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Coffee quality is determined by analyzing its chemical, physical, sensory and hygienic-sanitary characteristics. It is a product consumed worldwide with high economic value. Thus, it can undergo several types of adulteration (either fraudulent or accidental). It is commonly adulterated through blending with cheaper products that are not easily detected by consumers, which in turn modify its appearance or taste. The main adulterants found in ground coffee are processing byproducts, such as husks, straws and sticks and cereals, such as corn, rye, rice, barley and wheat due to their low prices, in addition to being rather similar to coffee and widely available. Therefore, the present work aims to quantify adulterants (corn, coffee husk and coffee straw) found in ground coffee using thermogravimetry and the multivariate regression analysis. Coffee and adulterants have been toasted at 200 °C, ground, sieved and mixed in 22 different ratios (1–50%, m/m). Blends have been investigated by derivative thermogravimetry analysis (DTG) by employing two different types of dynamic gas atmospheres (nitrogen and synthetic air). Then, its results were used to develop multivariate models using the partial least squares to quantify the adulterants. TGA curves show samples with higher overlapping thermal events; however, DTG results present a selective coffee event between 350 and 430 °C that enables quantification. There were also fewer prediction errors using nitrogen as dynamic gas (2.6%, 1.4% and 7.7% m/m for corn, coffee husk and coffee straw, respectively) with 3–4 latent variables. As for synthetic air, there were greater prediction errors (4.7% and 4.6% m/m for corn and coffee husk, respectively), but fewer if compared to another gas atmosphere for coffee straw (4.8% m/m) using 4–5 latent variables. A combination of thermogravimetry and chemometrics proved to be quite promising and suitable for quantifying common materials used to adulterate ground coffee.

This study aims to characterize erythromycin (ERY) estolate by thermogravimetry analysis and differential scanning calorimetry. For such a purpose, compatibility testing has been conducted using binary mixtures of four excipients (magnesium stearate, sodium starch glycolate, povidone and mannitol). A comparison of simulated and experimental TG curves was made using Pearson’s correlation coefficient so as to determine possible incompatibilities by the formation of volatile thermal degradation products. (r2 of around 0.91 was found for mixtures of magnesium stearate and mannitol, i.e., there might be interactions.) Dynamic thermal FT-IR spectroscopy and multivariate curve resolution (MCR-ALS) were used to identify incompatibilities before the occurrence of mass loss observed due to the chemical decomposition found through the TG. Infrared pure profiles were obtained as a function of the temperature of each component, thus revealing that it is an important and promising tool for monitoring solid-state phase transformations. Thereby, this methodology confirms that ERY shows incompatibilities regarding magnesium stearate and mannitol, and compatibilities concerning povidone and sodium starch glycolate.

Ketoconazole (KTZ) is an antifungal agent responsible for the inhibition of 14-α-demethylase sterol. The drug–excipient compatibility studies play an important role in pharmaceutical formulations development. Interactions between drug and excipients may affect the chemical nature, stability, bioavailability and consequently the therapeutic efficacy and safety profile. The main goal of this work was to evaluate the compatibility of KTZ with some excipients: corn starch, microcrystalline cellulose, colloidal silicon dioxide, lactose monohydrate and povidone, using differential scanning calorimetry and thermogravimetry (TG). Binary mixtures in a mass ratio of 1:1 between drug and excipient were used to make the study feasible. The comparison was performed using Tonset of the melt from pure drug and its enthalpy value (ΔHf) with respective values obtained for each binary mixture. Experimental and simulated TG/DTG curves were compared using the Pearson’s correlation coefficients to assess possible incompatibilities due to thermal decomposition of organic matter and/or gaseous products released. Thus, the excipients corn starch and colloidal silicon dioxide have been shown to be incompatible with KTZ.

The complexation between humic substances (HS) extracted from manure poultry and the rare earth element (REEs) cerium (Ce) was investigated. The coordination of Ce with humic and fulvic acids occurs mainly by the carboxylate groups, increasing the thermal stability of the HS due to the reorganization of its chemical structure. The leaching of Ce3+ in phosphate buffer solution indicates Ce-phosphate precipitation over time. The complexation between Ce and benzenedicarboxylic acids used as model molecule of the HS were investigated by means of density functional calculations (DFT). The coordination of [Ce(H2O)9]3+ and [Ce(OH)(H2O)8]2+ species with the benzenedicarboxylic groups occurs preferentially in the meta position that is less electrodefficient. These results are an important step towards understanding the interactions of soil elements with natural organic matter and aqueous systems.

Since the beginning of the HIV epidemic, research has been carried out to control the virus. Understanding the mechanisms of replication has given access to the various classes of drugs that over time have transformed AIDS into a manageable chronic disease. The class of protease inhibitors (PIs) gained notice in anti-retroviral therapy, once it was found that peptidomimetic molecules act by blocking the active catalytic center of the aspartic protease, which is directly related to HIV maturation. However, mutations in enzymatic internal residues are the biggest issue for these drugs, because a small change in biochemical interaction can generate resistance. Low plasma concentrations of PIs favor viral natural selection; high concentrations can inhibit even partially resistant enzymes. Food-drug/drug-drug interactions can decrease the bioavailability of PIs and are related to many side effects. Therefore, this review summarizes the pharmacokinetic properties of current PIs, the changes when pharmacological boosters are used and also lists the major mutations to help understanding of how long the continuous treatment can ensure a low viral load in patients.

In this study, biopolymer-based pH-sensitive hydrogels have been successfully prepared using alginate, κ-carrageenan and pectin aimed at the encapsulation of pancreatin (hydrolytic enzymes like α-amylase, lipase and protease) so as to preserve enzymatic activities. Hydrogels have been characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling degree and swelling profile. Encapsulation efficiency and in vitro studies on delayed release have also been evaluated. All hydrogels presented low swelling degree and enzyme release in a gastric medium. On the other hand, high swelling degree and enzyme release were observed in an intestinal medium. Alginate hydrogel achieved optimal results concerning encapsulation efficiency (18, 68 and 53% for α-amylase, lipase and protease, respectively) and delayed release (363, 7,673 and 17,497 U for α-amylase, lipase and protease, respectively) which has been afterwards compared to a commercial pancreatin formulation (CreonTM 10,000). Thus, it presented better performance than its commercial formulation, mainly in respect of lipase.

Chitosan is a biopolymer that forms hydrogels after swell in acid medium. The environment of the three-dimensional network of the chitosan-based hydrogels can be modified by its degree of swelling and crosslinking. In this way, nicotine was incorporated in the hydrogel formulations, with or without crosslinking with glutaraldehyde (0.01%), in different swollen states. Transdermal delivery of nicotine by chitosan-based hydrogels was studied in order to achieve the prolonged administration of the drug. Thermal analysis indicated a preliminary stability of these formulations, and the mechanism of drug release from hydrogels was dependent of the swelling degree and crosslinking. These formulations were able to control the transdermal flux of nicotine for up to 48 h following zero-order kinetics. The hydrogels with higher amounts of water or the partially dried crosslinked hydrogels reduced the partition of nicotine into the skin, leading to a minor transdermal flux of the drug (

The infrared spectroscopy method using attenuated total reflectance and multivariate calibration to quantify β-galactosidase in tablets was developed and validated. The calibration step was developed using 66 calibration samples and 13 different samples in the validation process. The assay range was from 80 to 120%, and the excipients were microcrystalline cellulose, magnesium stearate, colloidal silicon dioxide, croscarmellose sodium, and crospovidone. The spectra were recorded in the range of 4000–400 cm−1 as the average of 128 scans. The optimised model was obtained using six PLS factors, and a root mean square error of prediction (RMSEP) of 1.2% and the correlation coefficient was 98%. The assay of validation samples was also compared with the official U.S. pharmaceutical test. The method was shown to be more rapid and reagent free and can be used as an alternative method to biopharmaceutical quality control.

Humic substances are the main responsible for soil conditioning and are one of the major components of the composting product. However, there is still little information about their composition and...

Fosamprenavir calcium is an amprenavir prodrug of the protease inhibitors class used in the treatment of patients with acquired immunodeficiency syndrome (AIDS). Different solid forms of this drug are described in patents, in this sense studies on the physico-chemical characterization and stability are relevant for the selection of a solid form with adequate features for pharmaceutical purposes. In the present work form I (commercial) and amorphous of fosamprenavir calcium were characterized by the techniques of Differential Scanning Calorimetry (DSC), Thermogravimetry (TGA), Powder X-ray Diffraction (PXRD), Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Furthermore, the chemical and polymorphic stability of the commercial form were evaluated by DSC, PXRD, FTIR and High-Performance Liquid Chromatography (HPLC). In the studies of characterization, thermal analyses allied to spectroscopic methods (PXRD and FTIR) demonstrated that the presence of water in the crystalline structure of Form I is fundamental for maintaining its crystallinity. In studies of accelerated stability the techniques of DSC, PXRD and FTIR showed that Form I does not suffer phase change when submitted to controlled conditions of temperature and humidity. Moreover, HPLC and FTIR proved the chemical stability of this solid form of fosamprenavir, thus demonstrating its suitability for pharmaceutical purposes.

The present study investigated the encapsulation of β-galactosidase in carrageenan, pectin and its hybrid hydrogels by using the ionotropic gelation method. The material obtained was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG/DTG) and scanning electron microscopy (SEM). The effects of pH, temperature and storage time were evaluated in terms of the catalytic activity of the free and encapsulated enzyme. Addition studies were conducted evaluating the performance of catalytic activity in vitro conditions. Carrageenan, pectin and hybrid hydrogels presented encapsulation efficiency of 58 ± 1%, 72 ± 1% and 77 ± 2%, respectively. The pectin hydrogel showed the higher β-galactosidase activity in pH and temperature tests. However, the carrageenan hydrogel exhibited best stability after been stored for three months. Carrageenan and pectin hydrogels were 2.0 and 2.4 times more efficiently than commercial tablet in the releasing β-galactosidase under in vitro conditions, respectively. The results suggest that pectin and carrageenan hydrogels may be useful for the development of new formulation of β-galactosidase.

The use of theoretical calculation to determine structural properties of fulvate-metal complex (zinc, copper and iron) is here related. The species were proposed in the ratio 1:1 and 2:1 for which the molecular structure was obtained through the semi-empirical method PM6. The calculation of thermodynamic stability ([Formula: see text]) predicted that the iron complex were more exo-energetic. Metallic ions were coordinated to the phtalate groups of the model-structure of fulvic acid Suwannee River and the calculations of vibrational frequencies suggested that hydrogen bonds may help on the stability of the complex formation.

Innovative pharmaceutical development in an attempt to enhance the bioavailability of poorly water-soluble drugs is supporting the increase in solid dispersion (SD) technology by using different excipients and solvents. Ethinyl estradiol (EE) is an estrogen component that presents poor solubility and is commercialized at low concentrations (usually 30 or 35 μg). A full solid-state characterization of EE was conducted using differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and scanning electron microscopy to examine its physicochemical properties and polymorphic state. The main aim of this work was to develop and characterize a stable SD containing EE and pharmaceutical excipients, to enhance the drug solubility. For this task, four excipients (starch, microcrystalline cellulose, lactose, and PVP) and four solvents (ethanol, acetone, dichloromethane, and chloroform) were tested. Each prepared sample was monitored by DSC and PXRD to evaluate the SD formation. Stability tests were performed with the successful SD that was stored under three different conditions [75 % relative humidity (RH)/40 °C; 90 % RH/25 °C; and 0 % RH/25 °C] and analyzed after 15 and 30 days by DSC and PXRD. The results showed that polyvinylpyrrolidone combined with any solvents was able to consistently produce a stable solid dispersion with EE.

Roasted and ground coffee is targeted by fraudulent addiction of products. In this way the determination of contaminants in coffee has economic and nutritional importance. In this study, the coffee adulteration by corn were detected using DSC (differential scanning calorimetry) and FTIR (Fourier transform infrared spectroscopy) coupled to PCA (principal component analysis), and PLS (partial least squares) models. Three different levels of roasted and ground Coffea arabica L. were used to prepare mixtures with roasted and ground corn. The level of adulteration used was between 0.5 to 40% (m/m). It was observed that both DSC and FTIR coupled with PCA are able to discriminate adulterated from unadulterated samples of coffee by corn at levels below 1%. PLS models were built with DSC and FTIR data reaching good correlation between the values of estimated and reference concentrations, with RMSECV (root mean square error of cross-validation) lower than 3.5% for DSC data and 2.7% for FTIR data.

Changes in protein levels and lipid compositions in algal cells indicate the severity of stress related to toxic concentrations of heavy metals. In this study, the effects of exposure to cadmium and copper on Chlorella vulgaris and its capacity to remove metals were evaluated. The data revealed ion removal activity by microalgae under all treatments and different levels of protein expression after 48 h of exposure. Furthermore, we analyzed lipids contents to characterize them.

This study presents a comparison of partial least squares (PLS) and multivariate curve resolution (MCR-ALS) in the quantification of polymorphic forms I and II of fexofenadine. HCl in pharmaceutical tablets using near infrared chemical imaging (NIR-CI). The PLS model built using a standard normal variate (SNV) pre-processing method resulted in satisfactory fits between the reference and predicted values, with a root mean square error of prediction ( RMSEP) for both polymorphic forms below 1.5% (w/w). The MCR-ALS results were obtained using an augmented matrix and SNV pre-processing method. The lack of fit value for decomposition was 0.13%, the correlation coefficient between the pure spectra and the obtained spectral profiles was 99.94% and the RMSEP was below 6% (w/w). The MCR-ALS model efficiently quantified the polymorphic forms and generated distribution maps; however, the PLS model exhibited better recovery of the concentrations.

A full solid-state characterization of risperidone was conducted using differential scanning calorimetry (DSC), thermogravimetry (TG), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) to examine its physicochemical properties and polymorphism. The primary aim of this work was to study the compatibility of risperidone with pharmaceutical excipients using DSC to obtain and compare the curves of the active pharmaceutical ingredient (API) and the excipients with their 1:1 (w/w) binary mixtures. These same binary mixtures were turned to room temperature and analyzed by FT-IR combined with principal component analysis (PCA) to evaluate solid-state incompatibilities. The chemical incompatibilities of these samples were verified using a stability-indicating liquid chromatography (LC) method to assay for the API and evaluate the formation of degradation products. All of these methods showed incompatibilities between risperidone and the excipients magnesium stearate, lactose and cellulose microcrystalline.

Desloratadine (DL) is a selective antagonist of the histamine H1 receptor, which has been widely used to treat allergic symptoms, and stands out from other drugs in this therapeutic class because it does not cause sedative effects. In the present study, the physico-chemical properties of DL were fully characterized using six analytical techniques such as Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TG/DTG), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, Powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The DSC curve shows a sharp endothermic event at 158.4 °C, and the TG/DTG curve presents two decomposition events between 178.4 and 451.9 °C. A compatibility study involving DL and nine pharmaceutical excipients generally used in pharmaceutical formulations was performed. Physical binary mixtures of DL with each excipient were prepared in a 1:1 (w/w) ratio. After preparation, the samples were analyzed immediately and the results reveal solid-state interaction with anhydrous lactose, microcrystalline cellulose, magnesium stearate, and stearic acid.

This study has evaluated the performance of a multivariate statistical model to predict embryo implantation potential by processing data from the chemical fingerprinting of culture medium samples used for human embryo culture. The culture medium for 113 embryos from 55 patients undergoing ICSI was collected after embryo transfer. The samples were split into positive (n=29) and negative (n=84) implantation groups according their implantation outcomes (100% or 0% implantation). The samples were individually diluted and analyzed by electrospray ionization mass spectrometry (ESI-MS). Them/zratios and relative abundances of the major ions in each spectrum were considered for partial least square discriminant analysis. Data were divided into two subsets (calibration and validation), and the models were evaluated and applied to the validation set. A total of 5987 ions were observed in the groups. The multivariate statistical model described more than 82% of the data variability. Samples of the positive group were correctly identified with 100% probability and negative samples with 70%. The culture media used for embryos that were positive or negative for successful implantation showed specific biochemical signatures that could be detected in a fast, simple, and noninvasive way by ESI-MS. To our knowledge, this is the first report that uses MS fingerprinting to predict human embryo implantation potential. This biochemical profile could help the selection of the most viable embryo, improving single-embryo transfer and thus eliminating the risk and undesirable outcomes of multiple pregnancies.

The present study reports the synthesis and characterization of complexes formed among humic (HA) and fulvic acids (FA) derived from poultry wastes and ions Cu2+, Fe2+ and Zn2+. The release of such metals in a buffer solution simulating the soil solution was also evaluated. After complexation, the Fourier transform infrared (FTIR) spectra presented alterations in the absorption bands related to changes in the humic structure, thus indicating the complexation with phenolic and carboxylic groups. Thermogravimetric analyses demonstrated that complexed metals decreased the thermal stability of humic substances. Analyses by atomic absorption spectroscopy (AAS) demonstrated that the release of metals is directly related to the origin of the sample, type of interaction of metal and humic structure and conditions of the medium in which the complex is inserted.

Background Lactose intolerance is characterized by the absence of the enzyme lactase (beta-galactosidase) and affects two thirds of the world adult population. Our aim was to evaluate a lactase gastro-resistant formulation to ensure increased activity in the action site of the enzyme (lumen of the small intestine). Simultaneously, we also evaluated the commercial product stability and enzyme activity, because the product containing beta-galactosidase is classified as food supplement according to the Food and Drug Administration (FDA), so it is free to pass quality testing, efficacy and stability. So, it is possible that contain some irregularities as to the content and enzymatic activity. Methods The dissolution assay was performed using a dissolution test system and commercial product and the gastro-resistant formulation were evaluated according to a method adapted to the conditions recommended by United States Pharmacopeia (US Pharmacopeia) for gastro-resistant formulations. For the assessment of enzymatic activity throughout the dissolution test was employed the official method of lactase assay described in US Pharmacopoeia. This method is based on a colorimetric reaction which the substrate reacts with the enzyme generate a colored product further analyzed by UVVisible spectrophotometry. Results When carrying out dissolution test in commercial product it is noted that the existing formulation is not able to protect the enzyme from degrading action of gastric environment (a loss of 86.0 ± 0.8% of lactase activity was observed). Our proposed gastro-resistant pharmaceutical form there was no loss of activity during the acid step and the end of the dissolution test the found activity was 95 ± 1.3%. Conclusion The formulations proposed in this work using hypromellose capsules ensure the enzymatic activity of lactase, preventing its contact with the acid medium. For the other side, the results of commercial tablets for lactase release indicate a significant loss of enzyme activity due to the immediate release of the enzyme in the simulated gastric fluids.

The evaluation of sildenafil citrate (SC), the best-selling drug for treatment of impotence, for compatibility with various excipients was investigated using thermal and isothermal stress testing. Differential scanning calorimetry (DSC), hot-stage microscopy (HSM) and liquid chromatography (LC) with ultraviolet detection were successfully employed to investigate the compatibility between SC and various excipients commonly used in solid form in the pharmaceutical industry. The studies were performed using 1:1 (m/m) drug/excipient physical mixtures and samples were stored under accelerated stability conditions (40 °C at 75% relative humidity). All excipients tested (such as colloidal silicon dioxide, croscarmellose sodium, lactose, mannitol and sucrose) showed potential incompatibilities by DSC and LC analysis after accelerated stability testing. However, some incompatibilities were not detected by the DSC method and were observed only when LC analysis was performed. HSM was able to differentiate active pharmaceutical ingredient degradation from solubilisation, supporting the interpretation of DSC in excipients where thermal events either overlapped or disappeared. The combination of both the analytical techniques (DSC and LC) and use of a stability chamber is extremely helpful in detecting incompatibilities and providing more robust and accurate approaches for pre-formulation studies.

In this work, the base-catalyzed transesterification of soybean oil with ethanol was monitored on-line using mid-infrared spectroscopy (MIRS) and the yield of fatty acid ethyl esters (biodiesel) was obtained by (1)H NMR spectroscopy. The MIRS monitoring carried out for 12min, was performed using a cylindrical internal reflectance cell of PbSe in the range of 3707-814cm(-1) with eight co-added scans. Two different data treatment strategies were used: in the first, the models were built using the raw data and in the other, evolving factor analysis (EFA) was used to overcome the sensor time delay due to the on-line analysis, producing significantly better results. In addition, models based on partial least squares (PLS) using three batches for calibration and another for validation were compared with models with just one batch for calibration and three for validation. The models were compared between each other using root mean square error of prediction (RMSEP) and root mean square prediction difference (RMSPD), obtaining relative errors under 3%.

Pancreatin is a biotechnological product containing an enzyme complex, obtained from porcine pancreas, that is employed in treating pancreatic diseases. Experiments regarding the stability of the pharmaceutical formulation containing pancreatin were performed using standard binary mixtures with 6 excipients in a 1:1 ratio (m/m) and a commercial formulation. To accomplish these goals, samples were stored for 1, 3 and 6 months at 40 ± 1 °C and 75 ± 5 % relative humidity (RH) and 40 ± 1 °C and 0 % RH. Stress testing was also performed. All samples were analyzed to evaluate the α-amylase, lipase and protease activities through UV/Vis spectrophotometry. The results revealed that the excipient proprieties and the storage conditions affected enzyme stability. Humidity was a strong influencing factor in the reduction of α-amylase and protease activities. Stress testing indicated that pH 9.0 and UV light did not induce substantial alterations in enzyme activity.

Valsartan was submitted to forced degradation under acid hydrolysis condition as prescribed by the ICH. Degraded sample aliquots were separated via HPLC using a Hypersil ODS (C18) column (250 x 4.6 mm i.d., 5 µm). Either photodiode array (PDA) detection or mass spectrometry (MS) full scan monitoring of HPLC runs were used. HPLC-PDA failed to indicate Valsartan degradation under forced acid degradation, showing an insignificant peak area variation and that Valsartan apparently remained pure. HPLC-MS using electrospray ionization (ESI) and total ionic current (TIC) monitoring did not reveal any peak variation either, but inspection of the ESI mass spectra showed the appearance of m/z 306 and m/z 352 ions for the same retention time as that of Valsartan (m/z 436). These ions were identified as being protonated molecules of two co-eluting degradation products formed by hydrolysis. These assignments were confirmed by ESI-MS/MS with direct infusion of the degraded samples. The results showed that the use of selective HPLC-MS is essential for monitoring Valsartan degradation. Efficient HPLC separation coupled to selective and structural diagnostic MS monitoring seems therefore mandatory for comprehensive drug degradation studies, particularly for new drugs and formulations, and for method development. resumo Valsartana (VAL) foi submetida à degradação forçada em meio ácido conforme procedimento descrito no ICH. Os produtos de degradação (PDs) foram monitorados ao longo do tempo de degradação pela técnica de Cromatografia Líquida (LC) utilizando uma coluna Hypersil ODS (C18) (250 x 4,6 mm d.i., 5 µm). A detecção foi feita com dois detectores: espectrofotométrico (PDA) e espectrometria de massas (MS) por corrente iônica total. Ambas as técnicas falharam na identificação dos PDs obtidos ao longo do monitoramento, mostrando insignificantes variações na área do pico e permanecendo com pureza de pico ao longo de toda a eluição. Somente depois da avaliação por íon extraído (XIC), foi possível observar o aumento do íon m/z 306 e m/z 352 exatamente no mesmo tempo de retenção do íon molecular (m/z 436). Estes resultados mostram um caso simples e didático em que somente o uso de um método seletivo de LC-MS pode ser utilizado para monitorar produtos de degradação. Neste trabalho, é apresentado um caso real em que a separação por LC deve ser acoplada a métodos seletivos obtidos por MS, especialmente no estudo de PDs para novos fármacos, formulações e no desenvolvimento de métodos.

The use of theoretical calculation to determine structural properties of fulvate-metal complex (zinc, copper and iron) is here related. The species were proposed in the ratio 1:1 and 2:1 for which the molecular structure was obtained through the semi-empirical method PM6. The calculation of thermodynamic stability ([Formula: see text]) predicted that the iron complex were more exo-energetic. Metallic ions were coordinated to the phtalate groups of the model-structure of fulvic acid Suwannee River and the calculations of vibrational frequencies suggested that hydrogen bonds may help on the stability of the complex formation.

Since the last decade, the combined use of chemometrics and molecular spectroscopic techniques has become a new alternative for direct drug determination, without the need of physical separation. Among the new methodologies developed, the application of PARAFAC in the decomposition of spectrofluorimetric data should be highlighted. The first objective of this article is to describe the theoretical basis of PARAFAC. For this purpose, a discussion about the order of chemometric methods used in multivariate calibration and the development of multi-dimensional methods is presented first. The other objective of this article is to divulge for the Brazilian chemical community the potential of the combination PARAFAC/spectrofluorimetry for the determination of drugs in complex biological matrices. For this purpose, two applications aiming at determining, respectively, doxorrubicine and salicylate in human plasma are presented.

Ultraviolet-visible spectra of flower extracts of the Hibiscus rosa-sinensys L. var. regius maximus species have been measured between 240.02 and 747.97 nm at pH values ranging from 1.1 to 13.0. Deconvolution of these spectra using the Parallel Factor Analysis (PARAFAC) model permitted the study of anthocyanin systems without isolation and purification of the individual species. Seven species were identified: flavilium cation, carbinol, quinoidal base, and E and Z-chacone and their ionized forms. The concentration changes of flavilium cation, quinoidal basen, and E and Z ionized chalcones were determined as function of pH at the different wavelengths. The flavilium cation, quinoidal base, and ionized E-clacone are involved in tho stage kinetic processes, a fast one followed by a slower one. Ionized Z-chalcone obeys a simple first-order processes. The spectral profiles recovered by PARAFAC model are in excellent agreement with bands of experimental spectra reported in the literature for the individual species measured at specific pH values. These results complement those obtained using chemical and simple mathematical techniques and demonstrate how chemometric methods can resolve problems for complex systems.

Direct determination of doxorubicin (DXR), a cytotoxic anthracycline antibiotic, in human plasma was accomplished based on excitation–emission matrix (EEM) fluorescence measurements and multi-way chemometric methods based on parallel factor analysis (PARAFAC) and N-PLS. Several different procedures, such as residual analysis, core consistency diagnostic (CONCORDIA) and split-half analysis were employed to determine the correct number of factors in PARAFAC. These procedures converged to a choice of two factors, attributed to DXR and to the sum of two fluorescence species present in the plasma. Sample PARAFAC loadings were employed to build a regression model against concentration, resulting in a RMSECV of 0.060 μg ml −1 . N-PLS using two factors produced a RMSECV of 0.045 μg ml −1 . Figures of merit (FOM), such as sensitivity (SEN), selectivity (SEL) and limit of detection ( L D ) were determined for both PARAFAC and N-PLS.

A colorimetric method for the determination of zinc, copper and manganese as a quality control criterion in dialysis fluids is discussed. The spectrophotometric reagent was an aqueous solution of 1-(2-pyridylazo)-2-naphthol (PAN) in Triton (5% v/v) in order to obtain soluble micelles of the reagent and its chelates to perform measurements in aqueous phase. Multivariate calibration by the classical least square (CLS) method was adequate to assay the analytes and to verify the presence of other contaminants. Solutions of Zn, Cu and Mn ions in borate buffer (pH 9.2) were used to obtain the spectroscopic data for the calibrations. The modelling was investigated using “one analyte” standard solutions (Zn, Cu or Mn) and also mixtures of standard solutions (Zn, Cu and Mn). The results were compared in terms of the calculated RMSEP (Root Mean Square Error of Prediction) values. Recoveries about 100% were calculated using the methodology in synthetic samples of dialysis fluids and the interference of Ca, Mg, Fe, C...

A method for the simultaneous voltammetric determination of free sulfide and volatile alkythiols (methanethiol/ethanethiol) existing as contaminant in parenteral nutrition (PN) solutions was developed. The volatile sulfides (dihydrogensulfide and alkylthiols) formed in the formulations were distilled over 45 min at 47 degrees C in a purpose-made Conway cell. The analytes were quantified by differential pulse cathodic stripping voltametry (DPCSV) at the hanging mercury-drop electrode and determined, simultaneously as dihydrogensulfide and alkylthiols using a 60 s preconcentration time at -300 mV (versus Ag/AgCl, Cl(-) 3.0 mol l(-1)). The voltammetric signals were directly linear proportional to the sulfides concentrations in the PN solutions in the range 3-20 mumol l(-1) and detection limits of about 2 mumol l(-1) were calculated. Recoveries of sulfides from PN solutions in the range 90-110% were calculated using the method and nine commercial PN formulations were analyzed. Methanethiol and ethanethiol were quantified from their composite signals, and the mutual influence of the analytes on the DPCSV measurements is discussed.

A simultaneous separation and preconcentration of lead, cadmium, zinc and copper from high-salt content matrices for subsequent electrothermal atomic absorption spectrometric determination was developed. The metals were preconcentrated on a micro-column filled with polyethylene powder impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol. The determinations, without the interference of the saline matrix, were carried out after metals elution with a small volume of an ethanolic solution of nitric acid. The saline matrices were sodium, potassium, magnesium and calcium chlorides, sodium acetate and bicarbonate, which constitute concentrates for hemodialysis. The immobilisation capacity of the complexing agent is about 2.5 µmol per gram of polyethylene and the column capacity with respect to each metal is about 0.75 µmol per gram resin for copper, cadmium and zinc and 0.25 µmol per gram for lead. For the optimisation of the procedure, effects of sample flow rate and pH, eluent composition and concentration, and the influence of salts on the complexation of the metals were investigated. The proposed method was characterised by a precision of about 95% (n = 3) and recoveries from spiked samples of the salts were 81–112%. All results were in agreement with those obtained by anodic stripping voltammetry, the technique used for comparison. The method was applied to the analysis of saline concentrates for hemodialysis, where the investigated metals were found in concentrations between 3.1 µg l–1 for cadmium and 90.5 µg l–1 for zinc.

The electrooxidation of 1,2-benzopyrone (BP) was assessed via linear voltammetry and electrochemical impedance spectroscopy on a glassy carbon electrode in dibasic potassium phosphate buffer. The oxidation process for BP requires one electron and forms a ketone. This oxidation product was adsorbed by the electrode surface to form a film that blocks active sites and increases in thickness over consecutive measurements. The oxidation conditions were optimized using factorial design and Doehlert matrices. This electrochemical method was compared to high performance liquid chromatography (HPLC), which has a detection limit of 26.4 µmol L-1 for BP. The voltammetric results were statistically similar to those from HPLC; however, the method was faster, simpler, more easily acquired, more sensitive, and required less organic solvent.

Valsartan (VAL) is a highly selective blocker of the angiotensin II receptor that has been widely used in the treatment of hypertension. Active pharmaceutical ingredient compatibility with excipients (crospovidone, hypromellose, magnesium stearate, microcrystalline cellulose and titanium dioxide) is usually evaluated in solid pharmaceutical development. Compatibility and stability can be evaluated by liquid chromatography. Studies were performed using binary mixtures of 1:1 (w/w) VAL/excipient; samples were stored under accelerated stability test conditions (40 ºC at 75% relative humidity). The results indicate that VAL is incompatible with crospovidone and hypromellose, which reduced the VAL content and gave rise to new peaks in the chromatogram due to degradation products. Valsartana (VAL) é um bloqueador altamente seletivo do receptor da angiotensina II, que tem sido amplamente utilizado para o tratamento da hipertensão. Testes de compatibilidade com excipientes usualmente empregados em formulações sólidas são utilizados no desenvolvimento de formulações sólidas. Neste trabalho, realizaram-se testes utilizando misturas binárias na proporção 1:1 (m/m) de VAL/excipiente e as amostras foram armazenadas em condições de estabilidade acelerada (40 ºC em 75% de umidade relativa). Os resultados obtidos indicam a incompatibilidade de VAL com crospovidona e hipromelose, através da redução do teor de VAL e a presença de novos picos no cromatograma provenientes de produtos de degradação.

Diffuse reflectance near-infrared (DR-NIR) spectroscopy associated with partial least squares (PLS) multivariate calibration is proposed for a direct, non-destructive, determination of total nitrogen in wheat leaves. The procedure was developed for an Analytical Instrumental Analysis course, carried out at the Institute of Chemistry of the State University of Campinas. The DR-NIR results are in good agreement with those obtained by the Kjeldhal standard procedure, with a relative error of less than ± 3% and the method may be used for teaching purposes as well as for routine analysis.

Fourier transform mid-infrared spectroscopy (FT-MIR) coupled with a homemade attenuated total reflectance (ATR) flow-cell was used for on-line monitoring of a biotransformation reaction. The reaction was also monitored off-line by gas chromatography-mass spectrometry (GC-MS) enabling to establish a multivariate model for the infrared data based on partial least squares (PLS) regression. The method developed allowed the simultaneous determination of the substrate, two intermediates and the final product involved in the reduction reaction of 1-phenyl 1,2-propanedione at an initial concentration of 0.5% (v/v). The reaction was accomplished with a whole-cell suspension of Saccharomyces cerevisiae in a phosphate buffer of pH 3.0 at 32+/-1 degrees C. The ATR infrared monitoring was performed directly on the suspension cell without any separation process or extraction over 3h, totaling 188 spectra. The data were split into two subsets, with 158 times for calibration and 30 times for validation. The results showed that the proposed method may be used for on-line monitoring of the biotransformation reactions when the initial concentration is very low.

Atualmente o Brasil e o maior exportador mundial de aves respondendo por 41% do mercado de frango, com um aumento constante de producao. Entretanto, toda essa producao tem impacto no meio ambiente com o aumento do volume de dejetos. O descarte inadequado dos dejetos compromete o meio ambiente e saude publica, e na ausencia de reciclagem, perda de seu potencial energetico e fertilizante. Neste trabalho, os fertilizantes provenientes de esterco aviario, turfa mineral e padroes de acido humico e fulvico foram caracterizados por termogravimetria e difracao de raios-X, identificando o perfil de materia-orgânica nos materiais e sua fracao inorgânica. Tambem foi avaliado um processo para aumentar a fracao humica nos materiais. Os resultados comprovam a possibilidade das tecnicas de analise termica para a caracterizacao eficiente da materia-orgânica em fertilizantes orgânicos e diferenciacao entre acidos humicos e fulvicos. Termogravimetria: curvas TG de a) AHE = acido humico de CS, AHET = acido humico de CS tratado, AHP = acido humico padrao; b) AHT acido humico de turfa, AHTT = acido humico de turfa tratada, AHP = acido humico padrao. Faixa de aquecimento 30 a 600 °C; razao 10 °C min-1; fluxo de ar sintetico 100 mL min-1; cadinho alumina (n=1).

An easy and simple chromatographic method for the determination of riboflavin in bovine milk in the presence of tetracyclines was established. For this, the proteins were precipitated with trichloroacetic acid and the separation was carried out by reversed-phase HPLC with fluorescence detection. A C8 column was used with isocratic flow using a mobile phase consisting of 0.1 mol L-1 sodium acetate, 35 mmol L-1calcium chloride and 25 mmol L-1 EDTA : methanol (65:35 v/v). The method was validated by means of the following parameters: linearity (0.9980), linear range (0.50 - 1.30 µg mL-1), intra- and inter-assay precision (RSD < 0.5%), accuracy (recovery 92%), and detection and quantitation limits (0.75 µg mL-1 and 0.22 µg mL-1, respectively). The method was applied for analysis of full cream and skimmed milk, showing robustness in the presence of tetracyclines, and when compared with a spectrofluorimetric method showed no significant difference (p < 0.05) between the results obtained. Foi estabelecido um método cromatográfico rápido e simples para a determinação de riboflavina em leite bovino, na presença de tetraciclinas. Para tanto, as proteínas foram precipitadas com ácido tricloroacético e a separação realizada por CLAE em fase reversa com detector de fluorescência. Foi utilizada uma coluna C8 com eluição isocrática e fase móvel acetato de sódio 0,1 mol L-1, cloreto de cálcio 35 mmol L-1, EDTA 25 mmol L-1: metanol (65:35 v/v). O método foi validado mediante avaliação dos seguintes parâmetros: linearidade (0,9980), faixa linear (0,50 a 1,30 µg mL-1), precisão intra e inter-ensaio (RSD < 0,5%), exatidão (recuperação 92%) e limites de detecção e de quantificação (0,75 µg mL-1 e 0,22 µg mL-1, respectivamente). O método foi aplicado na análise de leite integral e desnatado, mostrando-se robusto na presença de substâncias fluorescentes como as tetraciclinas, e quando comparado com o método espectrofluorimétrico, não revelou diferença significativa (p < 0,05) entre os resultados obtidos.