George-Emil Baiulescu

Quality and Reliability in Analytical Chemistry

Quality in Chemical Analysis The Reliability in the Analytical Chemistry The Reliability of the Sampling The Connection between Reliability and Analytical Method The Connection between Reliability and Instruments The Reliability of Data Processing Analytical Process The Role of Standards and Standardization on Reliability of the Analytical Information References

Differential pulse cathodic stripping voltammetric determination of selenium in pharmaceutical products

The aim of this paper is to determine selenium from pharmaceutical products by differential pulse cathodic stripping voltammetry. Firstly, were established the optimum parameters for voltammetric determination of selenium (electrolyte, deposition time, pulse duration, pulse amplitude, etc.) and secondly, the content of selenium was determined in five pharmaceutical products. The drug samples were treated with a mixture of 6 ml HNO(3) and 1 ml H(2)O(2) in the microwave oven. Due to the matrix effects the method of addition is preferred. The peak potential is -0.545 V vs. Ag/AgCl, and the calibration curve is linear up to 0.125 ng/ml, but selenium was determined from pharmaceutical products used the calibration curve in the range 8-64 ng/ml, due to the concentration of selenium in these tablets.

Amiodarone-selective membrane electrode

Abstract A liquid membrane electrode based on an amiodarone-dipicrylamine ion-pair complex, dissolved in nitrobenzene as solvent, is proposed for the determination of amiodarone, an antiarrhythmic drug. The linear response covers the range 10−2–10−5 M amiodarone solution, with a slope of 57.3 mV/decade (pH range 0.80 to 4.80). The detection limit is 4 × 10−9 M. The electrode shows a good stability, reproducibility and fast response. The selectivity is good against K+ and Ca2+. There are two strong interfering ions, ephedrine and polyvinylprolidone. The characteristics of the electrode make it useful for the determination of amiodarone by direct and indirect potentiometric methods. Through the indirect potentiometric method, amiodarone can be determined as an active substance with an average recovery of 99.60% and a relative standard deviation of 0.67%, and this method can also be used for its determination in pharmaceutical dosage forms such as tablets and ampoules with a relative standard deviation less than 1%. The electrode can also be used for dissolution tests of amiodarone tablets. The physical processes are numerically simulated by typical equations. The apparent first-order rate constants for disintegration and dissolution processes have been calculated.

Determination of urinary oxalate using oxalate-selective membrane electrodes

The paper proposes two counter-ions for oxalate-selective liquid membrane construction: [Fe(o-phenanthroline)3]2+ (I) and [Fe(neocuproine)3]2+ (II). Nitrobenzene (NB) was used as solvent. The ion-selective membrane electrodes have a near-Nernstian response over the concentration ranges: 100–0.01 (I) and 100–0.1 (II) μmol/l, respectively. The limit of detection was 1 nmol/l for both membrane electrodes. The working pH ranges are: 2.0–8.0 (I) and 2.0–7.0 (II), respectively. Due to their response characteristics as well as to the results obtained for the recovery tests (relative standard deviation (RSD) <1%), the ion-selective membrane electrodes can be used for urinary oxalate determination.

The Construction of an Amperometric Immunosensor for the Thyroid Hormone (+)-3,3′,5-Triiodo-L-Thyronine (L-T3)

ABSTRACT A novel amperometric immunosensor based on graphite paste (graphite powder and paraffin oil) has been constructed. The graphite paste is impregnated with mouse monoclonal anti-(+)-3,3′,5-triiodo-L-thyronine (anti-T3). The immunosensor can be reliably used for L-T3 assay in thyroid and in drugs, using chronoamperometric technique, at ppb-ppt concentration levels. The potential used for L-T3 assay was 650 mV vs Ag/AgCl. The surface of the immunosensor can be regenerated by simply polishing, obtaining fresh immunocomposite ready to be used in a new assay.

Determination of Copper, Cadmium, Zinc And Lead In ArgeŞ River In Romania During Four Seasons By Inductively Coupled Plasma Atomic Emission Spectrometry And Anodic Stripping Voltammetry

ABSTRACT The paper represents a continued study of selected heavy metals concentration in the Argeş River, the fifth river in length from Romania. For the determination of metal ion concentration in Argeş river was used Atomic Absorption Spectrometry for sodium, potassium and magnesium; Direct Coupled Plasma Atomic Emission Spectrometry for calcium; Inductively Coupled Plasma Atomic Emission Spectrometry for copper, cadmium, zinc, aluminium, lead, titanium, zirconium, chromium, molybdenum, manganese, iron and nickel. Copper, cadmium, zinc and lead concentration were determined by ICP–AES and ASV and results were reliable. By comparison of the results a good agreement between these two techniques is observed.

Application of Electroseparation Methods in β-Agonist Drugs Characterization

The possibility of using electroseparation methods with UV/Vis detection in the study of some β-agonist drugs has been investigated. Clenbuterol, Salbutamol and Terbutaline were separated and quantitatively analyzed in various drugs. The influence of several parameters, such as pH, temperature, surfactants, column type and electrical values were studied. The electroseparation methods have shown good reproducibility, accuracy and short analysis time with a small sample preparation and low reagent consumption.

Moclobemide-selective membrane electrode and its pharmaceutical applications

A liquid membrane electrode prepared with moclobemide-dipicrylamine ion-pair complex, dissolved in nitrobenzene as solvent, was studied for analytical performance. The linear response covers the range 10(-3)-10(-6) M moclobemide solution, with a slope of 50.7 mV decade(-1) (pH range 3.5-8). The detection limit is 3 x 10(-7) M. The electrode shows stability, good reproducibility and fast response. The selectivity of the electrode is good. There are two important interfering ions: mianserin and thiamine (Vitamin B(1)). The compression excipients (such as Mg(2+), starch, talcum powder) do not interfere. These characteristics of the electrode enabled it to be used for the determination of moclobemide in drugs and as an active substance, via indirect and direct potentiometric methods. Via an indirect potentiometric method moclobemide, as an active substance, can be determined with an average recovery of 99.96% and a relative standard deviation of 0.85%, and this method can also be used for its determination in drugs with a relative standard deviation of < 2%. The electrode is useful for the determination of the dissolution rate of moclobemide tablets. The physical processes are numerically simulated by typical equations. The apparent first-order rate constants for disintegration and dissolution were calculated.

Analytical studies on the pollution of argeş river

Using two analytical techniques (ICP‐AES and ASV) the heavy metal pollution of Argeş River was studied. These techniques are characterized by similar analytical performances. The samples were collected from 13 sites starting from Capra Lake (altitude 2241 m) and finishing at Oltenita city (altitude 10 m). Argeş River is the fifth longest river in Romania after Siret, Mureş, Olt and Someş, its length is 340 km and the river flows through four cities, Curtea de Argeş, Piteşti, Gaeşti and Oltenita. The results of the determinations of Cu, Cd, Zn and Pb, indicate that the Argeş River shows relatively low pollution.

Analytical contributions to the evaluation of painting authenticity from Princely church of Curtea de Arges.

The present study contains the analyses performed for pigment samples taken from the Princely church of Curtea de Arges, one of the oldest churches in Romania. The results of our investigations have shown the source of these samples, thus being identified the pigments: natural ultramarine, cinnabar, red earth, and calcium carbonate in the painting from the 14th century, the pigments: lead white, zinc white, and Prussian blue in the repainting from the 19th century and the pigments zinc white, titanium dioxide white, bone white, yellow ochre, red ochre, green earth, artificial ultramarine, and mars red in the interventions carried out in the 20th century. The analyses consisted of light microscopy (LM) and microchemical tests, as well as energy dispersive X-ray (EDX) analysis. This system of analyses allows one to precisely determine the authenticity of certain pigments, thus avoiding the dating errors for different interventions carried out on the original mural painting from the Saint Nicholas Princely church of Curtea de Arges.