determination of arsenic and bromine in hot spring waters by neutron activation analysis

Concentrations of arsenic and bromine dissolved in hot spring waters have been determined by neutron activation analysis using 0.5 cm³ of sample waters without any chemical pretreatment. The samples prepared for neutron irradiation were simply pieces of filter papers which were infiltrated with samples. With the results of satisfactorily high accuracy and precision, this analytical method was found to be very convenient for the determinations of arsenic and bromine dissolved in water at ppm to sub-ppm levels.This revised version was published online in November 2005 with corrections to the Cover Date.     

Simultaneous determination of antimony,arsenic and copper by neutron activation analysis

A rapid procedure has been developed for the mutual separation of antimony and arsenic using tribenzylamine as the extracting agent. The extraction behaviours of Sb(III), Sb(V), As(III), As(V) and Au(III) have been studied as a function of the acidity of the aqueous phase. Various factors which affect the extraction of these complexes have been studied and optimized. The procedure was then applied to lead base alloy for the simultaneous determination of antimony, arsenic and copper. Chemical recoveries were quantitative and only about one hour is required for the chemical processing of duplicate samples.     

The use of instrumental neutron activation analysis for the determination of arsenic concentrations in poultry

There has been recent public concern over the use of organic arsenicals as medicaments and growth stimulators for poultry. In early studies, there was a correlation shown between the intake of arsenic and carcinogensis. Several investigators have strongly disputed these results. The purpose of this study was not to verify or discredit this carcinogenic theory but simply to determine if the arsenic levels in poultry could be measured using instrumental activation analysis. These analyses indicate that arsenic concentrations in poultry can be measured at levels below the mandatory maximum levels of arsenic in poultry.     

Study of arsenic reabsorption in the body by the neutron activation analysis after thermal springs treatments

At French spa, La Bourboule, arsenical mineral waters are applicated by several ways. The process and degree of absorption of water are not well known; so, we tried to study absorption, measuring arsenic concentration in the blood and in some organs. On rabbits, thirty minutes after the animal had drunk mineral water, the increase of arsenic concentration in its blood is about twenty times and it is only about three to nine time in lungs, bronchia and traches. On human subjects, it was observed an increase of five times in the blood, two hours after treatment.     

Study of arsenic and molybdenum retention in organism during hydrotherapy by neutron activation analysis

At La Bourboule (France), arsenic and molybdenum are contained in high concentrations in the watering place. So, we have applied thermal neutron activation analysis to determine arsenic and molybdenum amplitudes after the treatments in some organs for the first time. Their variations are determined in blood versus time. Contamination by experimental materials are reduced or evaluated to take them into account in the results. It appears that rabbits are better standards than rats to make preliminary studies with animals. These experiments have been completed with studies on man. After drinking, there is a specific accumulation of arsenic in breaths while, after aerotherapeutics, it happens in trachea. Our measures indicate minima in blood concentrations of arsenic and molybdenum at the tenth day of thermal spring treatment; there are maxima in urines at the same time. The overall radiochemical neutron activation analysis and gamma ray high resolution spectrometry appears as a unique and powerful procedure to resolve the difficult biomedical problems.     

Determination of arsenic and gallium in standard materials by instrumental epithermal neutron activation analysis

Epithennal neutron activation analysis has been applied to the determination of arsenic and gallium in standard materials at trace concentrations. The reduction of ²⁴Na activity compared to thermal neutron activation is advantageous. Arsenic detection limits (1σ) are 0.04 and 0.015 μg for inorganic and organic materials, respectively. The corresponding gallium detection limits, for the best cases, are 0.13 and 0.29 μg. Gallium determinations with the 834-keV photopeak of ⁷²Ga suffered interferences attributed to the threshold reaction ⁵⁴Fe(n,p) ⁵⁴Mn; the less intense ⁷²Ga peaks at 629 and 2200 keV provided quantitative results for all samples tested. Gallium detection limits with the less intense, but more reliable 629-keV peak were 0.9 and 0.1 μg for inorganic and organic materials, respectively. Arsenic determinations are best performed with the more intense ⁷⁶As 559-keV line, as the 657-keV line has an unknown interference.     

Simultaneous determination of arsenic and antimony in environmental samples by radiochemical neutron activation analysis

A radiochemical separation procedure using an inorganic exchanger, tin dioxide (TDO), for the separation of arsenic from antimony is reported here. This separation avoids the interference of 564 keV gamma-ray of¹²²Sb in the measurement of the 559 keV gamma-ray of⁷⁶As in neutron activation analysis. Environmental samples, after neutron irradiation and digestion, are taken up in 1M HCl–0.1M HF and passed through a TDO column which selectively retains arsenic. The effluent from the TDO column, after proper conditioning, is passed through an anion exchange column for quantitative retention of antimony. The procedure has been utilized for arsenic and antimony determination in NBS Orchard Leaves and NBS Albacore Tuna.     

Determination of arsenic,cadmium and zinc in river water by neutron activation analysis

A concentration apparatus has been developed for the determination of As, Cd and Zn in water by neutron activation. The preconcentration technique used for this purpose is based on the retention of As, Cd and Zn on the Rexyn 201 resin at pH 10. The apparatus used minimizes the manipulations needed for preconcentration and contamination by trace elements present in reagents. Eleven samples of water from rivers in the Montreal region were analyzed and the following concentrations were found (in μg/1): As 0.86–1.95, Cd 0.61–0.98 and Zn 4.6–12.9.     

Development of a non-invasive method for the determination of the macroscopic neutron cross sections of a sample matrix in large-sample prompt-gamma neutron activation analysis

In order to correct for neutron self-shielding in large-sample prompt gamma NAA, a method has been developed to determine the macroscopic scattering and absorption cross sections, i.e., Σ _a and Σ _s, using four Cu flux monitors placed around the sample. With Monte Carlo computations, the neutron densities throughout the sample and the resulting and the corresponding self-shielding factor as calculated from the Σ _a and Σ _s as obtained through the Cu monitors were compared to the true values. The derived Σ _a and Σ _s were found to be sufficiently accurate as long as Σ _t = Σ _a + Σ _s was less than 0.6 cm⁻¹ and Σ _s/Σ _t was greater than 0.1.     

Instrumental neutron activation analysis of high-purity gallium,arsenic, and gallium arsenide

Instrumental neutron activation analysis (INAA) has been applied to obtain useful data on impurity concentrations in ultra-pure materials whose matrix elements are strongly activated and create severe interference for several weeks after irradiation. An analytical procedure has been developed and used to determine Sc, Fe, Co, Zn, Se, Zr, Ag, In, Sn, Sb, Te, and Hg in high-purity gallium, arsenic, and gallium arsenide. Detection limits ranged from 50 ng/g for iron to 0.001 ng/g for scandium. Problems of contamination control, blank level, and standardization are discussed.