Peak Area Values Research Articles

Comparison of Five Derivatizing Agents for the Determination of Amphetamine-Type Stimulants in Human Urine by Extractive Acylation and Gas Chromatography-Mass Spectrometry

Five acylation reagents have been compared for use as derivatizing agents for the analysis of amphetamine-type stimulants (ATS) in urine by gas chromatography-mass spectrometry (GC-MS). The evaluated reagents were heptafluorobutyric anhydride, pentafluoropropionic anhydride, trifluoroacetic anhydride, acetic anhydride (AA) and N-methyl-bis(trifluoroacetamide). The ATS included amphetamine, methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyethylamphetamine (MDEA). A mixture of the ATS was added to urine (1 mL) followed by KOH solution and saturated NaHCO(3) solution. The sample was then extracted with dichloromethane and the derivatizing agent and 2 µL were injected into the GC-MS instrument. The derivatizing agents were compared with reference to the signal-to-noise (S/N) ratios, peak area values, relative standard deviations (RSDs), linearities, limits of detection (LODs) and selectivities. The acetic anhydride proved to be the best according to the S/N ratio and peak area results for amphetamine, MA, MDMA and MDEA. The best RSD values of peak areas and of S/N ratios at 3 µg/mL were also given by AA in cases of MDA, MDMA and MDEA. At 20 µg/mL, the lowest RSD values of peak areas for MDA and the lowest RSD values of S/N ratios for MA, MDA, MDMA and MDEA were again given by AA. Additionally, the highest correlation coefficients for MA, MDA, MDMA and MDEA and the lowest LOD results for MA, MDMA and MDEA were produced by AA.

Comparison of Fast Gas Chomatography–Surface Acoustic Wave (FGC-SAW) Detection and GC-MS for Characterizing Blueberry Cultivars and Maturity

A novel analytical method using fast gas chromatography-surface acoustic wave detection (FGC-SAW) was employed to rapidly characterize blueberry volatile profiles according to genotypes and fruit maturity. Fourteen FGC-SAW peaks were observed and 11 peaks were tentatively identified in the 15 s chromatogram. Peak identifications were confirmed by matching retention index values with similar values from GC-MS analyses of the same samples. Eighty peaks were observed in the 40 min GC-MS analysis of identical samples. Principal component analysis (PCA) score plots of FGC-SAW and GC-MS data both differentiated blueberries according to genotype, maturity stage, and harvest date even though FGC-SAW PCA's used far fewer peak area values. PCA plots clearly separated 'FL02-40', 'Snowchaser', 'Jewel', and 'Primadonna' blueberry cultivars into four quarters using two-dimensional PCA projections. FGC-SAW was also successful in differentiating three berry maturity stages in PCA score plots for both 'Jewel' and 'Primadonna' cultivars. FGC-SAW is an effective technique for rapid analysis of major blueberry volatiles, but could not determine many mid- and low-level volatiles as they were often coeluted with higher concentration volatiles.

Abstract 3965: An algorithm to detect somatic mutations in cancer specimens using mass spectrometric genotyping

Abstract Although advances in technology and the biological understanding of cancer pathogenesis have brought the goal of personalized cancer medicine closer, important challenges remain in several areas. One such challenge is the reliable and sensitive detection of somatic mutations in clinical tumor specimens. Somatic mutation detection in clinical tumor specimens is confounded by biological variables such as the percentage of tumor cells in a specimen, stromal contamination, sequence quality (particularly in DNA derived from formalin-fixed clinical samples), tumor heterogeneity and ploidy considerations. These and other experimental factors can lead to allele signal ratios very different from the 1:0, 1:1 or 0:1 ratio expected for a classically-defined SNP. Germline genotyping using the Sequenom MALDI-TOF mass spectrometry platform has been used to reliably detect single-nucleotide polymorphisms (SNPs) in a wide variety of samples. The automated genotype calling algorithm included with the Sequenom platform falters, however, when the ratio of allele peak signals for a given assay in a specific sample do not approximate the native algorithm's expectations of frequency, confounding accurate genotype calling by the system. We report here a cancer-specific algorithm for sensitive genotype calling of somatic mutations, based on an independent clustering of raw allele peak data for each assay run, and the identification and stratification of outliers from an empirical background (‘wildtype’) cluster of genotypes. Outliers from this cluster are then evaluated using a number of criteria to determine the quality and performance of the overall assay run, as well as the individual call; these factors include the relative signal-to-noise ratio (SNR) of each allele peak, the ratio of variant allele peak height to peak area, the percentage of signal lost in unextended probe (UEP) and relative distance of a putative mutation call from the wildtype cluster In a scatter plot of peak area values. Based on these criteria, a confidence value is assigned to each candidate outlier, allowing for stratification and prioritization of these candidates for validation. We applied the algorithm to samples run against the our OncoMap genotyping panel, comprised of 460 assays interrogating mutations in 33 cancer-associated genes. Candidate mutations produced by this algorithm correlate strongly with those called by users manually, and use of the algorithm increases the sensitivity and reliability of the OncoMap platform to detect somatic mutations in clinical tumor samples, particularly in FFPE-derived material. The algorithm code and documentation will be made publicly available in a form compatible with most Sequenom genotyping platform installations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3965. doi:1538-7445.AM2012-3965

Development of an online capillary comprehensive 2D‐LC system for the analysis of proteome samples

In the present contribution, a fully automated capillary comprehensive two-dimensional LC (LC×LC) method, for proteomic analysis, was developed for the first time. The investigated platform was characterized by the coupling of high-pH RP with low-pH RP separations thus ensuring the generation of high peak capacity despite the employment of identical stationary phases. The use of capillary columns in both dimensions allowed to reduce mobile-phase consumption and enhance sensitivity. Fraction transfer from the first to the second dimension was performed by means of two 2-position 6-port nano-switching valves, under stop-flow conditions. Values as high as 1208 and 955 were obtained for the theoretical and practical peak capacity, respectively. The investigated LC×LC system showed good retention time repeatibility with RSD values ranging from 0.8 to 6.0% for the first dimension and from 1.0 to 3.0% for the second dimension, respectively. RSD peak area values below 9.5% were also attained, thus demonstrating the precision of the LC×LC method employed.

Holistic analysis of seven constituents from three medicinal herbs composing Wuji pills in a single run by ultra performance liquid chromatography: application to quality control study

To enable effective quality control of the traditional Chinese medicine (TCM) preparation the Wuji pill, seven bioactive components, i.e. paeoniflorin, jatrorrhizine, coptisine, palmatine, berberine, evodiamine and rutaecarpine, from the three medicinal herbs composing Wuji pills have been selected as evaluation markers. Then an ultra-performance liquid chromatography (UPLC) method coupled with photodiode array (PDA) detection was developed and validated for simultaneous quantification of the 7 mark components in the Wuji pill. Optimum separation was achieved on a C18 column (50 × 2.1 mm i.d., 1.7 μm particle) through a 5.0 min gradient delivery of a mixture of A (acetonitrile) and B (0.1% aqueous phosphoric acid containing 1.38 mmol L−1 sodium dodecyl sulphonate (SDS) and 5% acetonitrile (v/v)) at a flow rate of 0.3 mL min−1 at 25 °C. Because of the different UV characteristics of these components, 3 detection wavelengths were used for quantitative analysis. All of the analytes showed good linearity (r of >0.999). The limit of detection and limit of quantitation for the analytes ranged from 0.005 to 0.15 μg mL−1 and from 0.01 to 0.50 μg mL−1, respectively. The method was validated for repeatability, precision, stability, accuracy, and selectivity. The RSD values of retention time and peak area were 0–0.3% and 0.1–0.9% for intra-assay, and 0.1–1.4% and 1.0–2.6% for inter-assay precision. Analysis repeatability and stability (24 h) were all lower than 2.0%. The recovery of the method was 96.1–97.5% with a RSD of 1.1–2.8%. The validated method was applied to the quality control of Wuji pills from different production batches.

Characterization of herbal medicine with different particle sizes using pyrolysis GC/MS, SEM, and thermal techniques

Analytical techniques have been used to characterize compounds from herbal medicine, its products and extracts. The objective of this study was to characterize a variety of particle sizes of Erythrina velutina Willd powder. The samples used in the study were named MUF01 (710 μm), MUF03 (180 μm) and MUF05 (75 μm). The techniques employed were scanning electron microscopy (SEM), thermal analysis such as thermogravimetry (TG) and differential thermal analysis (DTA) together with pyrolysis coupled to gas chromatography/mass spectrometry (Pyr-GC/MS). SEM enabled us to detect the existence of divergences from the expected results from the granulometry process. Thermal analytical techniques (TG and DTA) showed the thermal decomposition profile, corresponding to physical and chemical phenomena. The chromatographic data relative to the peak area of the compounds analyzed evidenced quantitative differences in the chemical compositions of the samples MUF01, MUF03, and MUF05 at 300, 450 and 600 °C. Neophytadiene 2,6,10-trimethyl, 14 and 3-eicosyne were identified by Pyr-GC/MS at 300, 450 and 600 °C, and it classified the samples according the peak area values, which were MUF05 > MUF03 > MUF01. SEM, DTA and TG confirmed this through particle size uniformity, heat flow, and mass loss, respectively.

Electromembrane extraction using stabilized constant d.c. electric current—A simple tool for improvement of extraction performance

This contribution presents an experimental approach for improvement of analytical performance of electromembrane extraction (EME), which is based on the use of stabilized constant d.c. electric current. Extractions were performed using a high voltage power supply, which provided stabilized constant d.c. current down to 1μA and facilitated current-controlled transfer of ions of interest from a donor solution through a supported liquid membrane (SLM) into an acceptor solution. Repeatability of the extraction process has significantly improved for EME at constant electric current compared to EME at constant voltage. The improved repeatability of the extraction process was demonstrated on EME-capillary electrophoresis (EME-CE) analyses of selected basic drugs and amino acids in standard solutions and in human urine and serum samples. RSD values of peak areas of the analytes for EME-CE analyses were about two-fold better for EME at constant electric current (2.8–8.9%) compared to EME at constant voltage (3.6–17.8%). Other analytical parameters of the EME-CE methods, such as limits of detection, linear ranges and correlation coefficients were not statistically different for the two EME modes. Moreover, EME at constant electric current did not suffer from SLM instabilities frequently observed for EME at constant voltage.

On-line coupling of a clean-up device with supported liquid membrane to capillary electrophoresis for direct injection and analysis of serum and plasma samples

A simple sample clean-up device with planar supported liquid membrane (SLM) was developed and coupled on-line to capillary electrophoresis (CE) for direct injection of human body fluids. Donor and acceptor compartments of the device were filled with diluted body fluid and deionized water, respectively, and the two solutions were separated by a thin SLM. Analytes of interest were selectively transported from the donor solution through the SLM into the acceptor solution by diffusion whereas interfering matrix components were efficiently retained on the SLM. Equilibrium between the concentrations of analytes at the SLM was obtained typically in 5min. Then a CE separation capillary was inserted into the acceptor compartment to firmly touch the SLM and the pretreated sample was hydrodynamically injected into the capillary. The analytical procedure was demonstrated by rapid pretreatment, on-line injection, and CE determination of selected amino acids in human serum and plasma samples. 1-Ethyl-2-nitrobenezene and bis(2-ethylhexyl) phosphate (15%, v/v) was used as the selective SLM for clean-up of the body fluids and 0.5M acetic acid was used as a background electrolyte solution for CE analysis of the pretreated amino acids. Concentrations of amino acids on acceptor side of the SLM reached 40–58% of their original concentrations in donor solution after 5min equilibration time and then remained constant proving that equilibrium was achieved at the SLM. Injection of the pretreated samples was highly repeatable with RSD values of peak areas 2.4–8.4% and 3.4–10.5% for standard solutions and real samples, respectively. Limits of detection between 0.75 and 2.5μM were achieved, corresponding to 3.75–12.5μM in 1:4 diluted real samples, which ensure sensitive determination of most amino acids in the body fluids. The developed method is fast, simple, efficient, cheap and selective and may be applied to determination of a wide range of analytes in various samples with complex matrices.

Intercompany Study to Evaluate the Robustness of Capillary Isoelectric Focusing Technology for the Analysis of Monoclonal Antibodies

Interlaboratory comparisons are essential to bringing emerging technologies into biopharmaceutical industry practice and regulatory acceptance. As a result, an international team including 12 laboratories from 10 independent biopharmaceutical companies in the United States and Switzerland was formed to evaluate the precision and robustness of capillary isoelectric focusing (CIEF) to assess the charge heterogeneity of monoclonal antibodies. The different laboratories determined the apparent pI and the relative distribution of the charge isoforms of a representative monoclonal antibody (rMAb) sample using the same CIEF method. Statistical evaluation of the data was performed to determine within and between-laboratory consistencies and outlying information. The apparent pI data generated for each charge variant peak showed very good precision between laboratories with percentage of RSD values of ≤0.5%. Similarly, the percentage of RSD for the rMAb charge variants percent peak area values are ≤4.4% across different laboratories with different analysts using different lots of ampholytes and multiple instruments. Taken together, these results validate the appropriate use of CIEF in the biopharmaceutical industry in support of regulatory submissions.

A Novel Pyridoxal 5′-Phosphate-dependent Amino Acid Racemase in the Aplysia californica Central Nervous System

D-aspartate (D-Asp) is found in specific neurons, transported to neuronal terminals and released in a stimulation-dependent manner. Because D-Asp formation is not well understood, determining its function has proved challenging. Significant levels of D-Asp are present in the cerebral ganglion of the F- and C-clusters of the invertebrate Aplysia californica, and D-Asp appears to be involved in cell-cell communication in this system. Here, we describe a novel protein, DAR1, from A. californica that can convert aspartate and serine to their other chiral form in a pyridoxal 5'-phosphate (PLP)-dependent manner. DAR1 has a predicted length of 325 amino acids and is 55% identical to the bivalve aspartate racemase, EC 5.1.1.13, and 41% identical to the mammalian serine racemase, EC 5.1.1.18. However, it is only 14% identical to the recently reported mammalian aspartate racemase, DR, which is closely related to glutamate-oxaloacetate transaminase, EC 2.6.1.1. Using whole-mount immunohistochemistry staining of the A. californica central nervous system, we localized DAR1-like immunoreactivity to the medial region of the cerebral ganglion where the F- and C-clusters are situated. The biochemical and functional similarities between DAR1 and other animal serine and aspartate racemases make it valuable for examining PLP-dependent racemases, promising to increase our knowledge of enzyme regulation and ultimately, D-serine and D-Asp signaling pathways.

Sweeping with Electrokinetic Injection and Analyte Focusing by Micelle Collapse in Two-Dimensional Separation via Integration of Micellar Electrokinetic Chromatography with Capillary Zone Electrophoresis

A novel integrated concentration/separation approach involving online combination of sweeping with electrokinetic injection and analyte focusing by micelle collapse (AFMC) with heart-cutting two-dimensional (2D) capillary electrophoresis (CE) in a single capillary was developed for analysis of Herba Leonuri and mouse blood samples. First, a new sweeping with an electrokinetic injection preconcentration method was developed to inject a large volume sample solution and significantly enhance detection sensitivity. Then, the preconcentration scheme was integrated to the 2D-CE to provide significant analyte concentration and extremely high resolving power. The sample was preconcentrated by sweeping with electrokinetic injection and separated in first dimension micellar electrokinetic chromatography (MEKC). Then, only a desirable fraction of the first dimension separation was transferred into the second dimension of the capillary by pressure and further analyzed by capillary zone electrophoresis (CZE) acting as the second dimension. As the key to successful integration of MEKC and CZE, an AFMC step was integrated between the two dimensions to release analytes from the micelle interior to a liquid zone and to overcome the sample zone diffusion caused by mobilization pressure. The injected sample plug lengths for flavonoids under 15 kV for 60 min were experimentally estimated as 546 cm. The dual concentration methods resulted in the increased detection factors of 6000-fold relative to the traditional pressure injection method. The relative standard deviation (RSD) values of peak height, peak area, and migration time were 2.7-4.5%, 1.9-4.3%, and 4.7-6.8% (n = 10), respectively. The limits of detection (S/N = 3) were in the range of 7.3-36.4 ng/L, and the theoretical plate numbers (N) were in the range of 1.7-4.3 × 10(4) plates/m. This method has been successfully applied to determine flavonoids in Herba Leonuri and postdosing mouse blood samples. The pharmacokinetic study also demonstrated that the proposed concentration/separation method was convenient and sensitive and would become an attractively alternative method for online sample concentration and separation in complex samples.

Structural modification in amorphous silica after exposure to low fluence 355 nm laser irradiation

UV laser irradiation induced structural modification in amorphous silica was characterized using Fourier transform infrared and X-ray induced photoelectron spectroscopy. Laser irradiation experiment was conducted using a 3 ω, 355 nm beam from a pulsed Nd-YAG laser with pulse length of 6.8 ns and laser repetition rate of 1 Hz at ambient conditions. The examined laser fluence was controlled at a relatively low level, ranging from 0 to 4 J/cm 2. The IR spectra revealed that the vibration frequency of the rocking mode of Si O Si covalent bond shifted to lower wave number, while the bending mode and asymmetric stretching mode of Si O Si covalent bond shifted to higher frequency. This result suggested that the length of Si O Si covalent bond was decreased, the bond angle was increased and the irradiation modified material was densified after irradiation. The high resolution XPS spectra of Si 2p and O 1s illustrated the chemical shift of silicon and oxygen ions after irradiation. The XPS chemical shift of the Si 2p peak about 1.1 eV revealed the existence of low valence silicon ions Si 3+ species in silica glass after irradiation. The chemical shift of the O 1s peak about 0.9 eV illustrated the emergence of non-bridging oxygen ions during laser irradiation. The deconvoluted peak area and FWHM value of low valence silicon ions and non-bridging oxygen ions all exhibited exponentially growth as the linearly elevation of laser fluence. UV laser-induced photolysis of Si O covalent bond was suggested to be responsible for the formation and increase of low valence silicon ions and non-bridging oxygen ions. These FT-IR and XPS data revealed that short range structural modifications were important structure alterations in silica glass before the emergence of distinct and large size damage crater.

Effect of the ω-acylceramides on the lipid organization of stratum corneum model membranes evaluated by X-ray diffraction and FTIR studies (Part I)

The lipid organization in the outermost layer of the skin, the stratum corneum, is important for the skin barrier function. The stratum corneum lipids are composed of ceramides (CER), free fatty acids (FFA) and cholesterol (CHOL). In the present study Fourier transform infrared (FTIR) and small-angle X-ray scattering (SAXS) techniques were utilized to evaluate the effect of three C18 fatty acid esterified ω-acylceramides (CER EOS) on the lipid organization of stratum corneum model membranes. FTIR spectra (scissoring and rocking bands) showed as a function of temperature significant line-shape changes for both components assigned to the orthorhombic phase. Second-derivative analyzes revealed a significant decrease in the interchain coupling strength (Δ ν values) for the samples formed by CER EOS with the linoleate (CER EOS-L) and oleate (CER EOS-O) moiety around 28.5 °C. However, only a gradual decrease in the Δ ν values was noticed for the mixture formed with CER EOS with the stearate moiety (CER EOS-S) over the whole temperature range. In the absence of CER EOS the decrease started already at 25.5 °C, demonstrating that CER EOS stabilized the orthorhombic lattice. This stabilization was most pronounced for the CER EOS-S. Spectral fittings allowed to evaluate the orientation changes of the skeletal plane within the orthorhombic unit cell ( θ values) for a given temperature range. From the best-fit parameters (peak area values), a decrease in the orthorhombic phase contribution to the scissoring band was also monitored as a function of the temperature. SAXS studies showed the coexistence of two lamellar phases with a periodicity of ∼5.5 nm (short periodicity phase, SPP) and ∼12 nm (LPP) in the presence of the CER EOS-L and CER EOS-O. However, no diffraction peaks associated to the LPP were detected for CER EOS-S. While CER EOS-S most efficiently stabilized the orthorhombic phase, CER EOS-L and CER EOS-O promoted the presence of the LPP. Therefore, the presence of all three CER EOS as observed in human stratum corneum may contribute to a proper skin barrier function.

Simple Extraction and Rapid HPLC Method for Tocopherol Analysis in Marine and Fresh-water Fish Species

A rapid high-performance liquid chromatographic (HPLC) method with simple extraction procedure for the determination of tocopherols in seafood was developed. A continuous isocratic elution system was used for the analysis with a mixture of acetonitrile and methanol. Tocopherols were identified by comparison of retention times and peak area values with standard of α-, β-, γ- and δ-tocopherols. The HPLC technique used showed good performance parameters (linearity r2 = 0.9999, and relative standard deviation (RSD) ≤ 12.38%). The total recoveries for each tocopherol were 99.7, 99.9, 99.8 and 99.7% for α, β, γ- and δ, respectively. This method was then applied to freshwater and seawater fish species to detect their tocopherol contents. Significant differences (P < 0.05) were observed in the content of tocopherol among fish species. The highest content was obtained from shrimp (81.3 mg/kg), while the lowest was found for whiting (9.8 mg/kg).

Improving precision of manual hydrodynamic injection in capillary electrophoresis with contactless conductivity detection

Reproducible injection in capillary electrophoresis has been difficult to achieve with manual injection techniques using simple injection devices, such as gravity injection (siphoning) or hydrodynamic sample splitting. We demonstrate that the injection reproducibility can be improved using very simple means. With hydrodynamic sample splitter, a passive micro-metering valve can be inserted in-line to regulate the sample flow rate through the splitter interface. A significant improvement of both reproducibility and repeatability was achieved. The reproducibility of RSD of the peak areas improved from 25.4% to 4.4%, while the repeatability was below 4.1% when micro-metering valve was used. Additional simple correction that can be used to further improve the variability of injected sample volumes in any hydrodynamic injection mode in CE with conductivity detection was proposed and verified. The measured EOF peak can serve as a simple indicator of the injected volume and can be effectively used for additional correction. By a linear function between the injection volume and the peak area of the EOF, the RSD values of peak areas for both manual gravity injection and hydrodynamic sample splitter were further improved below 2% RSD. The linearity of the calibration curve was also significantly improved. The proposed correction works even with slight differences in matrix composition, as demonstrated on the analysis aqueous soil extract of model mixture of five nerve agent degradation products.

The effect of polymer doses and extended mixing intensity on the geometric and rheological characteristics of conditioned anaerobic digested sludge (ADS)

The effect of polymer doses and extended mixing intensity (EMI) on the geometric and rheological characteristics of conditioned anaerobic digested sludge (ADS) was investigated. The results revealed that polymer doses had a distinct effect on the CST values of conditioned ADS, but that extended mixing intensity (EMI) did not show such effect at specific polymer dosage. The polymer doses, at which the maximum values of the initial peak height and area in the two kinds of rheograms appear, were as same as or close to 20.36kg/ton producing the lowest CST value for conditioned ADS-1. The maximum size and two-dimensional fractal dimensions of the conditioned ADS-1 aggregates were observed at a polymer dosage of 13.57kg/ton, while their one-dimensional fractal dimensions decreased as more polymer was added. The floccky test for conditioned ADS-2 at different extended mixing intensities during conditioning indicates distinct effects on the peak height and area under the rheograms. However, the minimum values of peak height and area in the Haake RV20 rheograms were given at an EMI of 30rpm (G=28.98s−1), while the maximum values were obtained at an EMI of 80rpm (G=126.21s−1). At an EMI equal to 28.98s−1, the most compact and largest aggregates were produced with less irregular boundaries and surfaces than at other EMIs. For ADS-1 and ADS-2, there were no good correlations between the rheological parameters and aggregate sizes, D2L or D2P. Moreover, the EMIs from 28.98s−1 to 425.95s−1 provided available hydraulic conditions for flocculation, while mixing intensities higher than 425.95s−1 led to stronger shear and deflocculation.

Methacrylate ester‐based monolithic columns for nano‐LC separation of tocopherols in vegetable oils

The separation and determination of tocopherols (Ts) in vegetable oils by nano-LC chromatography with UV-vis detection using lauryl methacrylate ester-based monolithic columns has been developed. The separation of Ts was optimized in terms of mobile phase composition on the basis of the best compromise among efficiency, resolution and analysis time. Using a mobile phase composed of ACN/methanol/water, an excellent resolution between Ts was achieved within 18 min. The LODs were lower than 0.26 μg/mL, being repeatability values of retention time and peak area below 0.15 and 3.1%, respectively. The method was applied to the quantification of Ts and tocotrienols present in several vegetable oils from different botanical origins.

Fast Separation and Determination of Sterols in Vegetable Oils by Ultraperformance Liquid Chromatography with Atmospheric Pressure Chemical Ionization Mass Spectrometry Detection

A method for the determination of sterols in vegetable oils by ultraperformance liquid chromatography (UPLC) with atmospheric pressure chemical ionization mass spectrometry detection has been developed. The separation of sterols was optimized in terms of mobile phase composition, column temperature and flow rate. The optimal conditions were achieved using an Acquity UPLC BEH C18 column (50 x 2.1 mm, 1.7 microm) with a mobile phase consistent of acetonitrile/water (0.01% acetic acid) using a linear gradient, at a flow rate of 0.8 mL min(-1) and column temperature of 10 degrees C, giving a total analysis time below 5 min. The determination was performed in selective ion recording mode. The limits of detection were in all cases below 0.07 microg mL(-1), with relative standard deviation values of retention times and peak areas below 0.4 and 5%, respectively. The content of main sterols present in several vegetable oils with different botanical origins was also established.

Sensitive and rapid determination of nitric oxide in human serum using microchip capillary electrophoresis with laser-induced fluorescence detection

Microfluidic chip capillary electrophoresis with laser-induced fluorescence detection is employed for direct determination of trace nitric oxide in human blood using diaminorhodamines as the fluorescence probe. Factors influencing the separation and detection processes were systematically studied. Complete and fast separation of the highly fluorescent triazole formed was achieved within 45 s, and the relative standard deviations values of migration time and peak area were less than 3%. The detection limit of NO was 3.0 nmol.L-1 (at a signal-to-noise ratio of 3) and the liner range was from 1.0 × 10-8 mol.L-1 to 3.0 × 10-6 mol.L-1. The method has been applied to the determination of NO in serum of healthy persons and patients suffering from diseases, with recoveries varying from 92.65 to 98.43%.

Modeling a gamma spectroscopy system and predicting spectra with Geant-4

An activity predictor software was previously developed to foresee activities, exposure rates and gamma spectra of activated samples for Radiation Science and Engineering Center (RSEC), Penn State Breazeale Reactor (PSBR), Neutron Activation Analysis (NAA) measurements. With Activity Predictor it has been demonstrated that the predicted spectra were less than satisfactory. In order to obtain better predicted spectra, a new detailed model for the RSEC NAA spectroscopy system with High Purity Germanium (HPGe) detector is developed using Geant-4. The model was validated with a National Bureau of Standards certified 60Co source and tree activated high purity samples at PSBR. The predicted spectra agreed well with measured spectra. Error in net photo peak area values were 8.6–33.6%. Along with the previously developed activity predictor software, this new model in Geant-4 provided realistic spectra prediction for NAA experiments at RSEC PSBR.