Comparative kinetics studies of thermal decomposition of kalium, respectively natrium oxalato-oxo-diperoxo molibdate

The aim of this paper is to present the comparative kinetics of thermal decomposition of K₂[MoO(O₂)₂(C₂O₄)] (kalium oxalato-oxo-diperoxo molibdate), respectively Na₂[MoO(O₂)₂(C₂O₄)] (natrium oxalato-oxo-diperoxo molibdate). The TG data were obtained at different heating rates: β = 2.5, 4, 5, and 10 °C min^?1 in air and nitrogen (50 mL min^?1), and the TG/DTG data were processed with the following methods: Friedman, Flynn–Wall–Ozawa and modified-NPK method.     

Kinetic of decomposition of some complexes under non-isothermal conditions

Kinetics of thermal decomposition of three structurally similar complexes Co₂Cu(C₂O₄)₃ (R-diam)₂, where R is ethyl, 1,2-propyl or 1,3-propyl, was studied under non-isothermal conditions and nitrogen dynamic atmosphere at heating rates of 5, 7, 10, 12 and 15 K min⁻¹. For data processing the Flynn-Wall-Ozawa and a modified non-parametric kinetic methods were used. By both methods the activation energy are in the range of 97–102 kJ mol⁻¹. The formal kinetic is r=kα(1−α)². Also a compensation effect between lnA and E was evidenced. The kinetic analysis lead to the conclusion of an identic decomposition mechanism by a single step process.     

Thermal stability of food additives of glutamate and benzoate type

Summary An unsaturated polyester/sisal flame retardant composite was formulated using decabromine diphenyl oxide associated with antimony trioxide as additives. The development and use of natural or vegetable fiber reinforced composites is increasing worldwide, since natural fibers come from renewable sources and their use contributes to the so-called 'green technology'. In the present study, the synergic effect of a bromine/antimony (3:1 molar ratio) based flame retardant system with 7.5% Br (mass/mass) added to composites investigated by TG, UL-94V and pyrolysis on a coupled Pyr-GC/MS device. The efficiency of the flame retardant system is confirmed by TG and UL-94V test where the composite containig flame retardant system obtained the highest classification (V-0).     

Rapid high-performance liquid chromatography-tandem mass spectrometry method for determination of pentoxifylline and its active metabolites M1 and M5 in human plasma and its application in bioavailability study

A new rapid, sensitive and selective liquid chromatography coupled with mass spectrometry method was developed and validated for the simultaneous quantification of pentoxifylline (PTX) and two major active metabolites in human plasma (M1 and M5). After a deproteinization step, chromatographic separation of the selected analytes was performed on a RP-C18 column. The detection of target compounds was in multiple reaction monitoring mode using an ion trap mass spectrometer equipped with an electrospray ion source. The method was validated and proved to be linear, accurate and precise over the range 5.08-406.14, 10.08-806.40 and 20.15-1611.60 ng/mL in case of PTX, M1 and M5, respectively. The major advantages of this method are the small sample volume, simple sample processing technique, the high sensitivity and the very good selectivity guaranteed by the MS/MS (in case of PTX) or MS/MS/MS (in case of M1 and M5) detection. The validated method has been successfully applied to a bioequivalence study.     

Determination of tramadol and O-desmethyltramadol in human plasma by high-performance liquid chromatography with mass spectrometry detection

A new simple, sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS) method for quantification of tramadol and its active metabolite O-desmethyltramadol in human plasma was validated. The tramadol and its metabolite were separated on a reversed phase column (Zorbax SB-C18, 100 mm x 3.0 mm I.D., 3.5 microm) under isocratic conditions using a mobile phase of a 10:90 (v/v) mixture of acetonitrile and 0.2% (v/v) trifluoroacetic acid in water. The flow rate was 1 ml/min at the column temperature 45 degrees C. In these chromatographic conditions, the retention times were 2.3 min for O-desmethyltramadol and 3.5 min for tramadol, respectively. The detection of both analytes was in SIM mode using an ion trap mass spectrometer with electrospray positive ionisation. The monitored ions were m/z 264 for tramadol and m/z 250 for its metabolite. The sample preparation was very simple and rapid and consisted in plasma protein precipitation from 0.2 ml plasma using 0.2 ml solution of perchloric acid 7%. Calibration curves were generated over the range of 2-300 ng/ml for both analytes with values for coefficient of correlation greater than 0.998 and by using a weighted (1/y) quadratic regression. The values of precision and accuracy for tramadol at quantification limit were less than 10.9% and 5.1, respectively, both for within- and between-run. For O-desmethyltramadol, precision and accuracy at quantification limit were 10.1% and -9.9% for within-run determinations and 6.7% and 10.4% for between-run determinations, respectively. The mean recovery for both analytes was 96%. Both tramadol and its metabolite demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. This is the first reported method for analysis of tramadol and O-desmethyltramadol in human plasma that uses protein precipitation as sample processing procedure. The method is very simple and allows obtaining a very good recovery of both analytes. The validated LC/MS method has been applied to a pharmacokinetic study of 50 mg tramadol tablets on healthy volunteers.     

Identification and quantification of phenolic compounds from Balanites aegyptiaca (L) Del (Balanitaceae) galls and leaves by HPLC-MS

Balanites aegyptiaca is a tropical plant which is widely used for medicinal purposes in several African countries, including Burkina Faso. Despite its widespread use, little is known about its phenolic content. This study sought to carry out a screening of the polyphenols from the leaves and galls of B. aegyptiaca. A high-performance liquid chromatography-mass spectrometry method was used to investigate the phenolic content in the parts of the plant studied here. The phenolic acid profile showed the presence of gentisic, p-coumaric, caffeic, ferulic and sinapic acids in the crude and hydrolysed extracts. The flavonoids pattern showed hyperoside, isoquercitrin, rutoside and quercitrin in the crude extract of leaves. Myricetol, quercetol and kaempferol were found after acid hydrolysis of the leaves extract. Ferulic acid, isoquercitrin, rutoside and quercitrin were identified as major phenolic compounds in this study.     

Theoretic analysis and experimental evidence for relationships between the derivative thermogravimetric curves and the Gramm–Schmidt profiles

In the field of thermogravimetric analysis, the evolved gas analysis is a hyphenated technique which allows an easy and rapid identification of the gaseous products resulting from thermodegradation under non-isothermal conditions. In the present paper, the relationships between the Gramm–Schmidt profile (GS) and the DTG curve (dm/dt) will be theoretically analyzed. So, there are two curves which have the extreme points at the same time (temperature) values and which have complementary concavity and convexity. By complex parallel processes, the relationship is more complex from the mathematical point of view. The discussed theoretic cases are connected with the experimental data obtained through the thermal analysis of aminophenazone, glycyrrhetinic acid, amlodipine maleate, verapamil, and a technical polymethane.     

Risperidone/Randomly Methylated β-Cyclodextrin Inclusion Complex—Compatibility Study with Pharmaceutical Excipients

Risperidone (RSP) is an atypical antipsychotic drug used in treating schizophrenia, behavioral, and psychological symptoms of dementia and irritability associated with autism. The drug substance is practically insoluble in water and exhibits high lipophilicity. It also presents incompatibilities with pharmaceutical excipients such as magnesium stearate, lactose, and cellulose microcrystalline. RSP encapsulation by randomly methylated β-cyclodextrin (RM-β-CD) was performed in order to enhance drug solubility and stability and improve its biopharmaceutical profile. The inclusion complex formation was evaluated using thermal methods, powder X-ray diffractometry (PXRD), universal-attenuated total reflectance Fourier transform infrared (UATR-FTIR), UV spectroscopy, and saturation solubility studies. The 1:1 stoichiometry ratio and the apparent stability constant of the inclusion complex were determined by means of the phase solubility method. The compatibility between the supramolecular adduct and pharmaceutical excipients starch, anhydrous lactose, magnesium stearate, and cellulose microcrystalline was studied employing thermoanalytical tools (TG-thermogravimetry/DTG-derivative thermogravimetry/HF-heat flow) and spectroscopic techniques (UATR-FTIR, PXRD). The compatibility study reveals that there are no interactions between the supramolecular adduct with starch, magnesium stearate, and cellulose microcrystalline, while incompatibility with anhydrous lactose is observed even under ambient conditions. The supramolecular adduct of RSP with RM-β-CD represents a valuable candidate for further research in developing new formulations with enhanced bioavailability and stability, and the results of this study allow a pertinent selection of three excipients that can be incorporated in solid dosage forms.     

Thermal analysis and high-temperature X-ray diffraction of nano-tricalcium phosphate crystallization

Calcium phosphate biomaterials have long ago attracted the interest of world-wide scientists because they form the main inorganic constituent of the human bones and teeth. Classical approaches to synthesize this ceramic material did not give satisfactory results until present, so new approaches are required. In this article the tricalcium phosphate achievement by a method which is a combination of sol–gel and classic precipitation from solution is presented, starting from CaCl₂ as calcium precursor and H₃PO₄ as phosphorus precursor, without pH adjustment. The reaction mixture was allowed to maturate for 2 months, the time influence on the precipitated material being presented in previous articles. Present studies aimed at the influence of temperature on the structural characteristics of precipitated and maturated material, by means of thermal analysis, X-ray diffraction, infrared spectroscopy, and high-temperature X-ray diffraction. A complex type thermal decomposition takes place while heating the sample to 1000 °C, with superposed and parallel processes. The sample goes through alternative amorphous and crystalline stages before final crystallization of β-tricalcium phosphate takes place. The high-temperature XRD studies offered the great advantage of being both a synthesis and a physico-chemical characterization technique, which along with thermal analysis and infrared spectroscopy, gave a lot of useful information in a very short time.