The determination of nanomolar levels of nitrite in fresh and sea water by cathodic stripping voltammetry

Adsorptive cathodic stripping voltammetry (CSV) is used for the determination of nitrite in natural waters, including sea water. The nitrite is first derivatised by diazotization with sulphanilamide, followed by coupling to 1-naphthylamine to produce an azo dye. This azo dye adsorbs on the mercury drop electrode and its reduction is fully reversible. The concentration of the dye is linearly related to the height of the reduction peak for nitrite concentrations between 0.3 and 200 nM. The optimal concentrations of sulphanilamide and naphthylamine are 2 mM and 0.1 mM, respectively, at a pH of 2.5. After diazotization and coupling, the differential-pulse CSV of the azo dye is done at pH 8.4 with an adsorption potential of ?0.3 V. The standard deviation of a determination of 4 nM nitrite is ±2% and the limit of detection is 0.3 nM for an adsorption time of 60 s. The linear range can be extended by using shorter adsorption times. These sensitivity in sea water is the same as that in fresh water. The concentration of the dye can also be measured by using anodic stripping voltammetry preceded by adsorptive collection at ?0.7 V, but this procedure is less sensitive than CSV.     

Extraction-photometric determination of thorium with chlorophosphonazo-III

A simple and rapid spectrophotometric determination of thorium is described. The thorium-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 2.0–3.0 M hydrochloric acid solution. Maximum absorbance occurs at 620 and 670 nm and Beer's law is obeyed at the latter wavelength over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.2·10⁴ l mole^-1 cm^-1 at 670 nm. Thorium can be determined in the presence of fluoride, oxalate, sulfate and EDTA. Many common cations do not interfere, but uranium, zirconium and niobium interfere seriously.     

Test strip for determination of nitrite in water

A disposable test strip is proposed for the determination of nitrite in waters. The strip is an inert rectangular strip of polyester with a 6 mm o.d. circular, transparent and colorless film attached to its surface. This film contains the chemicals required for reaction and fixation of the dye formed, sulfanilamide, N-(1-naphthyl)ethylenediamine on Nafion. When the test strip is placed in an acidified (pH 2.0) sample solution containing nitrite a red-violet color develops; the absorbance of this is measured at 536 nm. The linear range of the method depends on the time of equilibration of the test strip with the sample solution. When the equilibration time was 45 min, the linear range was 8.9-500 microg L(-1) whereas for an equilibration time of 60 min it was 4.7-200 microg L(-1). The detection limit was 1.4 microg L(-1) for an equilibration time of 60 min. The precision of the method, expressed as RSD, was 8.8 % at 100.0 microg L(-1). The method was applied, and validated chemometrically, for the determination of nitrite in different types of water (spring, mineral, tap, well, and sea).     

催化光度法测定水中痕量亚硝酸根

利用在硫酸介质中亚硝酸根催化溴酸钾氧化吖啶橙的褪色反应 ,建立了测定痕量亚硝酸根的新方法。方法检出限为 7.6× 1 0 -8mol/ L,线性范围 0～1 .1 2× 1 0 -6mol/ L。本法可用于测定雨水和自来水中的痕量亚硝酸根     

Extraction-photometric selective determination of trace perchlorates in potable waters

A method is proposed for the selective photometry determination of perchlorates in potable water with a detection limit of 2×10^?3 mg/L is proposed based on the extraction of its ion pair with the astrafloxin cation and absorbance measurements at 540 nm. The following ratios of matrix ions are acceptable (in parentheses): ClO^?, ClO ₂ ^? , ClO ₃ ^? , BrO ₃ ^? (500); I^? (1000); IO ₃ ^? (7000); HCO ₃ ^? , Cl^?,SO ₄ ^2? , NO ₃ ^? , Br^?, Na⁺, K⁺, Ca²⁺, Mg²⁺ (10000). The relative error of determination for ClO ₄ ^? is 20% in the range 4 × 10^-3-1 × 10^?2 mg/L and 10% in the range 1 × 10^-2–5 × 10^?2 mg/L.     

The determination of nitrate in sea water

A heterogeneous reduction method is described for the determination of nitrate in sea water. Nitrate is reduced to nitrite with 91% efficiency by passing the water through a column of amalgamated cadmium filings. The nitrite produced is determined spectrophotometrically by the method of BENDSCHNEIDER and ROBINSON. The method has a coefficient of variation of ca. 2% and is free from salt error. Temperature in the range o°–35° has no effect on the reduction. Interference from nitrite is discussed and a method is described for its destruction if necessary. Sulphide does not interfere.     

Spectrophotometric determination of nitrate and nitrite in natural water and sea-water

Nitrate and nitrite in natural waters are determined spectrophotometrically by passage through an amalgamated zinc reductor at pH 3.4 into iron(III)-Ferrozine solution. Interference by high levels of nitrite is eliminated by treatment with azide. Levels as low as 0.2 mug ml (expressed as nitrogen) can be determined with a precision of +/- 3%.     

Spectrophotometric determination of micro amounts of nitrite in water and soil

A spectrophotometric method for determination of micro amounts of nitrite in water and soil with p-aminoacetophenone and resorcinol is described. The interference of foreign ions can be eliminated by masking with complexing agents. Beer's law is obeyed up to 20 mug of NO(2)(-) in 60 ml of solution and the molar absorptivity at 435 nm is 5.27 x 10(4) l.mole(-1).cm(-1). The colour is stable for 10 hr. Results obtained by using the proposed method for water and soil samples agree well with those obtained by the Saltzman standard method.     

Extraction-photometric determination of trifluoromethanesulfonic acid with Methyl Violet

Optimal conditions were found for the formation of ion associates of trifluoromethanesulfonic acid with Methyl Violet. A procedure was developed for the extraction-photometric determination of trifluoromethanesulfonic acid in the air of the working area and atmospheric air.     

Extraction-photometric determination of indium in zinc-base alloys with bromopyrogallol red

The extraction-photometric determination of indium at the 5 p.p.m. level in highpurity zinc and zinc-base alloys is described. After a preliminary separation of indium by isopropyl ether extraction from hydrobromic acid medium, indium is determined by extraction into benzyl alcohol of its complex with bromopyrogallol red at pH 9.0. It is shown that 2:1, 1:1 and 1:2 complexes can be formed in aqueous and water-ethanol media; the 1:3 complex reported earlier was not found. The composition of the complexes extracted into benzyl alcohol from aqueous solutions at pH 6.5 and 9.0, was found to be 1:2.     

The spectrophotometric determination of nitrite in water with 8-quinolinol

The method is based on the formation of a purple azoxine dye by coupling diazotized p-nitroaniline with 8-quinolinol. Beer's law is obeyed at 550 nm in the range 2–28 μg NO₂^- per 25 ml. The molar absorptivity and Sandell sensitivity are 3.88 × 10⁴ l mol^-1 cm^-1 and 0.0012 μg cm^-2, respectively.     

The spectrophotometric determination of chromium in sea water

The coprecipitation of chromium from sea water by several precipitates was examined. With hydrous iron(III) oxide a recovery of chromium of >99% was obtained within the pH range 7.0–9.0 at a chromium level of ca. 0.4 μg/l. Chromium was separated from iron by anion exchange and determined spectrophotometrically using diphenylcarbazide. The method showed a precision of ±0.02 μg Cr/1. Chromium occurs in sea water in the 3+ oxidation state.     

Automatic determination of total carbohydrates in sea water

Summary The recommended method is based on the l-tryptophane/sulphuric acid reaction and has been adapted for a continuous flow system with the Technicon AutoAnalyzer. A supplementary run (cold run) is required with more than 10mol/l of nitrate. The presence of acetone or formaldehyde must be avoided. Total carbohydrates can be determined by this method within the range of 0.02–5mg/l. The relative coefficient of variation at the 1 mg/l level is 0.25 % (glucose).

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Automatische Bestimmung von Gesamt-Kohlenhydrat in Meerwasser

Zusammenfassung Die empfohlene Methode basiert auf der l-Tryptophan-Schwefelsäure-Reaktion und wurde dem Durchflußsystem des Technicon AutoAnalyzers angepaßt. Bei einem Nitratgehalt von mehr als 10mol/l ist zur Feststellung einer Korrektur ein zusätzlicher »kalter« Durchlauf notwendig. Aceton oder Formaldehyd dürfen nicht anwesend sein. Die Bestimmung kann im Bereich von 0.02–5 mg/l erfolgen und weist einen relativen Variationskoeffizienten von 0.25 % bei 1 mg/l auf (Glucose).

     

Extraction-photometric determination of uranium(IV) with chlorophosphonazo-III

A sensitive spectrophotometric method has been developed for the determination of uranium. The uranium(IV)-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 1.5–3.0 M hydrochloric acid solution. Maximal absorbance occurs at 673 nm and Beer's law is obeyed over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.1·10⁴ 1 mole^?1 cm^?1. Uranium can be determined in the presence of fluoride. sulfate and phosphate. Nitrate ion and elements (chromium, copper, iron) which affect the reduction of uranium(VI) or stability of uranium(IV) interfere.     

海水中有机污染物的光度法测定

海水中有机污染物在强碱性条件下被KMnO4所氧化。通过对生成物溶液中K2MnO4浓度的光度法测量（λ=430nm）,直接测定海水中有机物含量（以COD表示）。该方法的线性范围为0．40—4．50mg／L（以邻苯二甲酸氢钾＋甲酸钠体系为标准混合物溶液）,测定海水COD的相对标准偏差RSD为8．9％,回收率为90％～114％。