High-Throughput Quantitative Analysis of Amino Acids in Freeze-Dried Drops Using Time-of-Flight Secondary Ion Mass Spectrometry.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a promising analytical tool for molecular profiling in biological applications. However, its ultrahigh vacuum environment and matrix effects hamper the absolute quantitation of solution samples. Herein, we present a rapid high-throughput platform for quantitative ToF-SIMS analysis of amino acids in matrix deposits formed from freeze-dried solution drops through ice sublimation on a parylene film microarray substrate. Droplets of the amino acid solutions, which were mixed with stable isotope-labeled phenylalanine (F*) of high concentration (10 mM), were loaded on wells of the microarray, then frozen and evaporated slowly below the freezing point, forming continuous solid-phase F* matrix deposits. The amino acids (≤500 µM), adequately well dispersed throughout the F* matrix deposits on each well, were quantitatively analyzed by ToF-SIMS in a rapid and high-throughput fashion. The lower limit of quantitation reached below 10 µM.

Liquid chromatographic resolution of proline and pipecolic acid derivatives on chiral stationary phases based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid.

Two liquid chromatographic chiral stationary phases based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid were applied to the resolution of the amide derivatives of cyclic α-amino acids including proline and pipecolic acid. Among the five amide derivatives of proline, aniline amide was resolved best on the first chiral stationary phase, which contains two N-H tethering amide groups, with the separation factor of 1.31 and the resolution of 2.60, and on the second chiral stationary phase, which contains two N-CH3 tethering amide groups, with the separation factor of 1.57 and the resolution of 5.50. Among the five amide derivatives of pipecolic acid, 2-naphthyl amide was resolved best on the first chiral stationary phase with the separation factor of 1.30 and the resolution of 1.75, but 1-naphthylmethyl amide was resolved best on the second chiral stationary phase with the separation factor of 1.30 and the resolution of 2.26. In general, the second chiral stationary phase was found to be better than the first chiral stationary phase in the resolution of the amide derivatives of cyclic α-amino acids. In this study, the second chiral stationary phase was first demonstrated to be useful for the resolution of secondary amino compounds.

Polyphenolic profile and antioxidant effects of various parts of Artemisia annua L.

An annual Korean weed, Artemisia annua L., has been used as a folk medicine for the treatment of a number of diseases. Remarkably, among the 32 polyphenols characterized in various parts of plant tissue, including flowers, leafs, stems and roots, 10 compounds were detected for the first time using liquid chromatography-tandem mass spectrometry (LC/MS/MS). The quantification method was validated using structurally related external standards with determination coefficients (R(2) ) ≥0.9995. The limits of detection and quantitation were 0.068-3.932 and 0.226-13.108 mg/L, respectively. The recoveries estimated at 50 and 100 mg/L ranged between 60.6-92.2 and 61.3-111%, respectively, with relative standard deviations <12%. The roots contained the largest concentration of identified components, while the flowers contained the least. The antioxidant capacity evaluated in terms of 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging activities and reducing power was highest in the roots and lowest in the flowers. The findings are well correlated and suggest that the antioxidant capacities principally depend upon the polyphenol concentrations in each part of the plant.

The polyphenolic profiles and antioxidant effects of Agastache rugosa Kuntze (Banga) flower, leaf, stem and root.

Agastache rugosa Kuntze (Korean mint) is used as a spice and in folk medicine in East Asia. The present study identified a total of 18 polyphenols from the flower, leaf, stem and roots of this plant using high-performance liquid chromatography-tandem mass spectrometry. Fourteen of these compounds had not previously been identified in these plant tissues. Each polyphenol was validated in comparison with external calibration curves constructed using structurally related compounds, with determination coefficients >0.9993. The limits of detection and quantification were 0.092-0.650 and 0.307-2.167 mg/L, respectively. Recoveries of 61.92-116.44% were observed at two spiking levels, with 0.91-11% precision, expressed as relative standard deviation (except anthraquinone spiked at 10 mg/L). Hydroxycinnamic acid was the most abundant compound in the root, while the flowers showed the highest total flavonoid level. Antioxidant activities, determined in terms of reducing power, Fe(2+) chelating activity and the radical scavenging activities using α,α-diphenyl-ß-picrylhydrazyl and 2-2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, increased in a concentration-dependent manner; the highest activity was identified in the stems, followed by leaves > flowers > roots. These findings indicate that A. rugosa is a good source of bioactive compounds and can be used as a functional food.

Dietary-flavonoid-rich flowers of Rumex nervosus Vahl: Liquid chromatography with electrospray ionization tandem mass spectrometry profiling and in vitro anti-inflammatory effects.

Rumex nervosus is a plant species found widely in Eastern Africa and the Arabian Peninsula. In addition to its uses in traditional medicinal, the plant shows various biological activities, such as antiviral, antibacterial, and antioxidant activity. In this study, nine flavonols, six flavones, three flavanones, and one flavanol were characterized from the flowers of R. nervosus using liquid chromatography with electrospray ionization tandem mass spectrometry and literature data. Validation data indicated that the determination coefficients (R(2) ) were ≥ 0.9914. The limits of detection and quantification were in the ranges of 0.15-1.24 and 0.50-4.13 mg/L, respectively. Recoveries at 10 and 50 mg/L were 71.1-110.2 and 65.4-115.1%, with relative standard deviations of 7.4-40.1 and 2.1-13.0%, respectively. Quercetin 3-O-rhamnoside (10) was the dominant component, contributing 30.8% of total flavonoids (1003.0 ± 26.2 mg/kg fresh flower sample), whereas luteolin 6-C-glucoside (3) was the lowest yielding compound (0.1%). The 19 flavonoids identified were characterized for the first time. In vitro anti-inflammatory studies showed that this mixture can suppress the production of inflammatory mediators, including inducible nitric oxide synthase, cyclooxygenase-2, kappa B inhibitor, and interleukin-1ß, by down-regulating the nuclear factor-kappa B and mitogen-activated protein kinases pathways. The results of this study may provide information for processing R. nervosus as a potential source of functional food.

Flavonoid profiles of immature and mature fruit tissues of Citrus grandis Osbeck (Dangyuja) and overall contribution to the antioxidant effect.

Citrus fruits are a valuable functional food and their peel is used in East Asian folk medicine. In this study, the polar components of the fruit tissues of Citrus grandis Osbeck were analyzed using high-performance liquid chromatography-tandem mass spectrometry and compared with reported data. Among the 13 characterized compounds, eight flavonoids and one coumarin were identified for the first time in fruit tissues. The total amount of the identified components was the largest for the immature fruit peel, followed by mature fruit peel, mature fruit flesh, and immature fruit flesh. Naringin (2) and neohesperidin (3) were particularly rich in all samples. The antioxidant activity of the flavonoids extracted from fruit tissues increased in a dose-dependent manner. The activity of the fruit peels was significantly higher than that of the fruit flesh. Copyright © 2014 John Wiley & Sons, Ltd.

Development and validation of a high-performance liquid chromatography-tandem mass spectrometric method for simultaneous determination of bupropion, quetiapine and escitalopram in human plasma.

In the present study, an effective high performance liquid chromatography-tandem mass spectrometric (HPLC/MS/MS) method was developed and validated to simultaneously determine bupropion (BUP), quetiapine (QUE) and escitalopram (ESC) in human plasma using carbidopa as the internal standard. Chromatographic separation was achieved on a Waters Sun Fire C18 column using reversed-phase chromatography. The MS/MS experiment was performed in positive ion multiple reaction monitoring mode to produce product ions of m/z 240.3 → 184.2 for BUP, 384.2 → 253.1 for QUE, 325.3 → 109.3 for ESC and 227.2 → 181.2 for the internal standard. The method showed good linearity (R(2) ≥ 0.997), precision (relative standard deviation ≤7.5%), satisfactory intra- and interday accuracy (88.4-113.0%) and acceptable extraction recovery (87.2-115.0%), matrix effect (84.5.5-108.7%) and stability (92.3-103.5%). The method was successfully applied to determine the concentrations of BUP, QUE and ESC in human plasma samples.

Overcoming the Interfacial Photocatalytic Degradation of Nonfullerene Acceptor-Based Organic Photovoltaics by Introducing a UV-A-Insensitive Titanium Suboxide Layer.

Although recent dramatic advances in power conversion efficiencies (PCEs) have resulted in values over 19%, the poor photostability of organic photovoltaics (OPVs) has been a serious bottleneck to their commercialization. The photocatalytic effect, which is caused by incident ultraviolet-A (UV-A, 320-400 nm) light in the most commonly used zinc oxide (ZnOX) electron transport layer (ETL), significantly deteriorates the photostability of OPVs. In this work, we develop a new and facile method to enhance the photostability of nonfullerene acceptor-based OPVs by introducing UV-A-insensitive titanium suboxide (TiOX) ETL. Through an in-depth analysis of mass information at the interface between the ETL and photoactive layer, we confirm that the UV-A-insensitive TiOX suppresses the photocatalytic effect. The resulting device employing the TiOX ETL shows excellent photostability, obtaining 80% of the initial PCE for up to 200 h under 1 sun illumination, which is 10 times longer than that of the conventional ZnOX system (19 h).

Effect of the residual silanol group protection on the liquid chromatographic resolution of α-amino acids and proton pump inhibitors on a ligand exchange chiral stationary phase.

A new ligand exchange chiral stationary phase (new CSP) containing residual silanol group-protecting n-octyl groups on the silica surface was prepared by treating a ligand exchange CSP (original CSP) based on sodium N-[(R)-2-hydroxy-1-phenylethyl]-N-undecylaminoacetate bonded to silica gel with excess n-octyltriethoxysilane. The new and original CSPs containing an identical amount of chiral selector were applied to the resolution of α-amino acids and proton pump inhibitors (PPIs) including omeprazole, pantoprazole, lansoprazole, and rabeprazole. The separation factors (α) and resolutions (RS) were greater on the new CSP than on the original CSP except for the resolution of asparagine. The trends of the retention factors (k1) for the resolution of α-amino acids on the new and original CSPs with the variation of the organic modifier content in aqueous mobile phase were opposite to those for the resolution of PPIs. Removal of the nonenantioselective interactions between the residual silanol groups and the analytes and the improved lipophilicity of the new CSP were proposed to be responsible for the improved chiral recognition ability of the new CSP and the different retention behaviors of the enantiomers between the new and original CSPs.

Determination of the variations in levels of phenolic compounds in soybean (Glycine max Merr.) sprouts infected by anthracnose (Colletotrichum gloeosporioides).

BACKGROUND: Soybean sprouts (Kongnamool) are one of the most popular and nutritive traditional vegetables in East Asia. Anthracnose caused by Colletotrichum gloeosporioides is one of the most serious diseases of soybean sprouts. In order to obtain basic information for breeding and/or selecting soybean genotypes with increased natural defense against anthracnose, phenolic compounds were profiled for healthy and infected soybean (Glycine max Merr.) sprouts by using high-performance liquid chromatography coupled with tandem mass spectrometry. RESULTS: Tryptophan and eight phenolic compounds (daidzin, genistin, malonyldaidzin, malonylgenistin, daidzein, glycitein, genistein and coumestrol) were determined from healthy and inoculated sprouts. Total identified phenolic content was 40.02 ± 0.03 mg kg⁻¹, 99.4% of which was isoflavones. CONCLUSION: The monitoring suggested that de novo induced glycitein appeared to act as a phytoalexin in the defence mechanism of the soybean sprouts against C. gloeosporioides, and constitutively formed seven phenolic components that functioned as phytoanticipins in the diseased soybean sprouts.

3-[(2-chloroquinolin-3-yl)methyl]quinazolin-4(3H)-ones as potential larvicidal agents.

The larvicidal effect of series of 3-[(2-chloroquinolin-3-yl)methyl] uinazolin-4(3H)-ones, 5a-e, against Chironomus tentans Fabricius has been investigated. The results showed that tested compounds demonstrated strong larvicidal activity, and caused high percentage of mortality after 24 h at the doses of 40-100 g/ml, especially in the case of 3-[(2-chloro-8-methyquinolin-3-yl)methyl]quinazolin-4(3H)-one, 5b, that act as a promising larvicidal agent.

In Situ Doping of the PEDOT Top Electrode for All-Solution-Processed Semitransparent Organic Solar Cells.

The development of an ideal solution-processable transparent electrode has been a challenge in the field of all-solution-processed semitransparent organic solar cells (ST-OSCs). We present a novel poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) top electrode for all-solution-processed ST-OSCs through in situ doping of PEDOT:PSS. A strongly polarized long perfluoroalkyl (n = 8) chain-anchored sulfonic acid effectively eliminates insulating PSS and spontaneously crystallizes PEDOT at room temperature, leading to outstanding electrical properties and transparency of PEDOT top electrodes. Doped PEDOT-based ST-OSCs yield a high power conversion efficiency of 10.9% while providing an average visible transmittance of 26.0% in the visible range. Moreover, the strong infrared reflectivity of PEDOT enables ST-OSCs to reject 62.6% of the heat emitted by sunlight (76.7% from infrared radiation), outperforming the thermal insulation capability of commercial tint films. This light management approach using PEDOT enables ST-OSCs to simultaneously provide energy generation and energy savings, making it the first discovery toward sustainable energy in buildings.

Ultrahigh dielectric permittivity in oxide ceramics by hydrogenation.

Boosting dielectric permittivity representing electrical polarizability of dielectric materials has been considered a keystone for achieving scientific breakthroughs as well as technological advances in various multifunctional devices. Here, we demonstrate sizable enhancements of low-frequency dielectric responses in oxygen-deficient oxide ceramics through specific treatments under humid environments. Ultrahigh dielectric permittivity (~5.2 × 106 at 1 Hz) is achieved by hydrogenation, when Ni-substituted BaTiO3 ceramics are exposed to high humidity. Intriguingly, thermal annealing can restore the dielectric on-state (exhibiting huge polarizability in the treated ceramics) to the initial dielectric off-state (displaying low polarizability of ~103 in the pristine ceramics after sintering). The conversion between these two dielectric states via the ambient environment-mediated treatments and the successive application of external stimuli allows us to realize reversible control of dielectric relaxation characteristics in oxide ceramics. Conceptually, our findings are of practical interest for applications to highly efficient dielectric-based humidity sensors.

Plasma treatment effect on dye-sensitized solar cell efficiency of hydrothermal-processed TiO2 nanorods.

Atmospheric plasma (AP) treatment was carried out on TiO2 nanorods (NRs) that were hydrothermally grown on F-doped SnO2 (FTO)/glass. The effects of AP treatment on the surface of the TiO2 NRs were investigated, where the treatment involved the use of the reactive gases H2, N2, and O2. The surface energy of AP-treated TiO2 NRs was about 1.5 times higher than that of untreated TiO2 NRs (364.3 mJ/m2). After AP treatment, the increase of the peak area ratios of the Ti2O3 and TiO2 peaks in the XPS spectra resulted in a decrease in the number of oxygen vacancies in the TiO2 NRs. The efficiency of a dye-sensitized solar cell (DSSC) based on the N2-plasma-treated TiO2 NRs, which was approximately 1.11%, was about 79% higher than that of a DSSC based on the untreated TiO2 NRs.

Flavonoid profiling in three citrus varieties native to the Republic of Korea using liquid chromatography coupled with tandem mass spectrometry: contribution to overall antioxidant activity.

A mixture of flavonoid components was isolated from the fruit peel of three varieties of citrus native to Republic of Korea, Citrus leiocarpa Hort. ex Tanaka (CLHT), Citrus aurantium L. (CAL) and Citrus erythrosa Hort. (CEH), via 70% methanol extraction followed by ethyl acetate elution over a silica gel cartridge. The flavonoid components of the mixture were analyzed via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in positive-ion mode and a comparison of the reported data. Among 17 characterized components, two flavanones, four flavones and two coumarin derivatives in the fruit peel of the three varieties were identified for the first time. The individual characterized components were quantified via HPLC-UV. The flavanones dominated in CAL, whereas the flavones prevailed in CLHT and CEH. The antioxidant activity of the flavonoid mixture of the fruit peel was determined via DPPH•, ABTS•⁺ and reducing power assays. The antioxidant activity of CEH and CAL was greater than that of CLHT.

Healing Ion-Implanted Semiconductors by Hybrid Microwave Annealing: Activation of Nitrogen-Implanted TiO2.

In order to recover the damaged structure of a nitrogen-implanted TiO2 (N-I-TiO2) photoanode, hybrid microwave annealing (HMA) is proposed as an alternative postannealing process instead of conventional thermal annealing (CTA). Compared to CTA, HMA provides distinctive advantages: (i) facile transformation of the interstitial N-N states into substitutional N-Ti states, (ii) better preservation of the ion-implanted nitrogen in TiO2, and (iii) effective alleviation of lattice strain and reconstruction of the broken bonds. As a result, the HMA-activated photoanode improves the photocurrent density by a factor of ∼3.2 from 0.29 to 0.93 mA cm-2 at 1.23 VRHE and the incident photon-to-current conversion efficiency (IPCE) from ∼2.9% to ∼10.5% at 430 nm relative to those of the as-prepared N-I-TiO2 photoanode in photoelectrochemical water oxidation, which are much better than those of the CTA-activated photoanode (0.58 mA cm-2 at 1.23 VRHE and IPCE of 5.7% at 430 nm), especially in the visible light region (≥420 nm).

Improved device efficiency and lifetime of perovskite light-emitting diodes by size-controlled polyvinylpyrrolidone-capped gold nanoparticles with dipole formation.

Herein, an unprecedented report is presented on the incorporation of size-dependent gold nanoparticles (AuNPs) with polyvinylpyrrolidone (PVP) capping into a conventional hole transport layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The hole transport layer blocks ion-diffusion/migration in methylammonium-lead-bromide (MAPbBr3)-based perovskite light-emitting diodes (PeLEDs) as a modified interlayer. The PVP-capped 90 nm AuNP device exhibited a seven-fold increase in efficiency (1.5%) as compared to the device without AuNPs (0.22%), where the device lifetime was also improved by 17-fold. This advancement is ascribed to the far-field scattering of AuNPs, modified work function and carrier trapping/detrapping. The improvement in device lifetime is attributed to PVP-capping of AuNPs which prevents indium diffusion into the perovskite layer and surface ion migration into PEDOT:PSS through the formation of induced electric dipole. The results also indicate that using large AuNPs (> 90 nm) reduces exciton recombination because of the trapping of excess charge carriers due to the large surface area.

Efficient Photon Extraction in Top-Emission Organic Light-Emitting Devices Based on Ampicillin Microstructures.

The desire to enhance the efficiency of organic light-emitting devices (OLEDs) has driven to the investigation of advanced materials with fascinating properties. In this work, the efficiency of top-emission OLEDs (TEOLEDs) is enhanced by introducing ampicillin microstructures (Amp-MSs) with dual phases (α-/ß-phase) that induce photoluminescence (PL) and electroluminescence (EL). Moreover, Amp-MSs can adjust the charge balance by Fermi level (EF ) alignment, thereby decreasing the leakage current. The decrease in the wave-guided modes can enhance the light outcoupling through optical scattering. The resulting TEOLED demonstrates a record-high external quantum efficiency (EQE) (maximum: 68.7% and average: 63.4% at spectroradiometer; maximum: 44.8% and average: 42.6% at integrating sphere) with a wider color gamut (118%) owing to the redshift of the spectrum by J-aggregation. Deconvolution of the EL intensities is performed to clarify the contribution of Amp-MSs to the device EQE enhancement (optical scattering by Amp-MSs: 17.0%, PL by radiative energy transfer: 9.1%, and EL by J-aggregated excitons: 4.6%). The proposed TEOLED outperforms the existing frameworks in terms of device efficiency.

Determination of the change of flavonoid components as the defence materials of Citrus unshiu Marc. fruit peel against Penicillium digitatum by liquid chromatography coupled with tandem mass spectrometry.

A healthy fruit peel of Citrus unshiu Marc. and one infected by Penicillium digitatum were analysed for flavonoids via high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) in the positive mode with selected ion monitoring (SIM). Among 16 flavonoid components characterised in C. unshiu Marc., four flavanones and nine flavones were identified for the first time. The identified compounds were quantified by HPLC-UV. To investigate the function of the flavonoids as defence materials, the flavonoid content change of the fruit peel inoculated with P. digitatum was monitored by HPLC. The flavonoid concentration in the infected fruit peel decreased initially after the infection and then gradually increased before finally progressively decreasing.

Unusual enantiomeric separation due to residual amines in chiral crown ether stationary phase linked by long alkyl chain.

A new chiral stationary phase (CSP) in which (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was linked to a silica gel surface through a long alkyl chain and which did not contain additional aminoundecyl groups was prepared. Generally, when enantiomers containing a primary amine group are optically resolved using a crown-ether-type CSP, a higher resolution is achieved if the surface of the CSP does not contain any residual amine. In this study, the chiral separation factor and resolution factor of a CSP with a long alkyl chain such as the aminoundecyl group were unusually low in the absence of the residual aminoundecyl groups. In this study, a chiral column was prepared by introducing a chiral selector having a long alkyl chain on the surface of silica gel to separate enantiomers of α-amino acids. Furthermore, it was confirmed that the residual-amine-containing CSP, which was easier to synthesize, facilitated more effective enantiomeric separation than the CSP without residual amines.