Planilha de validação: uma nova ferramenta para estimar figuras de mérito na validação de métodos analíticos univariados

This work presents the VALIDATION SPREADSHEET, a public domain tool that can be used to evaluate the figures of merit for univariate analytical methods. A real example of BTEX determination in environmental samples is included to illustrate its use. The spreadsheet has been developed for Excel® and Open Office®, and is available on the internet at http//lqta.iqm.unicamp.br.

Determinação condutométrica de captopril em formulações farmacêuticas utilizando sulfato de cobre(II) como titulante

A simple and rapid conductometric method for captopril determination using copper(II) sulphate solution as titrant was developed. The method was based on the chemical reaction between captopril and Cu(II) ions yielding a precipitate. The conductance of the solution was monitored as a function of the added volume of titrant. The method was applied with success for captopril determination in three pharmaceutical formulations. The relative standard deviation for six successive measurements was smaller than 0.5%. Recovery values from three samples, ranging from 97.7 to 103%, were obtained.

Desenvolvimento de metodologia analítica para determinação de colesterol em ração para ruminantes através de planejamento experimental fatorial

A chromatographic method was developed for cholesterol determination in feed for ruminants using response surface methodology. Among the five approaches of sample preparation methods tested, the saponification of the sample without heating presented less interference in the gas chromatography. The method presented a relative standard deviation (RSD) of 4.3%, recoveries between 84 and 87% and detection limit of 0.001 mg of cholesterol per g of feed.

Determinação turbidimétrica do antidepressivo amitriptilina em sistema fia explorando a formação do par iônico com lauril sulfato de sódio

The present work purposes the development of an analytical method for amitriptyline determination in pharmaceutical formulations using FIA system. It was based on interaction of amitriplyline with sodium lauryl sulphate in acid medium (pH 2.5) resulting in the ion-pair formation turbidimetrically detected at 410 nm. The fitting regression equation for range curve from 2.0 x 10-3 up to 3.2 x 10-3 mol L-1 was found to be analytical signal = -2.7417 + 0.1538 [amitriptyline] (r = 0.99991) with a detection limit of 1.8 x 10-3 mol L-1. The precision assessed as relative standard deviation (n = 10) was found to be 2.40 and 1.94%, for the respective concentration of amitriplyline 2.0 x 10-3 and 3.2 x 10-3 mol L-1 and the sample throughout was 60 h-1. The accuracy of method was successfully assessed in pharmaceutical formulation after comparison with a reference analytical method.

Determinação espectrofotométrica em fluxo de cloro em água usando célula de longo caminho óptico e multicomutação

A multicommuted method for determination of chlorine in water samples using a 100-cm cell was developed. In this method, orto-Tolidine reacts with chlorine and the product was monitored at 438 nm. The analytical curve for chlorine was linear in concentration range from 1.34x10-6 to 2.01x10-5 mol L-1 with a detection limit of 9.40x10-8 mol L-1. A sampling rate of 45 h-1and a RSD of 1.0 % (n = 15) were obtained. The method was applied with success for chlorine determination in six water samples.

Resíduos de agrotóxicos em alimentos: uma preocupação ambiental global - Um enfoque às maçãs

This paper describes the use of pesticides in agriculture. Research has shown that significant quantities of pesticide residues have been found in many types of foods. Thus, an overview is given of pesticide residue determinations in fruits and vegetables, with special attention to apples. The toxicity and the adverse effects possibly caused by the exposure of these compounds are alerting the scientific community to develop studies about the validation of analytical methods for multiresidue pesticide determination in these samples. This review shows that pesticide-residue determination in apples is becoming a very important and challenging issue.

Sistema multicomutado de análise em fluxo para determinação de amônio e monocloramina em águas residuais e produtos de desinfecção

A binary sampling flow analysis system equipped with gas diffusion cell was developed for NH4+ and/or NH2Cl determination in wastewater and disinfection products samples based on the Berthelot reaction of the NH2Cl diffused through the semi-permeable PTFE membrane. The effect of the analytical conditions related to the reaction and flow parameters were evaluated and N-NH4+ and N-NH2Cl were determined in concentration ranges from 0.17 to 5 mg L-1 and from 0.5 to 14.5 mg L-1, respectively. Limits of detection (3σ) of 50 and 140 µg L-1 for N-NH4+ and N-NH2Cl were calculated, respectively, and RSD of 5 and 2% were calculated for 10 consecutive determinations of N-NH4+ (1 and 3 mg L-1) and N-NH2Cl (3 and 9 mg L-1), respectively with 30 determinations h-1.

Comparação entre métodos de quantificação em cromatografia gasosa: um experimento para cursos de química

This article describes an experiment designed to teach quantitative determination in gas chromatography (GC) in Organic and Analytical Chemistry practical classes. The experiment consisted of extracting and analyzing eugenol from clove seeds to perform a quantitative approach aimed at comparing results obtained by external and internal calibration procedures. Therefore, this experiment proved to be very effective tool to enhance students awareness on the need to understand different types of calibration in GC and on how to avoid common experimental errors, and to find the best ways to eliminate their interference during the quantitative analysis phase.

Determinação condutométrica de cloridrato de metformina em formulações farmacêuticas empregando nitrato de prata como titulante

A simple, precise, rapid and low-cost conductometric titration method for the determination of metformin hydrochloride (MET) in pharmaceuticals using silver nitrate as titrant is proposed. The method was based on the chemical reaction between the chloride of metformin hydrochloride molecule and Ag(I) ions, yielding the precipitate AgCl(s). The method was applied for MET determination in three pharmaceuticals and the obtained results with proposed method were in close agreement with those results obtained using an official method of the British Pharmacopoeia, at a 95% confidence level.

Determinação de olanzapina em formulações farmacêuticas por espectrofotometria: desenvolvimento e validação

Spectrophotometric methods of zero order, first and second derived order had been developed for olanzapine determination in tablets using ethanol and isopropanol as solvent. The two solvents revealed to be adequate. For the three methods the calibration curve coefficient of correlation had been greater than 0.9998 with limit of detection varying from 0.068 to 0.190 mg L-1, in ethanol, and 0.026 to 0.205 mg L-1, in isopropanol. The inter-day precision was inferior to 1.1 and 1.9 mg L-1 for ethanol and isopropanol, respectively. The average recoveries varied from 98 to 101%, in ethanol and 99 to 103% in isopropanol.

Determinação espectrofotométrica de cefalexina em formulações farmacêuticas explorando a sua reação de transferência de carga com a quinalizarina

This work proposes a new simple and fast spectrophotometric method for cephalexin determination in pharmaceutical formulations. The method is based on the charge transfer reaction between cephalexin and quinalizarin in dimethylsulfoxide medium. Several analytical parameters related to the system were optimized and the reaction was characterized in terms of stoichiometry. Also, association constant and apparent molar absorptivity of the product were determined. The method presented a limit of detection of 0.46 mg L-1 and a quantification limit of 1.5 mg L-1. It was successfully applied in the determination of cephalexin in two samples of commercial pharmaceutical formulations.

Determinação do teor de ésteres graxos em biodiesel metílico de soja por cromatografia gasosa utilizando oleato de etila como padrão interno

A method for ester content determination in soybean methyl biodiesel was studied, using ethyl oleate as internal standard. A biodiesel sample was analyzed and had its purity estimated as 92.8%. Method accuracy was evaluated by comparison with the result obtained via EN14103, with a relative difference of 0.1%. Repetitivity and intermediate precision were estimated as 2 and 1.5%, respectively.

Alternativas verdes para o preparo de amostra e determinação de poluentes fenólicos em água

The restricted availability of water sources suitable for consumption and high costs for obtaining potable water has caused an increase of the conscience concerning the use. Thus, there is a high demand for "environmentally safe methods" which are according to the principles of Green Chemistry. Moreover, these methods should be able to provide reliable results for the analysis of water quality for various pollutants, such as phenol. In this work, greener alternatives for sample preparation for phenol determination in aqueous matrices are presented, which include: liquid phase microextraction, solid phase microextraction, flow analysis, cloud point extraction and aqueous two-phase systems.

Determinação de enxofre em amostras vegetais por oxidação via seca em meio alcalino com detecção espectrofométrica

The sulphur take an essential role in plants and it is one of the main nutrients in several metabolic processes. The dry ash oxidation, using alkaline oxidizers agent, is the simplest and most economical form for the oxidation of Organic S to sulfate in plants. The objective of this work is to propose a method for sulfur determination in plants samples using dry ash oxidation and agent oxidizers alkaline. The quantification of S-SO4(2-) in samples was accomplished by turbidimetric method. The results demonstrated that the proposed method for oxidation alkaline was appropriate.

Desenvolvimento e validação de um método analítico por CLAE para quantificação de ácido ursólico em dispersões sólidas

Ursolic acid is a natural molecule that presents several pharmacological properties. In this work, an analytical method by RP-HPLC has been developed and validated for quantification of this drug in the solid dispersions, using PEG 6000 and Poloxamer 407 as polymers. The method was specific, linear in the range of 1.0-50.0 µg mL-1 (r<0.99), precise (CV < 5% for both inter- and intra-assays), accurate (maximum deviation of ± 13%), and robust to the parameters evaluated. This method has proved to be simple and useful for ursolic acid determination in solid dispersions, enabling its determination in pharmaceutical dosage form.