Analytical Letters

Pereira Lara, Paulo Celso; Silveira, Josianne Nicácio; Neto, Waldomiro Borges; Borba da Silva, José Bento

doi: 10.1080/00032710802237723pmid: N/A

Abstract The procedure proposed in this work includes a 50% v/v dilution of breast milk with TRIS (hidroximetilaminometano 80% v/v) or MEA (monoetanolamina 20% v/v) solutions and the introduction of 20 µL samples or analytical solutions in a graphite furnace. The optimization of the instrumental conditions was made using multivariate tools (fractional factorial and central composite design planning). The accuracy was tested with certified reference material (Infant Formulat NIST® 1846) using the optimized conditions for each diluent. The accuracy has only been acceptable when TRIS was used. The method used to determine Mn in breast milk with a limit of detection of 0.28 µg L−1 and a characteristic mass of 1.9 pg.

Mitić, Snežana S.; Micić, Ružica J.; Budimir, Milana V.

doi: 10.1080/00032710902809017pmid: N/A

Abstract A high sensitive, accurate and simple kinetic method has been developed for determination of trace of Co(II) ions, based on its strongly catalytic effect in the reaction oxidation of disodium-6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphtalenesulfonic acid (artificial color, Sunset Yellow FCF, E110 in text selected as SY) by hydrogen peroxide in borate buffer at pH of 9.5, by monitoring the rate of disappearance of SY. Reaction rate was monitored spectrophotometrically, at λmax of the SY at 478.4 nm. The optimum operating conditions regarding reagents concentration and temperature were established. The tangent method was adopted for constructing the calibration curve, which was found to be linear over the concentration range 1.18–17.67 ng ml−1 and 17.67–58.90 ng ml−1 of Co(II). The limit of detection (3σ) is 0.15 ng ml−1, and limit of quantification (10σ) is 0.5 ng ml−1. The effects of the other ions on the reaction rate were determined for an assessment of the selectivity of the method. The developed kinetic procedure was successfully applied for the determination of Co(II) in pharmaceutical and urine samples. The unique features of this procedure are that the determination can be performed at room temperature, and the analysis time is short. The newly developed method is high sensitive, simple, inexpensive and efficient for use in the analysis of a large number of samples.

Karthikeyan, S.; He, J.; Joshi, U. M.; Balasubramanian, R.

doi: 10.1080/00032710902807797pmid: N/A

Abstract A rapid, microwave-based extraction method was employed to oxidize all forms of nitrogen to nitrate in environmental samples using persulfate. The digest was then analyzed spectrophotometrically after an offline reduction of nitrate to nitrite using a cadmium reductor column was completed. The precision of the method was tested at the 0.5 mg l−1 level and was 5.2% (N = 10). The detection limit based on S/N = 3 was calculated to be 0.15 mg l−1. The method was thoroughly validated by comparison of analytical techniques and intralaboratory comparison studies.

Medina, R. Garrido; Malo, D. López; Calatayud, J. Martínez

doi: 10.1080/00032710902722103pmid: N/A

Abstract The present article deals with a new procedure for determination of the herbicide flumetsulam. The fluorimetric procedure is performed on the basis of photo-increased fluorimetric emission of the pesticide solution and by means of a multicommutation continuous-flow assembly. The alkaline solution containing the analyte is irradiated online and then directly forced through the fluorimeter flow cell. The analysis of different samples is completely automated, as the analyte separation was performed online by including a separation cartridge in the manifold. When dealing with solid samples (such as soil samples), the automation was completed by adding to the manifold the corresponding device for the aqueous extraction of the analyte from the sample suspension.

Suarez, Willian Toito; Bonifácio, Viviane Gomes; Madi, Alexandro Alves; Fatibello-Filho, Orlando

doi: 10.1080/00032710902722095pmid: N/A

Abstract A novel, simple, and rapid flow-injection method for the spectrophotometric determination of captopril in pharmaceutical products, using a solid-phase reactor with silver chloranilate (Ag2C6Cl2O4) immobilized in a polyester resin, is presented. This method explored the formation of an insoluble salt between Ag(I) and captopril in the solid-phase reactor, releasing chloranilate anion ( ). Then, this anion reacted with ferric ions to produce a complex, , which was monitored spectrophotometrically at 528 nm. The analytical curve was linear in the captopril concentration range from 1.0 × 10−5 to 5.0 × 10−4 mol l−1 with a detection limit of 8.0 × 10−6 mol l−1. The relative standard deviation (RSD) was 0.35% (n = 10) for a solution of 3.0 × 10−4 mol l−1 captopril solution, and an analytical frequency of 70 h−1 was obtained. The effects of excipients frequently found with captopril in pharmaceutical formulations, such as lactose, microcrystalline cellulose, starch, and magnesium stearate, were evaluated using the proposed flow-injection method. None of these substances caused significative interference in the proposed method. The method was successfully applied to the determination of captopril in pharmaceutical products, and the results were compared with results obtained using a potentiometric method.

Němcová, I.; Rychlovský, P.; Havelcová, M.

doi: 10.1080/00032710902726088pmid: N/A

Abstract A new method for flow-injection analysis (FIA) for the determination of penicillins based on the extraction and spectrophotometric determination of ion associates with selected thiazine dyes (methylene blue, azure A, and azure B) is proposed. The reaction conditions (cdye = 2 × 10−4 mol l−1, cKCl = 1 mol l−1, pH ≅ 6, λ = 635 nm) were found. The factorial design has been carried out to determine the optimum flow conditions. A wide linear dynamic range of calibration curves (5.1–700 µg ml−1 for penicillin V with all dyes, R = 0.9985) and good repeatability (e.g., relative standard deviation [RSD] = 4.6–0.6% in this concentration range for the reaction with azure B) were found. The detection limit for penicillin V is 1.5 µg ml−1, and the determination limit is 5.1 µg ml−1. The maximum analysis rate is 35 samples per h. The practical samples of pharmaceutics were tested. There are no interferences from the additives in pharmaceutics.

Wang, Yuane; Pan, Dawei; Qin, Wei

doi: 10.1080/00032710802585725pmid: N/A

Abstract A Nafion/ionophore, 4-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) composite coated and bismuth film modified glassy carbon electrode. (GC/NA-IONO/BiFE) was described to determine trace lead sensitively and selectively. The characteristics of such modified GC/NA-IONO/BiFE were studied by scanning electron microscopy and cyclic voltammetry. The influence of various experimental parameters upon the stripping lead signal at the GC/NA-IONO/BiFE was explored. Under the optimized conditions, the differential pulse voltammetric stripping response is highly linear over the 0.1–8.0 nM lead range examined (180 s preconcentration at −1.2 V), with a detection limit of 0.044 nM and good precision (RSD = 5.4% at 0.5 nM). Also applicability to seawater samples was demonstrated at such modified electrode. The high selectivity of ionophore coupled with the excellent electrochemical characteristics of bismuth endow the GC/NA-IONO/BiFE a promising and robust tool for monitoring of trace lead rapidly and precisely.

Ali Zamani, Hassan; Reza Ganjali, Mohammad

doi: 10.1080/00032710902807821pmid: N/A

Abstract In this work, we describe the construction, performance, and applications of an original ytterbium(III) sensor based on N1,N2-bis-[1-(2-hydroxy-1,2-diphenyl)ethylidene]ethanedihydrazide (BHDEH), which acts as a suitable carrier. Because it has a low detection limit of 4.2 × 10−7 M, the sensor response for the Yb(III) ion is Nernstian over a wide concentration range: four decades of concentration (1.0 × 10−6 to 1.0 × 10−2 M). The response time of the electrode is less than 10 s, it can be used in the pH range of 3.2–8.3, and its duration is at least 2 months without any considerable potential divergence. The sensor revealed very good selectivity for Yb(III) in the presence of several metal ions. To investigate the sensor analytical applicability, it was tested as an indicator electrode in the potentiometric titration of Yb(III) solution with standard EDTA solution. The proposed electrode was also used to determine fluoride ions in mouthwash.

Hosseini, Morteza; Ganjali, Mohammad Reza; Abkenar, Shiva Dehghan; Veismohammadi, Bahareh; Riahl, Siavash; Norouzi, Parviz; Salavati-Niasari, Masoud

doi: 10.1080/00032710902807839pmid: N/A

Abstract A new fluorescent sensor containing (1-[({2-[2-(2-hydroxy-1-naphtyl)-3-(2-{[(E)-1-(2-hydroxy-1-naphtyl)methylidene]amino}ethyl)-1-imidazolidinyl]ethyl}imino)methyl]-2-naphthol) (L) was synthesized for detecting La(III) ratiometrically. Complexation between compound L and La(III) with high selectivity gives rise to a great red shift from 430 to 522 nm in the emission spectra. In acetonitrile, the red shift of fluorescent emission upon lanthanium binding is due to the formation of a 1:1 metal–ligand complex. The fluorescent probe exhibits high selectivity over other common metal ions and mono-, di-, and trivalent cations, which indicates good selectivity for La(III) ions over a large number of interfering cations.

Ebrahimi, Mahmoud; Zamani, Hassan Ali

doi: 10.1080/00032710902807847pmid: N/A

Abstract A polyvinyl chloride (PVC) membrane sensor for ytterbium(III) ions was prepared, based on 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBT) as a membrane carrier. The sensor illustrates the following characteristics: a linear dynamic range of 1.0 × 10−6 to 1.0 × 10−2 M; a Nernstian slope of 19.7 ± 0.5 mV decade−1; a detection limit of 4.4 × 10−7 M; a response time of <10 s; and use for at least 2 months without any significant potential divergence in the pH range of 3.5–8.4. Moreover, the recommended selective sensor revealed a comparatively satisfactory selectivity regarding most of the alkali and alkaline earth ions and some of the transition-metal and heavy-metal ions. In fact, it was used as an indicator electrode in the Yb(III) potentiometric titration with ethylene diamine tetra-acetic acid (EDTA) and the determination of concentration of Yb(III) ions in soil and sediment samples.