Quantitative Analysis of Acetylsalicylic Acid by q-NMR (Quantitative-Nuclear Magnetic Resonance Spectroscopy)

Quantitative analysis is an important step during pharmaceutical drug development. Currently, the pharmaceutical industry uses high performance liquid chromatography (HPLC) for quantitative analysis of organic compounds as the preferred technique. The proton nuclear magnetic resonance (NMR) technique has an inherent ability to quantify a given analyte and may be used to quantify organic compounds. Quantitative nuclear magnetic resonance spectroscopy (q-NMR) of acetylsalicylic acid (ASA) was conducted using tert-butyl alcohol (tert-butanol) as the internal standard and deuterated chloroform (CDCl3) as the solvent. Preparations of ASA solutions in low and high concentration ranges, 1.0 mM – 10.1 mM and 10.0 mM – 100.1 mM respectively, were analyzed to determine a linear correlation between the concentrations of ASA with the intensities of methyl peaks and aromatic ring proton peaks using Topspin software. The q-NMR analysis of high concentration ASA solutions showed a strong linear correlation (R2 values \u3e 0.9994) and high precision (% RSD values \u3c 1%) for both the average methyl peak areas and the average aromatic ring proton peak areas. However, the low concentration ASA solutions showed a weak linear correlation (R2 values \u3e 0.9914) but, fairly good precision (% RSD values \u3c 5%) for both the average methyl peak areas and the average aromatic ring proton peak areas. Therefore, the q-NMR technique is a viable alternative for quantitative analysis of high concentration ASA methyl peak areas and aromatic ring proton peak areas, but it is not suitable for the low concentration ASA solutions. The low concentration (1.0 mM – 10.1 mM) ASA solutions were also analyzed by the conventional HPLC method; the results obtained were compared with the results from the q-NMR technique. A comparison of q-NMR data to HPLC data focused on linearity, precision, and acquisition time for the acetylsalicylic acid solutions at low concentrations. The HPLC data showed a strong linear correlation with an R2 value of 0.9997 and high precision with a % RSD \u3c 0.9% for the average ASA peak areas. A comparison of q-NMR data to HPLC data for the low concentration ASA solutions showed that the q-NMR technique used less solvents and less time for data acquisition

High-throughput evaluation of organic contaminant removal efficiency in a wastewater treatment plant using direct injection UHPLC-Orbitrap-MS/MS

Removal efficiency can be estimated from non-target data using the ratio of peak areas in effluent and influent

Machine learning for omics data analysis.

In proteomics and metabolomics, to quantify the changes of abundance levels of biomolecules in a biological system, multiple sample analysis steps are involved. The steps include mass spectrum deconvolution and peak list alignment. Each analysis step introduces a certain degree of technical variation in the abundance levels (i.e. peak areas) of those molecules. Some analysis steps introduce technical variations that affect the peak areas of all molecules equally while others affect the peak areas of a subset of molecules with varying degrees. To correct these technical variations, some existing normalization methods simply scale the peak areas of all molecules detected in one sample using a single normalization factor or fit a regression model based on different assumptions. As a result, the local technical variations are ignored and may even be amplified in some cases. To overcome the above limitations, we developed a molecule specific normalization algorithm, called MSN, which adopts a robust surface fitting strategy to minimize the molecular profile difference of a group of house-keeping molecules across samples. The house-keeping molecules are those molecules whose abundance levels were not affected by the biological treatment. We also developed an outlier detection algorithm based on Fisher Criterion to detect and remove noisy data points from the experimental data. The applications of the MSN method on two different datasets showed that MSN is a highly efficient normalization algorithm that yields the highest sensitivity and accuracy compared to five existing normalization algorithms. The outlier detection algorithm\u27s application on the same datasets has also shown to be efficient and robust

Decreasing the chromatographic quantitation uncertainty using the external standard and standard addition methods with additional standards

Три из известных методов количественного газохроматографического анализа (внешнего стандарта, абсолютной градуировки и стандартной добавки) в наибольшей степени «чувствительны» к воспроизводимости дозирования проб. Неконтролируемые потери компонентов проб во время этой операции закономерно приводят к увеличению как случайных, так и систематических погрешностей определений. Охарактеризованы модификации методов внешнего стандарта и стандартной добавки, заключающиеся во введении дополнительных стандартов в анализируемые образцы. Важно, что на химическую природу таких стандартов нет никаких ограничений, так как они необходимы только для вычисления относительных площадей пиков. Все вычисления далее проводят не с абсолютными, а с относительными площадями хроматографических пиков. Специальными экспериментами показано, что относительные стандартные отклонения относительных площадей пиков в 6-38 раз меньше, чем значения аналогичных статистических характеристик абсолютных площадей. Это позволяет проводить количественные определения с приемлемой точностью даже в условиях низкой воспроизводимости дозирования. Для выявления потерь проб на стадии дозирования предложено использовать гистограммы распределения площадей хроматографических пиков. Для их построения число параллельных определений должно быть не менее 20. Приведены расчетные соотношения для модифицированных методов внешнего стандарта и стандартной добавки с использованием дополнительных стандартов, в том числе для получения оценок случайных составляющих погрешностей определений.There are three methods from the known methods of the quantitative chromatographic analysis (external standard, absolute calibration, and standard addition) that are most “sensitive” to the reproducibility of the sample injection. Non-controlled constituents losses of the injected samples lead to the increase of both random and systematic errors of the results. The modifications of external standard and standard addition methods with the use of additional standards were characterized. It is important to note that there are no restrictions on the chemical origin of such standards, so far as they are required for calculation of the relative peak areas only. All calculations were conducted not with absolute, but with relative peak areas. Relative standard deviations of the relative peak areas were 6-38 times less than those of absolute peak areas, which was established in the result of special experiments. This allowed quantitation with the appropriate precision even at the low reproducibility of the injection. The use of histograms for the peak areas was recommended for revealing the losses of samples during injection. However, their application required at least 20 parallel experiments. The equations for calculations, including those for evaluations of values of possible errors, were presented for modified methods of external standard and standard addition supported with additional standards

Evaluation of extraction methods for untargeted metabolomic studies for future applications in zebrafish larvae infection models

Sample preparation in untargeted metabolomics should allow reproducible extractions of as many molecules as possible. Thus, optimizing sample preparation is crucial. This study compared six diferent extraction procedures to fnd the most suitable for extracting zebrafsh larvae in the context of an infection model. Two one-phase extractions employing methanol (I) and a single miscible phase of methanol/acetonitrile/water (II) and two two-phase methods using phase separation between chloroform and methanol/water combinations (III and IV) were tested. Additional bead homogenization was used for methods III and IV (III_B and IV_B). Nine internal standards and 59 molecules of interest (MoInt) related to mycobacterial infection were used for method evaluation. Two-phase methods (III and IV) led to a lower feature count, higher peak areas of MoInt, especially amino acids, and higher coefcients of variation in comparison to one-phase extractions. Adding bead homogenization increased feature count, peak areas, and CVs. Extraction I showed higher peak areas and lower CVs than extraction II, thus being the most suited one-phase method. Extraction III and IV showed similar results, with III being easier to execute and less prone to imprecisions. Thus, for future applications in zebrafsh larvae metabolomics and infection models, extractions I and III might be chosen

Secondary Crystallization of Isotactic Polystyrene

When isotactic polystyrene (i-PS) is crystallized from the melt or from the glassy state at rather large supercooling an additional melting peak appears on the curve during scanning in a differential calorimeter. The overall rate of crystallization deduced from the total peak areas as a function of crystallization time did not fit the Avrami equation well. When we omit the area of the additional melting peak in the kinetic analysis a much better fit is obtained. We also observed that no lamellar thickening occurs during isothermal crystallization. In view of the low degree of crystallinity of i-PS these results lead to the idea that a secondary crystallization process takes place within the amorphous parts of the spherulites resulting in this additional melting peak on the DSC curve. The large supercooling needed and the increase in peak area with increasing molecular weight make us suppose that intercrystalline links are probably responsible for the additional melting peak of bulk-crystallized i-PS. Electron microscopic studies of surface replicas of i-PS support this view.

The evaluation of the effects of steroid treatment on the tumor and peritumoral edema by DWI and MR spectroscopy in brain tumors

Objective To investigate the effects of dexamethasone on brain tumor and peritumoral edema by different sequences of magnetic resonance imaging (MRI). Materials and methods MRI was performed in 28 patients with brain tumor. Patients were divided into the 3 groups based on the histological diagnosis; Group I: high-grade glial tumor, Group II: low-grade glial tumor, and Group III: brain metastasis. The measurements of peritumoral edema volume and apparent diffusion coefficient (ADC) values were performed while the peak areas of cerebral metabolites were measured by spectroscopy in groups I and II. The changes in edema volumes, ADC values and cholin/creatine peak areas were compared. Results The volume of peritumoral edema was decreased in groups I and II, but increased in group III after dexamethasone treatment. These changes were not statistically significant for 3 groups. ADC value was decreased in group I and increased in groups II and III. Changes in ADC values were statistically significant. Cholin/creatine peak areas were decreased after dexamethasone in groups I and II, but these changes were also not significant. Conclusion Dexamethasone has no significant effect on the volume of peritumoral edema in glial tumor and metastasis. Moreover, dexamethasone increases the fluid movements in low grade gliomas and metastases, decreases in high grade gliomas. However, more comprehensive clinical studies are needed to show the effects of dexamethasone on brain tumors and peritumoral edema

Constituents of the rhizome of Curcuma aeruginosa and its DNA fingerprint

Identity of the rhizhome of Curcuma aeruginosa Roxb. was established by threetechniques: (1) the DNA fingerprint, (2) the chemical constituents of its volatile oils by usinggas chromatograph-mass spectrometer, and (3) thin-layer chromatography (TLC) of themethanol extract. These three techniques were used to differentiate C. aeruginosa from itssimilar species. Result from the polymerase chain reaction (PCR) amplification, differentpolymorphic bands between the two specimens were found. The relative amounts of camphor,curzerenone and epicurzerenone in the C. aeruginosa rhizome were 16.85, 16.81 and 3.5% oftotal peak areas, whereas 6.04, 0 and 62.84% of total peak areas were found in the Curcuma sp..The thin-layer chromatogram revealed that Curcuma sp. contained curcumine, whereas onlytraces were detected in C. aeruginosa.Keywords: Curcuma aeruginosa, Zingiberaceae, TLC, GC-MS and DNA fingerprint

In vitro effects of hydrogen peroxide combined with different activators for the in-office bleaching technique on enamel

The aim of this study was to evaluate the alteration of human enamel bleached with high concentrations of hydrogen peroxide associated with different activators. Fifty enamel/ dentin blocks (4 x 4 mm) were obtained from human third molars and randomized divided according to the bleaching procedure (n = 10): G1 = 35% hydrogen peroxide (HP -Whiteness HP Maxx); G2 = HP + Halogen lamp (HL); G3 = HP + 7% sodium bicarbonate (SB); G4 = HP + 20% sodium hydroxide (SH); and G5 = 38% hydrogen peroxide (OXB - Opalescence Xtra Boost). The bleaching treatments were performed in three sessions with a 7-day interval between them. The enamel content, before (baseline) and after bleaching, was determined using an FT-Raman spectrometer and was based on the concentration of phosphate, carbonate, and organic matrix. Statistical analysis was performed using two-way ANOVA for repeated measures and Tukey's test. The results showed no significant differences between time of analysis (p = 0.5175) for most treatments and peak areas analyzed; and among bleaching treatments (p = 0.4184). The comparisons during and after bleaching revealed a significant difference in the HP group for the peak areas of carbonate and organic matrix, and for the organic matrix in OXB and HP+ SH groups. Tukey's analysis determined that the difference, peak areas, and the interaction among treatment, time and peak was statistically significant (p < 0.05). The association of activators with hydrogen peroxide was effective in the alteration of enamel, mainly with regards to the organic matrix737516521FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP05/60082-4 01/14384-