Complexo-titrimetric determination of mercury using hexahydropyrimidine-2-thione as a selective masking agent

A simple, rapid, accurate and selective complexometric method is proposed for the determina-tion of mercury(Ⅱ). Mercury(Ⅱ) is first complexed with a known excess of EDTA and the surplusEDTA is back-titrated at pH 5. 0--6. 0 with lead nitrate, xylenol orange being used as indicator. Hexa-hydropyrimidine-2-thione (HPT) is then added to displace EDTA from the Hg-EDTA complex quan-titatively and the EDTA released is titrated with lead nitrate. Reproducible and accurate results areobtained for 2--55 mg of mercury, with a relative error of less than 0. 5% and standard deviation ofless than 0.04.     

Quantitative complexometric determination of mercury(II) in synthetic alloys and complexes using 2-thiazolinethiol as a masking agent

A simple, rapid and selective complexometric method is proposed for the determination of mercury(II). Mercury(II) and other related metal ions are first complexed with an excess of EDTA and the surplus EDTA is back-titrated with a standard lead nitrate solution at pH 5.0–6.0 (hexamine buffer) using xylenol orange as an indicator. A 0.2% solution of 2-thiazolinethiol in acetone is then added to displace EDTA from the Hg(II)-EDTA complex. The released EDTA is titrated with a standard lead nitrate solution as before. Reproducible and accurate results are obtained in the range of 0.8 g l^?1?15.8 g l^?1 of mercury with a relative error less than ±0.25% and a coefficient of variation (n = 6) not higher than 0.28%. The interference of various ions was studied and the method was employed for the analysis of mercury in its synthetic alloy mixtures and in complexes.     

Determination of palladium(II) using thiosemicarbazide as a replacing reagent

A simple, rapid, accurate, and selective complexometric method is proposed for the determination of palladium(II). Palladium(II), with associated diverse metal ions, is first complexed by adding a known excess of EDTA, and the uncomplexed EDTA is back titrated with lead nitrate solution in acetic acid-sodium acetate buffer (pH 5.0–6.0) until the end-point. Thiosemicarbazide (1%) solution in water is added to displace EDTA from the Pd-EDTA complex. The released EDTA is then titrated with the lead nitrate solution. Reproducible and accurate results are obtained in the concentration range of 1–10 mg of palladium with a relative error of less than 0.4% and a standard deviation of less than 0.02. The interference of many commonly associated metal ions was also studied. Advantages of this method over other complexometric methods of palladium determination are high-lighted.     

Complexometric determination of palladium(II) using thioacetamide as a selective masking agent

A simple, rapid and accurate complexometric method for the determination of palladium(II) is proposed, based on the selective masking property of thioacetamide towards palladium(II). In the presence of diverse metal ions, palladium(II) is complexed with excess of EDTA and the surplus EDTA is back titrated at pH 5-5.5 (acetic acid-sodium acetate buffer) with standard lead nitrate solution using xylenol orange as indicator. An excess of a 0.5% aqueous solution of thioacetamide is then added to displace EDTA from Pd(II)-EDTA complex. The released EDTA is titrated with the same standard lead nitrate solution as before. Reproducible and accurate results are obtained in the concentration range 0.5 mg - 17.80 mg of palladium with relative error of +/- 0.16% and coefficient of variation not exceeding 0.26%. The effect of diverse ions is studied. The method is used for the determination of palladium in its complexes, catalysts and synthetic alloy mixtures.     

Selective complexometric determination of mercury, using thiourea as masking agent

A method is described for selective complexometric determination of mercury, thiourea being used as masking agent. An excess of EDTA is added and the surplus EDTA is back-titrated with lead nitrate, with Xylenol Orange or Methylthymol Blue as indicator (pH 5-6). Thiourea is then added to decompose the mercury-EDTA complex and the liberated EDTA is again back-titrated with lead nitrate. The interference of various cations has been studied.     

Speciation analysis of mercury and lead in fish samples using liquid chromatography-inductively coupled plasma mass spectrometry

A liquid chromatography-inductively coupled plasma mass spectrometric (LC-ICP-MS) method for lead and mercury speciation analysis was described. Sample containing ionic lead and mercury compounds was subjected to liquid chromatographic separation before injection into the direct injection high efficiency nebulizer (DIHEN, 170-AA). The species studied include inorganic lead (Pb(II)), trimethyl lead (trimethyl-Pb), triethyl lead (triethyl-Pb), inorganic mercury (Hg(II)), methyl mercury (methyl-Hg) and ethyl mercury (ethyl-Hg), which were well separated by reversed-phase liquid chromatography with a C18 column as the stationary phase and a pH 2.8 solution of 0.2% (v/v) 2-mercaptoethanol, 1 mg L(-1) ETDA, 174.2 mg L(-1) sodium 1-pentanesulfonate and 12% (v/v) methanol as the mobile phase. The lead and mercury species in biological tissues were quantitatively extracted, into 10 g L(-1) EDTA and 0.2% (v/v) 2-mercaptoethanol solution taken in a closed centrifuge tube and kept on water bath, using microwaves at 65 degrees C for 2 min. The spike recovery of individual lead and mercury species determined by spiking the samples with suitable concentration of lead and mercury mixture standard were between 93% and 99%. The detection limits of the species studied were in the range 0.1-0.3 microg Pb L(-1) and 0.2-0.3 microg Hg L(-1). The procedure has been applied for the speciation analysis of two reference samples namely NRCC DOLT-3 Dogfish Liver and DORM-2 Dogfish Muscle and a swordfish sample obtained locally. The sum of the concentrations of individual species has been compared with the certified values for total lead and mercury to verify the accuracy of the method. The precision between sample replicates was better than 10% with LC-DIHEN-ICP-MS method.     

Determination of sulpha-drugs with ion-selective membrane electrodes

A liquid-membrane mercury(II)-sensitive electrode is used for determination of various sulpha drugs by addition of excess of mercuric nitrate and potentiometric back-titration of the surplus mercury(II) with EDTA. The performance of the electrode is compared with that of an Ag(2)S crystal-membrane electrode. Attempts to prepare a sulphamethoxazole-sensitive electrode failed.     

Selective complexometric determination of mercury with thiocyanate as masking agent

A method is proposed for selective complexometrie determination of mercury, thiocyanate being used as masking agent. An excess of EDTA is added and the surplus is back-titrated at pH 5-6 with lead nitrate, Xylenol Orange or Methylthymol Blue being used as indicator. Thiocyanate is then added to decompose the mercury-EDTA complex and the liberated EDTA is titrated with lead nitrate. The interference of various cations has been studied.     

Indirect complexometric determination of cadmium(II) using 1,10-phenanthroline as selective masking agent

An indirect complexometric method is described for the determination of cadmium(II), 1,10-phenanthroline being used as masking agent. Cadmium(II) in a given sample solution is initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 1,10-phenanthroline is then added and the EDTA released from the Cd-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 1.5–57 mg of Cd with relative errors 0.90% and standard deviations 0.06 mg. Cu(II), Co(II), Hg(II), Ni(II), Zn(II), Pd(II), Tl(III), Au(III) and Sn(IV) interfere, but can be easily masked. The method is applied for the determination of cadmium in synthetic alloy solutions.     

Complexometric determination of cadmium using 2-Mercaptoethanol as masking reagent

A complexometric method for the determination of cadmium(II) in presence of other metal ions is described based on the selective masking ability of 2-mercaptoethanol towards cadmium(II). Cadmium and other ions in a given sample solution are initially complexed with excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamethylentetramine), using xylenol orange as indicator. A known excess of 2-mercaptoethanol solution (10% alcoholic) is then added, the mixture is shaken well and the released EDTA from the Cd-EDTA complex is titrated against standard lead nitrate solution. The interferences of various ions are studied and the method is applied to the determination of cadmium in its complexes. Reproducible and accurate results are obtained for 3.5–25mg of Cd with relative errors 0.65% and standard deviations 0.06 mg.     

Bismuthiol as an analytical reagent

Summary Lead can be determined from its Bismuthiol II complex volumetrically by dissolving it in an excess of EDTA at a p_H of about 10 and titrating the excess of the EDTA against a magnesium or lead solution. In the same way silver can be determined by dissolving the complex in an excess of cyanide and back titrating the excess against a standard silver nitrate with iodide as the indicator. The results of the former are fairly accurate while those due to latter are highly satisfactory with silver less than 20 mg. With higher amounts of silver, however, the results are within +2%.Part VIII see Z. analyt. Chem. 156, 103 (1957).     

Complexometric Determination of Zinc(II) Using 2,2′-Bipyridyl as Selective Masking Agent

 An indirect complexometric method is described for the determination of zinc(II) using 2,2′-bipyridyl as masking agent. Zinc(II) in a given sample solution is initially complexed with an excess of EDTA and surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 2,2′-bipyridyl is then added, the mixture shaken well and the EDTA released from the Zn-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 3–39 mg of Zn with relative errors ≤ 0.5% and standard deviations ± 0.06 mg. The interference of various ions are studied. The method is applied for the determination of zinc in its alloys and ores. Received October 27, 1998. Revision June 10, 1999.     

Selective complexometric determination of copper in ores and alloys using 2,2′-bipyridyl as masking agent

An EDTA titration method is described for the determination of copper(II) in the presence of other ions based on the selective masking ability of 2,2′-bipyridyl. Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as an indicator. A known excess of 2,2′-bipyridyl solution (1% in 50% alcohol) is then added, the mixture is shaken well and the released EDTA from the Cu–EDTA complex is titrated against standard lead nitrate solution. The interference of various ions are studied and the method is applied to the determination of copper in its ores and alloys. Reproducible and accurate results are obtained for 2.54–25.40 mg of copper with S.D. values <0.04 mg.     

Determination of Mercury(II) with Dithizone by Diffuse Reflectance Spectrometry on a Fibrous Anion Exchanger

The possibility of the determination of mercury(II) with dithizone on the solid phase of a fibrous ion-exchange material filled with the AV-17 anion exchanger was studied. Mercury is adsorbed as an anionic complex. The sorption of mercury as chloride, iodide, sulfate, thiosulfate, nitrate, and EDTA complexes was studied. A procedure was proposed for the sorption–spectrometric determination of mercury with dithizone on a solid phase after sorption as the chloride complex. For improving the selectivity of the method, EDTA is added to the solution. The determination is affected only by Pd(II). The time of analysis is 15 min. The procedure was tested in the analysis of tap and river water and a solution modeling natural water.     

Dithiocarbaminoacetic acid as a masking agent in complexometry

Dithiocarbaminoacetic acid (TCA) forms very stable, water soluble complexes with a number of metal ions and is a suitable masking agent in complexometry. TCA masks from EDTA and complexometric indicators at pH 2-6 the following elements: bismuth(III), indium(III), thallium(III), cadmium(II), lead(II), mercury(II) and copper(II), thus making possible the complexometric determination of other elements in their presence.     

Indirect Complexometric Determination of Mercury(II) Using Potassium Bromide as Selective Masking Agent

 A complexometric method for the determination of mercury in presence of other metal ions based on the selective masking ability of potassium bromide towards mercury is described. Mercury(II) present in a given sample solution is first complexed with a known excess of EDTA and the surplus EDTA is titrated against zinc sulfate solution at pH 5–6 using xylenol orange as the indicator. A known excess of 10% solution of potassium bromide is then added and the EDTA released from Hg-EDTA complex is titrated against standard zinc sulfate solution. Reproducible and accurate results are obtained for 8 mg to 250 mg of mercury(II) with a relative error ± 0.28% and standard deviations ≤0.5 mg. The interference of various ions is studied. This method was applied to the determination of mercury(II) in its alloys. Received April 18, 2001 Revision October 10, 2001     

Anodic a.c. polarography of methylthymol blue

The anodic a.c. polarographic properties of methylthymol blue (MTB) were investigated in the supporting electrolyte of potassium nitrate containing buffer. The difference in the peak potentials of MTB and EDTA is a good measure of the difference in the stabilities of both chelates. The stability constant of mercury(II)-MTB complex was successfully determined on the basis of that reported for the mercury(II)-EDTA complex.     

Studies on metallochromic indicators--II. Zincon and its mercury and zinc complexes as indicators in EDTA titrations

Zincon has been found to be an excellent indicator in the titration of mercury(II) with EDTA at pH 5.5-7. Moreover the mercury(II)-Zincon and zinc-Zincon systems have been found to be suitable indicators in the direct EDTA titrations of Pb(2+), Cd(1+) and Ca(2+). Interference studies of a number of cations and anions have been made. Chloride and bromide can be tolerated in the titration of mercury(II), up to equivalent concentrations.     

Catalytic amperometric and catalytic constant-current potentiometric titrations of silver(I), palladium(II) and mercury(II)

Amperometry and constant-current potentiometry were used to follow the course of catalytic titrations of silver(I), palladium(II), and mercury(II) with potassium iodide. The Ce(IV)As(III) and Ce(IV)Sb(III) systems in the presence of sulphuric acid were used as indicator reactions. The possibilities of application of platinum, palladium, gold, graphite, and glassy-carbon indicator electrodes were investigated. Graphite appeared to be somewhat more advantageous than the other electrode materials. The effect of concentration of the components of the indicator reactions, the presence of organic solvents and acids on the shape of the catalytic titration curves was studied. Amounts of 30-3000 mug of silver(I) nitrate, 90-900 mug of palladium(II) chloride, 130-1300 mug of mercury(II) chloride, and 150-1500 mug of mercury(II) nitrate were determined with a relative standard deviation less than 1.0%. The results obtained were in good agreement with those of comparable methods. The catalytic titration method developed was applied to determination of mercury in Unguentum Hydrargyri.     

Potentiometric determination of mercury(ii) with ethylenediaminetetraacetic acid : Analysis of binary mixtures

Potentiometric determination of mercury(II) with EDTA using silver amalgam as indicator electrode, is suitable for 200 μg to 100 mg of mercury. Binary mixtures of mercury (II) with several other metals can be analysed by different methods involving masking agents, selective pH and differential titrations.