Solid-state Cu (II) ion-selective electrode based on polyaniline-conducting polymer film doped with copper carmoisine dye complex

A pencil graphite electrode coated by copper (II)–carmoisine dye complex in polyaniline (emeraldine base form) matrix (termed as PGE/PA/Cu-Car) was prepared and used as copper ion-selective electrode. The introduced electrode was found to have high selectivity toward copper ion (II) and exhibited wide working concentration range, low response time, and good shelf life. The sensor electrode showed a linear Nernstian response over the range of 5.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a slope of 29.7 ± 1 mV per decade change in concentration. A detection limit of 2.0 × 10⁻⁶ M was obtained. The optimum pH working range of the electrode was found to be 4.0–7.0.     

Adsorption and redox chemistry of cis-RuLL'(SCN)2 with L=4,4′-dicarboxylic acid-2,2′-bipyridine and L'=4,4′-dinonyl-2,2′-bipyridine (Z907) at FTO and TiO2 electrode surfaces

The electrochemical and spectroelectrochemical properties of the sensitizer dye Z907 (cis-RuLL'(SCN)₂ with L=4,4′-dicarboxylic acid-2,2′-bipyridine and L'=4,4′-dinonyl-2,2′-bipyridine) adsorbed on fluorine-doped tin oxide (FTO) and TiO₂ surfaces have been investigated. Langmuirian binding constants for FTO and TiO₂ are estimated to be 3 × 10⁶ M⁻¹ and 4 × 10⁴ M⁻¹, respectively. The Ru(III/II) redox process is monitored by voltammetry and by spectroelectrochemistry. For Z907 adsorbed onto FTO, a slow EC-type electrochemical reaction is observed with a chemical rate constant of ca. k = 10⁻² s⁻¹ leading to Z907 dye degradation of a fraction of the FTO-adsorbed dye. The Z907 adsorption conditions affect the degradation process. No significant degradation was observed for TiO₂-adsorbed dye. Degradation of the Z907 dye affects the electron hopping conduction at the FTO–TiO₂ interface.     

A multiplexed screening method for agonists and antagonists of the estrogen receptor protein

The estrogen receptor (ER) is regarded as a significant drug target because of its important physical and pathological function. In this article, we describe a novel screening method to obtain agonists and antagonists of ER. ER was immobilized onto an aldehyde-modified glass slide. The affinity of Cy3-labeled estradiol for ER protein microarrays was then determined. Two libraries, one containing 29 synthetic compounds and the other with 384 natural products that served as a model, were screened to find new ligands for ER. The IC₅₀ values obtained for tamoxifen and raloxifene were consistent with those found in the literature (4.85 × 10⁻⁷ M versus 1.74~4.23 × 10⁻⁷ M and 7.58 × 10⁻⁸ M versus 0.89~5.84 × 10⁻⁸ M, respectively). Finally, 65 active ligands (5 synthetic compounds and 60 natural products) of ER were identified. This novel method gave identical results to a conventional fluorescence polarization assay, thus verifying the accuracy of this simultaneous multireceptor screening method based on protein microarrays. The presented method is sensitive, accurate, and reliable, and shows great potential for use in high-throughput drug-screening research.     

Continuous Monitoring of Sulfur Dioxide with a Gas Permeation Denuder-Based System

 This study describes a continuous flow procedure for monitoring atmospheric sulfur dioxide using a planar gas permeation denuder (GPD) and a fiber optic spectrometer. When gaseous samples are directed through a GPD which consists of a gas-permeable membrane of poly(vinylidene) difluoride and two perspex blocks with engraved channels of mirror image, the fraction of sulfur dioxide passing the membrane is absorbed in a flowing stream of 5.0×10⁻⁴ mol L⁻¹ 5,5′-dithiobis(2,2′-dinitrobenzoic acid) (DTNB) in 0.025 mol L⁻¹ phosphate buffer of pH 7.0, and reacts with DTNB to yield a yellow product. This product is monitored spectrophotometrically at 410 nm with a miniature charge-coupled device (CCD) fiber optic spectrometer. The analytical range of sulfur dioxide is easily adjusted via the flow rate of DTNB solution, normally from 200 ppb to 94 ppm (v/v). The procedure is hardly interfered with by coexisting metal and non-metal species, except for hydrogen sulfide in the atmosphere. The error caused by hydrogen sulfide at a sulfur dioxide level (in ppm) of 2% is less than ±10%. With the proposed procedure, the result for a mimetic air sample is very close to that of the ultraviolet fluorescence method. Correspondence: College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China. e-mail: yli@chem.pku.edu.cn Received August 12, 2002; accepted November 9, 2002     

Application of a trazodone-selective electrode to pharmaceutical quality control and urine analyses

A trazodone-selective electrode for application in pharmaceutical quality control and urine analysis was developed. The electrode is based on incorporation of a trazodone-tetraphenylborate ion exchanger in a poly(vinyl chloride) membrane. The electrode showed a fast, stable and Nernstian response over a wide trazodone concentration range (5 × 10⁻⁵−1 × 10⁻² M) with a mean slope of 59.3 ± 0.9 mV/dec of concentration, a mean detection limit of 1.8 × 10⁻⁵± 2.2 × 10⁻⁶ M, a wide working pH range (5–7.5) and a fast response time (less than 20 s). The electrode also showed good accuracy, repeatability, reproducibility and selectivity with respect to some inorganic and organic compounds, including the main trazodone metabolite. The electrode provided good analytical results in the determination of trazodone in pharmaceuticals and spiked urine samples; no extraction steps were necessary. Dissolution testing of trazodone tablets, in different conditions of pH and particle size, based on a direct potentiometric determination with the new selective electrode is presented as well.     

Voltammetric sensor for nitrite determination based on its electrocatalytic reduction at the surface of p-duroquinone modified carbon paste electrode

A p-duroquinone (tetramethyl-p-benzoquinone) modified carbon paste electrode (DMCPE) was employed to study the electrocatalytic reduction of nitrite in aqueous solutions using cyclic voltammetry (CV), double potential-step chronoamperometry, and differential pulse voltammetry (DPV). It has found that under an optimum condition (pH 1.00), the reduction of nitrite at the surface of DMCPE occurs at a potential of about 660 mV less negative than that of an unmodified carbon paste electrode (CPE). The catalytic rate constant, k′_h, based on Andrieux and Saveant theoretical model was calculated as for scan rate 10 mV s^-1. Also, the apparent diffusion coefficient, D _app, was found as 2.5 × 10^–10 and 3.61 × 10^–5 cm² s^-1 for p-duroquinone in carbon paste matrix and nitrite in aqueous buffered solution, respectively. The values for αn_α were estimated to be −0.65 and −0.19 for the reduction of nitrite at the surface of DMCPE and CPE, respectively. The electrocatalytic reduction peak currents showed a linear dependence on the nitrite concentration, and a linear analytical curve was obtained in the ranges of 5.0 × 10^–5 M to 8.0 × 10^–3 M and 6.0 × 10^–6 M to 8.0 × 10^–4 M of nitrite concentration with CV and DPV methods, respectively. The detection limits (2σ) were determined as 2.5 × 10^–5 M and 4.3 × 10^–6 M by CV and DPV methods. This method was also applied as a simple, selective and precise method for determination of nitrite in real samples (the weak liquor from the wood and paper factory of Mazandaran province in Iran) by using a standard addition method.     

Comparison of different sample treatments for the analysis of ochratoxin A in wine by capillary HPLC with laser-induced fluorescence detection

Ochratoxin A (OTA) is a mycotoxin naturally found in various foods, including wine. As OTA is considered as a possible human carcinogen, the maximum concentration for this compound has been established at 2 μg kg⁻¹ in wine by the EU (Directive (CE) No 1881/2006). Typically, immunoaffinity columns have been used for its extraction. However, simpler, more efficient and less contaminant extraction systems are demanding. In this work, dispersive liquid–liquid microextraction using ionic liquid as extractant solvent (IL-DLLME) and the QuEChERS procedure, have been evaluated and compared for extraction of OTA in wine samples. Laser-induced fluorescence (LIF, He–Cd Laser excitation at 325 nm) coupled with capillary HPLC has been used for the determination of OTA, using a sodium dodecyl sulfate micellar solution in the mobile phase to increase the fluorescence intensity. Matrix-matched calibration curves were established for both methods, obtaining LODs (3× S/N) of 5.2 ng·L⁻¹ and 85.7 ng·L⁻¹ for IL-DLLME and QuEChERS, respectively. Clean extracts were obtained for white, rose and red wines with both methods, with recoveries between 88.7–94.2% for IL-DLLME and between 82.6–86.2% for QuEChERS. The precision was evaluated in terms of repeatability (n = 9) and intermediate precision (n = 15), being ≤ 8.5% for IL-DLLME and ≤ 5.4% for QuEChERS.     

Simultaneous and sensitive determination of procaine and its metabolite for pharmaceutical quality control and pharmacokinetic research by using a graphite paste electrode

A simple, rapid, sensitive, and accurate method for simultaneous electrochemical determination of procaine and its metabolite (p-aminobenzoic acid, PABA) for pharmaceutical quality control and pharmacokinetic research was developed using a graphite paste electrode. The differential pulse voltammetric results revealed that procaine and p-aminobenzoic acid, respectively, showed well-defined anodic oxidation peaks on a carbon paste electrode with a current peak separation of 155 mV at a scan rate of 100 mV s⁻¹. This well separation of the current peaks for these two compounds in voltammetry enables us to simultaneously determine them. Good linearity (r > 0.998) between oxidation peak current and concentration was obtained in the range of 5.0 × 10⁻⁷–5.0 × 10⁻⁵ M for procaine and 5.0 × 10⁻⁷–2.0 × 10⁻⁵ M for PABA in pH 4.50 acetate buffer solution. The detection limit for both analytes is 5 × 10⁻⁸ M (S/N = 3:1). The present voltammetric method has been successfully used to determine trace p-aminobenzoic acid in procaine hydrochloride injection and procaine in plasma with a linear relationship of current to its concentration ranging from 1.0 × 10⁻⁶ to 5.0 × 10⁻⁵ M (correlation coefficient of 0.9981) with a low detection limit of 5.0 × 10⁻⁷ M (S/N = 3:1). This validated method is promising to the study of pharmacokinetics in Sprague–Dawley rat and rabbit plasma after an intravenous administration of procaine hydrochloride injection.     

Direct electrochemistry and electrocatalysis of nitrite based on nano-alumina-modified electrode

Simple and sensitive electrochemical method for the determination of nitrite, based on a nano-alumina-modified glassy carbon electrode (GCE), is described. Nitrite yields a well-defined oxidation peak whose potential is 0.74 V at the nano-alumina-coated GCE in 0.1 mol L⁻¹ phosphate buffer (pH 5.0). Compared with bare GCE, the nano-alumina-modified GCE has evident catalytic effect towards the oxidation of nitrite, and its peak current can be significantly enhanced. Some of the experimental parameters were optimized for the determination of nitrite. The oxidation peak current was proportional to nitrite concentration in the range of 5.0 × 10⁻⁸–1.1 × 10⁻³ mol L⁻¹, and a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ was obtained. This method has been successfully used to the determination of nitrite in sausage sample. Furthermore, results obtained by the method have been compared with spectrophotometric method.     

Simple sensor for simultaneous determination of dihydroxybenzene isomers

A simple sensor based on bare carbon ionic liquid electrode was fabricated for simultaneous determination of dihydroxybenzene isomers in 0.1 mol L⁻¹ phosphate buffer solution (pH 6.0). The oxidation peak potential of hydroquinone was about 0.136 V, catechol was about 0.240 V, and resorcinol 0.632 V by differential pulse voltammetric measurements, which indicated that the dihydroxybenzene isomers could be separated absolutely. The sensor showed wide linear behaviors in the range of 5.0 × 10⁻⁷–2.0 × 10⁻⁴ mol L⁻¹ for hydroquinone and catechol, 3.5 × 10⁻⁶–1.535 × 10⁻⁴ mol L⁻¹ for resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were 5.0 × 10⁻⁸, 2.0 × 10⁻⁷, 5.0 × 10⁻⁷ mol L⁻¹, respectively (S/N = 3). The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater and the recovery was from 93.9% to 104.6%.     

Simultaneous determination of uric acid and ascorbic acid at the film of chitosan incorporating cetylpyridine bromide modified glassy carbon electrode

A glassy carbon electrode (GCE) modified with the film composed of chitosan incorporating cetylpyridine bromide is constructed and used to determine uric acid (UA) and ascorbic acid (AA) by differential pulse voltammetry (DPV). This modified electrode shows efficient electrocatalytic activity and fairly selective separation for oxidation of AA and UA in mixture solution. UA is catalyzed by this modified electrode in phosphate buffer solution (pH 4.0) with a decrease of 80 mV, while AA is catalyzed with a decrease of 200 mV in overpotential compared to GCE, and the peak separation of oxidation between AA and UA is 260 mV, which is large enough to allow the determination of one in presence of the other. Under the optimum conditions, the anodic peak currents (I _pa) of DPV are proportional to the concentration of UA in the range of 2.0 × 10⁻⁶ to 6.0 × 10⁻⁴ M, with the detection limit of 5.0 × 10⁻⁷ M at a signal-to-noise ratio of 3 (S/N = 3) and to that of AA in the range of 4.0 × 10⁻⁶ to 1.0 × 10⁻³ M, with the detection limit of 8.0 × 10⁻⁷ M (S/N = 3).     

Voltammetric sensor for glutathione determination based on ferrocene-modified carbon paste electrode

The electrocatalytic oxidation of glutathione (GSH) has been studied at the surface of ferrocene-modified carbon paste electrode (FMCPE). Cyclic voltammetry (CV), double potential step chronoamperometry, and differential pulse voltammetry (DPV) techniques were used to investigate the suitability of incorporation of ferrocene into FMCPE as a mediator for the electrocatalytic oxidation of GSH in buffered aqueous solution. Results showed that pH 7.00 is the most suitable for this purpose. In the optimum condition (pH 7.00), the electrocatalytic ability of about 480 mV can be found and the heterogeneous rate constant of catalytic reaction was calculated as . Also, the diffusion coefficient of glutathione, D, was found to be 3.61 × 10^–5 cm² s⁻¹. The electrocatalytic oxidation peak current of glutathione at the surface of this modified electrode was linearly dependent on the GSH concentration and the linear analytical curves were obtained in the ranges of 3.2 × 10^–5 M–1.6 × 10^–3 M and 2.2 × 10^–6 M–3.5 × 10^–3 M with cyclic voltammetry and differential pulse voltammetry methods, respectively. The detection limits (3σ) were determined as 1.8 × 10^–5 M and 2.1 × 10^–6 M using CV and DPV, respectively. Finally, the electrocatalytic oxidation of GSH at the surface of this modified electrode can be employed as a new method for the voltammetric determination of glutathione in real samples such as human plasma.     

Development and validation of an HPLC-UV detection assay for the determination of rufinamide in human plasma and saliva

The development of a simple and rapid high-performance liquid chromatography (HPLC) method for the determination of the new antiepileptic drug rufinamide (RFN) in human plasma and saliva is reported. Samples (250 μl) are alkalinized with ammonium hydroxide (pH 9.25) and extracted with dichloromethane using metoclopramide as internal standard. Separation is achieved with a Spherisorb silica column (250 × 4.6 mm i.d., 5 μm) at 30 °C using as mobile phase a solution of methanol/dichloromethane/n-hexane 10/25/65 (vol/vol/vol) mixed with 6 ml ammonium hydroxide. The instrument used was a Shimadzu LC-10Av chromatograph and flow rate was 1.5 ml min^-1, with a LaChrom L-7400 UV detector set at 230 nm. Calibration curves are linear [r ² = 0.998 ± 0.002 for plasma (n = 10) and r ² = 0.999 ± 0.001 for saliva (n = 9)] over the range of 0.25–20.0 μg ml^-1, with a limit of quantification at 0.25 μg ml^-1. Precision and accuracy are within current acceptability standards. The assay is suitable for pharmacokinetic studies in humans and for therapeutic drug monitoring.     

CO<Subscript>2</Subscript> corrosion inhibition of X-70 pipeline steel by carboxyamido imidazoline

The corrosion inhibition of X-70 pipeline steel in saltwater saturated with CO₂ at 50 °C with carboxyamido imidazoline has been evaluated by using electrochemical techniques. Techniques included polarization curves, linear polarization resistance, electrochemical impedance, and electrochemical noise measurements. Inhibitor concentrations were 0, 1.6 × 10⁻⁵, 3.32 × 10⁻⁵, 8.1 × 10⁻⁵, 1.6 × 10⁻⁴, and 3.32 × 10⁻⁴ mol l⁻¹. All techniques showed that the best corrosion inhibition was obtained by adding 8.1 × 10⁻⁵ mol l⁻¹ of carboxyamido imidazoline. For inhibitor concentrations higher than 8.1 × 10⁻⁵ mol l⁻¹ a desorption process occurs, and an explanation has been given for this phenomenon.     

FAD-modified SiO2/ZrO2/C ceramic electrode for electrocatalytic reduction of bromate and iodate

SiO₂/ZrO₂/C carbon ceramic material with composition (in wt%) SiO₂ = 50, ZrO₂ = 20, and C = 30 was prepared by the sol–gel-processing method. A high-resolution transmission electron microscopy image showed that ZrO₂ and the graphite particles are well dispersed inside the matrix. The electrical conductivity obtained for the pressed disks of the material was 18 S cm⁻¹, indicating that C particles are also well interconnected inside the solid. An electrode modified with flavin adenine dinucleotide (FAD) prepared by immersing the solid SiO₂/ZrO₂/C, molded as a pressed disk, inside a FAD solution (1.0 × 10⁻³ mol L⁻¹) was used to investigate the electrocatalytic reduction of bromate and iodate. The reduction of both ions occurred at a peak potential of −0.41 V vs. the saturated calomel reference electrode. The linear response range (lrr) and detection limit (dl) were: BrO₃ ⁻, lrr = 4.98 × 10⁻⁵–1.23 × 10⁻³ mol L⁻¹ and dl = 2.33 μmol L⁻¹; IO₃ ⁻, lrr = 4.98 × 10⁻⁵ up to 2.42 × 10⁻³ and dl = 1.46 μmol L⁻¹ for iodate.     

Simultaneous determination of catechol and hydroquinone based on poly (diallyldimethylammonium chloride) functionalized graphene-modified glassy carbon electrode

Simultaneous determination of catechol (CC) and hydroquinone (HQ) were investigated by voltammetry based on glassy carbon electrode (GCE) modified by poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G). The modified electrode showed excellent sensitivity and selectivity properties for the two dihydroxybenzene isomers. In 0.1 mol/L phosphate buffer solution (PBS, pH 7.0), the oxidation peak potential difference between CC and HQ was 108 mV, and the peaks on the PDDA-G/GCE were three times as high as the ones on graphene-modified glass carbon electrode. Under optimized conditions, the PDDA-G/GCE showed wide linear behaviors in the range of 1 × 10⁻⁶−4 × 10⁻⁴ mol/L for CC and 1 × 10⁻⁶−5 × 10⁻⁴ mol/L for HQ, with the detection limits 2.0 × 10⁻⁷ mol/L for CC and 2.5 × 10⁻⁷ mol/L for HQ (S/N = 3) in mixture, respectively. Some kinetic parameters, such as the electron transfer number (n), charge transfer coefficient (α), and the apparent heterogeneous electron transfer rate constant (k _s), were calculated. The proposed method was applied to simultaneous determine CC and HQ in real water samples of Yellow River with satisfactory results.     

A compact miniaturized continuous flow system for the determination of urea content in milk

A multicommutation-based flow system with photometric detection was developed, employing an analytical microsystem constructed with low temperature co-fired ceramics (LTCC) technology, a solid-phase reactor containing particles of Canavalia ensiformis DC (urease source) immobilized with glutaraldehyde, and a mini-photometer coupled directly to the microsystem which monolithically integrates a continuous flow cell. The determination of urea in milk was based on the hydrolysis of urea in the solid-phase reactor and the ammonium ions produced were monitored using the Berthelot reaction. The analytical curve was linear in the urea concentration range from 1.0 × 10⁻⁴ to 5.0 × 10⁻³ mol L⁻¹ with a limit of detection of 8.0 × 10⁻⁶ mol L⁻¹. The relative standard deviation (RSD) for a 2.0 × 10⁻³ mol L⁻¹ urea solution was lower than 0.4% (n = 10) and the sample throughput was 13 h⁻¹. To check the reproducibility of the flow system, calibration curves were obtained with freshly prepared solutions on different days and the RSD obtained was 4.7% (n = 6). Accuracy was assessed by comparing the results of the proposed method with those from the official procedure and the data are in close agreement, at a 95% confidence level.     

Electrochemical behaviors of metol on ionic-liquid-modified carbon paste electrode and its analytical application

The electrochemical behaviors of metol on an ionic liquid N-butylpyridinium hexafluorophosphate modified carbon paste electrode (IL-CPE) were studied in this paper. The results indicated that a pair of well-defined quasi-reversible redox peaks of metol appeared with the decrease of overpotential and the increase of redox peak current, which was the characteristics of electrocatalytic oxidation. The electrocatalytic mechanism was discussed and the electrochemical parameters were calculated with results of the charge-transfer coefficient (α) as 0.45, the electrode reaction rate constant (k _s) as 4.02 × 10⁻³ s⁻¹, and the diffusion coefficient (D) as 6.35 × 10⁻⁵ cm²/s. Under the optimal conditions, the anodic peak current was linear with the metol concentration in the range of 5.0 × 10⁻⁶ ∼ 1.0 × 10⁻³ mol/L (n = 11, γ = 0.994) and the detection limit was estimated as 2.33 × 10⁻⁶ mol/L (3σ). The proposed method was successfully applied to determination of metol content in synthetic samples and photographic solutions.     

Electrochemical methods for simultaneous determination of trace amounts of dopamine and uric acid using a carbon paste electrode incorporated with multi-wall carbon nanotubes and modified with α-cyclodextrine

In this work, we investigate the electrochemical activity of dopamine (DA) and uric acid (UA) using both a bare and a modified carbon paste electrode as the working electrode, with a platinum wire as the counter electrode and a silver/silver chloride (Ag/AgCl) as the reference electrode. The modified carbon paste electrode consists of multi-walled carbon nanotubes (>95%) treated with α-cyclodextrine, resulting in an electrode that exhibits a significant catalytic effect toward the electro-chemical oxidation of DA in a 0.2-M Britton–Robinson buffer solution (pH 5.0). The peak current increases linearly with the DA concentration within the molar concentration ranges of 2.0 × 10⁻⁶ to 5.0 × 10⁻⁵ M and 5.0 × 10⁻⁵ to 1.9 × 10⁻⁴ M. The detection limit (signal to noise >3) for DA was found to be 1.34 × 10⁻⁷ M, respectively. In this work, voltammetric methods such as cyclic voltammetry, chronoamperometry, chronocuolometry, differential pulse and square wave voltammetry, and linear sweep and hydrodynamic voltammetry were used. Cyclic voltammetry was used to investigate the redox properties of the modified electrode at various scan rates. The diffusion coefficient (D, cm² s⁻¹ = 3.05 × 10⁻⁵) and the kinetic parameters such as the electron transfer coefficient (α = 0.51) and the rate constant (k, cm³ mol⁻¹ s⁻¹ = 1.8 × 10³) for DA were determined using electrochemical approaches. By using differential pulse voltammetry for simultaneous measurements, we obtained two peaks for DA and UA in the same solution, with the peak separation approximately 136 mV. The average recovery was measured at 102.45% for DA injection.     

Kinetic Determination of Nanogram Levels of Manganese(II) by Naphthol Blue Black–Potassium Periodate–1,10-Phenanthroline System

 The catalytic effect of manganese(II) on the oxidation of Naphthol Blue Black, with potassium periodate in the presence of 1,10-phenanthroline in weakly acidic media is studied. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 618 nm. Under the optimum conditions (3 × 10⁻⁵ mol dm⁻³ Naphthol Blue Black, 6 × 10⁻⁴ mol dm⁻³ potassium periodate, 1 × 10⁻⁴ mol dm⁻³ 1,10-phenanthroline, 0.1 mol dm⁻³ acetate buffer – pH 4.0, 60 °C, 5 min) manganese(II) in the range 0.08–4 ng cm⁻³ can be determined by the fixed-time method with a detection limit of 0.025 ng cm⁻³. The influence of foreign ions on the accuracy of the results is investigated. The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of manganese in cucumbers, garlic cloves and parsley leaves. Received June 12, 2000. Revision December 12, 2000.