Determination of nitrate in sea water by cadmium-copper reduction to nitrite

1967 ◽  
Vol 47 (1) ◽  
pp. 23-31 ◽  
Author(s):  
E. D. Wood ◽  
F. A. J. Armstrong ◽  
F. A. Richards
Keyword(s):  
Standard Deviation ◽  
Sulphuric Acid ◽  
Sea Water ◽  
Colorimetric Method ◽  
Zinc Powder ◽  
Small Samples ◽  
Nitrosyl Chloride ◽  
Sensitivity Limit ◽  
High Concentrations

An accurate, dependable determination of 0–60 μg-at./l. of NO−3-N in sea water has been developed. The sample is treated with tetrasodium ethylenediaminetetraacetate solution and passed through a column of copperized cadmium filings. A nearly quantitative reduction of nitrate to nitrite results. Nitrite is then determined by a diazotization method. Neither sulphide nor high nitrite concentrations interferes. Approximately eight samples per hour per column can be analysed with a standard deviation of 0.12 μg-at./l. at the 20 μg-at./l. level.IntroductionAccurate determinations of nitrate ions in sea water have been difficult, especially under shipboard conditions.The colorimetric method described by Harvey (1926, 1930) and improved by Cooper (1932), Zwicker & Robinson (1944), and others uses strychnidine in concentrated sulphuric acid to produce a red colour. The reagent lacks reliable sensitivity, because it is dependent on the rates of mixing and cooling.In a method by Armstrong (1963), the absorbance of nitrosyl chloride in the UV region is measured with a spectrophotometer. While the method is good for small samples containing high concentrations of nitrate, the use of concentrated sulphuric acid and lack of sensitivity limit its use in routine analysis.A method in which nitrate is quantitatively reduced to nitrite would be advantageous, because nitrite can be readily determined by the sensitive diazotization method proposed by Griess (1879). Several such methods have been proposed. FØyn (1951), Vatova (1956), and Chow & Johnstone (1962) used zinc powder for the reduction, but the reduction is sensitive to temperature, and it is necessary to centrifuge or filter each sample.

scholarly journals The determination of silicate in sea water

1951 ◽  
Vol 30 (1) ◽  
pp. 149-160 ◽  
Author(s):  
F. A. J. Armstrong
Keyword(s):  
Sulphuric Acid ◽  
Sea Water ◽  
Picric Acid ◽  
Colorimetric Method ◽  
Ammonium Molybdate ◽  
Potassium Chromate ◽  
Distilled Water ◽  
Yellow Colour ◽  
Standard Solutions

Silicon in sea water may be present in suspension, in particles of clay or sand, as a constituent of diatoms, etc., or in solution. Some silicon in solution occurs in the form of silicate. This is usually estimated by the colorimetric method of Diénert & Wandenbulcke (1923), which makes use of the yellow colour of the silicomolybdic acid which is formed when ammonium molybdate and sulphuric acid are added to the water (Atkins, 1923). The colour may be compared with that of standard solutions of picric acid (Diénert & Wandenbulcke, 1923) or potassium chromate (Swank & Mellon, 1934). The method is simple but the colour in sea water is often faint and is not easy to match visually, nor is its intensity strictly proportional to the concentration of silicate. Less colour is produced in sea water than in standard solutions made with distilled water and this ‘salt error’ must be allowed for (Brujewicz & Blinov, 1933; Wattenberg, 1937; Robinson & Spoor, 1936).

scholarly journals Spectrophotometric determination of nicradipine and isradipine in pharmaceutical formulations

2009 ◽  
Vol 15 (2) ◽  
pp. 69-76 ◽  
Author(s):  
S.M. Al-Ghannam ◽  
A.M. Al-Olyan
Keyword(s):  
Standard Deviation ◽  
Detection Limit ◽  
Reaction Pathway ◽  
Pharmaceutical Preparations ◽  
Pharmaceutical Formulations ◽  
Molar Absorptivity ◽  
Zinc Powder ◽  
Conditional Stability ◽  
Conditional Stability Constant

A sensitive spectrophotometric method was developed for the determination of some 1,4-dihydropyridine compounds namely, nicardipine and isradipine either in pure form or in pharmaceutical preparations. The method is based on the reduction of nicardipine and isradipine with zinc powder and calcium chloride followed by further reduction with sodium pentacyanoaminoferrate (II) to give violet and red products having the absorbance maximum at 546 and 539 nm with nicardipine and isradipine, respectively. Beer's law was obeyed over the concentration range 8.0-180 ?g/ml with the detection limit of 1.67 ?g/ml for nicardipine and 8.0-110 ?g/ml with the detection limit of 1.748 ?g/ml for isradipine. The analytical parameters and their effects on the reported methods were investigated. The molar absorptivity, quantization limit, standard deviation of intercept (Sa), standard deviation of slope (Sb) and standard deviation of the residuals (Sy/x) were calculated. The composition of the result compounds were found 1:1 for nicardipine and 1:2 for isradipine by Job's method and the conditional stability constant (Kf) and the free energy changes (?G) were calculated for compounds formed. The proposed method was applied successfully for the determination of nicardipine and isradipine in their dosage forms. The results obtained were in good agreement with those obtained using the reference or official methods. A proposal of the reaction pathway was presented.

Chemical Method for the Determination of Vitamin D in Evaporated Milk With Elimination of Cholesterol by Digitonin Precipitation

1969 ◽  
Vol 52 (6) ◽  
pp. 1189-1195 ◽  
Author(s):  
J Eisses ◽  
H Dk Vries
Keyword(s):  
Vitamin D ◽  
Standard Deviation ◽  
Calibration Curve ◽  
Chemical Method ◽  
Colorimetric Method ◽  
Sterol Content ◽  
Alumina Column ◽  
Decomposition Products ◽  
Colorimetric Measurement

Abstract The colorimetric method of Jones et al. for the determination of vitamin D in evaporated milk, based on theUSPXVI method, was modified to obtain a simpler colorimetric measurement and more accurate results. The main modification is the elimination of nearly all cholesterol, according to the procedure of Den Herder for the determination of the sterol content of fats, by precipitation with digitonin in the saponified mass. The Florex column, used in the procedure of Jones et al. for the elimination of decomposition products of vitamin A, was omitted since it gave high blank values; an alumina column was substituted. The resulting method, when applied to samples of evaporated milk to which a known quantity of vitamin D had been added, showed a recovery of 78% with a standard deviation of 6%, using a calibration curve based on crystalline vitamin D. Data from these measurements, as well as data from vitamin D determination on several brands of fortified and unfortified evaporated milk, are presented.

THE DETERMINATION OF SMALL AMOUNTS OF FLUORINE IN WATER

1940 ◽  
Vol 18b (6) ◽  
pp. 151-159 ◽  
Author(s):  
Osman James Walker ◽  
Gordon Roy Finlay
Keyword(s):  
Sulphuric Acid ◽  
Perchloric Acid ◽  
Colorimetric Method ◽  
Fluorine Content ◽  
Sodium Ions ◽  
Ferric Ions ◽  
Titration Method

In the survey of Alberta waters in which fluorine content is compared with the prevalence of mottled teeth, the titration method and the colorimetric method for determining fluorine have not always given comparable results. Good results with the titration method are obtained when distillation is carried out with perchloric acid instead of with sulphuric acid. It was found that the colorimetric method is affected by more than 2 p.p.m. of phosphate, aluminium, or ferric ions, and by over 120 p.p.m. of sulphate ions. Moderate amounts of manganous, ferrous, silicate, chloride, and sodium ions do not interfere. When the water contains over 2 p.p.m. of phosphate, aluminium, or ferric ions, or if the water is coloured, the titration method is used. A scheme for correcting for sulphate ions is proposed. The titration method and the colorimetric method used in this laboratory for determining fluorine in waters are given in detail.

Volumetric Determination of Malathion, Using Dichlorofluorescein as Indicator

1976 ◽  
Vol 59 (1) ◽  
pp. 216-218
Author(s):  
Miguel Siquiroff ◽  
Ricardo Pollero ◽  
Rodolfo Goyena
Keyword(s):  
Standard Deviation ◽  
Petroleum Ether ◽  
Silver Nitrate ◽  
Ethyl Ether ◽  
Colorimetric Method ◽  
Florisil Column ◽  
Average Recovery ◽  
Florisil Column Chromatography ◽  
Volumetric Determination

Abstract A method has been developed which is based on alkali cleavage of malathion and volumetric determination of the resulting dimethylphosphorodithioate with silver nitrate, using dichlorofluorescein as the indicator. Pure malathion standards were analyzed by the proposed method, yielding a standard deviation of 0.27. Four typical malathion formulations containing talc, wheat flour, and anionic and nonionic emulsifiers were analyzed by both the proposed method and the former official first action colorimetric method with comparable results. Potential interferences from surfactants currently employed in liquid formulations are avoided by the use of Florisil column chromatography. Malathion is eluted from the column with petroleum ether-ethyl ether with an average recovery of 92.5%.

scholarly journals Unsegmented flow approach for on-line monitoring of pH, conductivity, dissolved oxygen and determination of nitrite and ammonia in aquaculture

1994 ◽  
Vol 16 (2) ◽  
pp. 59-62 ◽  
Author(s):  
A. C. Ariza ◽  
P. Linares ◽  
M. D. Luque de Castro ◽  
M. Valcárcel
Keyword(s):  
Dissolved Oxygen ◽  
Continuous Monitoring ◽  
Sea Water ◽  
Flow System ◽  
Photometric Determination ◽  
Fish Feed ◽  
Fish Breeding ◽  
On Line ◽  
High Concentrations

A fully automated flow system for on-line monitoring of analytes/parameters of interest in aquaculture is described. The approach has been optimized for the photometric determination of nitrite and ammonia and the continuous monitoring of pH, conductivity and dissolved oxygen, but these analytes/parameters are readily changeable as required. The system has been tested by monitoring these species in the input and output sea water streams of tanks at a fish breeding farm and also by monitoring water containing high concentrations of fish feed.

Colorimetric Determination of Selenium in Premixes and Supplements

1992 ◽  
Vol 75 (2) ◽  
pp. 269-271 ◽  
Author(s):  
Jeffrey A Hurlbut ◽  
Roger G Burkepile ◽  
Carolyn A Geisler
Keyword(s):  
Sulfuric Acid ◽  
Formic Acid ◽  
Coefficient Of Variation ◽  
Colorimetric Method ◽  
Colorimetric Determination ◽  
High Concentrations

Abstract A colorimetric method Is described for the determination of 100-10 000 μg selenlum/g premix. Selenium Is present in premixes as either selenite or selenate. Moderate to high concentrations of several common minerals are tolerated. The premix is briefly digested In a sulfuric acid-perchloric acidsodium molybdate mixture, boiled in 10% NaCI solution, made basic, and centrifuged. Aliquots are taken if necessary. The mixture Is then acidified with formic acid, treated with hydroxylamlne hydrochlorlde- EDTA, and complexed with 3,3 - dlamlnobenzldlne. The pH Is adjusted, and an extraction Is performed with toluene. The absorbance is measured at 420 nm. Recoveries for 100- 10 000 μg selenlum/g premix ranged from 88 to 104%, with an average of 97%. The coefficient of variation ranged from 1.6 to 6.9%, with an average of 4.2%.

Collaborative Study of a Colorimetric Determination of Nitrate in Tobacco

1969 ◽  
Vol 52 (4) ◽  
pp. 756-759
Author(s):  
C James Rosene
Keyword(s):  
Sulfuric Acid ◽  
Standard Deviation ◽  
Systematic Error ◽  
Collaborative Study ◽  
Colorimetric Method ◽  
Water Soluble ◽  
Colorimetric Determination ◽  
Error Standard Deviation

Abstract A colorimetric method for determining water-soluble nitrate in tobacco was studied by 14 laboratories on eight Burley and two cigar filler tobacco samples with nitrate levels of 0.5–2.4%. In the method, ground tobacco is extracted with water and filtered, and an aliquot is then treated with 2,4-xylenol in sulfuric acid; then the resulting 6-nitro-2,4-xylenol is removed by distillation and measured spectrophotometrically at 450 µm. Results show that, althoughthe precision standard deviation among laboratories is generally acceptable, the systematic error standard deviation is unacceptably high. This study will be continued.

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