邻—甲酚酞光度法快速测定饲料中钙

以钙与邻-甲酚酞在pH11的乙醇胺-硼酸缓冲溶液中的紫色反应,建立了快速测定饲料中钙的光度法,λ_(max)=570nm,测定的线性范围为0～10μg/6ml,ε=1.8×10~4,加标回收率为98%～101%,RSD为3.6%,用于饲料中钙的快速测定,取得了满意结果.     

Kinetic determination of formaldehyde and hexamethylenetetramine with a cyanide-selective electrode

An automatic potentiometric reaction-rate method is described for the determination of formaldehyde and hexamethylenetetramine. The formaldehyde reacts with cyanide, and the reaction rate is followed with a cyanide-selective electrode. The time required for the reaction to consume a fixed amount of cyanide, and therefore for the potential to increase by a preselected amount (8.0 mV), is measured automatically and related directly to the formaldehyde concentration. The average error for the determination of 60–300 μg of formaldehyde in a sample volume of 1.00 ml was about 1.3%. Amounts of hexamethyl-enetetramine in the range 50–250 μg in a sample volume of 0–050 ml were determined after acid hydrolysis to formaldehyde with an average error of about 1.6%. Measurement times were in the range 18–80 s for both determinations. The method has been applied to the determination of hexamethylenetetramine in pharmaceutical preparations.     

Kinetic photometric determination of copper at the nanograms per millilitre level in real samples

A highly sensitive and selective kinetic method is proposed for the determination of nanogram amounts of copper(II) based on its catalytic effect on the oxidation of 3-hydroxybenzaldehyde azine by potassium peroxydisulphase in an ammoniacal medium. The rate of the reaction is monitored spectrophotometrically at 465 nm and the method allows the determination of copper concentrations in the range 0.5–18 ng ml^?1 with a relative standard deviation of about 2%. The proposed method is virtually specific to copper and has been applied satisfactorily to its determination in a variety of food and industrial samples. A possible mechanism for the catalysed reaction is proposed.     

Chemiluminescence during the oxidation of alcohols by permanganate: application to the determination of ethanol in gin

Chemiluminescence is observed during the oxidation of ethanol with potassium permanganate under very acidic conditions. Factors affecting the chemiluminescence signal are discussed. Based on this chemiluminescence reaction, a method for the determination of alcohol in gin was developed. The method, which has a detection limit of 0.3% (v/v) and a relative standard deviation of about 1% at 40.0% (v/v), was used in the determination of ethanol in three different brands of gin with no sample preparation.     

Some aspects of the winkler determination of oxygen in water

The reactions in the Winkler determination of oxygen have been examined with a rotating platinum electrode and a recording polarograph. In this manner the extent of the reaction has been determined over the pH range 7-10; at a pH of 7 only about 5% of the dissolved oxygen reacts; at a pH of 9 or above the reaction is essentially quantitative. The reaction of dissolved oxygen with manganese(II) is quite rapid. The sluggish response of the polarograph recorder prevented an accurate determination of the rate, but the reaction half-times were about 2 sec or less over the pH range used.     

Determination of niobium in zirconium-niobium alloys

A rapid control determination of niobium in 50% zirconium/50% niobium master-alloy is described; it is a direct spectrophotometric procedure, based on the reaction of niobium ions with hydrogen peroxide in concentrated sulphuric acid. The procedure is suitable for the examination of zirconium alloys containing niobium in the range 0.1 to about 60%. At least 1% of chromium, cobalt, copper, manganese, nickel or tantalum, does not interfere. Interference due to optical absorption by the peroxy-complexes of titanium, tungsten, molybdenum and vanadium is not significant in the determination of niobium above about 1%, provided that these metals are not in excess of about 0.5%, 0.25%, 0.1% and 0.02%, respectively. To compensate for optical absorption due to iron(III), a solution of the sample, not treated with peroxide, is used.     

Simultaneous spectrofluorimetric determination of iron and manganese by a differential kinetic catalytic method

A kinetic method is presented for the simultaneous determination of iron(III) and manganese(II) based on the different reaction rates resulting from the catalytic effect of both metal ions on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide in an ammoniacal medium. The reaction is monitored spectrofluorimetrically at 440 nm and with excitation at 365 nm. Two sets of reaction conditions are established to maximize the effect of manganese compared to iron, and vice versa, and the data are evaluated from simultaneous equations. Mixtures of these metal ions at ng ml^?1 levels for iron/manganese ratios from 8:1 to 1:2 can be determined with an accuracy and precition of about 3% and 1%, respectively. The methods has been applied successfully to the determination of both metals in aluminium and copper alloys, beer, cheeses and soils.     

A fluorimetric kinetic method for the determination of organophosphorus and organocarbonyl compounds

A direct reaction rate method is proposed for the rapid, sensitive determination of organophosphorus and organocarbonyl compounds, based on a fluorimetric SCHOENEMANN reaction. From 0.02 to 100 μg/ml of benzoyl chloride, benzoyl bromide, phthalic anhydride, diisopropyl phosphorofluoridate, parathion, methyl parathion, diethyl chlorophosphate and dimethyl chlorothiophosphate can be determined with an accuracy and precision of about 1.5%.     

Potentiometric study of reaction between tetrabutylammonium periodate and phenothiazine in chloroform; application to the analysis of phenothiazine derivatives

The reaction between tetrabutylammonium periodate and phenothiazine in the presence of the strong acids in chloroform was studied by potentiometry and the reaction pathways were determined. The oxidimetric titration conditions of phenothiazine derivatives using a standardized chloroform solution of tetrabutylammonium periodate were optimized and a potentiometric detection of end points was utilized. The relative standard deviation for the determination of 5 mg phenothiazines was obtained about 1-1.5%. The method was applied for the determination of phenothiazines in various pharmaceutical preparations after extraction into chloroform.     

火焰原子吸收光谱法测定铜冶炼渣中镍

通过对铜冶炼渣化学组成和性质的研究,确定了测定镍的实验方法。铜冶炼渣中二氧化硅含量在20%~40%,硫含量10%~20%,样品的分解具有一定的难度,必然影响镍的测定结果,因此需在样品分解过程中加入一定量的氟化氢铵、溴使二氧化硅生成四氟化硅、硫生成硫化氢挥发除去,溶液中其余共存元素主要有铜、银、铁、锌等元素不干扰测定结果,在硝酸(5%)介质中,用火焰原子吸收光谱法测定镍的含量,测定范围为0.01%~1%,加标回收率在99.5%~100.4%,测定结果的相对标准偏差(n=7)在0.61%~1.18%,检出限为0.004μg/mL,方法快速,简捷,能够满足日常生产检测需要。     

Extraction-spectrophotometric determination of small amounts of boron in copper metal and copper-base alloys with methylene blue

A sensitive and rapid spectrophotometric method for the determination of small amounts of boron in copper metal and some copper alloys is described. The method is based on the extraction of a BF(4)(-)-Methylene Blue complex into dichloroethane after decomposition of the sample with hydrogen peroxide and sulphuric acid. The optimum reaction conditions and the influence of alloying elements have been investigated. Boron contents in the range 0.00-0.1% can be determined with a relative error ranging from about 9 to 2%.     

Kinetic determination of sulphonamides at the millimolar level by the continuous addition of reagent technique

A kinetic method for the determination of sulphonamides by the continuous addition of reagent (CAR) technique is reported. The method involves the formation of an azo dye between 1-naphthol and a diazonium salt, which is in turn obtained on reaction between the free primary aryl amine of the sulphonamide and sodium nitrite in a weak acid medium. The reaction is monitored via the initial rate of change of the absorbance of the azo dye formed at 470 nm, which is proportional to the sulphonamide concentration. Practical problems associated with this type of reaction for the determination of sulphonamides were readily avoided by using the CAR technique. Sulphonamides can be determined in the range 3 × 10^?6 ?3 × 10^?5 M with a relative standard deviation of about 1% and a sampling frequency of 25 h^?1 (triplicate runs). The proposed method is simple and rapid and insensitive to the presence of excipients; it proved useful for the determination of sulphonamides in pharmaceutical samples.     

Indole as a reagent for nitrite in aqueous solution

A fairly selective and sensitive spectrophotometric method for the trace determination of nitrite in aqueous solution is described. The titled ion reacts with indole in acidic medium to form a soluble pink-red product, which is measured at 530 nm. Maximum absorbance is achieved in 10 min and remains constant for about 45 min. This method is applicable to water samples containing 0–2 μg/ml with a relative error of 0.0 to–0.8%, and relative standard deviation of 0.3–0.8%, depending on the concentration level. The optimum reaction conditions affecting and related to the color reaction and interferences due to foreign ions have been studied.     

A New Catalytic Reaction for the Determination of Nanomolar Concentrations of Iron(III)

Abstract

On the basis of theoretical considerations, a new catalytic reaction for the determination of nanomoler iron(III) concentrations has boon propesod, nomoly the oxidation of sulfanilic acid by potassium periodate using 1,10-phenanthroline as an activator. The optimum conditions for Fe(III) determination have been established as a result of kinetic studies.

The reaction ensures a low detection limit (2×10^?8 M), low coefficient of variation about 5% and high selectivity.     

Improved procedure for determining tellurium with Bismuthiol II

An improved procedure for the determination of tellurium with Bismuthiol II is described. Ammonium sulphate is found to increase the rate of complex formation and to enhance the sensitivity of the reaction by about 20%.     

Flow injection chemiluminescence determination of thiamine based on its enhancing effect on the luminol-hydrogen peroxide system

A new flow injection chemiluminescence (CL) method is proposed for the determination of thiamine, based upon its enhancing effect on the CL reaction of luminol with hydrogen peroxide in alkaline solution. The method allows the determination of thiamine within 0.05-8 mug ml(-1) range with a detection limit (3sigma) of 0.01 mug ml(-1). The relative standard deviation is 1.4% (n=11, 0.5 mug ml(-1) thiamine) and the sample throughput is about 90 samples h(-1). The method was successfully applied to the determination of thiamine in pharmaceutical preparations.     

Flow Injection Catalytic Determination of Vanadium using the Indicator Reaction between Victoria Blue B and Bromate and A Citric Acid Activator

ABSTRACT

A flow injection catalytic method is proposed for determination of trace vanadium based on its catalytic action on a new indicator reaction between Victoria blue B (VBB) and potassium bromate in the presence of citric acid as an activator and in dilute sulfuric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of VBB injected at the maximum absorption wavelength of 618 nm. The detection limit is 0.5 ng ml^?1 and is independent of the initial valence state of vanadium. The relative standard deviation is 1.5% obtained from 11 standard solutions each containing 40 ng ml^?1 of vanadium. The sampling rate is about 15 samples per hour. This method is very simple and has been applied to the determination of trace vanadium in some natural waters with recoveries of 93-103%.     

Ultraviolet spectrophotometric determination of copper in copper ores by flow-injection analysis

A flow-injection analysis (FIA) method for the ultraviolet spectrophotometric determination of copper in copper ores is described. The ore samples are dissolved in concentrated perchloric acid, the excess acid is neutralized with ammonia solution, and the resulting solution is used for the determination of copper. The UV-FIA system is based on the reaction of copper (II) ions with pyrophosphate and subsequent measurement of the absorbance of the dipyrophosphatocuprate (II) complex at 240 nm. The main factors which control the formation of this complex and the FIA variables influencing the system are discussed. The calibration graph is linear from 2-50 ppm copper. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative standard deviation. Results obtained compare well with those obtained by atomic absorption spectrometry.     

KBrO3氧化甲基紫褪色动力学光度法测定食品中痕量钒

基于0.004 mol/L的柠檬酸介质中,痕量V(Ⅴ)催化KBrO3氧化甲基紫的褪色反应,建立了测定痕量V(Ⅴ)的动力学光度法。方法的检出限为1.23μg/L,线性范围为0～0.16μg/mL。讨论了酸度、反应物浓度、温度、反应时间、干扰离子等因素的影响,确定了该体系反应的最佳条件。在25 mL溶液中,测定2.0μg V(Ⅴ)的RSD为1.9%(n=11)。方法可用于测定小麦和苹果中的痕量V(Ⅴ),RSD为1.1%～2.7%,标准加入回收率为97.6%～99.0%。