Electroanalytical study of benzodiazepinooxazoles: Haloxazolam

Summary The polarographic behaviour of 10-bromo-11 b-(2-fluorophenyl)-2,3,7,11 b-tetrahydrooxazolo [3,2-d][1,4] benzodiazepin-6(5H)-one (Haloxazolam) was studied in the pH range 1–13. Haloxazolam suffers a hydrolysis process, which can be followed by polarography. The reduction processes of Haloxazolam and its hydrolysis products are irreversible and their currents are diffusion-controlled. This behaviour was compared with that observed for other members of benzodiazepinooxazoles. Two polarographic methods have been developed upon the basis of the reduction of both the protonated iminium form (0.05 mol/l HCl, measurement time: 5 min) and the benzophenone produced in the hydrolysis process (pH 13.25, measurement time: 17 min). The relationship between reduction peak current and concentration is linear up to at least 6.62×10^–5 mol/l for both methods. A higher sensitivity was obtained for the method based on the benzophenone reduction (detection limit 1.06×10^–7 mol/l; 40 g/l). The reproducibility of the both methods in terms of relative standard deviation was inferior to 2%.     

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%.

---

Polarographische Untersuchung eines Benzodiazepinoxazols: Oxazolam

     

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.

---

Bestimmung von Oxytetracyclin in Urin und Humanserum durch Differential-Pulspolarography

     

Electroanalytical study of a benzodiazepinooxazole: Mexazolam

Summary The electroanalytical behaviour of 10-chloro-11b-(2-chlorophenyl)-2,3,7,11b-tetrahydrooxazolo[3,2-d][1,4]-benzodiazepin-6(5H)-one (Mexazolam) was studied in the pH-range 1–13. The compound suffers a hydrolysis process, which can be followed by voltammetric techniques. The reduction process of Mexazolam is irreversible in the whole pH range 1–13 studied; the cathodic reactions of its hydrolysis products are irreversible at pH values lower than 7 and reversible in neutral and alkaline media at a scan rate range of 0.1–40 V·s^–1. The electrode process attributed to the reduction of the carbonyl group is predominantly adsorption-controlled and the reduction of the iminium group of the different species of Mexazolam is diffusion-controlled. A differential pulse polarographic method has been developed upon the basis of the reduction of the protonated iminium form. The relationship between reduction peak current and concentration is linear up to at least 13 ppm. The reproducibility of the method in terms of relative standard deviation (RSD) was smaller than 1.6% for ten determinations, at a concentration level of 5.51×10^–6 and 2.62×10^–5 mol/l. A determination limit of 80 ppb was obtained.     

Polarographic study of a triazolobenzodiazepine: Estazolam

Summary The polarographic behaviour of 8-chloro-6-phenyl-4H-s-triazolo(4,3-a)-(1,4)-benzodiazepine (estazolam) was studied in the pH range 3–10. The reduction process is irreversible and the current is diffusion-controlled. The linear relationship between current and estazolam concentration permits its polarographic determination in the range 3.4·10^–7–1.0·10^–4 M. The detection limit was 1.7·10^–7 M. The reproducibility of the method in terms of its relative standard deviation was 1.00% and 1.14% using ten determinations at the 2.4·10^–5 M and 3.4·10^–6 M levels respectively.

---

Polarographische Untersuchung des Triazolbenzodiazepins Estazolam

     

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.

---

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.

---

---

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

Determination of tetramethrin (neo-pynamin) by differential pulse voltammetry with a carbon paste electrode modified with sepiolite

Summary A method is described for the determination of tetramethrin (neo-pynamin) by differential pulse voltammetry with a carbon paste electrode modified with 10% (w/w) sepiolite. Preconcentration was carried out under open circuit conditions in 0.01 mol/l acetic acid/potassium acetate medium at pH 5.3 over 10 min, recording the voltammogram in 0.01 mol/l of KH₂PO₄/K₃PO₄ at pH 12. This led to the appearance of a peak at –1.32 V against SCE at 40 mVs^–1 and a pulse amplitude of 100 mV. Under these conditions determination limits of 45 ng ml^–1 were achieved. The method was applied to the determination of tetramethrin in soil and water samples.

---

Bestimmung von Tetramethrin (Neo-Pynamin) durch Differential-Puls-Voltammetrie unter Verwendung einer mit Sepiolit modifizierten Kohlepaste-Elektrode

     

Some electroanalytical aspects of using pulse polarography for determination of Ge(IV)

Summary Presented data give some informations of analytical importance as a result of pulse polarographic investigations of Ge(IV) in KCl solutions within pH range 3–12 at Ge concentration from 1×10^–4 to 2.5×10^–6 M. It was shown that Ge(IV) can be polarographically active in acidic solution but its reduction interferes with hydrogen gas development. The addition ofp-quinone enables the determination of Ge(IV) without this interfering effect.Suggested explanation of the observed changes in polarographic curves dependent on pH and Ge concentration based on the existence of several polarographically active forms.

---

Elektroanalytische Bemerkungen zur pulspolarographischen Bestimmung von Ge(IV)

Zusammenfassung Unsere Ergebnisse bieten einige Informationen über die pulspolarographische Bestimmung von Ge(IV) in KCl-Lösungen innerhalb pH 3–12 und bei Ge-Konzentrationen zwischen 10^–4 und 2,5×10^–6 M. Es wurde gezeigt, daß Ge(IV) in saurer Lösung polarographisch aktiv ist, seine Reduktion aber durch Wasserstoff-Entwicklung gestört wird. Der Zusatz vonp-Chinon beseitigt diese Störung. Die Änderung der polarographischen Kurven je nach Ge-Konzentration und pH beruht vermutlich auf der Existenz verschiedener polarographisch aktiver Formen.

     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.     

Determination of sulphhydryl compounds in physiological fluids by liquid chromatography with polarographic detection

Summary A polarographic detector with a horizontal, fast dropping mercury electrode has been applied for the determination of thiols in physiological fluids. To establish suitable detection conditions first some basic studies on the polarographic behaviour of penicillamine, glutathione and cysteine were performed. This type of detection shows a high selectivity and reasonably low detection limits for sulphhydryl compounds. Detection limits of 6×10^–7 mol l^–1 for penicillamine and cysteine and 8×10^–7 mol l^–1 for glutathione were found. A good linearity has been observed over a concentration range of three orders. The detector has successfully been applied to the determination of penicillamine in urine and serum samples.

---

Bestimmung von Sulfhydrylverbindungen in physiologischen Flüssigkeiten durch Flüssigkeits-Chromatographie mit polarographischer Detektion

Zusammenfassung Ein polarographischer Detektor mit horizontaler, schnell tropfender Quecksilberelektrode wurde zur Bestimmung von Thiolen in physiologischen Flüssigkeiten angewendet. Zur Feststellung geeigneter Bedingungen wurden zunächst grundlegende Untersuchungen zum polarographischen Verhalten von Penicillamin, Glutathion und Cystein durchgeführt. Das Verfahren bietet hohe Selektivität und niedrige Nachweisgrenzen (6 · 10^–7 mol/l für Penicillamin und Cystein, 8 · 10^–7 mol/l für Glutathion). Linearität besteht über drei Größenordnungen. Der Detektor wurde mit gutem Erfolg für die Penicillaminbestimmung in Harn und Serum verwendet.

---

---

Dedicated to Prof. Dr. H. Weisz on occasion of his 60th birthday

---

On leave from the Technical University of Gdansk     

Polarographic behaviour and determination of beclomethasone dipropionate

The polarographic behaviour of beclomethasone dipropionate in Britton-Robinson buffers containing 40% methanol as a solubilizer has been studied. Over the pH range 1.8–12, a cathodic wave was produced, which was characterised as being irreversible, diffusion controlled and free from adsorption phenomena. The number of electrons involved in the reduction was found through comparative study with spironolactone. Using direct current polarographic mode, the limiting current concentration plot is rectilinear over the range 2.5 × 10^–5 to 4 × 10^–4 mol/1 with a detection limit of 2.5 × 10^–6 mol/1. A method has been developed for the determination of the drug in aerosols and creams, the results being in agreement with those obtained by the official method.     

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.

---

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.

     

Determination of nanomolar levels of guanine by differential-pulse adsorptive cathodic stripping voltammetry of its copper(II) complex

Guanine is determined at the 5.0×10^–10 –2.0×10^–7 mol/l level by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper (II) complex at –0.21 V vs. Ag-AgCl electrode. The optimum analytical conditions were found to be Britton-Robinson buffer solution (pH 4.8), an accumulation potential of 0.0 V and an accumulation time of 3 min. Under these conditions, the detection limit is 5.0×10^–10 mol/l and the relative standard deviation 2.6% for 1.0×10^–7 mol/l guanine. The method is compared with the previous voltammetric methods. The presence of some purine derivatives does not interfere.     

Differential pulse-polarographic determination of organotin compounds coated on fishing nets

Summary The pulse-polarographic behaviour of tributyltin chloride (TBTC) and dibutyltin dichloride (DBTC) in ethanol-water mixtures has been studied. The effects of temperature, pH, modulation amplitude, solvent and supporting electrolyte compositions were investigated. The reduction processes are complicated and pH-dependent. DBTC gave one reversible reduction wave and TBTC showed a quasi-reversible one and also several irreversible waves. Both the organotin compounds in the concentration of 10^–7 mol/l were determined by differential pulse polarography. The method was successfully applied to the analysis of commercially available fishing nets. Detection limits were 2.2×10^–7 and 6.2×10^–8 mol/l for TBTC and DBTC, respectively.

---

Differential-puls-polarographische Bestimmung von Organozinnverbindungen auf Fischernetzen

Zusammenfassung Das puls-polarographische Verhalten von Tributylzinnchlorid (TBTC) und Dibutylzinndichlorid (DBTC) in Ethanol-Wasser-Gemischen wurde untersucht und die Wirkung von Temperatur, pH, Modulationsamplitude sowie Zusammensetzung des Lösungsmittels und Leitelektrolyts geprüft. Die Reduktionsprozesse waren kompliziert und abhÄngig vom pH. DBTC ergab eine reversible Reduktionswelle, TBTC eine quasireversible Welle, sowie daneben einige irreversible Wellen. Beide Organozinnverbindungen konnten in einer Konzentration von 10^–7 mol/l durch Differential-Puls-Polarographie bestimmt werden. Die Methode wurde erfolgreich auf die Analyse von handelsüblichen Fischernetzen angewandt. Die Nachweisgrenzen lagen bei 2,2·10^–7 (TBTC) bzw. 6,2 · 10^–8 mol/l (DBTC).

This work was supported in part by a Grant-in-Aid for Scientific Research No. 554164 from the Ministry of Education. The authors wish to thank Mr. Y. Komatsu, Clean Kagaku Co., Tokyo, who offered the fishing net samples.     

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.

---

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

     

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.

---

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

     

Polarographic studies on some arylarsonic acids

Summary The polarographic behaviour of a series of substituted phenylarsonic acids over the concentration range 5×10^–5M–10^–3M and pH range 0–3 was studied and a mechanism for the polarographic reduction proposed, taking into account the results of various analyses performed on the products of macro-scale electrolytic reductions. A method for the analysis of phenylarsonic acids utilising the reduction wave is also presented.

---

Polarographische Untersuchungen einiger Arylarsonsäuren

Zusammenfassung Das polarographische Verhalten einer Reihe von substituierten Phenylarsonsäuren wurde im Konzentrationsbereich 5 · 10^–5M–10^–3M bei pH 0–3 untersucht und ein Mechanismus für die polarographische Reduktion aufgestellt, der auch die Ergebnisse von elektrolytischen Reduktionen im Makrobereich berücksichtigt. Eine Methode für die Analyse von Phenylarsonsäuren, mit Hilfe der polarographischen Reduktionsstufe wird beschrieben.

---

---

Research Institute for Technical Physics of the Hungarian Academy of Sciences, Budapest IV.     

Determination of acipimox in capsules by differential pulse polarography

A differential pulse polarographic (DPP) method has been developed for the determination of acipimox in its pharmaceutical formulations. Using Sörensen buffer pH 6.0 as supporting electrolyte a single, irreversible peak occurred at –0.79 V vs an Ag/AgCl reference electrode. The peak height vs concentration plot was found to be linear over the range of 10^–6 to 6 × 10^–4 mol/l. The detection limit is 60ng/ml. The analysis of a series of 10 Olbetam® 250 mg capsules showed an overall standard deviation of ± 4.18 mg and a S_rel of ± 1.66%, respectively.     

Polarographische Studien an Uran(VI)-Verbindungen. I

Zusammenfassung Die polarographische Reduktion von Uran(VI) in schwefelsaurer Lösung an der Quecksilbertropfelektrode wurde untersucht und eine square-wave-polarographische Bestimmungsmethode ausgearbeitet, mit der noch 7·10^–7 Mol Uran/l in Gegenwart 20 anderer Metallionen gut reproduzierbar bestimmt werden können.

---

Polarographic studies on uranium(vi) compounds, i

Summary The reduction of uranium(VI) in sulphuric acid solutions has been studied polarographically at the dropping mercury electrode and a square wave polarographic method for the determination up to 7·10^–7 M uranium in presence of 20 other metals is described.

     

Differential pulse polarographic determinations of iodate, bromate and periodate

Summary The application of differential pulse polarography for quantitative trace determination of iodate, periodate and bromate has been investigated. Optimum conditions were found (pulse amplitude 100 mV, scan rate 2 mV s^–1, drop time 2 s). The detection limit for IO ₃ ^– , BrO ₃ ^– and IO ₄ ^– is ca. 2.4×10^–6M at pH 3 whereas at pH 9.3 the reduction of IO ₃ ^– and IO ₄ ^– gave concentration sensitive peak heights down to 9.9 ×10^–7M. A differential pulse polarographic method has been developed for the simultaneous determination of iodate-bromate or periodate-bromate.

---

Bestimmung von Iodat, Bromat und Periodat durch Differential-Pulse-Polarographie

Zusammenfassung Optimale Bedingungen zur Bestimmung dieser Ionen im Spurenbereich wurden ausgearbeitet (Pulsamplitude 100 mV, Scangeschwindigkeit 2 mV s^–1, Tropfzeit 2 s). Die Nachweisgrenze für die drei Ionen liegt bei 2,4 · 10^–6 M für pH 3. Bei pH 9,3 ergaben sich für Iodat und Periodat konzentrationsabhängige Peakhöhen bis herab zu 9,9 · 10^–7 M. Da der Bromatpeak bei wesentlich negativerem Potential auftritt als der Iodat bzw. Periodatpeak konnten Iodat und Bromat bzw. Periodat und Bromat nebeneinander bestimmt werden.