The heterometric microdetermination of mercury with mercaptobenzthiazole in the presence of an excess of foreign metals

1. A general method is presented for the determination of 1–2 mg mercuric mercury, in the absence of complexing agents, in 20 ml solution, with an error of 0–3 %. The solution may contain: Ca, Ba, Mg, Zn, Mn, Ni, Co or Cd as nitrate of sulphate in a concentration of 0.2M. The concentration of Pb should be <0.1M and that of Al, Cr or Fe ?0.05M. 2. A special method is presented for the determination of mercury (1–2 mg Hg in 20 ml) in the presence of large excesses of bismuth (?98%) by using ethylendiammetetraacetate. Error 0–3 %. 3. A method is presented for the determination of mercury in excesses of copper in an acetic acid solution which contains ethylendiaminetetraacetate. 4. A special method is presented which permits the determination of 1–2 mg mercury in 30 ml solution which contains large excesses of copper (up to 98% or more). The titration is carried out in an alkaline solution of trisodiumcitrate. The titration proceeds rapidly. Error 0–2%.     

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%.     

Heterometric microtitration of copper with oxine

A new heterornetric method is presented for a quick micro-determination of copper with oxine. A few tenths of a mg of copper in 20 ml of solution may be determined with an accuracy of a few tenths of a microgram per nil. The determination is made at room temperature and takes 10–15 minutes.     

Micro-heterometric determination of cadmium with sodium diethyldithiocarbamate

0.5 mg of Cadmium in 20 ml aqueous solution can be determined heterometrically at 20°C with sodium diethyldithiocarbamate. The solution may contain 99–99.9% of Ca, Ba, Mg, Zn, Mn, Al, Cr(lll), Fe(III), Sb(III) or Pb. Titration time: 10–15 min. Error generally 0–1%.     

Application of fast grey RA to the spectrophotometric determination of copper in serum of Egyptian camels

The ortho-ortho hydroxy azo dye 15690-Solochromate Fast Grey RA, C.I. mordant black 15 (reddish navy-bluish black) has been used as a reagent for the successful estimation of copper in serum of camels. To determine copper, extract 5 ml of serum with 2, 1, and 1 ml of 20% trichloroacetic acid; dilute the combined extracts to 100 ml; to 5 ml of the diluted extracts add 2 ml of 0.2 M ascorbic acid and 3 ml 0.005% aqueous solution of the reagent; after complete development of the pink color of Cu-FG (15 minutes) measure the extinction at 555 mμ.     

The heterometric microdetermination of mercury of mercaptobenzthiazole

The heterometric determinations of murcury or mercaptobentlnazole are very sensitive reactions. An aqueous or a dilute alcoholic solution is used and the titration may lie carried out at pH 2–10. If meicaptobenzlhiazole is determined, two analytical end-points are obtained : the first gives an estimate, the second gives the precise end-point. In all cases, the insoluble Hg(MBT)₂ is obtained, The presence of larger amounts of strong acids is disadvantageous Large amounts of acetic acid cause distuibances in aqueous solution; dilute alcoholic .solution is therefore used The theoretical end-point is obtained by the intersection of two lines. In acid solution a horizontal maximum density line is obtained at the end ot the reaction, in alkahne solution a maximum point is obtained instead. 1–2 mg mercury or meicaptobenzthiazole may be determined in 20–30 ml solution with an error of 0–3% 'Ihe titration time is 10–20 mniutes     

Novel UV assay for protein determination and the characterization of copper-protein complexes by mass spectrometry

A very simple, highly selective and sensitive assay of proteins based on the biuret absorption in the ultraviolet region has been developed. The well-known biuret assay is based on the reaction of proteins with copper ions under strong alkaline conditions to form a copper-protein complex. Yet, copper ions may seriously interfere with the determination if the measurement is made in the UV range. In the present approach, proteins mobilize copper ions from insoluble salts at different pH values, and the copper-protein complexes are investigated by UV spectrophotometry and mass spectrometry. Upon using copper phosphate, free copper ions do not interfere with the determination from 540 to 240 nm. Copper absorbance slowly increases from 240 to 190 nm where a blank with the reagents is recommended. A maximum absorbance for the copper-protein complex was found at 226 nm and high pH value. The stoichiometries of the copper-protein complexes measured directly with a mass spectrometer are pH dependent: half of the peptides without any histidine residue chelate just a single Cu²⁺ ion at pH 7.4 but each such peptide mobilizes from 1 to 6 Cu²⁺ ions at pH 10.3. To determine proteins, 1-1.5 ml of 1.8% KOH solution with 0-20 μg ml⁻¹ protein is treated with 25 mg of copper phosphate powder. The mixture is powerfully stirred, centrifuged, and the absorbance of the supernatant is measured at 226 nm in 1 cm quartz cuvettes against a blank of the reagents. The color system obeys Beer's law in the range 0.1-20 μg ml⁻¹ protein at this wavelength. The molar absorptivity value proved to be a characteristic of each protein being analyzed. Therefore, individual proteins should be used to plot calibration curves. This assay proved to be over 100 times more sensitive than the classical biuret procedure. The method is highly selective and the determination is little affected by the presence of other substances. All other important analytical parameters were studied and practical applicability of the method has been verified by the analysis of some biological materials.     

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.     

Spectrophotometric determination of trace copper in water samples with thiomichlersketone

A simple and sensitive spectrophotometric method for determination of trace copper in water samples is proposed. In the presence of pH 4.6 HAc-NaAc buffer solution and surfactant polyethylene octyl phenyl ether (OP) medium, copper reacts with thiomichlersketone (TMK) to form a stable 1:4 complex. The complex Cu(II)-TMK-OP shows maximum absorbance at 500 nm with a molar absorptivity value of 5.7x10(4) l mol-1 cm-1. Beer's law is obeyed for copper concentrations in the range of 0-15 microg/25 ml. The average recovery of copper is between 95.8 and 106%. The method has been applied for determination of trace copper in different water samples with satisfactory results.     

原子荧光光谱法测定铜合金中铋元素含量方法改进

基于原子荧光光谱法测定铋元素时检出限低、测定结果稳定且准确等优点,研究原子荧光光谱法测定铜合金中铋元素含量的方法。在标准系列中加入相近浓度的铜元素标准溶液,原子荧光光谱法测定铜合金中铋元素含量。称取0.1 g样品,加入10 mL硝酸溶解,10%硫脲-5%抗坏血酸溶液7.5 mL预处理样品。在20μg/L的铋标准溶液中加入6 mL浓度为1000μg/mL的铜元素标准溶液。结果表明:在0~20μg/L范围内,该方法线性关系良好,线性方程为I=138.1670c+43.8572,相关系数为0.9996,所测定的样品中铋元素含量的相对误差在-4.3%~7.7%之间,精密度在0.4%~4.7%之间。原子荧光光谱法可作为铜合金中铋元素含量测定的方法。     

The Stability of Monolith CuZSM-5 Catalysts for the Selective Reduction of Nitrogen Oxides with Hydrocarbons: I. Synthesis and Characterization of Bulk CuZSM-5 Catalysts

The effects of ion-exchange conditions (the pH, the copper concentration in solution, and the solution-to-zeolite volume ratio) and the Si/Al atomic ratio of HZSM-5 zeolite on the concentration and state of copper in bulk CuZSM-5 catalysts and on the catalytic activity in the selective reduction of NO with propane were studied. It was found that the concentration and state of copper in the catalysts essentially depend on the pH of the solution used for ion exchange and on the copper concentration in this solution. An increase in the solution-to-zeolite volume ratio has almost no effect on the above characteristics. Regardless of the Si/Al atomic ratio of zeolite and of the pH of solution, a maximum activity (NO conversion) of the resulting catalyst is attained even at an exchange level (Cu/Al) close to 100% (80–140%). The absolute value of this catalytic activity depends only on the reaction temperature and is equal to 22–31% at 300°C or 85–97% at 400–500°C. The above exchange level is maximally attainable at pH 6 in the chosen range of copper acetate concentrations in solution (2–10 mg/ml accounted as CuO). An increase in the pH of ion exchange up to 100% allows a wider variation in the exchange level and the state of copper in the zeolite with the same range of copper concentration in the solution. However, at Cu/Al 100% (up to 430%), the catalyst activity is independent of the exchange level. The state of copper in freshly prepared samples affects the stability of the catalysts in storage. In turn, the state of copper depends on ion-exchange conditions and the Cu/Al ratio.     

Bulk acoustic wave sensor for the ion chromatographic determination of copper in human plasma

By using ion chromatography with series bulk acoustic wave detection, a method for the determination of copper in human blood plasma has been developed. The advantages of the good selectivity of ion chromatography and the highly sensitive response of SBAW have been combined to improve detection limit, accuracy and reproducibility. The detection limit (3) of the method to copper is 0.3 g/ml. The relative standard deviation for the determination of 1.0 g/ml of copper is 2.1% (n=7). For the IC analysis, the analytical column is a Shim-pack IC C1 column, and the mobile phase is 4.0 mM tartaric acid/2.0 mM ethylenediamine solution with pH 4.2. This system has been applied to the determination of Cu in blood plasma from healthy people or patients with renal failure.     

The determination of copper in sea water by atomic absorption spectrometry with a graphite atomizer after elution from chitosan

Copper in sea water was determined by passing 1 1 of persulphate-pretreated sea water through a 30×3 mm chitosan column, and eluting with 20 ml of a 1% solution of 1,10-phenanthroline, or with 20 ml of 1 M sulphuric acid. Copper was determined in the eluates by hot graphite atomic absorption spectrometry. The result for Adriatic sea water (Ancona, Italy) was 6.06±0.56 μg Cu 1^?1. Diethylaminoethylcellulose, p-aminobenzylcellulose and Dowex A-1OO were also tested; Dowex A-100 collects only a minor part of the copper present in sea water.     

Heterometric micro-determination of cobalt with α-nitroso-β-naphthol in the presence of foreign metal

A heterometric method is presented for the determination of cobalt in solutions or other metals. The cobalt comprises 0.1–3% of the total metal content. The amount of cobalt determined is 0.2–0.5 mg in 20 ml of solution. The titration generally takes 10–20 minutes at room temperature, and the error is 0–3%.     

Adsorptive voltammetric determination of copper with a benzoin oxime graphite paste electrode

A method for the determination of trace amounts of copper with a chemically modified carbon press-formed electrode is described. Copper could be accumulated at the electrode by complexing with benzoin oxime in ammonia buffer, then reduced at a constant potential of −0.4 V (vs. SCE) in nitric acid solution. Finally, a well-defined stripping peak could be obtained by scanning the potential in a positive direction. The response depends on the concentration of copper and accumulation time. For an accumulation time of 5 min the detection limit is about 1 ng/ml and the linear range is from 2 ng/ml to 4000 ng/ml, with a relative standard deviation of 5%. Many common metal ions have little or no effect on the determination of copper. The recommended procedure was applied to the determination of trace amounts of copper in natural water, and the results are in agreement with those of atomic-absorption spectrometry.     

Chemical separation and determination of chromium(VI) from small quantities of cationic impurities

Summary A procedure has been worked out for the chemical and radiochemical separation of traces of chromium(VI) from its mixtures with copper, nickel, zinc and cadmium. The method is based on selective deposition, under predetermined experimental conditions, of the cations on silica gel, leaving the total quantity of the chromium in solution. The procedure has been used for the complete analysis of binary mixtures of Cr(VI) with copper and nickel. The separated chromium in solution is determined iodometrically (1 to 5 mg) or spectrophotometrically (5 to 20g). The deposited cationic component (0.2 to 0.5 mg) is brought into solution by elution with ca. 20 ml of 1N HCl, and determined by the complexometric method.

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Zusammenfassung Ein Verfahren zur chemischen und radiochemischen Trennung von Chrom(VI)-spuren aus Gemischen mit Kupfer, Nickel, Zink oder Cadmium wurde ausgearbeitet. Es beruht auf der unter bestimmten Versuchsbedingungen selektiven Bindung dieser Kationen an Kieselgel, während das gesamte Chrom in Lösung bleibt. Das Verfahren wurde für die vollständige Analyse binärer Gemische von Chrom(VI) mit Kupfer bzw. Nickel verwendet. Das abgetrennte Chrom wurde jodometrisch (1 bis 5 mg) oder spektralphotometrisch (5 bis 20yg) bestimmt. Das absorbierte Kation (0,2 bis 0,5 mg) wird mit zirka 20 ml n Salzsäure eluiert und komplexometrisch bestimmt.

     

Heterometric micro-determination of uranium (VI) by precipitation with ferrous cyanide

A method is presented fur the determination of uranium (VI) by a heterometric titration with K₄[Fe(CN)₆]. 0.5–3 mg of uranium in 10 ml solution may be determined in 15–20 minutes. The error amounts to 0–3%.     

Photometric determination of copper with N-(dithiocarboxy)sarcosine after preconcentration with amberlite xad-2 resin

The copper(II) chelate of N-(dithiocarboxy)sarcosine (DTCS) is sorbed on a column of Amberlite XAD-2 resin from a pH-7 phosphate solution (0.1M) and stripped with a pH-9.0 ammonia solution (0.2M) in 60% methanol. The absorbance of the eluted chelate is measured at 432 nm against water. Sodium nitrilotriacetate, sodium tripolyphosphate, and EDTA can be used to mask interfering metal ions other than mercury(II), the resulting complexes not being sorbed on the resin. The mercury(II) chelate of DTCS is also sorbed on and stripped from the column along with the copper chelate, but does not interfere in the photometric determination of copper, because it is colourless. The recovery of copper(II) is quantitative from test solutions (50–500 ml) of any salinity up to that of sea-water. Concentration factors of up to about 20 are obtained. The method is highly selective for copper and can be applied to its determination in sea-water.     

Preconcentration of copper with the ion-pair of 1,10- phenanthroline and tetraphenylborate on naphthalene

A solid ion-pair material produced from 1,10-phenanthroline and tetraphenylborate on naphthalene provides a simple, rapid and fairly selective means of preconcentrating copper from up to 1000 ml of aqueous samples (about 200-fold concentration is possible). Copper is quantitatively adsorbed in the pH range 1.6–10.4 at a flow rate of 3 ml min^?1. The solid mass (0.2 g) is dissolved from the column with 5 ml of dimethylformamide (DMF) and copper is measured by atomic absorption spectrometry at 324.7 nm. Linear calibration is obtained for 2–28 μg of copper in 5 ml of DMF solution. Replicate determination of 14 μg of copper gave a mean absorbance of 0.220 (n = 7) with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.093 μg ml^?1. After optimization, the method was applied to determine trace copper in standard reference materials, natural waters, beverages and hair.     

Factorial design for optimization of experimental variables in preconcentration of copper by a chromotropic acid loaded Q-Sepharose adsorbent

An agarose-based anion exchanger (Q-Sepharose) was loaded with chromotropic acid (CTA) and used for column preconcentration and determination of copper by flame AAS. Preliminary experiments indicated that a sample pH of 5.7-6.5 is best suited for accumulation of copper and a 2.5 ml portion of a 0.02 mol l⁻¹ HCl solution can efficiently desorb the analyte from the column. An incomplete factorial design was used for optimization of five different variables that affect recovery of copper. The results indicated that ionic strength, pH and sample volume variables are the most important effects, respectively. Hence, these variables and their possible interactions were studied more carefully. In optimized conditions, the column could tolerate up to 0.18 mol l⁻¹ sodium nitrate in the matrix. A 5 ml portion of a 0.02 mol l⁻¹ CTA was sufficient for loading of a 0.5 ml column prior to preconcentration of copper from a 150 ml sample solution. Matrix ions of Ca²⁺, Mg²⁺, Na⁺ and K⁺ and potentially interfering ions of Pb²⁺, Ni²⁺, Cd²⁺, Co²⁺, Zn²⁺ and Mn²⁺ with relatively high concentrations did not have any significant effect on the recovery of the analyte. A preconcentration factor of 60 and a detection limit of 1.0 μg l⁻¹ was obtained for the determination of copper by the flame AAS method. A precision better than 2.5%, expressed as R.S.D., was also achieved. Application of the method to tap water and two different river water samples resulted in values well confirmed by direct determinations with ET-AAS.