UV Spectrophotometric Data Research Articles

Resolution of overlapping spectra using chemometric manipulations of UV-spectrophotometric data for the determination of Atenolol, Losartan, and Hydrochlorothiazide in pharmaceutical dosage form

Simultaneous determination of atenolol (ATN), losartan potassium (LOS), and hydrochlorothiazide (HCZ) in presence of HCZ impurity B was conducted by chemometric approaches and radial basis function network (RBFN) using UV-spectrophotometry without preliminary separation. Three chemometric models namely, classical least-squares (CLS), principal component regression (PCR), and partial least-squares (PLS) along with RBFN were utilized using the ternary mixtures of the three drugs. The multivariate calibrations were obtained by measuring the zero-order absorbance of the mixtures from 250 to 270 nm at the interval of 0.2 nm. The models were built covering the concentration range of (4.0 to 20.0), (3.8 to 20.2), and (0.9 to 50.1) μg mL−1 for ATN, LOS, and HCZ, respectively. The regression coefficient was calculated between the actual and predicted concentrations of the 3 drugs using CLS, PCR, PLS and RBFN. The accuracy of the developed models was evaluated using the root mean square error of prediction (RMSEP) giving satisfactory results. The proposed methods were simple, accurate, precise and were applied efficiently for the quantitation of the three components in laboratory-prepared mixtures, and in dosage form showing good recovery values. In addition, the obtained results were compared statistically with each other using ANOVA test showing non-significant difference between them.

Smart Multivariate Spectrophotometric Determination of Two Co-Administered Autoimmune Drugs; Sulfasalazine and Pentoxifylline; in Bulk and Spiked Human Plasma.

Sulfasalazine and pentoxifylline are co-prescribed together to treat psoriasis and pemphigus vulgaris. Sulfasalazine is an anti-inflammatory, immunosuppressant, and antibiotic drug, while pentoxifylline is a vasodilator and immunosuppressant. The spectra of the two drugs and plasma suffer from severe overlap. This work aims to simultaneously determine sulfasalazine and pentoxifylline in their binary mixture and spiked human plasma by the assessment of their UV spectral data. Two model updated chemometric methods were established using principal component regression and partial least-squares regression models. The two models were validated in accordance with the U.S. Food and Drug Administration guidelines for bioanalysis and were applied for the determination of both drugs in synthetic mixtures or spiked human plasma. Accuracy and precision were within the accepted limits. In addition, three different assessment methods were used to evaluate the environmental greenness of the proposed models. The two updated models are simple, rapid, sensitive, and precise, and could be easily applied in QC laboratories for determination of sulfasalazine and pentoxifylline, without any preliminary separation steps or interference from plasma matrix. Two updated chemometric models called principlal component regression and partial least-squares regression were established for determination of sulfasalazine and pentoxifylline in spiked human plasma using UV spectrophotometric data.

Comparative Chemometric Manipulations of UV-Spectrophotometric Data for the Efficient Resolution and Determination of Overlapping Signals of Cyclizine and Its Impurities in Its Pharmaceutical Preparations.

Cyclizine (CYZ), a commonly used antiemetic drug, has two pharmacopeial toxic impurities, 1-methylpiperazine (MPZ) and diphenylmethanol (DPM). When CYZ parenteral formulations are administered intravenously, both impurities are poisonous, toxic, and harmful to the human body. Cyclizine was determined along with its hazardous impurities MPZ and DPM by green multivariate calibration using UV-spectroscopic data. Three multivariate algorithms were used to resolve and quantify overlapped spectral signals: principal component regression (PCR), partial least squares (PLS), and synergistic intervals partial least squares (siPLS). A concentration set containing 16 distinct combinations of CYZ, MPZ, and DPM was randomly prepared, and the absorbance values of the concentration set were determined using the 376 point-wavelength set with an interval of 0.2 nm between 200 and 275 nm. Good linear correlations were established for CYZ, MPZ, and DPM in the concentration ranges of 5.00-25.0, 0.50-2.50, and 0.50-2.50 µg/mL, respectively. The ideal spectral range and associated combinations were chosen based on the lowest root mean error of prediction (RMSEP) and correlation coefficient values (r). The siPLS approach performed better than the PCR and PLS models. The combination of four subintervals, 1, 3, 4, and 7, demonstrated the greatest effect, with RMSEP values of 0.0272, 0.0053, and 0.0315 for CYZ, MPZ, and DPM, respectively, and correlation coefficients of 0.9991, 0.9999, and 0.9997, in order. Various assessment tools were used to evaluate and measure the greenness profile of the established methods. The proposed methods were validated using internal and external validation sets. The three methods were effectively used to determine CYZ in its pure form and parenteral formulations, as well as its toxic impurities. The acquired results were compared statistically to those obtained using the reported HPLC method. Cyclizine and its toxic impurities can be determined spectrophotometrically by using the three developed chemometric models.

Chemometric Quality Assessment of Doxylamine Succinate With Its Degradation Product: Implementation of Two Predictive Models on UV-Spectrophotometric Data of Anti-Emetic Binary Mixture.

The combination of pyridoxine hydrochloride (PYR) and doxylamine succinate (DOX) as an antiemetic binary mixture is used to treat nausea and vomiting during pregnancy. Two validated, accurate, and selective chemometric models were developed to assay binary mixture in the presence of DOX oxidative degradation product (DOX DEG) that could be characterized using LC-MS. Partial least squares (PLS) regression and principal component regression (PCR) were selected for the determination of our binary mixture in presence of degradation. To exhibit a training set of 25 mixtures that had various percentages of tested substances in five level 3 variables, an experimental design was chosen. A set of 18 synthetic mixtures in the concentration range 10.0-50.0 μg/mL, 12.00-20.0 μg/mL, and 6.0-30.0 μg/mL for PYR, DOX, and DOX DEG, respectively, were used in the construction of the calibration models.Then set of seven synthetic mixtures with different concentrations were used in the construction of the validation models. In validation samples with low root mean square error of prediction (RMSEP), the suggested models successfully predicted the concentrations of our drugs. The models developed were evaluated by RMSEP calculation, and the values obtained were 0.341, 0.196, and 0.388 for PYR, DOX, and DOX DEG, respectively, using PLS. While using PCR, RMSEP calculation and the values obtained were 0.400, 0.256, and 0.375 for PYR, DOX, and DOX DEG, respectively. The developed models were validated according to ICH strategies. The corresponding methods are suitable to determine PYR and DOX in pure form, pharmaceutical dosage form, and in the presence of DOX DEG product. The study of drug breakdown pathways is very important nowadays, so even in the presence of degradation and extreme spectral overlapping, the suggested PLS and PCR spectrophotometric approaches were able to identify PYR and DOX.

Multivariate Model Update Chemometric Methods for Determination of Prednisolone and Esomeprazole in Spiked Human Plasma: A Comparative Study.

Prednisolone (PRD) is an immunosuppressant and anti-inflammatory drug, although it may cause peptic ulcers as a side effect. Esomeprazole (ESO) is used for the treatment of peptic ulcers, therefore the two drugs are co-administered in cases of organ transplantation and autoimmune diseases. This work aims to determine the two drugs simultaneously, in bulk, and in spiked human plasma by eliminating the overlap of their spectra and the interference of the plasma matrix. Two simple and effective updated chemometric models-principal component analysis (PCA) and partial least squares (PLS)-were established using UV spectrophotometric data. The two updated models have been validated according to the U.S. Food and Drug Administration guidelines with acceptable results. The results were statistically compared with those of the reported methods, where no significant difference was found, indicating the validity of the developed methods. The two updated models have been successfully applied for prediction of the proposed drugs with good accuracy and precision. The two updated models are simple, rapid, sensitive, and precise and could be easily applied in quality control laboratories for determination of PRD and ESO, without any preliminary separation steps or interference from plasma matrixes. Two model updated chemometric models, PCA and PLS, were established for determination of PRD and ESO in spiked human plasma using UV spectrophotometric data.

Development of novel univariate and multivariate validated chemometric methods for the analysis of dasatinib, sorafenib, and vandetanib in pure form, dosage forms and biological fluids

New precise, responsive and selective univariate and multivariate chemometric spectrophotometric methods were developed and validated for determination of vandetanib (VTB), dasatinib (DTB), and sorafenib (SFB) in pure form, tablets, spiked human (plasma and urine). Determination of these drugs is essential because of their therapeutic benefits. These methods included double divisor ratio spectra derivative univariate method and chemometric multivariate method including partial least-squares (PLS) and principal component regression (PCR). A novel univariate method was developed for the estimation of these drugs. This method depends on the UV-Spectrophotometric data for simultaneous analysis of a ternary overlapped mixture. The Double divisor ratio spectra derivative absorption minima at 358.4 nm was used for quantification of VTB, absorption maxima at 300.3 nm for quantification of DTB and absorption maxima at 259.8 nm for quantification of SFB. This method shown a linearity in the extent of 2–9 μg/mL for VTB and DTB and over the concentration range of 3–9 μg/mL SFB within correlation coefficient (r2) of 0.9999. This method was successfully applied to pure form, tablet dosage form, spiked human (urine and plasma). Chemometric PLS and PCR models were found to be linear in the range of 2–9, 2–9, and 3–9 μg/mL for VTB, DTB and SFB, respectively. These models were estimated using eighteen mixtures as calibration set and seven mixtures as validation set. In the original data, the minimum root mean square error of prediction (RMSEP) was 0.11, 0.09 and 0.09 for VTB, DTB and SFB by PLS and 0.05, 0.04 and 0.03 by PCR while in the derivative data, the RMSEP was 0.09, 0.10 and 0.09 by PLS and 0.06, 0.06 and 0.03, by PCR for VTB, DTB and SFB, respectively. These methods were applied for the determination of the drugs in pure form and dosage form. Updating PLS model permitted the determination of the VTB, DTB and SFB in spiked human urine, plasma and drug-dissolution test of their tablet.

Speciation of Molybdenum(VI) in Chloride Media at Elevated Mo Concentrations

Speciation of Mo(VI) in chloride media (0.5–11 M HCl) at elevated Mo concentrations (0.1–300 mM Mo) was investigated using UV spectroscopy. In addition to five major monomeric species, H2MoO4, H3MoO4+, H3MoO4Cl, MoO2Cl2, and MoO2Cl3–, chemometric analysis of UV spectra suggests the presence of three cationic dinuclear species that predominate in solutions of 1–4.5 M HCl at >20 mM Mo concentrations. Thermodynamic values and molar absorptivity spectra were calculated from UV spectrophotometric data using refined numerical methods. The stability constants determined for three Mo dimers are log β = 3.53 ± 0.05 (H2Mo2O52+), log β = 3.60 ± 0.04 (H3Mo2O53+), and log β = 2.91 ± 0.03 (H3Mo2O6Cl2+).

Linear Support Vector Regression and Partial Least-Squares for Determination of Dapoxetine Hydrochloride and Tadalafil in Binary Pharmaceutical Mixtures.

Dapoxetine (DAP) is a serotonin-norepinephrine reuptake inhibitor, and Tadalafil (TAD) is a phosphodiesterase type-5 inhibitor. Both are coformulated as tablets called Erectafil® for treatment of erectile ejaculation. DAP and TAD were analyzed in their binary mixtures and pharmaceutical formulations using two multivariate calibration chemometric models. Partial least-squares (PLS) and linear support vector regression (SVR) models were applied using two factor-four level experimental design and UV-spectrophotometric data. They were compared to each other, and their advantages and disadvantages were discussed. The developed methods succeeded to determine DAP and TAD in different ratios with good results regarding International Conference on Harmonization guidelines. Linearity ranges were 2-15 μg/mL and 3-30 μg/mL for DAP and TAD, respectively, with good accuracy of 100 ± 0.37 for DAP and 100 ± 0.8 for TAD regarding PLS model and 100.04 ± 0.32 for DAP and 99.89 ± 0.77 for TAD regarding SVR model. Good precision values of 0.787 for DAP and 0.793 for TAD regarding PLS model and 1.105 for DAP and 0.930 for TAD regarding SVR model were obtained. The two models were applied on the dosage forms and statistically compared with the published HPLC method with no significant difference regarding accuracy and precision. The two models can be utilized for routine analysis and QC of DAP and TAD in their bulk and pharmaceutical formulations. The SVR model gives better results and generalization ability than those of the PLS model regarding accuracy and prediction error, while the latter is better for being simpler and faster.

Análisis cuantitativo de una mezcla binaria a partir de datos espectrofotométricos UV usando un método alterno

This work describes a laboratory exercise useful for an instrumental analysis course. In the exercise, an alternative method is applied to carry out the quantitative analysis of a binary mixture from UV spectrophotometric data. For this purpose, a mixture with known concentrations of 4-aminobenzoic acid and nicotinic acid was prepared, its absorbances at several wavelengths in the interval of 242 to 330 nanometers were recorded, and the resulting data were subjected to the alternative procedure. In this one, a simple transformation on the absorbance equation of the mixture is applied to obtain a linear relationship from which the concentrations of the components are calculated. In spite of its simplicity, the method produces a very good agreement between the calculated concentrations and the actual ones, errors within 2% have been found. The exercise provides an interesting alternative to the conventional procedure customarily taught in an instrumental analysis course.

A single MCR-ALS model for drug analysis in different formulations: Application on diazepam commercial preparations

A multivariate curve resolution – alternating least squares (MCR-ALS) analysis was used to quantify diazepam (DZP) in thirty commercial liquid formulations. MCR calibration was run on the UV spectrophotometric data of the commercial DZP samples over the range 200–400nm, allowing the resolution of the drug signal and then the excipients contained in all the formulations. A single model MCR for the determination of the drug in all samples was then built through the adoption of the correlation constraint. This model was optimized by an appropriate selection of the most useful wavelength ranges and then validated on external samples. DZP concentrations in the pharmaceutical formulations were measured by HPLC-DAD analysis. The performance of the MCR model was compared with that from application of classical partial least squares regression (PLSR). The results, in terms of error of prediction, were very satisfactory, reaching a relative error below of 1.66% against 2.56%, respectively.

A novel pure component contribution algorithm (PCCA) for extracting components’ contribution from severely overlapped signals; an application to UV-spectrophotometric data

A novel, simple and accurate algorithm capable of extracting the contribution of each component from a mixture signal where the components are completely overlapped was developed. It is based on the development of a coded function which eliminates the signal of interfering components using mean centering as a processing tool; finally the pure contribution of each component is extracted. The algorithm allows the determination of each component as a single one. It was validated by the use of simulated data set of three overlapped signals and tested against simulated random noise. Two fit values were developed and calculated for optimization, one to test that that the absorptivity values of the extracted spectra are within the confidence limits of the slope and the other is the correlation between the pure and extracted spectra. It has been successfully applied to real UV data of binary mixture of Ibuprofen and Paracetamol and ternary mixture of Amiloride hydrochloride, Atenolol and Hydrochlorothiazide in tablets and capsules, respectively. The results were compared to previously reported separation method and no significant difference was found regarding both accuracy and precision.

Multivariate curve resolution of incomplete fused multiset data from chromatographic and spectrophotometric analyses for drug photostability studies

An advanced and powerful chemometric approach is proposed for the analysis of incomplete multiset data obtained by fusion of hyphenated liquid chromatographic DAD/MS data with UV spectrophotometric data from acid–base titration and kinetic degradation experiments. Column- and row-wise augmented data blocks were combined and simultaneously processed by means of a new version of the multivariate curve resolution-alternating least squares (MCR-ALS) technique, including the simultaneous analysis of incomplete multiset data from different instrumental techniques. The proposed procedure was applied to the detailed study of the kinetic photodegradation process of the amiloride (AML) drug. All chemical species involved in the degradation and equilibrium reactions were resolved and the pH dependent kinetic pathway described.

Синтез, физико-химические свойства и противосудорожная активность комплекса ГАМК с производным каликс[4]арена

Синтезирован комплекс на основе 5,11,17,23-тетра-трет-бутил-25,27-бис[карбоксиметокси]-26,28-дигидроксикаликс[4]арена с гамма-аминомасляной кислотой, его строение подтверждено методами ИК-, УФ-, 1Н ЯМР-спектроскопии, масс-спектрометрии и флуориметрии. На основании данных спектрофотометрического титрования показана способность производного каликс[4]арена формировать комплексы состава 1:1 и 2:1 (лиганд: гость). Отмечено, что синтезированный комплекс обладает пролонгированной противосудорожной активностью, оценка которой проводилась с помощью метода определения минимальных эффективных доз коразола, вызывающих клонико-тонические судороги и тоническую экстензию.

A study of pH-dependent photodegradation of amiloride by a multivariate curve resolution approach to combined kinetic and acid–base titration UV data

Amiloride photostability at different pH values was studied in depth by applying Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) to the UV spectrophotometric data from drug solutions exposed to stressing irradiation. Resolution of all degradation photoproducts was possible by simultaneous spectrophotometric analysis of kinetic photodegradation and acid-base titration experiments. Amiloride photodegradation showed to be strongly dependent on pH. Two hard modelling constraints were sequentially used in MCR-ALS for the unambiguous resolution of all the species involved in the photodegradation process. An amiloride acid-base system was defined by using the equilibrium constraint, and the photodegradation pathway was modelled taking into account the kinetic constraint. The simultaneous analysis of photodegradation and titration experiments revealed the presence of eight different species, which were differently distributed according to pH and time. Concentration profiles of all the species as well as their pure spectra were resolved and kinetic rate constants were estimated. The values of rate constants changed with pH and under alkaline conditions the degradation pathway and photoproducts also changed. These results were compared to those obtained by LC-MS analysis from drug photodegradation experiments. MS analysis allowed the identification of up to five species and showed the simultaneous presence of more than one acid-base equilibrium.

A Mathematical Approach for the Simultaneous In Vitro Spectrophotometric Analysis of Rifampicin and Isoniazid from Modified-Release Anti-TB Drug Delivery Systems

Dissolution testing with subsequent analysis is considered as an imperative tool for quality evaluation of the combination rifampicin-isoniazid (RIF-INH) combination. Partial least squares (PLS) regression has been successfully undertaken to select suitable predictor variables and to identify outliers for the generation of equations for RIF and INH determination in fixed-dose combinations (FDCs). The aim of this investigation was to ascertain the applicability of the described technique in testing a novel oral FDC anti-TB drug delivery system and currently available two-drug FDCs, in comparison to the United States Pharmacopeial method for analysis of RIF and INH Capsules with chromatographic determination of INH and colorimetric RIF determination. Regression equations generated employing the statistical coefficients satisfactorily predicted RIF release at each sampling point (R(2)>or=0.9350). There was an acceptable degree of correlation between the drug release data, as predicted by regressional analysis of UV spectrophotometric data, and chromatographic and colorimetric determination of INH (R(2)=0.9793 and R(2)=0.9739) and RIF (R(2)= 0.9976 and R(2)=0.9996) for the two-drug FDC and the novel oral anti-TB drug delivery system, respectively. Regressional analysis of UV spectrophotometric data for simultaneous RIF and INH prediction thus provides a simplified methodology for use in diverse research settings for the assurance of RIF bioavailability from FDC formulations, specifically modified-release forms.

The protonation thermodynamics of cyclodextrin-containing polymers for drug inclusion

A poly(amido-amine), PAA, bearing β-CD units in the side chain was synthesized by a polyaddition reaction of 1,4-bis-acryloyl-piperazine with 6-monodeoxy-6-monoamino-β-cyclodextrin (β-CD-NH2). Unlike the simple β-CD-NH2 with a greater basicity constant (log K = 8.60), the polymer revealed an unusual polyelectrolyte behaviour with a lower basicity constant (log K° = 6.29) of the tertiary nitrogen atom, that is strongly dependent on the degree of protonation α of the whole macromolecule. It follows the modified Henderson–Hasselbalch equation with n = 1.75, in a wide α-range. The greater (−46.1 kJ/mol) and the lower (−27.6 kJ/mol) enthalpy (ΔH°) changes of the compounds were in line with the protonation of a primary or a tertiary nitrogen atom. The calorimetric data suggested that the PAA protonation destroyed a packing structure formed by two rigid β-CD side chains interacting head-to-head. The UV spectrophotometric data showed that the PAA exhibits affinity towards the l-ascorbic acid at low pH (pH 2.46) with an isosbestic point at 241 nm and a slight blue shift of the maximum absorption of the ascorbic acid (244 nm) on PAA additions.

Quantitative determination of the total content of flavonoids in Flavozid and Immunoflazid syrups

New syrup compositions Flavozid and Immunoflazid that contain 2% Proteflazid (ethanol extract of wild Deschampsia caespitosa L. and Calamagrostis epigeios L.) have been developed. The total content of flavonoids in both syrups is of the level of 4 – 6 gmL, which complicates the development of an analytical method. A new method for quantitative determination of flavonoids in the aforementioned syrups has been developed on the basis of differential UV spectrophotometry of their complexes with aluminum chloride. The proposed method is introduced into the Manufacturer’s Pharmacopoeic Article for the syrups. The existing formulation of Flavozid and Immunoflazid syrups is based on the active pharmaceutical ingredient Proteflazid, which was first developed and registered in Ukraine in 2001 and is the alcohol extract of wild Deschampsia caespitosa L. and Calamagrostis epigeios L. Proteflazid prepared using the original technology was recommended for use in medical practice as a composition with direct antiviral and immunomodulating action with properties of an interferon activator and DNA protease inhibitor in virus-infected cells [1 – 3]. The principal biologically active compounds of Proteflazid are flavonoids similar to quercetin (rutin), the molecules of which are based on a flavone oxygen-containing heterocycle. However, the mixture of Proteflazid flavonoids did not contain those that are frequently used as standards. Therefore, the development of a quantitative determination method for flavonoids in the syrup, where the content of Proteflazid and the corresponding flavonoids is 2% (or 4 – 6 gmL) of the starting extract, is of definite scientific interest. The goal of our work was to develop a method that would enable quantitative determination of total flavonoids, which absorb in the UV and visible spectral regions, using aluminum chloride as a complex-forming reagent. The glycoside species were converted to the aglycons by preliminary boiling of the syrup in the presence of HCl in order to increase the total amount of flavonoids in the analytes. Acid hydrolysis of the glucosides in the syrup was carried out in an excess of conc. HCl taken at 1% of the volume of the investigated syrup. The optimum conditions for acid hydrolysis with time were determined from the degree of conversion of the glycoside component into aglycons with TLC monitoring and UV spectrophotometric data. Aglycons from the syrup were extracted by ethylacetate. Solvent was vacuum distilled until production of a pasty residue that was dissolved in ethanol (96%). Studies of the optimum conditions for complexation using freshly prepared aluminum chloride (5%) in ethanol (96%) showed that increasing the volume of the solution to greater than 1 mL in the analyte did not improve the optical density parameters of the aluminum-chloride complex of the flavonoids. The maximum optical density was retained over 25 – 40 min at wavelength 422 nm. A solution with all components of the test solution with the exception of aluminum chloride was used as a reference to compensate for absorption at 420 – 424 nm of the starting extract before complex formation with aluminum chloride. Considering the complex flavonoid composition of the starting material, known standards from various flavonoid groups were used for the quantitative determination. However, the absorption maximum of the complex with aluminum chloride of none of them agreed with that for the com

Formulation and Statistical Optimization of a Novel Crosslinked Polymeric Anti‐Tuberculosis Drug Delivery System

The crux of this research was the pragmatic investigation into the formulation of a reconstitutable multiparticulate anti‐tuberculosis drug delivery system for facilitated administration for the attainment of segregated gastrointestinal (GI) delivery of rifampicin (RIF) and isoniazid (INH) in order to address issues of unacceptable RIF bioavailability on coadministration with INH. Ionotropically crosslinked polymeric enterospheres for delivery of INH to the small intestine were developed via a response surface methodology for the design and optimization of the formulation and processing variables. A 34 Box‐Behnken statistical design was constructed. The concentration of zinc sulfate salting‐out and crosslinking electrolyte, the crosslinking reaction time, the drying temperature (DT), and the concentration of triethyl citrate plasticizer were varied for determination of their effect on the molar amount of zinc (nZn) incorporated in the crosslinked enterosphere, drug entrapment efficiency (DEE), and mean dissolution time (MDT) at t2h in acidic media (0.1 M HCl). Complexometric determination of zinc cations (Zn2+) revealed that 23.70–287.89 mol of Zn2+ per mole of polymer were implicated in crosslink formation. DEE of 27.92% to 99.77% were obtained. Drug release at t2h ranged from 1.67% to 73.04%. The salting‐out and crosslinking agent significantly affected nZn (p = 0.034) and the DEE (p = 0.000), as did the concentration of plasticizer employed (p = 0.000 and 0.002, respectively). High DTs (>42.5°C) also significantly improved DEE (p = 0.029). ZnSO4 had a significant effect on the MDT (p = 0.000). A dry dispersible multiparticulate system incorporating the optimally designed INH‐loaded enterospheres and RIF was developed. Bivariate regression analysis of UV spectrophotometric absorbance data allowed in vitro resolution of RIF and INH release at simulated gastric pH.

Truffles decontamination treatment by ionizing radiation

A research project, funded by the Italian Ministry of Research and the European Union, is in progress aimed to develop processes to enhance, by irradiation, the safety and the wholesomeness of fresh products relevant for Italian food industry. Irradiation was performed on truffles, since the bacterial contamination impairs their trade in foreign countries. The microbial population and the shelf life under refrigeration were studied either on samples untreated or on samples submitted to γ-rays in a 1–2.5 kGy dose range. The effect of the treatment was monitored by UV and NMR techniques. Total microbial population and the shelf life prolongation were investigated. The synergistic effect of the dose, the packaging under vacuum and the storage/irradiation temperature resulted in a direct effect on the microbial load, spoilage and shelf life. After the irradiation, small variations in the intensity of some NMR resonances due to aromatic compounds and other unassigned compounds were observed. As confirmed by UV spectrophotometric data, these phenomena seemed to originate from a small degradation of polyphenols; the induced growth of soluble phenols suggested that the 1.5 kGy dose can be considered as the radiation dose threshold beyond which clear chemical modifications on truffles appear.

Diffuse reflectance UV–Visible spectroscopy for the qualitative and quantitative study of chromophores adsorbed or grafted on silica

Diffuse reflectance UV–Visible spectroscopy (DRUV) is used to study the adsorption and grafting of the pyrene derivative 1 on different types of silicas. For the adsorbed silicas, the formation of dimeric aggregates is evidenced both by DRUV and by fluorescence spectroscopy. The processing of the UV spectrophotometric data allows, as in solution, the determination of apparent equilibrium constants and of the spectra of the dimer. From these results, two sets of silicas are distinguished according to the amount of dimer formed and to its UV spectrum. Lower amounts of dimeric species are found on silica with either large pore size or low particle size. The spectrum in this case is only slightly red-shifted relative to that of the monomeric compound. When the pore size decreases, dimer formation is more significant and its spectrum is more characteristic. The results obtained for adsorbed silicas were quantitatively treated and the Kubelka–Munk function, F( R), plotted against the concentration. Attempts to estimate the loading of silicas grafted with 1 were undertaken. It appears that small particle size silica gives rise to the highest loading and to the best quality DRUV spectra as a consequence of a minor amount of fluorescent dimer. On the other hand, it is shown that the loading of grafted silica is difficult to control by the used grafting process and that milder conditions are required.