Analytical Letters

Sadeghi, Susan; Shamsipur, Mojtaba

doi: 10.1080/00032710008543033pmid: N/A

A PVC membrane electrode for Pb2 ions based on tetraphenylporphyrin was prepared. The sensor exhibits a Nernstian response for lead ions over a wide concentration range (1.0 x 10−5-1.0 x 10−2 M). The limit of detection is 8.5 x 10−6M. It has a response time of 15 s and can be used for at least three months without any divergence in potential. The proposed electrode shows a fairly good discriminating ability towards Pb2 ion in comparison to some alkali, alkaline earth, transition and heavy metal ions. The electrode can be used in the pH range 5.0 to 7.5. It was used as an indicator electrode in potentiometric titration of lead ion.

Reshetilov, A.N.; Iliasov, P.V.; Knackmuss, H.J.; Boronin, A.M.

doi: 10.1080/00032710008543034pmid: N/A

Parameters of three Nitrobacter based sensor models have been studied for the purpose of creation of a nitrite analyzer that could be used for assay of nitroaromatics. It was shown that the sensor based on N. vulgaris strain was most suitable for development of such a device. The sensor possessed high

Basavaiah, K.; Srilatha, ; Swamy, J. Manjunatha; Krishnamurthy, G.

doi: 10.1080/00032710008543035pmid: N/A

A simple, rapid and sensitive method for the determination of six phenothiazine drugs, either in pure form or in pharmaceutical formulations, is described. The method is based on the formation of stable phenothiazine free radical by the use of potassium periodate as the chromogenic reagent in sulphuric acid medium. The reaction is suggested to proceed via oxidation of the phenothiazine nucleus into a semiquinonoid radical. The wavelengths of maximum absorption range from 500 to 525nm. Molar absorptivities range from

Álvarez-Lueje, A.; Sturm, J.C.; Núñez-Vergara, L.J.; Carbajo, J.; Squella, J.A.

doi: 10.1080/00032710008543036pmid: N/A

Clonixin, a non-steroid analgesic, can be both reduced at the mercury electrode and oxidised at the glassy carbon electrode. The anodic response shows well-defined waves in a pH range between pH 2-12. The polarographic response shows two irreversible waves or peaks in the range between pH 1-6 shifting cathodically when pH increases. Above pH 7.0 all the signals disappeared. The first signal in the dpp mode at pH 1.8 was selected for analytical use. The polarographic

Ren, Yulin; Gou, Yuhui; Tang, Zhen; Liu, Peiyi; Guo, Yie

doi: 10.1080/00032710008543037pmid: N/A

This paper demonstrates the usefulness of near-infrared (NIR) spectra and artificial neural network (ANN) in nondestructive quantitative analysis of pharmaceuticals. Real data sets from near-infrared reflectance spectra of analgini powder pharmaceutical were used to build up an artificial neural network to predict unknown samples. The parameters affecting the network were discussed. A new network evaluation criterion, the degree of approximation, was employed. The overfitting was discussed. Owing to the good nonlinear multivariate calibration nature of ANN, the predicted result was reliable and precise. The relative error of unknown samples was less than 2.5%

Paschoal, L. R.; Tessarolo, F. S.

doi: 10.1080/00032710008543038pmid: N/A

Only the simultaneous analysis of the amount of Fe2− and the possible presence of Fe3+ in ferrous sulfate heptahydrated (FeSO4. 7 H2O) can guarantee covered tablets, drops or syrups with insured quality. This work suggests that these analysis are accomplished through spectrophotometric method by use of the 1, 10-phenanthroline as chelate. Thus, at 510 nm the absorption is only due to the complex of the ligand with Fe2− and at 390 nm the absorption is indicative of Fe2+/3+ coordinated. Pharmaceutical raw matter and covered tablets were analyzed. Techniques of thermogravimetric analysis (TG-DTG) were used for the knowledge of the regions of loss of water of the FeSO4. 7 H2O for the relationship to its stoichiometry.

Toral, M. Inés; Richter, Pablo; Lara, Nelson; Escudero, M. Teresa; Soto, César

doi: 10.1080/00032710008543039pmid: N/A

A second derivative spectrophotometric method has been developed for the determination of palladium and platinum in mixtures. The method is based on the formation of the platinum and palladium complexes with 3-(2-thiazolylazo)-2, 6-diaminopyridine, (2, 6-TADAP), in the presence of 1.7 M perchloric acid solution, upon heating at 90° C for 30 min and on the subsequent direct derivative spectrophotometric measurement. The zero-crossing approach and the graphic method were used for determination of platinum and palladium, respectively. Each analyte was determinated in the presence of one another in the ranges 8.9×10-7 -3.1×10-5 M for platinum and 4.6×10-7 - 6.8×10-5 M, for palladium. The detection limits achieved (3a) were found to be 2.7×10-7 M of platinum and 1.4×10-7 M of palladium. The relative standard deviations were in all instances less than 1.0%. In this work is included a study of effect of interferents and the application of the proposed method in synthetic mixtures.

Armstrong, Daniel W.; Wang, Xiande; Beesley, C. R.

doi: 10.1080/00032710008543040pmid: N/A

Although diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is mainly used for powdered solid samples, it was found to be highly effective for the analysis of certain gemstones. Small amounts of oils and resins used to fill cracks and fissures in substandard (included) emeralds and rubies could be detected. Because of their very low levels, these organic adulterants can be difficult to detect by measurement of the infrared transmittance spectrum. Rubies have a significantly larger “window-of-detection” for organic clarifying agents than do emeralds. In some cases the spectral information was sufficient to identify the oil or polymer resin. Emeralds that were treated over 20 years ago are still easily identified. The position of the emerald or ruby in the sample holder can affect the intensity of C-H and O-H stretching frequencies as well as those brands characteristic to the gemstones.

Amine, A.; Moscone, D.; Palleschi, G.

doi: 10.1080/00032710008543041pmid: N/A

A rapid method based on Seliwanoff's reaction to distinguish between UHT and sterilised milk was proposed. Lactulose was determined directly in milk with no treatment. Analysis of raw milk and its carbohydrates showed that the only interference was the relatively high concentration of lactose, which imposes the lower limit of detection. Small variations of lactulose (9mg dL−) during heat treatment could be observed when the absorbance was measured against pretreated milk (blank). This method showed a linear range between 17–170mg dL− and a detection limit lower than that of the official HPLC method. This novel procedure was compared with a commercially available enzymatic method and the results obtained correlated well.

Lenarczuk, Tomasz; Roszczyk, Iwona; Koncki, Robert

doi: 10.1080/00032710008543042pmid: N/A

Plastic cuvettes coated chemically with Prussian Blue films were investigated as quick disposable spectrophotometric test for mercapto-compounds. The determination is based on discoloration of the coating film due to its reduction by analyte. The changes of film absorbance were measured at 720 nm. It was found that the cuvettes can be used for selective determination of cysteamine, β-mercaptoethanol and L-cysteine in millimolar ranges of concentration. The test is useful for determination of L-cysteine and N-acetylcysteine in pharmaceutical products.