KMnO4-OP Chemiluminescence system for FIA determination of hydrogen peroxide

A fast and simple KMnO₄-OP chemiluminescence system for flow-injection analysis of hydrogen peroxide is described. When a mixture of sample and OP is injected into acidic KMnO₄, solution in a flow-cell, strong chemiluminescence occurs. The response is linear to the concentration of hydrogen peroxide in the range of 1.0 × 10^–8 to 6.0 × 10^–5 mol/l with 0.1 mol/l permanganate, and the upper limit of linear response could be extended to 6 × 10^–3 mol/l by increasing the permanganate concentration. The relative standard deviation of the method is between 1.6 and 2.3%. The detection limit is 6.0 × 10^–9 mol/l. This method is suitable for automatic and continuous analysis and has been successfully tested for determination of hydrogen peroxide in rain water. The chemiluminescence intensity was found to be remarkably enhanced in the presence of the OP micellar system.     

Simultaneous determination of sodium dodecyl sulphate and sodium linear-dodecylbenzenesulphonate with 1-stearyl-4-(4-aminonaphthylazo)-pyridinium bromide by spectrophotometry

A rapid and sensitive spectrophotometric method for the simultaneous determination of sodium dodecyl sulphate (SDS) and sodium linear-dodecylbenzenesulphonate (DBS) with 1-stearyl-4-(4-aminonaphthylazo)-pyridinium bromide (SAPB) is described using the difference at the maximum absorption wavelength of the SDS- and the DBS-ion associate. SDS and DBS have been determined independently by measuring their respective absorbances at the maximum absorption wavelength. The apparent molar absorptivities of the SDS- and the DBS-ion associate are 8.0×10⁴ l mol^–1 cm^–1 at 445 nm and 4.5×10⁴ l mol^–1 cm^–1 at 424 nm, respectively. The calibration graph for SDS is linear in the range from 0.1 to 1.0×10^–6 mol/l in the presence of 1.2×10^–6 mol/l DBS and for DBS from 0.8 to 2.0×10^–6 mol/l in the presence of 8.0×10^–7 mol/l SDS. The relative standard deviation (n=15) for 8.0×10^–7 mol/l SDS is 3.4% and for 1.6×10^–6 mol/l DBS 2.1%. The proposed method has been applied to the simulatenous determination of SDS and DBS in river water samples.     

Spectrofluorimetric determination of benzodiazepinooxazoles

Summary A study of fluorescence properties of Cloxazolam and Oxazolam has been carried out. pK_a-values were calculated and a spectrofluorimetric method was developed in acidic hydroalcoholic medium for the determination of the drugs. The fluorescence intensity was linear with the concentration up to at least 6.00×10^–6 mol/l for Cloxazolam and 5.17×10^–6 mol/l for Oxazolam. Detection limits obtained were 2.91×10^–8 mol/l and 4.56×10^–8 mol/l for Cloxazolam and Oxazolam, respectively. Spectrofluorimetric methods were applied to the determination of both drugs in pharmaceuticals and errors lower than 2.5% were obtained. Spectrophotometric determination methods were also developed.     

Determination of traces of iron with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse polarographic method for the determination of iron employing the catalytic maximum wave has been studied. A well-defined differential pulse polarographic peak for iron(III) in Britton-Robinson buffer solution containing 50 mol/l N-(2-hydroxyethyl) ethylenediamine N,N,N-triacetic acid (HEDTA) and 5 mmol/l KBrO₃ is observed in the potential range from +0.2 to –0.3 V vs. SCE. The peak current is very large compared to that of the Fe(III)/EDTA complex, being proportional to the concentration of iron(III) between 1.00×10^–8 and 3.58×10^–6 mol/l under optimum conditions. The relative standard deviations for 3.58×10^–7 mol/l and 1.79×10^–6 mol/l iron(III) were 1.38 and 0.54%, respectively (n=5), and the calculated detection limit was 5.2×10^–9 mol/l iron(III). The method has been applied to the determination of iron in fresh snow and rain waters.

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Spurenbestimmung von Eisen mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Das Verfahren beruht auf der Tatsache, daß in Britton-Robinson-Puffer (mit 50 mol/l HEDTA und 5 mmol/l KBrO₃) im Potentialbereich von +0,2 bis –0,3 V gegen SKE ein gut definierter puls-polarographischer Peak für Eisen(III) auftritt. Der Peakstrom ist im Vergleich zu dem des Fe(III)/EDTA-Komplexes sehr groß und ist unter optimalen Bedingungen im Konzentrationsbereich von 1,00·10^–8 bis 3,58·10^–6 mol/l der Eisen(III)-Konzentration proportional. Die relative Standardabweichung beträgt 1,38% bzw. 0,54% (n=5) für 3,58·10^–7 mol/l bzw. 1,79·10^–6 mol/l Fe(III). Die berechnete Nachweisgrenze liegt bei 5,2·10^–9 mol/l Fe(III). Das Verfahren wurde zur Eisenbestimmung in Schnee- und Regenwasser eingesetzt.

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This work was supported in part by a Grant-in-Aid for Scientific Research from Hokkaido-prefecture, 1982.     

Studies on the voltammetric behaviour of salicyl fluorone and gallium-salicyl fluorone complex

In the NH₄Cl supporting electrolyte, within the pH range from 1 to 5, an irreversible adsorptive reducing wave of salicyl fluorone(SAF) was obtained. The electrode process was verified as follow: On the surface of mercury electrode, the adsorption of SAF obeys Frumkin isotherm.In 0.2 mol/l potassium hydrogen phthalate/HCl buffer solution, at pH 3.0, the sensitive adsorptive complex wave of Ga-SAF was obtained by linear sweep voltammetry. The composition of the electroactive complex was determined as Ga:SAF = 11. The peak height of the complex is proportional to the concentration of Ga(III) in the range of 1.5 × 10^–9 to 6.0 × 10^–7 mol/l, the detection limit is 1.0× 10^–9 mol/l. The proposed method has been applied to the determination of gallium content in aluminium alloys.     

Simultaneous determination of Dy, Eu, Sm and Tb by laser induced-time resolved derivative fluorescence

Summary In this paper, a highly sensitive laser fluorimetric system coupled with microcomputer is described and the laser induced fluorescence of ternary complexes formed by RE (RE = Dy, Eu, Sm, and Tb) with TFA (Trifluoroacetylacetone) and TOPO (Trioctylphosphine oxide) is studied. The emission spectra (excited at 310 nm) of the TFA/TOPO complexes of the rare earths show that the strongest emission bands are located at 560 nm for Dy, 614 nm for Eu, 644 nm for Sm, and 544 nm for Tb. Thus, it is preferable to establish the detection at these wavelengths. However, it is difficult to detect one single component with high selectivity in a mixed sample, because the emission bands in the 500–700 nm region overlap. In order to improve the selectivity, time resolved and derivative techniques are introduced. The effects of foreign ions on the determinations of these four elements are investigated. The linear relationships between derivatives and the concentrations of Dy, Eu, Sm, and Tb are 5×10^–8 to 5×10^–6 mol/l, 5×10^–10 to 1×10^–7 mol/l, 1×10^–9 to 2×10^–6 mol/l, and 2×10^–9 to 2×10^–6 mol/l, respectively. The method was used to determine simultaneously the amounts of Dy, Eu, Sm, and Tb in their mixtures and yttrium oxide without pre-separation.     

Selective method for the determination of gold by anodic stripping voltammetry

A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au³⁺ reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5×10^–8 to 1×10^–6 mol/l. The relative standard deviation for 2×10^-7 mol/l HAuCl₄ was 4.2% (n=5). The detection limit was 4×10^-9 mol/l. The accuracy of the method was verified by the determination of gold in reference materials.     

Determination of morphine in process streams by sequential injection analysis with chemiluminescence detection

A procedure for the determination of morphine in process streams by sequential injection analysis based on the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium hexametaphosphate is presented. The chemiluminescence emission has been monitored using an in-house detection system which consisted of a fibre optic flowthrough cell and a sensitive, low dark current, photomultiplier tube. The calibration graph (range 2 × 10^–8 to 1 × 10^–4 mol/l) was not linear over the entire range of concentration, with a polynomial equation of best fit of y = 1.0 × 10¹⁵ x³ – 2.2 × 10¹¹ x² + 1.3 × 10⁷ x – 8.3. The calibration function approximates linearity over the concentration range 2.5 × 10^–6 to 3.0 × 10^–5 mol/l where the slope of the log-log plot is 1.09 ± 0.16. The detection limit was estimated at about 10^–8 mol/l from the response of the lowest calibration standard (2.5 × 10^–8 mol/l) which gave a signal to noise ratio of 3 : 1. Although the structurally related codeine did not interfere significantly the results suggest that this method may be susceptible to matrix effects, dependent on the location of sampling from the process stream.     

A novel amperometric sensor and chromatographic detector for determination of parathion

A novel amperometric sensor and chromatographic detector for determination of parathion has been fabricated from a multi-wall carbon nano-tube (MWCNT)/Nafion film-modified glassy-carbon electrode (GCE). The electrochemical response to parathion at the MWCNT/Nafion film electrode was investigated by cyclic voltammetry and linear sweep voltammetry. The redox current of parathion at the MWCNT/Nafion film electrode was significantly higher than that at the bare GCE, the MWCNT-modified GCE, and the Nafion-modified GCE. The results indicated that the MWCNT/Nafion film had an efficient electrocatalytic effect on the electrochemical response to parathion. The peak current was proportional to the concentration of parathion in the range 5.0×10^–9–2.0×10^–5 mol L^–1. The detection limit was 1.0×10^–9 mol L^–1 (after 120 s accumulation). In high-performance liquid chromatography with electrochemical detection (HPLC–ED) a stable and sensitive current response was obtained for parathion at the MWCNT/Nafion film electrode. The linear range for parathion was over four orders of magnitude and the detection limit was 6.0×10^–9 mol L^–1. Application of the method for determination of parathion in rice was satisfactory.     

Adsorptive stripping voltammetric determination of cobalt in the presence of dimethylglyoxime and cetyltrimethylammonium bromide

A sensitive procedure for determination of micro-traces of Co(II) by adsorptive stripping voltammetry is proposed. The procedure exploits the enhancement of the cobalt peak obtained by use of the system Co(II)–dimethylglyoxime–piperazine-1,4-bis(2-ethanesulfonic acid)–cetyltrimethylammonium bromide. Using the optimized conditions, a detection limit (based on the 3 criterion) for Co(II) of 1.2×10^–11 mol L^–1 (0.7 ng L^–1) was achieved. The calibration plot for an accumulation time of 30 s was linear from 5×10^–11 to 4×10^–9 mol L^–1. The procedure was validated by analysis of certified reference materials and natural water samples.     

Adsorptive accumulation voltammetry of copper(II) using complex formation reaction with salicylideneamino-2-thiophenol

Summary The cathodic stripping voltammetry of copper(II) was investigated with a method, based on the adsorptive accumulation of the Cu(II)-salicylideneamino-2-thiophenol (SATP) complex on a hanging mercury drop electrode. The copper(II)-SATP complex could be accumulated on the electrode at –0.20 V in 0.01 mol/l nitric acid. The reduction peak of the copper complex was observed by scanning the potential in a negative direction in the differential pulse mode. The calibration curve for copper was linear over the range 5×10^–9–1×10^–7 mol/l. This method was applied to determine copper(II) in GSJ (Geological Survey of Japan) standard rock reference materials.     

Determination of cerium in rare earth ores by fluorescence quenching of rhodamine 6G

A fluorescence quenching method has been developed to determine cerium with rhodamine 6G. The method is based on the oxidation of rhodamine 6G by cerium(IV) in sulfuric acid solution. The linear calibration range is 4.0 × 10^–7 -1.6 × 10^–6mol/L. The detection limit is 1.0 × 10^–7 mol/L. The relative standard deviation was 1.0% (n = 5). The method has been used to determine cerium in rare earth ores, with satisfactory results. The method offers the advantages of simplisity, sensitivity and selectivity.     

Determination of traces of vanadium with the catalytic maximum wave in differential pulse polarography

Summary A differential pulse-polarographic method has been studied for the determination of vanadium employing the catalytic maximum wave. A well-defined differential pulse polarographic peak is observed in the potential range from –0.2 to –0.7 V vs. SCE for vanadium(V) in 10 mmol 1^–1 NaCl containing 10 mmol 1^–1 acetic acid, 40 mmol 1^–1 pyrocatechol, and 2.5 mmol 1^–1 KBrO₃. The peak current is very large and proportional to the concentration of vanadium(V) between 1×10^–7 and 1×10^–6 mol 1^–1. The relative standard deviation at 0.5 mol l^–1 vanadium(V) was 2.06% (n=7). This method has been successfully applied to the determination of vanadium in standard materials such as pond sediment.

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Spurenbestimmung von Vanadium mit Hilfe der katalytischen Maximumsstufe in der Differential-Puls-Polarographie

Zusammenfassung Ein gut definierter differentialpuls-polarographischer Peak wurde für Vanadium(V) in 10 mmol/l NaCl-Lösung, die 10 mmol/l Essigsäure, 40 mmol/l Brenzcatechin und 2,5 mmol/l KBrO₃ enthielt, beobachtet (Potentialbereich –0,2 bis –0,7 V gegen SCE). Der Peakstrom ist sehr groß und die Vanadiumkonzentration im Bereich von 1×10^–7 bis 1×10^–6 mol/l proportional. Die relative Standardabweichung betrug 2,06% (n=7) bei 0,5 mol/l Vanadium(V). Das Verfahren wurde mit gutem Erfolg zur Vanadiumbestimmung in Standardproben (z.B. Teichsediment) eingesetzt.

     

Polarographic study of a benzodiazepinooxazole: Oxazolam

Summary The polarographic behaviour of 10-chloro-2,3, 7,11b-tetrahydro-2-methyl-11b-phenyloxazolo-[3,2-d][1,4]-benzodiazepin-6(5H)-one (Oxazolam) was studied in the pH range 1–12. The reduction processes of Oxazolam and its hydrolysis product are irreversible and their currents are predominantly diffusion-controlled. The linear relationship between current and Oxazolam concentration in sulphuric acid medium permits its polarographic determination up to 6.08×10^–5 mol/l. The detection limit was 1.52×10^–7 mol/l (50 ppb). The reproducibility of the method in terms of relative standard deviation was 1.74% and 1.85% for ten determinations at 1.48×10^–5 mol/l and 1.37×10^–6 mol/l levels, respectively. The method developed was applied to the determination of the compound in its formulations, Hializan-10 mg, obtaining errors lower than 2%.

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Polarographische Untersuchung eines Benzodiazepinoxazols: Oxazolam

     

Determination of trace europium by use of the new fluorescence system europium–sparfloxacin–1,10-phenanthroline–sodium dodecyl sulfate

A new lanthanide-sensitized luminescence system: europium–sparfloxacin–1,10-phenanthroline–sodium dodecyl sulfate has been discovered. The spectrofluorimetric properties of the system were studied. The effect of experimental conditions on the fluorescence intensity was defined. Under the optimum conditions, the fluorescence intensity of the system is a linear function of the concentration of europium in the range 5.0×10^–9–1.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–10 mol L^–1. The system was used for the determination of trace amounts of europium in rare earth samples with satisfactory results.     

Determination of oxytetracycline in urine and human serum by differential pulse polarography

Summary A differential pulse polarographic method for the determination of oxytetracycline in urine and human serum in acid media (HClO₄ of pH 2) is proposed. The effects of the amount of sample taken and the concentration of HClO₄ present were investigated. The detection limit was 5.5×10^–6 mol/l. The standard deviation of the determination of 5.5×10^–5 mol/l of oxytetracycline in 2 ml of urine was 1.7×10^–6 mol/l and that of the determination of 5.5×10^–5 mol/l of oxytetracycline in 2 ml of human serum was 1.9×10^–6 mol/l.

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Bestimmung von Oxytetracyclin in Urin und Humanserum durch Differential-Pulspolarography

     

Determination of Mo(VI) with 2-benzylideneiminobenzohydroxamic acid (2-BIBH) in urine by cathodic stripping voltammetry

Summary Controlled adsorptive accumulation of Mo(VI)-2-BIBH at the hanging mercury drop electrode (HMDE) provides the basis for the direct stripping measurement of Mo(VI) in nanomolar concentration. The cathodic stripping response is evaluated with respect to experimental parameters such as preconcentration time, preconcentration potential and others. A differential pulse cathodic stripping voltammetric method for the determination of Mo(VI) with 2-BIBH in urine is proposed. The detection limit is 10^–9 mol/l Mo(VI), standard deviation for 5×10^–8 mol/l is ±1.58×10^–9 mol/l.

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Bestimmung von MolybdÄn(VI) mit 2-BenzylideniminobenzohydroxamsÄure (2-BIBH) in Harn durch kathodische Stripping-Voltammetrie

     

Determination of cobalt in the presence of high concentrations of zinc by differential pulse polarography

Summary Cobalt(II) can be determined in 0.1 mol/l Na₃citrate + 0.1 mol/l NH₄Cl + 0.08% dimethylglyoxime as supporting electrolyte in the presence of a 50 000-fold excess of zinc by differential pulse polarography. The limit of determination is 4.2×10^–5 mol/l Co (2.5 mg/l). Linear calibration curves are obtained within the range of 1×10^–7 to 5×10^–6 mol/l cobalt without zinc and in the presence of 5×10^–3 mol/l Zn. The analytical method developed is suitable for the determination of cobalt in zinc plant solutions.

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Cobaltbestimmung in Gegenwart hoher Zinkkonzentrationen mit Hilfe der Differential-Puls-Polarographie

     

Voltammetric copper(II) determination with a montmorillonite-modified carbon paste electrode

The clay mineral montmorillonite has been tested as modifier for the carbon paste electrode with a novel electrode modification technique. The differential pulse voltammetric determination of copper(II) by means of this modified carbon paste electrode has been studied. A detection limit of 4×10^-8 mol/l has been achieved after 10 min preconcentration under open circuit conditions with subsequent anodic stripping voltammetry. The calibration curve for Cu(II) is linear in the range of 4×10^-8–8×10^-7 mol/l. Pb interferes in a 10-fold molar and Cd and Hg in a 100-fold molar excess. The interference by humic ligands is significant.     

Enzyme sensor for L-lactate using differential pulse amperometric detection

An enzyme sensor using differential pulse (DP) amperometric detection has been developed based on the measurement of the reduction current of the oxidized form of -nicotinamide adenine dinucleotide (NAD⁺) consumed by an enzyme reaction. This biosensor has the definite advantage to prevent interference caused by electrooxidative species such as ascorbate and uric acid and exhibits higher sensitivity and selectivity in comparison to the classical DC amperometric detector. The linear detection range of this biosensor was 5.0×10^–5 — 5.0×10^–4 mol/l and the relative standard deviation (R.S.D.) at 2.5×10^–4 mol/l was 5.0%.