A modified nitroso-r method for the determination of cobalt in sea water

The existing colorimetric nitroso-R method for the determination of biologically important cobalt in sea water described by Thompson and Laevastu has been studied in detail, modified and improved. A procedure is recommended in which an approximately five-fold increase in sensitivity is achieved in the measurement of the nitroso-R chelate through close control of : pH, development time of complex, conditions for decomposition of excess reagent, and employment of a wavelength of 425 mμ. The size of the water sample required for an analysis is reduced from 10 to 21. For optimum results it was found necessary for a minimum period of 7 days to elapse following precipitation with sodium carbonate prior to filtration and analysis. A previously unreported salt effect in the procedure is described which requires either construction of a calibration curve from sea water spiked with cobalt or a correction in use of standards in distilled water.A precision was obtained with a 1–2% relative standard deviation throughout range of concentrations used, with an accuracy of 3.0% at 0.5 p.p.b.     

The gravimetric determination of nickel with dimethylglyoxime in the presence of copper

Summary A detailed investigation has been made of the gravimetric determination of nickel with dimethylglyoxime in the presence of copper. Copper interference is eliminated by precipitation in a solution containing tartrate and thiosulphate at a p_H of 5.5–6.5. The solubility of the nickel dimethylglyoxime complex has been determined as a function of temperature, p_H and alcohol concentration.     

The determination of nickel with dimethylglyoxime in the presence of iron and cobalt

A method for the determination of nickel in the presence of both ferric iron and cobalt is presented. The nickel is precipitated directly with dimethylglyoxime, without the prior reduction of the iron. The interference of the iron and cobalt is eliminated by the addition of N,N-dihydroxyethylglycine, which chelates the iron and prevents the formation of the iron-cobalt-dimethylglyoxime contaminant.     

A rapid solvent extraction method for the determination of radio-iodine in sea water.

A solvent extraction procedure for the determination of radio-iodine in sea water is described. The water is treated with alkaline permanganate to remove algae, and, after removal of permanganate, the iodide is oxidized to iodine for extraction into toluene. The radio-iodine with carrier is stripped from the solvent then re-extracted into a smaller volume of toluene for liquid scintillation counting and colorimetric determination of carrier recovery as iodine. 2-Methyl-1-butene is used to decolorize the toluene-iodine solution under u.v. light and avoid colour quenching during counting. Samples spiked with iodine-131 showed essentially quantitative recovery from 1.0 l of sea water with a typical recovery of 80–85% of carrier. The method is applicable in the presence of high concentrations of many foreign ions and the decontamination factor for a number of radionuclides is greater than 10³. The limit of detection is less than 5.0 · 10^-9 μCi ml^-1.     

A spectrophotometric method for the determination of nickel

A photometric method for the determination of nickel using versene is described. Up to 20 mg of nickel can be determined with a maximum deviation of ± 0.10 mg. The effect of interfering elements, concentrations, accuracy and limitations of the method are discussed.     

Heterometric microtitration of nickel with dimethylglyoxime

A new “heterometric” method is presented for the microdetermination of nickel with dimethylglyoxime. ? 0.5 μg of nickel in 20 ml of solution may be determined. The error lies between zero and 0.4 mg per ml. Solutions of dimethylglyoxime which contains ? 1 mg dimethylglyoxime in 20 ml of solution may be determined with a nickel solution. The error lies between zero and 0.5 μg per ml. The time required for a titration at room temperature is 5–10 minuten.     

A semi-automatic alkaline peroxodisulphate method for the routine determination of total dissolved nitrogen in sea water

Nydahl's method for the determination of dissolved organic nitrogen (DON) in distilled water has been modified for the determination of total dissolved nitrogen (TDN) in sea water. Samples (9 cm³) are digested batch-wise with alkaline potassium peroxodisulphate solution. An improved buffering system permits the automatic measurement of the nitrate formed, and allows the analysis of 50–80 samples per day. DON may be determined as the difference between TDN and the sum of inorganic nitrogen species. The standard deviation of TDN determinations is 0.7 μg N dm^-3 at about 15 μg TDN dm^-3. The method is applied to a range of samples including tanker ballast water, oil platform production water, and zooplankton.     

A new chemiluminescence method for the determination of nickel ion

A new chemiluminescence (CL) phenomenon described as the second-chemiluminescence (SCL) was observed and a strong CL signal was detected, when Ni(II) ion was injected into the mixture after the end of the reaction of potassium permanganate with alkaline luminol. The possible CL mechanism is proposed based on the kinetic curve of the CL reaction, CL spectra, UV-vis spectra and some other experiments. A flow-injection analysis for the determination of nickle(II) ion has been developed, based on the catalysis of nickel(II) ion on the CL reaction between potassium manganate produced on-line and luminol under alkaline condition. Under the optimum conditions, the SCL intensity is linear with the concentration of nickel(II) ion in the range of 8.0-200.0 microg l-1 and 0.2-2.0 mg l-1. The R.S.D. was 4.5% for 11 determinations of 250 microg l-1 nickel(II) ion and the detection limit (3sigma) for nickel(II) ion was 0.33 microg l-1. The method was applied to determine nickel(II) ion in synthetic samples with satisfactory results.     

Gas chromatographic method for the determination of selenite and total selenium in sea water

A method is described for the determination of dissolved selenite and total selenium in natural waters. The detection limit is approximately 10 pmol l^-1 and the reproducibility ±2.4% (1σ) at 394 pmol l^-1. A 100-ml sample containing selenite is reacted with 4-nitro-o-phenylenediamine to form 5-nitropiazselenol which is extracted into toluene and then determined by gas chromatography with an electron-capture detector. Other forms of selenium can be determined after photo-oxidizing samples under controlled pH conditions. This leads to a reproducible proportionation of species between selenite and selenate. The method has been used successfully to analyze samples both at sea and in the laboratory.     

Rapid determination method of radiocesium in sea water by cesium-selective resin

A rapid and precise method of determining radiocesium corresponding to 5 mrem/y, the Japan AEC's guideline, was proposed. The development and practical performance of cesium-selective resin and the determination method was described in this paper. The resin was prepared by the formation of ammonium molybdophosphate in the structure of Amberlite XAD-7 resin. It took only 3 hours to carry out all the procedures the authors proposed. This value represents 1/10∼1/2 of the time of conventional method. The concentration of¹³⁷Cs and¹³⁴Cs in sea water was determined to be 0.13∼0.16 pCi/1 and less than 7.1·10⁻² pCi/1, respectively.     

A neutron activation procedure for the determination of dissolved silver in sea water

A neutron activation procedure has been developed for the determination of silver in sea water. The element is preconcentrated by an anion-exchange procedure. The concentrate is submitted to irradiation with thermal neutrons. Silver-11Om is separated from other radionuclides by means of a conventional radiochemical separation scheme. The method gave a coefficient of variation of ± 10% at a silver level of 40 ng l^?1.