Determination of phosphorus in steels by radiochemical neutron activation analysis

The viability of radiochemical neutron activation analysis as a method for certification of phosphorus in steels was tested by analysis of SRM low alloy steels. Preliminary results are generally in agreement with certified values. The limit of detection, as defined by Currie¹, was determined to be 5 μg/kg.     

The analysis of phosphorus and chlorine in natural waters by alpha-particle activation

Using activation by 16 MeV α-particles quantitative analysis has been carried out for P and Cl in natural waters with a reproducibility of ±5%. Limits of detection of 0.1 and 0.4 ppm were obtained for the two elements, respectively. The method is applied to the determination of P and Cl in water samples taken in the environment of Amsterdam.     

Determination of chromium in low-alloy steels by atomic-absorption spectrophotometry

Iron causes severe depression of the signal in determination of chromium by atomic-absorption spectrophotometry in an air-acetylene flame. This effect can be eliminated by addition of hydroxylamine hydrochloride and use of a fuel-rich flame. Addition of iron to the standard solutions is not necessary for up to 300 ppm of iron in the test solution.     

Determination of rare-earth elements in steels by radiochemical neutron activation analysis

For the separation of rare-earth elements from steel, with a cation exchange resin, separation experiments were performed on NIST reference materials of SRM-363 and SRM-364. Iron, Na, Cr, Mn, Co, Cu, As, Mo, Sb and W were separated in 2M hydrochloric acid, five rare-earth elements, La, Ce, Pr, Nd and Sm and three other elements, Hf, Zr and Ba were separated using 8M nitric acid. Each element was determined by a single comparator method using two monitors, gold and cobalt.     

Determination of phosphorus in semiconductor grade silicon by neutron activation analysis

A method of determination of phosphorus in silicon has been elaborated. The separation of phosphorus is based on the extraction of phosphomolybdic complex in the presence of hold-back carriers of Ta and Au. Contamination factors for various impurities were determined. The lower limit of determination equals 3·10^?11 g P. Types of errors in the determination of concentration profiles are discussed.     

The determination of calcium in yttrium oxide by alpha-particle activation analysis

The determination of calcium in yttrium oxide through the⁴⁰Ca(α, p)⁴³Sc reaction was studied, using a post-irradiation radiochemical separation procedure. The half-life of⁴³Sc was determined to be 3.87 hr. The chemical recovery was about 70%. The detection limit was about 10 ppb, for a 30 min irradiation at an alpha-particle beam current of 1 μA (E_α=13.4 MeV) and γ−γ coincidence counting (background counts being<1, cpm), with counting starting at 4 hours after the end of irradiation. Four samples of a batch of yttrium oxide (A.R.) were analyzed, and found to contain 13.9±1.0 ppm of calcium.     

Determination of traces of phosphorus in gallium arsenide by radiochemical neutron activation analysis

A radiochemical separation procedure has been developed to determine traces of phosphorus in gallium arsenide. In this procedure the indicator nuclide³²P is separated from all other long-lived activation products in high purity. The resulting eluate is sufficiently pure to allow -counting. Because of the high -energy of³²P (1710 keV) the activity can be measured via the Cerenkov effect, whereas most radionuclides, because they have essentially lower -energies, are discriminated by this technique, so that the selectivity of the measurement of³²P is improved considerably. A detection limit of 1 ng/g was achieved when using samples of 50 mg, a thermal neutron flux of _th=1·10¹³n·cm^–2·s^–1, an irradiation time of 36 hours and a measuring time of 1 hour.     

Determination of sulfur in steels by radiochemical neutron activation analysis with liquid scintillation counting

A method has been developed for the determination of low-level sulfur in steels by radiochemical neutron activation analysis. During sample irradiation, ³⁵S is produced by the ³⁴S(n,γ)³⁵S reaction. Irradiated steels are mixed with sulfur carrier and dissolved in HCl/HNO₃. Sulfur is reduced to H₂S by reaction with HI/H₃PO₂/HCl. The evolved H₂S is absorbed in dilute NaOH, which is mixed with scintillation cocktail for the measurement of ³⁵S by liquid scintillation counting. Sulfur carrier yield is determined by iodometric titration. Chlorine is also determined by RNAA in order to correct for ³⁵S produced via the ³⁵Cl(n,p)³⁵S reaction. Sulfur has been determined at mass fractions as low as ≈5 mg/kg in ultra-high-purity iron using this method.     

Determination of silicon,phosphorus and sulfur in alloy steel by neutron activation analysis

Silicon, phosphorus, and sulfur in alloy steel were determined by neutron activation analysis involving rapid radiochemical separation procedures. The standard deviations for silicon, phosphorus, and sulfur were 1.6%, 2.3%, and 2.4% respectively; the sensitivity limits were 3.2, 0.20, and 2.50 p.p.m., respectively. The three constituents could be determined in alloy steel within 2 h of the irradiation.     

Determination of calcium,phosphorus and fluorine in bone by instrumental fast neutron activation analysis

The determination of fluorine, calcium and phosphorus in bone by instrumental fast neutron activation analysis is described. Results for the IAEA standard material “Animal Bone” A3-74 re: Ca=313±10 mg/g, P=155±5 mg/g and F-613±20μg/g. The accuracy for all three elements is≤4%, precision being about 3%. The limit of determination for F is 120 μg, for Ca 30 mg and for P 1 mg in a sample of 500 mg.     

Non-destructive analysis of phosphorus by neutron activation analysis in biochemical products

A method of neutron activation analysis is described for the quantitative determination of phosporus in nucleic acids, nucleotides and glucose-6-phosphate in amounts of 0.1 to 200 μg, without any chemical separation. This technique may be usefully applied to the measurement of the phosporus content in organic materials and biochemical preparations. The procedure involves a short neutron activation in a nuclear reactor and measurement of the Cerenkov radiation emitted by the irradiated capsule after a suitable decay period. Possible interferences due to other induced radionuclides are discussed.     

Determination of sodium and phosphorus in organophosphorus compounds by fast-neutron activation

A method is described for the determination of sodium and phosphorus using the NG-160 neutron generator and an automated pneumatic transport device. The reactions²³Na (n, p)²³Ne and³¹P(n, α)²⁸ Al are utilized for the determination of sodium and phosphorus, respectively. For the determination of sodium, hermetically sealed vials are indispensable. The time required for one determination is 6 to 8 min. A rapid method for the determination of macro-amounts of sodium against a phosphorus background is also described, leading to the general conclusion that isotopes with γ-quantum energies close to 0.51 MeV can be determined against a background of positron radiation sources in a well-type crystal.     

The determination of chromium in low-alloy irons and steels by atomic absorption spectrophotometry

An atomic absorption spectrophotometric procedure for the determination of 0.001–0.50% chromium in low-alloy iron and steel is described. The sample is dissolved in phosphoric-sulphuric acid before atomisation. The method is rapid, preliminary separations are not required and the accuracy obtained with standard samples is well within the permissible range for routine determinations.     

Determination of phosphorus using derivative neutron activation

For the determination of phosphorus in different matrices, the derivative neutron activation analysis is especially applicable to aqueous samples, since the conventional neutron activation analysis is not useful for the determination of phosphorus. Phosphorus when reacted with ammonium molybdate 4 hydrate and ammonium metavanadate forms molybdo vanado phosphoric acid. This complex is preconcentrated by extracting into methyl isobutyl ketone. The organic phase containing the molybdo vanado phosphoric acid is neutron activated and the phosphorus is determined through the activation product of ⁵²V. Preparation of this complex, its stoichiometry, application to trace level determination of phosphorus and improved detection limit are discussed. This method was applied for the analysis of industrial effluent samples.     

Determination of phosphorus in biological samples by thermal neutron activation followed by β--counting

Phosphorus has been determined using the ^- emitter³²P by instrumental neutron activation analysis (INAA) in several NBS and IAEA standards and samples of biological origin such as human and animal blood, cancerous tissue, edible plant leaves, diets, milk samples, etc. The method involves thermal neutron irradiation for 2–10 h in a reactor followed by ^--counting on an end-window gas flow proportional counter using an aluminium filter. The results are within ±10% of the certified values in most cases.     

Heteropoly acids in the determination of phosphorus by neutron activation analysis

Phosphorus is selectively extracted as molybdovanadophosphoric acid (MVPA) and determined indirectly using⁵²V. Silicon, germanium, arsenic, fluoride and tannic acid do not interfere. The sensitivity for phosphorus was 1421±13 counts⁵²V per ng P ml^–1 with a detection limit of 0.2 ng P ml^–1. The precision is ±10% over the range 0.7±70 ng P ml^–1. The sensitivity is four orders of magnitude greater than for conventional neutron activation analysis (NAA) using the³¹P(n, )²⁸ Al reaction and a SLOWPOKE II reactor. Greater selectivity for phosphorus is obtained than by direct measurement of³²P by beta ray spectroscopy.     

A study of the extraction of phosphovanadomolybdic acid and application to the neutron activation analysis of phosphorus in steels

Ancient silver-copper-tin alloyed Gaulish coins have been analyzed using 14 MeV neutron activation analysis. The method used takes into account all the differences in composition, geometry, position of irradiation and counting that may exist between the sample and the reference. The results of the analysis are accurate and permit interesting numismatic conclusions.     

Determination of phosphorus by instrumental neutron activation and bremsstrahlung measurement in bone samples

The application of charge plate technique in studying the recoil reactions of¹²⁸I species originating from iodoform following neutron capture in pyridine medium is discussed emphasis being placed on the problem of reactions of energetic iodine species with the radiolytically generated quasi-free electrons. Ag/AgI electrodes, under a potential gradient of 83 V·cm^–1 are employed in collecting the nucleogenic iodine species from the irradiated iodoform-pyridine mixtures. It is observed that only¹²⁸I^– species are deposited on the anode plate showing a fairly high order of radioactivity. Collected activities are increased with increasing concentration of iodoform in the system, however, no¹²⁸I^– species are deposited on cathode surface and the activities are found nil upto the concentration range studied. It could be deduced that the recoil reactions taking place in pure iodoform are specifically influenced by the chemical reactivity of pyridine thereby govems the electrode deposition pattem in iodoform-pyridine molecular liquid mixtures.Part III:M. R. Zaman, S. P. Mishra, J. Chem. Soc. Pakistan, 16 (1994) 163.Work done in the Department of Chemistry, Banaras Hindu University, India, while holding a Fellowship of the Department of Human Resource Development, Govemment of India.