Identification and quantification of seven volatile n-nitrosamines in cosmetics using gas chromatography/chemical ionization-mass spectrometry coupled with head space-solid phase microextraction

Choi, N.R.,Kim, Y.P.,Ji, W.H.,Hwang, G.S.,Ahn, Y.G. Pergamon Press ; Elsevier Science Ltd 2016 Talanta Vol.148 No.-

<P>An analytical method was developed for the identification and quantification of seven volatile n-nitrosamines (n-nitrosodimethylamine [NDMA], n-nitrosoethylmethylamine [NMEA], n-nitrosodiethylamine [NDEA], n-nitrosodipropylamine [NDPA], n-nitrosodibutylamine [NDBA], n-nitrosopiperidine [NPIP], and n-nitrosopyrrolidine [NPYRD]) in water insoluble cream type cosmetics. It was found that the head space-solid phase microextraction (HS-SPME) was suitable for extraction, clean up, and pre-concentration of n-nitrosamines in the cream type samples so its optimal conditions were investigated. Identification and quantification of n-nitrosamines using single quadrupole gas chromatography/mass spectrometry (GC/MS) in chemical ionization (CI) mode were carried out with accurate mass measurements. Their accurate masses of protonated molecular ions were obtained within 10 mDa of the theoretical masses when sufficiently high signal was acquired from the unique calibration method using mass and isotope accuracy. For the method validation of quantification, spiking experiments were carried out to determine the linearity, recovery, and method detection limit (MDL) using three deuterated internal standards. The average recovery was 79% within 20% relative standard deviation (RSD) at the concentration of 50 ng/g. MDLs ranged from 0.46 ng/g to 36.54 ng/g, which was satisfactory for the directive limit of 50 ng/g proposed by the European Commission (EC). As a result, it was concluded that the method could be provided for the accurate mass screening, confirmation, and quantification of n-nitrosamines when applied to cosmetic inspection. (C) 2015 Elsevier B.V. All rights reserved.</P>

N-doped TiO₂ nanotubes coated with a thin TaO_<i>x</i>N_<i>y</i> layer for photoelectrochemical water splitting: dual bulk and surface modification of photoanodes

Kim, Hyoung-il,Monllor-Satoca, Damiá,n,Kim, Wooyul,Choi, Wonyong The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.1

<P>TaON is a good photoanode material with a suitable band structure for water splitting as well as coupling with TiO<SUB>2</SUB> for efficient charge separation. However, the synthesis of TaON that requires high temperature nitridation (850 °C) limits the combination with other materials. In this work, we deposited a thin amorphous TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer on N-doped TiO<SUB>2</SUB> nanotubes (N-TNTs) through low temperature nitridation (500 °C) and demonstrated its successful performance as an efficient photoanode for water-splitting. Since the preparation temperature is low, TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> on N-TNTs has a unique amorphous structure with a smooth thin layer (5 nm). It is proposed that the thin amorphous TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer plays dual roles: (i) surface sensitization and/or charge rectification at the heterojunction between the TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer and N-TNTs, and (ii) passivation of N-TNT surface trap states to retard the charge recombination. TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer-decorated N-TNTs as dual modified TNTs (N-doping in the bulk and TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> overlayer deposition on the surface) have significantly improved both visible (<I>ca.</I> 3.6 times) and UV (<I>ca.</I> 1.8 times) activities for PEC water-splitting as well as the faradaic efficiency (<I>ca.</I> 1.4 times, <I>η</I> = 98%) for H<SUB>2</SUB> production. Making the amorphous TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer crystalline at higher temperatures reduced the PEC activity of the hybrid photoanode, in contrast, which indicates that the amorphous TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer deposition on N-TNTs through low temperature nitridation (500 °C) is optimized for the PEC activity. A range of spectroscopic and electrochemical techniques were systematically employed to investigate the properties of the PEC process.</P> <P>Graphic Abstract</P><P>Thin amorphous TaO<SUB><I>x</I></SUB>N<SUB><I>y</I></SUB> layer-coated <I>N</I>-doped TiO<SUB>2</SUB> nanotubes successfully serve as a water splitting photoanode. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4ee02169j'> </P>

Effects of Type of Oilseed and Level of Concentrate on Fermentation, Biohydrogenation of Fatty Acids and Conjugated Linoleic Acid Production in a Rumen-Simulated Continuous Culture System

Choi, N. J. 한국동물자원과학회 2003 한국축산학회지 Vol.45 No.4

본 연구는 사료 내 농후사료의 비율을 높임으로서 불포화 지방산의 반추위 내 by-pass율의 향상 가능성을 조사하고, 아마종실과 전지대두 급여 시 CLA 생산을 상호 비교하기 위하여 연속배양장치를 이용하여 수행하였다. 지방 급원에 따른 발효 성상의 차이는 보이지 않았다. 한편 사료 내 농후사료 비율이 높은 (80%) 처리구는 농후사료 비율이 낮은 (40%) 처리구와 비교하여 pH는 감소하였으나, 암모니아, 총 휘발성 지방산, acetate, butyrate 및 valerate 농도가 증가되었다. 지방급원 (전지대두 vs 아마종실)과 사료 내 농후사료 비율은 organic matter(OM), total nitrogen, neutral detergent fiber(NDF) 및 acid detergent fiber (ADF)의 소화율에 영향을 끼치지 않았다. 반면에 전지대두는 아마종실과 비교하여 trans C18:1, C18:2 n-6 및 C18:3 n-3 유출율은 증가시켰다. 지방 급원에 의한 CLA flow는 영향을 받지 않았으나 사료내 농후사료 비율이 높을 때와 전지대두와 아마종실의 함량이 높았을 때는 증가되었다. 수소 첨가현상은 C18:1 n-9 와 C18:2 n-6에서 지방 급원에 의하여 영향을 받지 않았으나, 아마종실 처리구에서는 C18:3 n-3 과 총 C18 불포화지방산의 수소 첨가현상이 전지대두 처리구와 비교하여 높은 비율로 발생했다. 한편 사료내 농후사료 비율이 높을 때 처리구에서 C18:2 n-6, C18:3 n-3 및 총 C18 불포화 지방산의 수소 첨가현상은 농후사료 저 처리구와 비교하여 감소되었다. This experiment employed a rumen simulated continuous culture system to examine the possibility of improving the rumen bypass of polyunsaturated fatty acids (PUFA) by using a high proportion of concentrate in feed, and compared soya an linseed in terms of conjugated linoleic acid (CLA) production. NO effect of type of fat source was observed on ruminal fermentation. A high proportion of concentrate (80%) in the feed decreased (P<0.001) vessel ? but increased (P<0.01) ammonia nitrogen, total VFA, acetate, butyrate and valerate concentrations compared with a low proportion (40%). Fat sources (soya vs. linseed) and concentrate ratio in the feed did not affect digestibilities of organic matter (OM), total nitrogen, neutral detergent fiber (NDF) and acid detergent fiber (ADF). Soya incerased the flows of trans C18:1, C18:2 n-6 and C18:3 n-3 compared with linseed. The difference in fat source alone did not affect the flow of CLA but this was increased when high levels of soya and linseed were associated with a high proportion of concentrate in the fee. There was no effect of fat source on biohydrogenation of C18:1 n-9 and C18:2 n-6, but biohydrogenation of C18:3 n-3 and total C18 PUFA was higher with the linseed than with the soya treatment. A high proportion of concentrate decreased biohydrogenation of C18:2 n-6, C18:3 n-3 and total C18 PUFA compared with a low proportion.

Direct analysis of site-specific N-glycopeptides of serological proteins in dried blood spot samples

Choi, N. Y.,Hwang, H.,Ji, E. S.,Park, G. W.,Lee, J. Y.,Lee, H. K.,Kim, J. Y.,Yoo, J. S. Springer Science + Business Media 2017 Analytical and Bioanalytical Chemistry Vol.409 No.21

<P>Dried blood spot (DBS) samples have a number of advantages, especially with respect to ease of collection, transportation, and storage and to reduce biohazard risk. N-glycosylation is a major post-translational modification of proteins in human blood that is related to a variety of biological functions, including metastasis, cell-cell interactions, inflammation, and immunization. Here, we directly analyzed tryptic N-glycopeptides from glycoproteins in DBS samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) without centrifugation of blood samples, depletion of major proteins, desalting of tryptic peptides, and enrichment of N-glycopeptides. Using this simple method, we identified a total of 41 site-specific N-glycopeptides from 16 glycoproteins in the DBS samples, from immunoglobulin gamma 1 (IgG-1, 10 mg/mL) down to complement component C7 (50 mu g/mL). Of these, 32 N-glycopeptides from 14 glycoproteins were consistently quantified over 180 days stored at room temperature. The major abundant glycoproteins in the DBS samples were IgG-1 and IgG-2, which contain nine asialo-fucosylated complex types of 16 different N-glycopeptide isoforms. Sialo-non-fucosylated complex types were primarily detected in the other glycoproteins such as alpha-1-acid glycoprotein 1, 2, alpha-1-antitypsin, alpha-2-macroglobulin, haptoglobin, hemopexin, Ig alpha 1, 2 chain C region, kininogen-1, prothrombin, and serotransferrin. We first report the characterization of site-specific N-glycoproteins in DBS samples by LC-MS/MS with minimal sample preparation.</P>

Microstructural, chemical states and electrical properties of Au/CuO/n-InP heterojunction with a cupric oxide interlayer

Balaram, N.,Rajagopal Reddy, V.,Sekhar Reddy, P.R.,Janardhanam, V.,Choi, Chel-Jong Elsevier 2018 Vacuum Vol.152 No.-

<P><B>Abstract</B></P> <P>Cupric oxide (CuO) is synthesized by simple chemical bath deposition method and deposited on n-type InP substrate using e-beam evaporation technique. First, the structural and chemical compositional analysis of CuO/n-InP are analysed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD and XPS results confirmed that the formation of CuO on n-type InP substrate. Then, Au/CuO/n-InP heterojunction is fabricated with a CuO interlayer and correlated its results with the Au/n-InP Schottky junction (SJ). The barrier height (Φ<SUB>b</SUB>) and ideality factor (n) are extracted through I-V and C-V methods and the respective values are 0.66 eV (I-V)/0.80 eV (C-V) and 1.24, and 0.78 eV (I-V)/0.94 eV (C-V) and 1.62 for the SJ and HJ diodes, respectively. By applying Cheung's and Norde functions, the Φ<SUB>b</SUB>, ideality factor and series resistance (R<SUB>S</SUB>) are derived for the SJ and HJ diodes. The derived interface state density (N<SUB>SS</SUB>) of HJ is lower than the SJ; results demonstrated that the CuO interlayer plays an important role in the decreased N<SUB>SS</SUB>. The Poole-Frenkel emission is the dominant current conduction mechanism in reverse bias of both SJ and HJ diodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Structural and chemical properties of CuO films are analysed by XRD and XPS. </LI> <LI> Barrier height of Au/n-InP SJ was modified by CuO interlayer. </LI> <LI> Heterojunction has a good rectification ratio compared to the Schottky junction. </LI> <LI> The interface state density of HJ is lower as compared to the SJ. </LI> <LI> Poole-Frenkel mechanism is found to dominate in both SJ and HJs. </LI> </UL> </P>

Effect of N₂O-mediated calcination on nickel species and the catalytic activity of nickel catalysts supported on γ-Al₂O₃ in the steam reforming of glycerol

Choi, Y.,Kim, N.D.,Baek, J.,Kim, W.,Lee, H.J.,Yi, J. Pergamon Press ; Elsevier Science Ltd 2011 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.36 No.6

The steam reforming of glycerol over supported nickel catalysts is a promising and cost-effective method for producing hydrogen. The activity of nickel catalysts supported on γ-Al<SUB>2</SUB>O<SUB>3</SUB> is low, primarily due to the formation of inactive nickel species during high temperature calcination in air. In order to address this problem, a Ni/γ-Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was prepared by calcination at 700 <SUP>o</SUP>C in a nitrous oxide (N<SUB>2</SUB>O) environment. The N<SUB>2</SUB>O calcined catalyst showed an enhanced activity for the steam reforming of glycerol. A variety of characterization techniques (XRD, TPR, XPS and H<SUB>2</SUB> Chemisorption) confirmed that the high temperature N<SUB>2</SUB>O calcination resulted in a significant decrease in the levels of nickel aluminate. The N<SUB>2</SUB>O calcination also led to an enhancement in the amount of NiO as well as nickel ions present on the surface of the catalyst. Interestingly, compared to an air calcined catalyst, the N<SUB>2</SUB>O calcined catalyst contained larger nickel particles after reduction but the N<SUB>2</SUB>O calcined catalyst had a much larger nickel surface area and dispersion, which resulted in higher glycerol conversion and hydrogen yield.

Highly active and durable nitrogen doped-reduced graphene oxide/double perovskite bifunctional hybrid catalysts

Kim, N. I.,Afzal, R.,Choi, S.,Lee, S.,Ahn, D.,Bhattacharjee, S.,Lee, S. C.,Kim, J.,Park, J. Y. Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.25

<P>A-site cation doping in perovskite-based materials with the general ABO(3) formula has a significant effect on the bifunctional oxygen activity (oxygen evolution and reduction reactions) of chemically stable electrocatalysts, enabling the design of highly active, durable, and cost-effective catalysts. In particular, the oxygen activity of double perovskite-structured NdBa0.5Sr0.5Co1.5Fe0.5O5+delta (NBSCF) is 0.973 V, which is much greater than that of previously reported transition metal-based nanostructures. This result is verified by examination of the electronic structure, oxidation state, and electrical properties of the perovskite-based materials using density functional theory (DFT) calculations, the iodometric titration method, X-ray photon spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS) analysis. Further improvements of NBSCF for bifunctional oxygen activity are made by incorporating these synergistic hybrid structures with nitrogen doped-reduced graphene-based (N-rGO) nanostructures (NBSCF/N-rGO). The NBSCF/N-rGO has an oxygen electrode activity of 0.766 V, which is superior to that of other previously reported transition metal-based nanostructures and compares favorably to that of precious metal electrocatalysts. Furthermore, strong N-rGO provides considerably greater electrochemical long-term stability and integrity to NBSCF/N-rGO hybrid catalysts under continuous chronopotentiometric and long-term potential sweep testing conditions for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR).</P>

Analysis of fucosylation in liver-secreted N-glycoproteins from human hepatocellular carcinoma plasma using liquid chromatography with tandem mass spectrometry

Ji, E. S.,Hwang, H.,Park, G. W.,Lee, J. Y.,Lee, H. K.,Choi, N. Y.,Jeong, H. K.,Kim, K. H.,Kim, J. Y.,Lee, S. Springer Science + Business Media 2016 Analytical and Bioanalytical Chemistry Vol.408 No.27

<P>Fucosylation of N-glycoproteins has been implicated in various diseases, such as hepatocellular carcinoma (HCC). However, few studies have performed site-specific analysis of fucosylation in liver-secreted proteins. In this study, we characterized the fucosylation patterns of liver-secreted proteins in HCC plasma using a workflow to identify site-specific N-glycoproteins, where characteristic B- and/or Y-ion series with and without fucose in collision-induced dissociation were used in tandem mass spectrometry. In total, 71 fucosylated N-glycopeptides from 13 major liver-secreted proteins in human plasma were globally identified by LC-MS/MS. Additionally, 37 fucosylated N-glycopeptides were newly identified from nine liver-secreted proteins, including alpha-1-antichymotrypsin, alpha-1-antitrypsin, alpha-2-HS-glycoprotein, ceruloplasmin, alpha-1-acid glycoprotein 1/2, alpha-2-macroglobulin, serotransferrin, and beta-2-glycoprotein 1. Of the fucosylated N-glycopeptides, bi- and tri-antennary glycoforms were the most common ones identified in liver-secreted proteins from HCC plasma. Therefore, we suggest that this analytical method is effective for characterizing fucosylation in liver-secreted proteins.</P>

Complete degradation of perchlorate using Pd/N-doped activated carbon with adsorption/catalysis bifunctional roles

Kim, Y.N.,Lee, Y.C.,Choi, M. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.65 No.-

Although perchlorate (ClO<SUB>4</SUB><SUP>-</SUP>) has a detrimental effect on human health, there have been only limited solutions for its complete degradation due to its extraordinary chemical stability. Physical adsorption using activated carbons and ion-exchange resins can provide fast, economic methods for perchlorate removal, but energy-efficient and environmentally benign ways for the disposal and regeneration of perchlorate-saturated adsorbents should be developed. Here we demonstrated an integrated process synergistically combining the strengths of physical adsorption and catalytic degradation by using 0.1wt.% Pd on N-doped activated carbon (Pd/N-AC) as an adsorption/catalysis bifunctional material. During the perchlorate adsorption from polluted water, the N-doped carbon surface provides increased number of adsorption sites for perchlorate compared to pristine carbon surface. After the carbon is saturated with perchlorate, the perchlorate concentrated on the carbon surface can be fully decomposed into non-toxic chloride (Cl<SUP>-</SUP>) by the catalytic function of supported Pd in H<SUB>2</SUB> atmosphere. Notably, the N-doped carbon surface and adsorbed water synergistically enhance the catalytic decomposition rate of perchlorate. As a result, Pd/N-AC showed complete perchlorate decomposition even at very mild condition (333K). The perchlorate adsorption/catalytic decomposition cycle could be repeated up to five times without loss of perchlorate adsorption capacity.

Mapping the Research Landscape of Wastewater Treatment Wetlands : A Bibliometric Analysis and Comprehensive Review

C. C. Vispo,N. J. D. G. Reyes,H. S. Choi,M.S. Jeon,L. H. Kim 한국습지학회 2023 한국습지학회지 Vol.25 No.2

인공습지(CW)는 도시 폐수처리를 위한 효과적인 기술로, 물리-화학적 및 생물학적 자연처리과정을 통해 오염 물질 이 제거된다. 본 연구는 서지학적 분석 방법을 통하여 인공습지의 현재까지의 연구 진행 상황과 향후 연구 동향을 조 사하였다. 인공습지를 통한 페수 처리 성능 평가 분석을 위하여 최근 출판된 논문(오픈 액세스 학술지 포함) 100편 을 기반으로 종합적 분석 및 검토를 수행하였다. 분석 결과, 스페인, 중국, 이탈리아, 미국이 논문 출판수가 두드러지 는 것으로 나타났다. 논문에서 가장 많이 사용된 핵심용어는 수질(n=19), 식물 정화(n=13), 강우유출수(n=11), 인(n=11) 순으로 나타났으며, 수질개선과 영양염류 제거에 대한 인공습지의 효율성 관련 연구가 폭넓게 연구되고 있는 것으로 분석되었다. 검토된 다양한 유형의 인공습지 중 Hybrid 형태의 인공습지가 TSS(95.67%) 및BOD(88.67%)으 로 오염물질 저감효율이 가장 높은 것으로 나타났으며, VSSF, HSSF는 TSS 제거(83.25% 및 78.83%)에 가장 효과적 인 것으로 조사되었다. VSSF 습지는 가장 높은 COD 제거 효율(71.82%)을 보였다. 일반적으로 인공습지에서 물리적 처리(예: 침전, 여과, 흡착)와 생물학적 메커니즘(예: 생분해)은 TSS, BOD, COD 제거 효율에 영향을 미치기 때문이 다. Hybrid 형태의 인공습지는 호기성 및 혐기성 조건, 다양한 식생 유형, 다양한 매체 구성 등의 다양한 인자와 여러 처리 과정을 통해 미생물 활성도 증가 및 질소 처리를 통해 TN(60.78%)의 높은 저감효과를 보였다. FWS 형태의 인 공습지는 퇴적물에 결합된 인을 침전 및 식물의 흡수를 통해 높은TP 제거효율(54.50%)로 나타났습니다. 일반적으로 인공습지에는 식물 정화 능력이 뛰어난 Phragmites, Cyperus, Iris 및 Typha 이 적용되고 있다. 본 연구는 향후 도시 지역에서 발생되는 폐수 처리를 위한 지속 가능한 대안으로 제시 가능할 것으로 사료된다. Constructed wetlands (CWs) are effective technologies for urban wastewater management, utilizing natural physico-chemical and biological processes to remove pollutants. This study employed a bibliometric analysis approach to investigate the progress and future research trends in the field of CWs. A comprehensive review of 100 most-recently published and open-access articles was performed to analyze the performance of CWs in treating wastewater. Spain, China, Italy, and the United States were among the most productive countries in terms of the number of published papers. The most frequently used keywords in publications include water quality (n=19), phytoremediation (n=13), stormwater (n=11), and phosphorus (n=11), suggesting that the efficiency of CWs in improving water quality and removal of nutrients were widely investigated. Among the different types of CWs reviewed, hybrid CWs exhibited the highest removal efficiencies for BOD (88.67%) and TSS (95.67%), whereas VSSF, and HSSF systems also showed high TSS removal efficiencies (83.25%, and 78.83% respectively). VSSF wetland displayed the highest COD removal efficiency (71.82%). Generally, physical processes (e.g., sedimentation, filtration, adsorption) and biological mechanisms (i.e., biodegradation) contributed to the high removal efficiency of TSS, BOD, and COD in CW systems. The hybrid CW system demonstrated highest TN removal efficiency (60.78%) by integrating multiple treatment processes, including aerobic and anaerobic conditions, various vegetation types, and different media configurations, which enhanced microbial activity and allowed for comprehensive nitrogen compound removal. The FWS system showed the highest TP removal efficiency (54.50%) due to combined process of settling sediment-bound phosphorus and plant uptake. Phragmites, Cyperus, Iris, and Typha were commonly used in CWs due to their superior phytoremediation capabilities. The study emphasized the potential of CWs as sustainable alternatives for wastewater management, particularly in urban areas.