EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。     

The application of salicylaldoxime in solvent extraction : Part II. Spectrophotometric determination of copper with 2-(5-nitro-2-pyridylazo)-1-naphthol after separation with salicylaldoxime

A highly sensitive spectrophotometric method for the determination of traces of copper with 2-(5-nitro-2-pyridylazo)-l-naphthol (5N-α-PAN) has been developed. At a pH of 3–4copper(II) is selectively extracted into chloroform as its salicylaldoxime chelate and then stripped into an aqueous acid solution; the pH is adjusted to 9.3, and 5N-α-PAN is added. The 1:2 chelate between copper(II) and the reagent, which promptly precipitates, is extracted into chloroform and measured at 598 nm. The molar absorptivity is 86,000. The application of the method to the analysis of high-purity magnesium and cobalt is described.     

Kinetic spectrofluorimetric determination of trace ascorbic acid based on its inhibition on the oxidation of pyronine Y by nitrite

A highly sensitive spectrofluorimetric method is proposed for the determination of trace amount of ascorbic acid using a new indication. The method is based on the inhibition of ascorbic acid on the oxidation of pyronine Y (PRY) by nitrite. The detection limit for ascorbic acid is 0.012 microg ml(-1), the linear range of the determination is 0.02-0.36 microg ml(-1). Analytical parameters, such as reagent concentration, pH, reaction temperature and time, were optimized. The relative standard deviations of eleven replication determinations of 0.12 and 0.24 microg ml(-1) ascorbic acid were 1.4 and 0.72%, respectively. This method has been used to determine ascorbic acid in pharmaceuticals, vegetables, fruits and soft drink with satisfactory results.     

Procedure for determination of trace ions in boric acid by matrix volatilization-ion chromatography

A method for determination of anions and cations in boric acid is proposed by matrix volatilization. The boric acid matrix was eliminated as trimethyl borate ester in a vapour phase matrix elimination (VPME) system using a mixture of glycerol-methanol. In this VPME system, in situ reagent purification, sample decomposition and digest evaporation were achieved in a single step. Trace anions were separated on anion-exchange column (IonPac AS17) by an isocratic elution with 15 mM sodium hydroxide and the cations on a cation-exchange column (IonPac CS12) by 20 mM hydrochloric acid as eluents. Method detection limits (3sigma) for most ions ranged from 0.3 to 8 ng/g (ppb). Recovery experiments combined with comparison of data obtained by other methods were employed to verify the accuracy of the proposed method. Application of the method to determine trace levels of anions like acetate, oxalate, sulfate, phosphate and cations such as lithium, sodium, potassium, magnesium and calcium in two highly pure grades of boric acid using ion chromatography is demonstrated.     

Synthesis of 2,4-Dihydroxybenzaldehyde-Isonicotinylhydrazone and Its Fluorescence Reaction with Aluminium

A new fluorescent reagent, 2,4-dihydroxybenzaldehyde-isonicotinylhydrazone (DHBI), is synthesized and characterized by elemental analysis and infrared spectra (KBr disks). The fluorescent reaction of aluminium(III) with the new reagent has been studied. The fluorescent excitation and emission wavelengths of the complex are at 394 and 484 nm, respectively. The optimum pH range is 4.2–4.6; hence the pH is controlled in the optimum interval with a buffer solution (sodium formate–formic acid) of pH 3.3. The linear range of the method is 0–6 μg/25 ml. The molar ratio of aluminium to reagent is found to be 1:1. The proposed method has been used for the determination of trace aluminium in drinking water and edible bicarbonate of sodium with satisfactory results.     

酸性络蓝K双波长信号系数光度法测定钙镁

基于在氢氧化钠溶液中,钙、镁均与酸性络蓝K(ACBK)形成暗红色配合物,提出了测定钙和镁的双波长信号系数光度法.该法不仅消除了钙、镁之间的吸收干扰,且消除了一定量的共存离子的干扰.利用褪色法与生色法的吸光度之和作为信号吸光度,使方法的灵敏度大为提高.测定钙、镁总量时,分别用钙、镁吸收曲线正峰与负峰上的等吸收波长470.5 nm(λPa)及559.5 nm(λNa)处测定吸光度APa和ANa,求得总量的信号系数fs为2.439.于λPa470.5 nm处测得任一浓度钙、镁试液的吸光度APa′,其信号吸光度As=fsAλPa′.测定镁时,以试剂ACBK褪色对钙配合物生色的完全相消干扰的波长539 nm(Pa)作为测定波长,负峰波长583 nm为Na.按相同方法测得镁的信号系数fs为4.148.     

Indirect spectrophotometric determination of ascorbic acid with ferrozine by flow-injection analysis

A FIA indirect spectrophotometric determination of ascorbic acid was developed using its reducing action on Fe(III) in acidic medium and following the spectrophotometric determination of the reduced iron by using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine) as chromogenic reagent in buffered medium (pH 5.5) and monitoring the absorbance signal at 562 nm. A three-line manifold with two reaction coils was used: in the first reaction coil, ascorbic acid reduces Fe(III) to Fe(II); and in the second one, the complexation reaction is developed. The linear range of the method was 0.5-10 mug ml(-1) of ascorbic acid, the detection limit being 0.028 mug ml(-1). The proposed method was sensitive, rapid (sampling rate of 90 samples h(-1)) and reproducible (RSD 0.19%, n=10). Satisfactory results were obtained in the determination of ascorbic acid in pharmaceutical preparations, fruit juices and urine testifying the applicability of the method to real samples.     

A sequential injection system for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples.

A sequential injection methodology for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples is proposed. A single manifold is used for the determination of the three analytes, and the same protocol sequence allows the sequential determination of calcium and magnesium (the sum corresponds to the water hardness). The determination of both metals is based on their reaction with cresolphtalein complexone; mutual interference is minimized by using 8-hydroxyquinoline for the determination of calcium and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for the determination of magnesium. Alkalinity determination is based on a reaction with acetic acid, and corresponding color change of Bromcresol Green. Working ranges of 0.5 - 5 mg dm(-3) for Ca, 0.5 - 10 mg dm(-3) for Mg, and 10 - 100 mg HCO3- dm(-3), for alkalinity have been achieved. The results for water samples were comparable to those of the reference methods and to a certified reference water sample. RSDs lower than 5% were obtained, a low reagent consumption and a reduced volume of effluent have been accomplished. The determination rate for calcium and magnesium is 80 h(-1), corresponding to 40 h(-1) per element, while 65 determinations of alkalinity per hour could be carried out.     

Spectrophotometric determination of iron with 1-hydroxy-4-sulpho-2-naphthoic acid

1-Hydroxy-4-sulpho-2-naphthoic acid (H(3)L) is proposed as a spectrophotometric reagent for determination of iron. It gives a red-brown chelate, FeL(6-)(3), with lambda(max) 500-520 nm at pH 8 ( = 3.3 x 10(3) l. mole(-1). cm(-1)). In this wavelength region the reagent has no absorption. Most common cations and oxo-anions do not interfere. In the determination of iron in polymetallic iron ores and aluminium alloys the relative error and relative standard deviation of the method were found to be better than 1 and 0.5%, respectively. 1-Hydroxy-4-sulpho-2-naphthoic acid seems to be a more sensitive and accurate reagent for iron than 5-sulphosalicylic acid, and the number of interfering ions is smaller than in the 1,10-phenanthroline or thiocyanate methods.     

Flow injection spectrophotometric determination of boron in plant material with azomethine-H

A simple, fast method for the determination of boron in plant extracts is described. The method utilizes injection of 1.0 ml of an acid plant digest into a 0.1 M hydrochloric acid stream, with further addition of a buffer—masking solution and azomethine-H as the colour-forming reagent. Effects of pH, kinetics of colour reaction development, sample volume, reagent composition and interferences are described. The proposed method allows the analysis of plant extracts with boron contents in the range 0.1–6.0 ppm at a rate of 60 determinations per hour, with a reagent consumption of 2 mg of azomethine-H per sample. The precision is good (r.s.d. < 1%) and the results agree with those obtained by the curcumin method.     

A simultaneous EDTA-metric determination of calcium and magnesium with antipyrylazo III and thymolphthalexon

The simultaneous determination of calcium and magnesium in natural materials (limestone and dolomite) can be made by EDTA-metric titration at pH 13.0–13.3 and 10.2–10.5 indicated by antipyrylazo III (diantipyrylaxo; 3,6-diantipyrylazo-4,5-dihydroxy-2, 7-naphthalenedisulfonic acid) and thymolphthalexon (3′,3″-bis[bis(carboxymethyl)aminomethyl]-thymolphthalein), respectively. Sodium cyanide and triethanolamine are used as masking reagents, hydroxylamine hydrochloride is the bleaching (reducing) reagent to remove the antipyrylazo III color for the subsequent magnesium titration. Antipyrylazo III is also a convenient indicator for EDTA-metric determination of copper(II) in aqueous ammonia.     

4-(N,N-diethylamino) benzaldehyde thiosemicarbazone in the spectrophotometric determination of palladium

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate-hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 microgmL(-1). The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36 - 3.24 microg mL(-1). The yellow Pd(II)-DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity of the complex from Beer's data, for D = 0.001, is 0.0032 microg cm(-2). The composition of the Pd(II)-DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.     

Synthesis and analytical applications of 2,4-dinitro-6-chlorophenylazothymol

The newly synthesized 2,4-dinitro-6-chlorophenylazothymol, a weak acid with pK(a) 8.33 +/- 0.04 at 27 degrees, is proposed as a sensitive spot reagent for magnesium, with an identification limit of 0.14 microg at pH 10.5-11.6. Silver and manganese(II) interfere but can be masked by means of cyanide and periodate respectively. There is little interference by anions. The reagent also serves as an acid-base indicator with a transition interval of pH 7-9, giving a sharp colour change at the equivalence point.     

Dehydroacetic acid as a reagent for the separation and gravimetric determination of copper(II), aluminium and beryllium

Dehydroacetic acid is proposed as a reagent for the gravimetric determination of copper(II), aluminium and beryllium at pH 3.0-6.0, 3.0-6.0 and 7.5-9.5 respectively. Copper is weighed as the complex Cu(C(8)H(7)O(4))(2). Aluminium and beryllium are weighed as Al(2)O(8) and BeO. The reagent is easy to prepare.     

Spectrophotometric determination of tranexamic acid in pharmaceutical bulk and dosage forms.

In this study, a simple, fast, accurate and sensitive spectrophotometric method has been developed for the determination of tranexamic acid in bulk and pharmaceutical preparations. The method is based on the reaction of ninhydrin with the primary amino group of tranexamic acid in the basic medium at pH 8.0. The reaction produces a bluish-purple color which absorbs maximally at 565 nm. Beer's law was obeyed in the range of 3-40 microg ml(-1) with molar absorptivity of 5.093 x 10(3) L mol(-1) cm(-1). The effects of various factors such as temperature, heating time, concentration of reagent, color stability and interferences were investigated to optimize the procedure. The results have been validated analytically and statistically. The proposed method has been applied for the determination of tranexamic acid in bulk and pharmaceutical preparations with good results.     

环氧琥珀酸(盐)测定方法探讨

本文以含0.1 mol/L盐酸的氯化镁饱和溶液为加成试剂,进行了环氧基测定的探讨,并考察了反应时间、反应温度对分析准确度的影响。实验结果标明,在反应温度60℃条件下,反应45 min后,分析相对误差降至1%以内;与离子色谱测定方法比较,其测定结果吻合,可用于工业化生产中环氧琥珀酸(盐)的测定。     

Spectrophotometric determination of trace amounts of thallium with 7-(4,5-dimethylthiazolyl-2-azo)-8-hydroxyquinoline-5-sulphonic acid

A new reagent, 7-(4,5-dimethylthiazolyl-2-azo)-8-hydroxyquinoline-5-sulphonic acid, has been examined to evaluate its usefulness as a spectrophotometric reagent for thallium(III). A purple-red complex is formed in aqueous solution at pH 4-5 in the presence of cetylpyridinium chloride and the stoichimetric ratio is 1:2 (Tl:reagent). The apparent stability constant is 1.5 x 10(11). The effect of diverse ions has been studied and a method for determining trace amounts of thallium is proposed.     

Ultraviolet spectrophotometric determination of tungsten(VI) with ammonium 1-pyrrolidinecarbodithioate

A simple and rapid ultraviolet spectrophotometric method is proposed for the determination of trace amounts of tungsten(VI) with ammonium 1-pyrrolidinecarbodithioate (APDC). The method is based on measurement of the absorbance of the tungsten APDC complex in fairly concentrated hydrochloric acid medium; no extraction is required. The complex is formed at an initial acidity of 6M hydrochloric acid and has an absorption maximum at 250 nm. The high absorption of the reagent blank at 250 nm disappears on decomposition of excess of reagent by heating. Beer's law is obeyed over the range 0.43–3.2 ppm of tungsten(VI). The molar absorptivity of the complex is 4.5 × 10⁴ l.mole⁻¹ .cm⁻¹ at 250 nm. Tenfold amounts of aluminium, magnesium, calcium, cobalt, iron(II), lead, silver, sodium and titanium do not interfere in the determination of 50 μg of tungsten (VI).     

Microdetermination of magnesium in biological fluids

A modified procedure for the spectrophotometric determination of serum magnesium is described in which a direct addition of serum is made to a two-piece color reagent system. One solution contains an optimized concentration of the color reagent Magon, 1-azo-2-hydroxy-3-2-(2,4-dimethylcarboxanilido)-naphthalene-1′-(2-hydroxybenzene-5-sulfonate) sodium salt, in a dimethyl sulfoxide medium for binding magnesium and also EGTA, ethylene-bis(oxyethylenenitrilo)-tetraacetic acid, for binding calcium. The other is an alkaline solution of dilute cyanide to bind copper and iron and provide the optimum reaction pH. By means of these ingredients the simple procedure involves a reaction with serum magnesium while masking the interference of calcium and trace metals and allowing the reaction to take place without either separation or deproteinization steps. Optimized characteristics are shown for a linear reaction involving a variable reaction blank in the procedure where calcium is measured against a blank that is constant in its makeup. The linearity of the procedural reagent blank, with respect to its own concentration, helps attain the required linear results for the overall system and this is described by spectral studies.     

Ion exchange chromatography of aluminum using 3-carboxy-2-naphthylamine-N,N-diacetic acid as a fluorescent post-column chelating reagent

Ion exchange chromatography of aluminum ion using 3-carboxy-2-naphthylamine-N,N-diacetic acid (CNDA) as a fluorescent post-column chelating reagent was studied. The solution containing ammonium chloride and hydrochloric acid was used for the eluent, and acetate buffer solution containing CNDA was used for the post column chelating reagent. The peak of aluminum was separated from that of calcium, magnesium and zinc, and the chromatogram was not affected by copper(II) and iron(III). The calibration curve gave linear plots with a range of 0.0027-0.54 ppm aluminum, the regression coefficient of correlation (r2) was 1.000, and the detection limit (S/N = 3) was 0.3 ppb, indicating that the method could determine aluminum with high sensitivity. It was demonstrated that CNDA is a useful metallofluorescent reagent for aluminum. This method has been successfully applied to the determination of aluminum in some tea drinks.