Métodos imunoquímicos para análise de contaminantes ambientais: conceitos, estado da arte e perspectivas

Immunoassay techniques provide simple, powerful and inexpensive methods for analysis of environmental contaminants. However, the acceptance of immunoassays is dependent on the clear demonstration of quality and validity compared to more traditional techniques. In this review, primarily, the understanding and the fundamentals of immunoassay methods are given in order to make good use of immunoassays, especially of EIA tests. Special attention is given to the concepts related to the enzyme-linked immunosorbent assay (ELISA) formats, such as inhibition concentration at 50% (IC50), detection limit (LOD), cross-reactivity (CR %). It is also explained why some immunoassays are quantitative methods whereas others can only be used as screening methods. A list of main commercial kits for detection of priority pollutants is given in order to help analysts. Others formats, such as flow-injection immunoassay analysis (FIIA), immunoassay chromatography and immunosensors are also cited.

Aplicação de análise de componentes principais para verificação de atribuições de sinais nos espetros de RMN ¹H: o caso dos 3-aril (1,2,4)-oxadiazol-5-carboidrazida benzilidenos

The ¹H NMR data set of a series of 3-aryl (1,2,4)-oxadiazol-5-carbohydrazide benzylidene derivatives synthesized in our group was analyzed using the chemometric technique of principal component analysis (PCA). Using the original ¹H NMR data PCA allowed identifying some misassignments of the proton aromatic chemical shifts. As a consequence of this multivariate analysis, nuclear Overhauser difference experiments were performed to investigate the ambiguity of other assignments of the ortho and meta aromatic hydrogens for the compound with the bromine substituent. The effect of the 1,2,4-oxadiazol group as an electron acceptor, mainly for the hydrogens 12,13, has been highlighted.

Análise enantiosseletiva de fármacos: contribuições da cromatografia líquida de alta eficiência e eletroforese capilar

The demand for analytical methods suitable for accurate and reproducible determination of drug enantiomers has increased significantly in the last years. High-performance liquid chromatography (HPLC) using chiral stationary phases and capillary electrophoresis (CE) are the most important techniques used for this purpose. In this paper, the fundamental aspects of chiral separations using both techniques are presented. Some important aspects for the development of enantioselective methods, particularly for the analysis of drugs and metabolites in biological samples, are also discussed.

Informações essenciais para a caracterização de um sistema de análise em fluxo

Essential aspects for characterization of a flow-based analytical procedure or system are discussed in order to permit the composition of a checklist that will lead to a protocol for reporting results and systems in flow analysis. Aspects more related to chromatographic procedures are not considered. The intent is to present normalized proposals in the field of flow analysis for practitioners and developers.

Análise de praguicidas organofosforados em água por extração em fase sólida (SPE) utilizando discos C18 e cromatografia em fase gasosa: avaliação da contaminação do reservatório de Furnas (MG-Brasil)

Solid phase extraction (SPE) in C18 disks has been optimized and validated for extraction of 5 organophosphorus (OP) pesticides in water. Extraction has been followed by separation and detection by gas chromatography/flame photometry. Excellent linearity was obtained for all compounds (r greater than 0.99), with CVs between 1.0-6.9%, recoveries between 73-95% and quantification limits between 2.5-5.0 µg L-1. Samples from Furnas dam were analyzed monthly during one year and 10% showed OP pesticide residues.

Diazepam e nordiazepam em plasma: métodos de extração líquido-líquido e em fase sólida no pré-tratamento de amostras para análise cromatográfica em fase líquida

Analysis of diazepam (DZP) and its active metabolite nordiazepam (NDZP) in plasma is commonly performed in clinical medicine to ensure proper therapeutic effects while minimizing the incidence of toxicity. This study aimed to optimize analytical parameters and compare two pre-treatment techniques, liquid-liquid (LLE) and solid phase extraction (SPE), as well as liquid chromatographic conditions to analyze simultaneously DZP and NDZP in plasma from 20 patients treated with a daily dose of 10 mg. Both techniques showed to be well in line with the international criteria for analytical validation, which permitted to quantify DZP (66.2 - 1148.6 ng mL-1) and NDZP (138.5 - 808.6 ng mL -1) in all samples. The correlation coefficients between SPE and LLE were respectively 0.9729 for DZP and 0.9643 for NDZP.

Alendronato de sódio: metodologias para análise quantitativa

This paper presents a review of some published proposals for the analysis of sodium alendronate. The drug is an aminobisphosphonate compound used to inhibit the osteoclastic resorption of bone, and different methods were developed for its quantitative determination. These methodologies employed reversed-phase or ion-exchange HPLC analysis, both associated with different detectors: UV and fluorescence detection after derivatization of the drug, conductivity and refractive index detectors, as well as the indirect UV detection. Titrimetry and spectrophotometry (with previous complexation of the drug), which are simpler procedures, were also described, but they showed poor specificity when compared to liquid chromatography.

Análise de fármacos em material biológico: acoplamento microextração em fase sólida "no tubo" e cromatografia líquida de alta eficiência

A new solid phase microextraction (SPME) system, known as in-tube SPME, was recently developed using an open tubular fused-silica capilary column, instead of an SPME fiber, as the SPME device. On-line in-tube SPME is usually used in combination with high performance liquid chromatography. Drugs in biological samples are directly extracted and concentrated in the stationary phase of capillary columns by repeated draw/eject cycles of sample solution, and then directly transferred to the liquid chromatographic column. In-tube SPME is suitable for automation. Automated sample handling procedures not only shorten the total analysis time, but also usually provide better accuracy and precision relative to manual techniques. In-tube SPME has been demonstrated to be a very effective and highly sensitive technique to determine drugs in biological samples for various purposes such as therapeutic drug monitoring, clinical toxicology, bioavailability and pharmacokinetics.

Desenvolvimento de colunas cromatográficas de meios de acesso restrito proteína-imobilizada e suas avaliações para análise de fármacos com injeção direta de plasma humano

A series of bovine serum albumin-immobilized supports have been prepared and used as restricted access media (RAM) columns. Restricted-access supports combine size-exclusion of proteins and other high-molar-mass matrix components with the simultaneous enrichment of low-molar mass analytes. These characteristics were chromatographically evaluated for the columns. The RAM-BSA (Bovine Serum Albumin) columns showed excellent performance for exclusion of human plasma protein with good retention capacity for a series of acidic, basic, and neutral drugs.

Análise quiral por espectrometria de massas através da utilização do método cinético

Novel and quantitative mass spectrometry methods for rapid and accurate enantiomeric excess determination are presented. These methodologies use electrospray ionization (ESI) and mass spectrometry (MS) to detect and analyze, via collision-induced dissociation (CID), mass-selected transition metal complexes that promote enantio especific interactions. The data from CID are conveniently treated by the kinetic method, a sensitive linear free energy method of treating mass spectrometric results. Four different variations of this methodology are described: single ratio method (S R), quotient ratio method (Q R), fixed ligand method (S Rfixed), and quotient ratio method with fixed ligand (Q Rfixed). These individual methods are compared and their main features discussed in detail.

Análise estatística e optimização de perfis de redução termoprogramada (TPR)

The effect of operational variables and their interaction in TPR profiles was studied using a fractional factorial experimental design. The heating rate and the reducing agent concentration were found to be the most important variables determining the resolution and sensitivity of the technique. They showed opposite effects. Therefore, they should be manipulated preferentially in order to obtain optimized TPR profiles. The effect of sample particle size was also investigated. The tests were carried out within a Cu/Zn/Al2O3 catalyst used for the water-gas shift reaction that presented two distinct species of Cu2+ in TPR profiles.

O efeito SERS na análise de traços: o papel das superfícies nanoestruturadas

Surface-Enhanced Raman Scattering - SERS - underwent huge advances since a single-molecule Raman spectrum was obtained in 1997. New theoretical and experimental approaches emerged since then leading to a better understanding of the enhancement mechanisms and to a significant improvement in the Raman signal. This review presents the current status of the SERS effect and the promising ways of designing and preparing high performance SERS-active substrates.

Integração de técnicas analíticas e proposta de experimentos para cursos de graduação em análise instrumental: uso de espectrômetro de absorção atômica para medidas de absorção molecular

Simple experiments are proposed for measuring molecular absorption of chromate and dichromate ions using an atomic absorption spectrometer. The experiments can help undergraduate students in instrumental analysis courses understand important aspects involving conceptual and instrumental similarities and differences between frequently used analytical techniques. Hollow cathode lamps were selected with wavelengths in the region of molecular absorption of chromate and dichromate. Calibration curves were obtained and the linear dynamic range was evaluated. Results were compared with those obtained in a molecular absorption spectrometer. The molar absorptivities obtained were also compared.

Metodologia para análise simultânea de ácido nicotínico, trigonelina, ácido clorogênico e cafeína em café torrado por cromatografia líquida de alta eficiência

A reverse phase liquid chromatography method was developed for simultaneous determination of trigonelline, caffeine, nicotinic and chlorogenic (5-CQA) acids in roasted coffee. A gradient of acetic acid/acetonitrile was used as mobile phase and detection was carried out in the UV. The samples were extracted with acetonitrile/water (5:95 v/v) at 80 ºC/10 min. Good recovery (89 to 104%), repeatability and linearity were obtained. Detection limits of 0.01, 0.15, 0.04 and 0.04 mg mL-1 were observed for nicotinic acid, trigonelline, 5-CQA and caffeine. The method, applied to arabica and robusta coffees with different degrees of roasting, was efficient and fast (~35 min) and also allowed identification of cinnamic acids.

Variação química do óleo essencial de Hyptis suaveolens (L.) Poit., sob condições de cultivo

This study was performed to establish the correlation between the growth conditions and essential oil composition of Hyptis suaveolens from Alfenas (MG), Brazil. The plants were grown in a greenhouse, four treatments were used and they were harvested at two different periods of time (60 and 135-day-old plants). The essential oil composition was determined by GC-MS analysis. The terpenes spathulenol, globulol, dehydroabietol, a-cadinol and beta-phellandrene were the major constituents found in the essential oil. Oxygenated sesquiterpenes represented the main group of constituents in most of the treatments. The major changes in the essential oil composition were found in 135-day-old plants grown under NPK deficiency. We also identified three groups of volatile components that have not been previously described in H suaveolens.