A precise,direct, heterometric micro-determination of mercury with diethyldithiocarbamate in excesses of metals ethylenediaminetetraacetate solutions

0.3–1.2 mg mercury in 20 ml aqueous solution is analysed with sodium diethyldithiocarbamate. The solution may contain any amount of other bivalent metal or iron (III), bismuth or thorium. A corresponding excess of ethylenediaminetetraacetate and ammonia must then be added. The error is 0–2%.     

A quick and precise heterometric determination of iron with aluminon in excesses of foreign metals

A method is presented for the heterometric determination of 0.2–0.5 mg ferric iron with aluminon. The analysed solution may contain excesses of coloured or colourless foreign bi-or trivalent Cations. The latter may make up ? 99.5% of the total metal content. The working conditions were studied. The determination lasts 10–15 minutes and the error is 0–2%.     

A quick and precise heterometric microdetermination of traces of palladium in metals with nitron

A heterometric study was made of the reaction between palladium chloride and nitron in thiocyanate solutions in the presence of excesses of various masking agents.A method is presented for the hetorometric determination of ~0.5 mg palladium in 20 ml aqueous solution with nitron, which can be carried out within 5–10 mn. The solution to be analysed may in general contain ~99.5% of the following foreign metals as cations: Ca⁺², Ba⁺², Mg⁺², Zn⁺², Mn⁺², Co⁺², Ni⁺², Al⁺³, Fe⁺³, Cr⁺³, UO₂⁺², Cu⁺², Cd⁺², Hg⁺², Pb⁺², Tl⁺, Sb⁺³,Bi⁺³, Th⁺⁴, Ce⁺³ and ZrO⁺². The error is between 0 and 1%.     

A heterometric micro-determination of lead with sodium diethyldithiocarbamate

The reaction between lead and sodium diethyldithiocarbamate is studied hcterometrically. The influence of the milieu, conditions of acidity and of different complexing agents, was studied. 0.02–0.04 mg lead per ml of solution can be determined either alone or in the presence of large excesses of other metals. A titration is carried out at 20°C in 8–15 minutes with an error of 0.0–1.0%. The analysed solution may contain ~ 99.5% of the following cations: Ca⁺². Sr⁺², Ba⁺², Mg⁺² Zn⁺², Mn⁺², Ni⁺², Co⁺², Al⁺³, Cr⁺³, Fe⁺³, Cd⁺². Cu⁺², Sb⁺³, Hg⁺², Ag⁺.     

A rapid and precise heterometric method for the determination of traces of phosphoric or arsenic acid with nitron and molybdate

The precipitation of phosphomolybdate or arsenomolybdate with nitron was studied by heterometry at various acidities. A rapid and precise heterometric method is presented for the determination of 0.03–0.08 mg of phosphorus (or 0.06–0.16 mg of arsenic). Foreign salts can be tolerated often in 100–200-fold molar amounts. No interference is caused by Ca, Ba, Mg, Zn, Cr³⁺, Fe, Mn, Co, Ni, Al, U(VI), Cd, Cu, Pb, Hg²⁺, Ag, Zr or Th. Iodide, silicic acid, tartrate or pyrophosphate can also be tolerated.The titration time is 10–15 min and the error is usually less than 1%.     

A fast and precise heterometric determination of thallium(I) with sodium tetraphenylborate

The heterometric titration of thallium(I) with sodium tetraphenylborate, at various pH values and in the presence of salts and different complexing agents, was studied; 1.5–0.75 mg of thallium(I) could be determined within 3–4 min, and the error was negligible. Of the complexing agents studied, sodium pyro- and tripolyphosphate had a specific influence, raising the sensitivity about 4-fold, and no interference was caused by the presence of 30–130-fold molar excesses of the following metals: Ca, Mg, Zn, Mn, Co, Ni, Fe(III), Al, UO₂(II), Cd, Cu(II), Pb, Bi(III), Ag, V(V), Mo(VI) W(VI) and Th. Pd, Au(III) and Pt(IV) did not interfere.     

Direct heterometric microtitration of copper with oxine in the presence of other metals

A new heterometric method is presented for a rapid micro-determination of copper with oxine. 1 mg of copper in 20 ml of solution may be determined with an accuracy of 0-I-0 microgram per ml. The solution may contain 95% Me or Al, 98% Zn, Mn, Co. Ni, Cd or Cr and 99-8% Pb. The determination is made at room temperature and takes 10–20 minutes.     

The heterometric micro-determination of copper with quinaldic acid in the presence of foreign metals

1. During the heterometric determination of copper, bivalent cations may be present in solution in large excesses (>95%) and no complexing agents are necessary. In the presence of zinc, excesses of citrate of tartrate must be added. Error: 0—2 %. 2. Excesses of chromium or aluminum (>95%) are without effect. In the presence of an excess of iron (>95%) the determination is made by the addition of tartrate which increases the maximum density value obtained. Error: 0—3%.     

A precise heterometric micro-determination of lead or citric acid

A new heterometric method was presented for the micro-determination of lead with alkal) citrate or for the micro-determination of citric acid with lead nitrate. The analysed solution may contain 0.1–1.0 mg of lead or citric acid per one ml. The error lies between zero and 1 % in 50% alcoholic solution.     

A quick heterometric microdetermination of calcium as sulfate in excesses of magnesium or other supplements

An alcoholic solution of calcium chloride (2–4 mg Ca) which contains ≧ 95% magnesium as chloride besides other impurities can be titrated directly heterometrically with a standardized alcoholic sulfuric acid solution. The titration lasts about 15 minutes at room temperature. Error 0–2%.     

Extraction-spectrophotometric determination of traces of antimony in copper and lead metals and in lead-base alloy with pyrocatechol violet and tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of antimony in copper and lead metals and in lead-base alloy. Optimal conditions have been established for the extraction and determination of antimony. Antimony (III) is extracted from a potassium iodide—sulfuric acid or a hydrobromic—sulfuric acid medium with toluene and converted to an antimony-pyrocatechol violet (PV) complex. The complex is then extracted with tri-n-octylamine (TOA) and the absorbance of the resulting ternary Sb(III)—PV-TOA complex is measured at 555 nm. As little as 0.5 p.p.m. of antimony in copper metal and 0.2 p.p.m. of antimony in lead metal and lead-base alloy can be determined.     

Square-wave polarographic determination of traces of copper in water

Summary A square-wave polarograph [3] has been used to determine trace amounts of copper in potable water and in Iowa River water. By using a combination of sodium chloride (1.0 M) and perchloric acid (0.07 M) as a supporting electrolyte under acidic conditions (pH<1), 2 ppb copper could be determined in the samples without and with preconcentration. Copper in the samples was determined with reproducibility of ± 0.13 ppb and so this technique is more reliable than a more used determination of complex salts by atomic absorptionspectrophotometry.

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Bestimmung von Spuren Kupfer in Wasser durch Square-Wave-Polarographie

Zusammenfassung Ein früher [3] beschriebener Square-Wave-Polarograph wurde zur Spurenbestimmung von Kupfer in Trink- und Flußwasser (Iowa River) benutzt. Der verwendete Grundelektrolyt war 1,0 M an NaCl und 0,07 M an HClO₄ (pH<1). Noch 2 ppb Cu konnten mit und ohne Vorkonzentrierung bestimmt werden. Die Reproduzierbarkeit war ± 0,13 ppb. Das Verfahren ist zuverlässiger als die Bestimmung über Komplexsalze durch Atomabsorptionsspektrophotometrie.

One of the authors wishes to thank Prof. Dr. F. Duke for the acception at the University of Iowa and Prof. Dr. B. Teak for the discussion.     

The diethyldithiocarbamate of mercury: composition,structure and analytical application: A heterometric study

0.3–1.2 mg of mercury (= Hg(NO₃)₂) in 20 ml aqueous solution, can be titrated heterometrically with sodium diethyldithiocarbamate (NaCBM).Vice versa, 0.5–1.0 mg NaCBM in 20 ml aqueous solution can be titrated heterometrically with mercuric nitrate.In both cases the error is mostly equal to zero. The insoluble Hg(CBM)₂ is obtained in both cases.     

Copper salicylaldoxime and its use in the heterometric microdeterminatton of copper in the presence of foreign metals

1. The initial precipitation of copper-salicylaldoxime occurs at pH~1.5.Between pH 1.5 and 3.0, the precipitation is incomplete. A complete precipitation occurs in the pH-region of 3–10. Between pH 10.1 and 10.7 the precipitate redissolves At higher pH's a clear solution is obtained. 2. The solubility of copper salicylaldoximate is about ten times greater in 0.01M sulfuric acid (~0.5·10^-4 mol) than in 0.1M acetic acid. 3. In 10 ml of 0.1M acetic acid solution in the presence of ~99% foreign bivalent metals, one mg copper could be determined heterometrically with an error of 1–2%. 4. In the presence of ~95% alumin um or chromium, either citrate or tartrate (0.2M) were used as masking agents. In the presence of iron (~ 95%), clear end-points were obtained only with citrate. One mg of copper could be determined with an error of 0–3%. 5. Whichever pH is used, copper is not precipitated in the presence of ethylenediaminetetraacetate.     

Extraction-spectrophotometric determination of traces of bismuth in lead,copper and nickel metals,and in copper-base alloys with tri-n-octylamine

A rapid and sensitive spectrophotometric method has been developed for the determination of bismuth in lead, copper and nickel metals, and in copper-base alloys. Optimal conditions have been established for the extraction and determination of bismuth. Bismuth is extracted with a benzene solution of tri-n-octylamine in the presence of hydrobromic acid and the absorbance of the extract (bromo-complex of bismuth) at 380 nm is measured. As little as 0.5 p.p.m. of bismuth in these metals and alloys can be determined.     

Ion chromatographic determination of traces of some oxoanions with direct spectrophotometric detection

Investigation of the use of a single analytical procedure using the non-suppressed ion chromatographic method with direct spectrophotometric detection capable of determining eight oxoanions simultaneously is presented in this paper. Potassium phosphate was found to be the most suitable eluent for UV absorbance detection at 205 nm. Oxoanions AsO³⁻₃, SeO²⁻₃, AsO³⁻₄, VO⁻₃, SeO²⁻₄, WO²⁻₄, MoO²⁻₄ and CrO²⁻₄ were detected at ng ml⁻¹ levels with well separated peaks at retention time < 25 min. The working range is in the range ng ml⁻¹ to 50 μg ml⁻¹. The method is sufficiently sensitive to determine As (V), V(V), Mo(VI) and Cr(VI) anions (and NO⁻₃) directly in a river water sample. The accuracy of these results was established by comparison with conventional atomic absorption methods.     

Spectrophotometric extractive titrations for the determination of traces of metals

A modification of extractive titrations, spectrophotometric end-point determination, is proposed. There is no need to discard the organic layer after each extraction because specially constructed titration cells are used. Precise, rapid and selective determination of microgram amounts of single cations, and in favourable cases pairs of cations, is possible.     

A selective lon-exchange separation and spectrophotometric determination of traces of copper in silicate rocks

Summary A combined cation-exchange separation-spectrophotometric procedure has been worked out for the accurate determination of traces of copper in silicate rocks. Silicates are opened up with sulfuric and hydrofluoric acids. The residue is taken up into a 0.5 M hydrochloric acid −0.05 M oxalic acid −1% hydrogen peroxide solution and loaded on a strongly acidic cation-exchange resin column. Polyvalent ions including ferric ions do not adsorb on the column, while copper (II) retains together with divalent metal ions as well as aluminum (III). Copper (II) can selectively be eluted by a small volume of 0.05 M thiosulfate solution. This fraction is sufficiently pure to allow a direct spectrophotometric determination of copper with Na-DDTC without the addition of tartrate and EDTA as masking agents. Quantitative results are quoted for the determination of copper in international standard rocks of the Geological Survey of Japan (GSJ) and the U.S. Geological Survey (USGS).     

Simultaneous determination of traces of heavy metals by solid-phase spectrophotometry

A coupling sensitive solid phase spectrophotometric (SPS) procedure for determination of traces of heavy metals (Me-SPS) and multicomponent analysis by multiple linear regressions (MA), a simple methodology for simultaneous determination of metals in mixtures was inaugurated. The Me-SPS procedure is based on sorption of heavy metals on PAN-resin and direct absorbance measurements of colour product Me-PAN sorbed on a solid carrier in a 1-mm cell. This methodology (Me-SPS-MA) was checked by simultaneous determination of metals in synthetic mixtures with different compositions and contents of metals important in pharmaceutical practice: Zn, Pb, Cd, Cu, Co, and Ni. Good agreement between experimental and theoretical amounts of heavy metals is obtained from the recovery test (78.3–110.0%). The proposed method enables determination of particular metal ion at the ng mL⁻¹ level and it was successfully applied to the determination impurities from heavy metal traces in pharmaceutical substances (Cu in ascorbic acid, Pb in glucose, and Zn in insulin). The proposed procedure could be possible contribution to the development of pharmacopoeial methodology for a heavy metals test.