A collaborative study of four methods of assay of benzylpenicillin

The assay of benzylpenicillin by iodimetric titration, spectrophotometry with a mercury(II) chloride—imidazole reagent, titration with mercury(II) nitrate in acetate buffer solution, and titration with mercury(II) perchlorate in aqueous pyridine solution, was examined in four laboratories. The first two methods were applied to two samples (the third one being the reference sample), the mercury(II) nitrate titration to three, and the mercury(II) perchlorate method to two samples. The four methods gave very similar results, but the purity obtained with the mercury(II) perchlorate method was slightly lower, and this procedure is less desirable because pyridine is used as solvent. There were no great differences in the relative standard deviations of the four methods. The titration with mercury(II) nitrate is preferred because it is an absolute method.     

Coulometric titration of copper(II) with electro-generated chromium(II)

The current efficiency for the electrogeneration of chromium(II) for use as a coulometric titrant was studied for several supporting electrolytes. With a mercury cathode and a 0.1 M chromic sulfate-0.1 M potassium chloride medium, 0.8 to 2.8 mg of copper (II) in 110 ml of solution can be titrated using potentiometric end-point detection.     

Novel mercury(II) complexes of meso-tetraphenylporphyrin and N-methylporphyrins

Treatment of meso-tetraphenylporphyrin, H₂TPP, with just over one equivalent of mercury(II) acetate in methylene chloride-THF gives mercury(II) meso-tetraphenylporphyrin, HgTPP. With excess of mercury(II) acetate, H₂TPP and HgTPP afford a novel dimetallic mononuclear porphyrin, AcOHgTPPHgOAc. In contrast, HgTPP reacts with mercury(II) chloride to give the chloro-analogue, ClHgTPPHgCl, but there is no reaction between H₂TPP and mercury(II) chloride. Demetallation of HgTPP in methylene chloride containing small amounts of hydrogen chloride proceeds via the dimetallic compound, ClHgTPPHgCl, to give free base HTPP. The reaction rate is dependent upon acid concentration suggesting that the rate determining step is protonation, but dilution causes no decrease in the rate; a mechanism which invokes the intermediacy of monohydrogen-meso-tetraphenylporphyrinatomercury(II) chloride, H(TPP)HgCl, in the formation of ClHgTPPHgCl and in its subsequent decomposition into H₂TPP, is proposed.N-Methylporphyrins react with mercury(II) acetate in methylene chloride-tetrahydrofuran to give the corresponding N-methylporphyrinatomercury(II) acetates, Me(P)HgOAc.     

Mercury-assisted solvolyses of alkyl halides : Simple procedures for the preparation of nitrate esters,acetate esters,alcohols and ethers

The reactions of a wide variety of alkyl halides with mercury(I) and/or (II) nitrate in 1,2-dimethoxyethane, mercury(II) acetate in acetic acid, aqueous mercury(II) perchlorate, and mercury(II) perchlorate in alcohol solvents have been investigated; as a result, simple high yield procedures for the conversion of alkyl halides into the corresponding nitrate esters, acetate esters, alcohols and ethers have been developed.     

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals

Summary Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are attended with fair accuracy within 0.02 ml titrant and with reasonable jumps from 60 to 90 mv per 0.1 ml of mercuric nitrate solution or from 170 to 200 mv per 0.1 ml of potassium iodide solution.     

Preparation and Spectral Investigation of Bis[N(2-methyl-phenyl) 4-Nitro-thiobenzamidato] mercury(II), Bis[N(2-methoxy-phenyl) 4-Nitro-thiobenzamidato]mercury(II), and Bis[N(2-chloro-phenyl) 4-Nitro-thiobenzamidato]mercury(II) Complexes

Several preparative routes to bis[N(substituted-phenyl) 4-nitro-thiobenzamidato] mercury(II) complexes are presented, including the reaction of mercury(II) oxide, fluoride, chloride, bromide, cyanide, acetate, and nitrate with N(substituted-phenyl) 4-nitro-thiobenzamide derivatives. ¹ H-NMR, Raman, and IR measurements confirmed the complexation of mercury to sulphur.     

The use of ozone as the primary digestion reagent for the cold vapor mercury procedure

Ozone was tested as an alternative digestion/oxidation system to the permanganate/peroxidisulfate currently used in the cold vapor mercury method. The results indicate that the digestion of comparable size samples to the 'Standard Method' was complete in less than 2 min. A 0.5 ml (10 ppb) sample size was completely oxidized in less than 30 s. The batch system used produced a limit of detection (LOD) for mercury(II) chloride, methylmercury chloride, and phenylmercury acetate of about 0.5 ppb.     

Behavior of mercury(II) salts in electrothermal atomic absorption spectrometry : Application to the Determination of Thiosulfate

Mercury(II) salts have different decomposition temperatures in a graphite tube or tantalum coil used for electrothermal atomic absorption spectrometry. The nitrate, perchlorate and acetate were spontaneously reduced to mercury vapor at room temperature, but the thiosulfate, sulfide, cyanide and bromide were reduced only on heating. Chloride and thiocyanate in a graphite furnace and iodide in a tantalum coil did not give mercury absorbance on heating. Thiosulfate (1–10 × 10^?6 M) was determined by addition to mercury(II) nitrate in acetate buffer, removing the response from the excess mercury(II) nitrate by drying below 100° C in the graphite furnace, and measuring the mercury absorbance on heating, which was proportional to the thiosulfate concentration.     

Cation exchange behaviour of strontium on dowex 50W-X8: Separation from mixtures

The cation exchange chromatography of strontium on Dowex 50W-X8 is described. Nitric acid hydrochloric acid. ammonium chloride, sodium nitrate, ammonium acetate and citric acid were examined as eluants. Strontium can be separated frum important fission products such as caesium zinc, cadmium, silver and zirconium and also from uranium(VI), thorium, bismuth, iron(IIl) copper(Il) and mercury(II).     

The determination of total gaseous mercury in air at background levels

A method is described for the determination of the total gaseous mercury in air at concentrations ranging from ca. 0.1 ng m^-3 to 1μg m^-3. The method is based on the collection of mercury species on gold-coated quartz wool followed by detection with an atomic absorption detector. The collection efficiencies for mercury, dimethylmercury, methyl-mercury(II) chloride, and mercury(II) chloride are nearly quantitative at flow rates up to 10 1 min^-1 and at temperatures up to 50°C. The absolute detection limit of the method is 20 pg of mercury. Under field conditions the precision of the analytical procedure was 14.5% (n=5) for 400-l samples of air and a mercury concentration of 1.5 ng m^-3. Measurements of the mercury distribution in the atmosphere show an ambient background level in clean air masses of 1.0–4.0 ng m^-3.     

Solvation of thiocyanate complexes of mercury(II) by 2-hexylpyridine from aqueous mineral acid solutions

The extraction of trace amounts of mercury(II) by 2-hexylpyridine dissolved in benzene from aqueous mineral acid solutions has been studied. The replacement of chloride, nitrate and sulfate ions by the potentially ambidentate, linear and less basic thiocyanate group offers interestingly high extraction coefficients. The value of the distribution coefficients may be lowered by complexing mercury with oxalate, thiosulfate, acetate or citrate ions in the aqueous phase. The possible mechanism of extraction has been discussed in the light of the results of extraction isotherms and slope analysis data. Distribution coefficients and separation factors of several metal ions relative to mercury(II) are reported for the three mineral acid systems and the possible removal of mercury along with some other inorganic pollutants from aqueous solutions is suggested.     

Characteristics of a new catalytic hydrogen current observed with albumin in the presence of cobalt(III) or (II) at the hanging mercury drop electrode

When the hanging mercury drop electrode (HMDE) is placed in a solution which is 0.1 M in ammonia and 0.1 M in ammonium chloride and about 5 to 10×10^?4M in cobalt(III)-hexamine or cobalt(II) chloride and in very small concentrations of bovine serum albumin (BSA), the protein is slowly adsorbed. When the adsorption is highly incomplete and the HMDE is kept for 30 s at about ?1.05 V vs. SCE, “active cobalt’ is deposited as a complex (Co(0)BSA). This is anodically oxidized at about 0.0 V to unstable Co(I)BSA). When the electrode is then rapidly (500 mV s^?1) cathodized, a catalytic hydrogen current (i_c) with peak at circa ?1.45 V is observed. In this way it is even possible to detect and estimate BSA in concentrations of the order of 10^?12M. A detailed study has been made of the characteristics of i_c under several conditions. “Active cobalt” on the HMDE does not affect Brdi?ka currents. Cystine and cysteine also yield the catalytic hydrogen current i_c under the same conditions as does BSA.     

Linear-sweep polarographic determination of active chlorine in aqueous solutions containing phenylthiourea

The linear-sweep polarographic determination of active chlorine is based on its reaction with phenylthiourea in acidic phosphate buffer (pH 2.5) containing potassium chloride. The product, C,C-diphenyldithiodiformamidine, is strongly adsorbed and then reduced at a mercury electrode with two peaks at about ?0.35 V and ?0.87 V (vs. SCE). In the presence of 0.05 M potassium chloride, the potential of the first peak shifts positively to ?0.31 V. This peak provides high sensitivity and selectivity for the determination of traces of active chlorine. The linear range is 1×10^?7?2.5×10^?5 M and the detection limit is 5×10^?8 M (3.6 μg l^?1). The method is used for the direct determination of active chlorine in tap water. The mechanism of the reaction was studied by cyclic voltammetry, electrolysis and potentiometric titration. The first peak (?0.35 V) is ascribed to the reduction of a mercury (II) sulfide film produced by reaction of the adsorbed dithio product with mercury. In the presence of 0.05 M chloride, the formation of a mixed HgS·xHg₂Cl2 film shifts the peak to ?0.31 V.     

Preconcentration of inorganic mercury with an anion-exchange resin and direct reduction—aeration measurements by cold-vapour atomic absorption spectrometry

Inorganic mercury ions (5–50 ng l^-1) present in natural waters (500 ml) are concentrated on anion-exchange resin (0.2 g; chloride form) in a batchwise operation. The resin is filtered off and introduced into a bubbler containing tin(II) solution. The adsorbed mercury ions are reduced to the metal and vaporized with a stream of air in a closed system. Satisfactory recoveries are obtained for sea waters made 0.1 M in nitric acid, and for river and spring waters also made 0.1 M in nitric acid or 0.01 M in ammonium thiocyanate. The method preconcentrates traces of inorganic mercury ions by an order of magnitude, and is also effective in preventing mercury loss during sample storage.     

A dip-and-read test strip for the determination of mercury(II) ion in aqueous samples based on urease activity inhibition.

A sensitive dip-and-read test strip for the determination of mercury in aqueous samples based on the inhibition of urease reaction by the ion has been developed. The strip has a circular sensing zone that containing two layers: the top layer is a cellulose acetate membrane where urease is immobilized on it; the bottom layer is a pH indicator wafer that is impregnated with urea. The principle of the measurement is based on the disappearance of a yellow spot on the pH indicator wafer. The elapsing time until the disappearance of the spot which depends on the concentration of mercury(II) ion is measured with a stopwatch. Under the experimental conditions, as low as 0.2 ng/ml mercury can be observed with the detection range from 0.2 to 200 ng/ml in water. Organomercury compounds give essentially the same response as inorganic mercury. Heavy-metal ions such as Ag(I), Cu(II), Cd(II), Ni(II), Zn(II), and Pb(II) as well as other sample matrixes basically do not interfere with the mercury measurement.     

Lower limits of the potentiometric titration of perchlorate using a perchlorate ion-selective electrode

Three titrants (tetraphenylarsonium chloride, tetraphenylphosphonium chloride, and tetra-n-pentylammonium bromide) were evaluated for the potentiometric determination of perchlorate. The emf levels were monitored with a perchlorate ion-selective indicator electrode and a double-junction reference electrode. The tetraphenylonium salts were equivalent, yielding the same precision and magnitude of potentiometric breaks. Considerably smaller breaks were obtained with tetra-n-pentylammonium bromide, which, therefore, is not recommended as titrant.The lower limits for the potentiometric titration of perchlorate at ambient temperature were extended to ~0.09 mmol per 50 ml (1.7 × 10^?3N) from the previous 0.25 mmol per 50 ml. If Gran plots are used, they can be further extended to ~0.01 mmol per 50 ml (2.1 × 10^?4N).     

An ultrasensitive catalytic method for metal ions and cyanide-containing organic compounds

Ultrasensitive methods are described for the detection and determination of cyanide-containing organic compounds and of various metal ions. The methods are based either on the hydrolysis of the organic compounds to give cyanide ion, which then catalyzes the reduction of o-dinitrobenzene via formation of the cyanohydrin anion of p-nitrobenzaldehyde, or on the inhibition of this catalytic reaction by silver-(I), mercury(II), copper(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) which form cyanide complexes. By these methods, tetracyanoethylene, p-chlorobenzylidine malononitrile, or benzoyl cyanide (0.1–10 μg/ml) may be determined with a deviation of about 2%, and Ag(i). Hg(II) (0.02–0.2 μg/ml), Cu(II) (0.003–0.030 μg/ml), Co(II) (0.06–0.40 μg/ml) and Ni(II), Zn(II) and Cd(II) (1–10 μg/ml) can be determined with a deviation of about 3%.     

Indirect spectrophotometric determination of chloride by solvent extraction as tris(1,10-phenanthroline)iron(II) thiocyanate

An indirect spectrophotometric method for the determination of small amounts of chloride in fresh waters is described. Chloride ions react with mercury(II) thiocyanate to liberate thiocyanate ions, which can be selectively extracted into nitrobenzene with tris(1,10-phenanthroline)iron(II) chelate cations. The red color (516 nm) of the organic phase measured against a reagent blank is proportional to the initial concentration of chloride ions in the aqueous phase. At least an equimolar amount of tris(1,10-phenanthroline)iron(II) chelate and a 3-fold amount of mercury(II) thiocyanate are needed; the optimal pH range is 1.5–3.5. Beer's law is obeyed over the concentration range of 0.8–5.6 10^-5 M of chloride. The color stability and the apparent sensitivity are better than those of the mercury(II) thiocyanate-iron(III) method. Large amounts of sulphate, phosphate, fluoride, carbonate, acetate, potassium, sodium, and ammonium ions had negligible or no effect ; bromide, iodide, cyanide, sulphide, and thiocyanate interfere.     

Spectrophotometric determination of mercury in soils with triphenyltetrazolium chloride

The formation of the acidocomplex of mercury(II) with triphenyl-tetrazolium chloride is studied spectrophotometrically in water-organic media. The composition of the complex is established as TTC:Hg:I = 1:1:1. The molar absorptivity (255) = (6.45 +/- 0.12) x 10(4) 1 mole(-1). cm(-1) is determined. The selectivity of the reaction is studied and the method for determination of mercury(II) 0.1-0.8 mug/ml is shown. Extraction investigations of the system discussed were carried out. The characteristic values for the extraction equilibrium and the equilibrium in the aqueous phase was determined: extraction constant K(ex) = 3.16 x 10(4), distribution constant K(D) = 20.67, and association constant = 1.53 x 10(3). 5 A rapid and sensitive extractive-photometric method for determination of mercury(II) in soil was developed. The determination was carried out without preliminary elimination of mercury.     

Fluorescence and crystal structures of new mercury(II) macrocyclic N-heterocyclic carbene complexes with ether chains

Polyerther-linked mercury(II) carbene complexes are synthesized by the reaction of carbene precursores with mercury(II) acetate. The binuclear carbene complexes with the chloride ion linkage are easily prepared by the reaction of mononuclear mercury carbene complexes with tetrabutylammoium chloride. The crystal structures reveal that the fluorescence of mercury complexes are related to the coordination mode of the ligands.