Photostability of Ferulic Acid and Its Antioxidant Activity Against Linoleic Acid Peroxidation

Ferulic acid (4‐hydroxy‐3‐methoxycinnamic acid), a phenyl‐propenoid derivative of cinnamic acid, can undergo photolysis upon UV irradiation. The photodegradation kinetics of ferulic acid were thus investigated in different systems. The micellar solutions did not protect the acid from photodegradation. On the contrary, they catalyzed its degradation at a variable extent depending on the surfactant structure. The photodegradation of ferulic acid in microemulsions was slower than in micelles and near to that in water. TiO₂, habitually employed as a physical sunscreen, showed photocatalytic action toward ferulic acid degradation especially at higher initial concentration of ferulic acid. The action of ferulic acid on the peroxidation of linoleic acid in micelles and microemulsions also was evaluated. When the ferulic acid is absent the peroxidation is continuous while when it is present an induction time of 40 minutes or higher was observed. Accordingly, it is likely that linoleic acid acts as photosensitizer for ferulic acid, and that in turn ferulic acid acts as an antioxidant for linoleic acid, reducing the rate of peroxidation.     

Possibilities of Mass Spectrometry and Tandem-Mass Spectrometry in the Analysis of Cellulose Ethers

The investigation of the substituent pattern of cellulose and starch ethers and esters on various structural levels as in the glucosyl unit, along the polymer chain, and over the polymer molecules, still is a very challenging task. By means of mass spectrometric methods as ESI-MS or MALDI-TOF-MS the composition of oligosaccharide mixtures which represent the substituent distribution in the original polymer can principally be determined. However, to obtain reliable quantitative data mass spectra must be recorded under appropriate instrumental conditions and after special sample preparation While O-methyl/O-methyl-d₃-oligosaccharides give representative data with the mentioned MS techniques and FAB-MS as well, hydroxyalkyl ethers require labelling with a quaternary ammonium tag and MALDI-TOF-MS to prevent discrimination of lower substituted oligosaccharides. In this way, information on the neighbourhood of glucosyl units in the polymer chain is available which – together with the monomer composition – is a valuable parameter to describe a random or a heterogeneous pattern with regions of local higher densities of substituents compared to the random model, a regular distribution, or a block-like substituent pattern, i.e. a more clustered localisation of substiuents in the polymer chain. In addition, tandem-mass spectrometry (ESI-MSⁿ) allows to gain further insight in the composition of isomeric oligosaccharide derivatives of the same m/z ratio and to calculate the complete monomer composition of methyl celluloses.     

类肝素化合物的傅立叶变换离子回旋共振-电喷雾质谱研究

采用负离子模式的电喷雾傅立叶变换离子回旋共振质谱(ESI-FTICR-MS)对3个合成的肝素类化合物DHα、THα和THβ进行了全扫描一级谱和持续非共振辐照碰撞诱导解离(SORI-CID)串联质谱分析。样品浓度10μmol/L,流动泵注射直接进样。化合物中的磺酸胺和磺酸酯结构容易在一般电喷雾条件下发生分解,失去一个或者多个SO3,一级全扫描谱图中得到的谱峰均是带有单电荷或者双电荷的准分子离子峰。在串联质谱中,部分双电荷离子发生解离时,其二级谱图中子离子由单电荷子离子和双电荷子离子共同组成。通过对谱峰的局部放大,利用同位素峰的峰间距,能直接给出子离子的带电荷情况。同时,结合FTICRMS提供的高质量精度质谱数据,能够对所选取母离子的碎裂途径进行确认。离子质荷比测量的平均误差小于3.0×10-6。为结构复杂的类肝素化合物的质谱分析提供了借鉴。     

Effect of Reactive Species Photogenerated by the Ultraviolet Irradiation of TiO2 on the Peroxidation of Linoleic Acid

This article shows that hydroxyl radicals adsorbed on the surface of TiO₂ (Ti-^?OH groups) account for about 70–100% of the photocatalytic peroxidation of linoleic acid under UVB irradiation, which results into malondialdehyde production. The experimental data are silent concerning the involvement of ¹O₂ in the process, although an upper limit of 30% can be hypothesized, while an involvement of surface-bound holes into the lipoperoxidation process can be excluded.     

Deposition of Diamondlike Carbon Film and Mass Spectrometry Measurement in CH4/N2 RF Plasma

The deposition of diamondlike carbon (DLC) film and the measurements of ionic species by means of mass spectrometry were carried out in a CH₄/N₂ RF (13.56 MHz) plasma at 0.1 Torr. The film deposition rate greatly depended on both CH₄/N₂ composition ratio and RF power input. It was decreased monotonically as CH₄ content decreased in the plasma and then rapidly diminished to negligible amounts at a critical CH₄ content, which became large for higher RF power. The rate increased with increasing RF power, reaching a maximum value in 40% CH₄ plasma. The predominant ionic products in CH₄/N₂ plasma were NH⁺ ₄ and CH₄N⁺ ions, which were produced by reactions of hydrocarbon ions, such as CH⁺ ₃, CH⁺ ₂, CH⁺ ₅, and C₂H⁺ ₅ with NH₃ molecules in the plasma. It was speculated that the production of NH⁺ ₄ ion induced the decrease of C₂H⁺ ₅ ion density in the plasma, which caused a reduction in higher hydrocarbon ions densities and, accordingly, in film deposition rate. The N⁺ ₂ ion sputtering also plays a major role in a reduction of film deposition rate for relatively large RF powers. The incorporation of nitrogen atoms into the bonding network of the DLC film deposited was greatly suppressed at present gas pressure conditions.     

Flavonoids: Antiplatelet Effect as Inhibitors of COX-1

Flavonoids are compounds with a benzopyranic structure that exhibits multiple pharmacological activities. They are known for their venotonic activity, but their mechanism of action remains unclear. It is thought that, as this mechanism is mediated by prostaglandins, these compounds may interfere with the arachidonic acid (AA) cascade. These assays are designed to measure the antiplatelet aggregation capacity of quercetin, rutin, diosmetin, diosmin, and hidrosmin, as well as to evaluate a potential structure−activity ratio. In this paper, several studies on platelet aggregation at different concentrations (from 0.33 mM to 1.5 mM) of different flavone compounds are conducted, measuring platelet aggregation by impedance aggregometry, and the cyclooxygenase (COX) activity by metabolites generated, including the activity of the pure recombinant enzyme in the presence of these polyphenols. The results obtained showed that quercetin and diosmetin aglycones have a greater antiplatelet effect and inhibit the COX enzyme activity to a greater extent than their heterosides; however, the fact that greater inhibition of the pure recombinant enzyme was achieved by heterosides suggests that these compounds may have difficulty in crossing biological membranes. In any case, in view of the results obtained, it can be concluded that flavonoids could be useful as coadjuvants in the treatment of cardiovascular pathologies.     

Accuracy in the Isotope Dilution Mass Spectrometry of Uranium in Rubidium Uranium Sulphate Rb2U(SO4)3

Abstract

Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb₂U(SO₄)₃) employing isotope dilution thermal ionisation mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb₂U(SO₄)₃ by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb₂U(SO₄)₃ could be determined with an accuracy better than 0.1% employing the HClO₄ treatment for proper isotopic exchange between the spike and sample isotopes.     

Thermal decomposition of cobalt nitrato compounds: Preparation of anhydrous cobalt(II)nitrate and its characterisation by Infrared and Raman spectra

The thermal decomposition of Co(NO₃)₂·6H₂O (1) as well as that one of NO[Co(NO₃)₃] (Co(NO₃)₂·N₂O₄) (2) was followed by thermogravimetric (TG) measurements, X-ray recording and Raman and IR spectra. The stepwise decomposition reactions of 1 and 2 leading to anhydrous cobalt(II)nitrate (3) were established. In N₂ atmosphere, cobalt oxides are finally formed whereas in H₂/N₂ (10% H₂) cobalt metal is produced. Rapid heating of cobalt(II)nitrate hexahydrate causes melting (formation of a hydrate melt) and therefore side reactions in the hydrate melt by incoupled reactions and evolution/evaporation of different species as, e.g., HNO₃, NO₂, etc. In case of larger amounts in dense packing in the sample container, the formation of oxo(hydoxo)nitrates is possible at higher temperature. For 2, its thermal decomposition to 3 was followed and its decomposition mechanism is proposed.     

ZnCl2与氧化胰岛素B链结合位点和切割位点的质谱指认

采用电喷雾质谱和串联质谱研究了氧化胰岛素B链与ZnCl₂的键合作用并成功地确定了切割位点。质谱研究显示在pH值2.5及40 ℃条件下，Zn²⁺通过与氧化胰岛素B链的氨基酸侧链His5,His10和Arg22结合，选择性地水解了肽键Asn3-Gln4, His5-Leu6, Gly8-Ser9和Glu21-Arg22。     

高效液相色谱-串联质谱法分离鉴定绿原酸及其相关杂质

建立了高效液相色谱-串联质谱法（HPLC-MS/MS)分离和鉴定绿原酸及其相关杂质的方法。采用C18色谱柱(5 μm,4.6 mm×150 mm),乙腈-水（含0.1%甲酸）(体积比为8∶92)为流动相,经HPLC-MS/MS和HPLC-二极管阵列检测器在线检测,对工业绿原酸中的奎尼酸、咖啡酸、绿原酸同分异构体等8个相关杂质的结构进行了鉴定。     

液相色谱-串联质谱法测定强化食品中叶酸的含量

采用液相色谱-电喷雾电离串联质谱法测定强化食品(饮料、大米、奶粉、含乳饮料、饼干及果冻)中的叶酸含量。采用多种方法确保叶酸检测的准确性:1优化前处理操作步骤,并使用铝箔避光保存;2加入二丁基羟基甲苯(BHT)作为叶酸的抗氧化保护剂;3加入甲氨蝶呤作为内标物,抵消复杂基质的干扰。方法系统考察了提取条件对回收率的影响,并采用Waters HSS T3(2.1 mm×50 mm,1.7μm)反相色谱柱,以甲醇-10 mmol/L醋酸铵(p H 6.3)为流动相进行梯度洗脱分离,多反应监测(MRM)正离子扫描模式,以内标法进行定性和定量分析。该方法在0.05~100 ng/m L浓度范围内线性关系良好,定量下限为0.01~0.5 mg/kg,回收率为72.0%~109%,相对标准偏差(RSD)为3.8%~11.8%。该方法简单快速,灵敏度、准确度和精密度均能满足强化食品中叶酸的测定要求。     

液相色谱-串联质谱法测定人参中申嗪霉素的残留

建立了液相色谱-电喷雾串联质谱测定人参中申嗪霉素残留量的分析方法。人参样品经水浸泡,乙腈提取,分散固相萃取净化,色谱分离后,采用ESI-MS/MS在正离子多反应监测(MRM)模式下进行检测,选择定量离子对为m/z 225.1/179.1,定性离子对为m/z 225.1/125.1,外标法定量。该方法对于人参中申嗪霉素的定量下限为0.01 mg/kg,在0.5~10μg/L质量浓度范围内,峰面积与含量呈良好线性关系,相关系数大于0.99。对人参中申嗪霉素在0.01,0.02,0.10 mg/kg加标水平下的回收率为82%~100%,相对标准偏差均不大于6.8%。结果表明,该方法操作简单、快速,灵敏度和准确度高,可满足人参中申嗪霉素残留量的检测要求。     

Effect of Propylene Glycol and Ethanol on the UVB-Induced Peroxidation of Linoleic Acid and Lipids of Porcine Skin,in the Presence of Different TiO2 Specimens

Titanium dioxide is a sunscreen pigment with photocatalytic activity. We studied the behavior of different TiO₂ specimens used in cosmetic products on the UVB-induced peroxidation of linoleic acid as model substrate and of porcine skin, at different pH values. Lipoperoxidation of linoleic acid occurred to a lower extent with the coated compared to the uncoated TiO₂, and it decreased at pH 7.0 compared to 4.0. The addition of organic additives such as propylene glycol and ethanol induced a significant reduction of the lipoperoxidation activity, particularly with the most reactive TiO₂ specimens. Similar results were obtained with the porcine skin.     

A comparison of quantitative theoretical results of the bonding in Ni(CO)4 and Ni(N2)4

Using non-empirical calculations the details of bonding in Ni(CO)₄ and in the analogous Ni(N₂)₄ are investigated.For Ni(CO)₄ some previous results are confirmed. In the calculation on Ni(N₂)₄ the close resemblance with Ni(CO)₄ is quite remarkable. The main difference is contained in the fact that carbon has a lower -electron density than nitrogen and that therefore the *-orbital in CO is lower in energy and geometrically more favourable for back donation.From the calculations we find a difference in metal-ligand bond energy between the carbonyl complex and the dinitrogen complex of approximately 18 kcal/mol.     

液相色谱-串联质谱法测定水稻中生长素及其氨基酸结合物

建立了同时测定水稻中吲哚-3-丁酸(IBA)、吲哚-3-乙酸(IAA)及其7种氨基酸结合物的液相色谱-串联质谱( HPLC - MS/MS)检测方法.样品在4℃下于80％甲醇中浸提12 h后,经混合阴离子交换反相固相萃取(MAX)净化,以5 mmol/L的甲酸铵溶液和甲醇为流动相,在C18柱上进行液相色谱分离,电喷雾正...     

Rapid and Sensitive Liquid Chromatography-Tandem Mass Spectrometry for Quantification of Glycyrrhetic Acid in Human Plasma

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry(LC-MS/MS) for the determination of glycyrrhetic acid in human plasma with ginsenoside Rh2 as internal standard was developed and validated. The plasma samples were prepared via liquid-liquid extraction with ethyl acetate. Chromatographic separation was accomplished on a Venusil MP-C18(50 mm×2.1 mm, 5 μm i.d.) column at 25 °C. The mobile phase consisted of acetonitrile/5 mmol?L-1 ammonium acetate(10:90, volume ratio) at a flow rate ...     

Synthesis,Quantification, and Characterization of Fatty Acid Amides from In Vitro and In Vivo Sources

Fatty acid amides are a diverse family of underappreciated, biologically occurring lipids. Herein, the methods for the chemical synthesis and subsequent characterization of specific members of the fatty acid amide family are described. The synthetically prepared fatty acid amides and those obtained commercially are used as standards for the characterization and quantification of the fatty acid amides produced by biological systems, a fatty acid amidome. The fatty acid amidomes from mouse N₁₈TG₂ cells, sheep choroid plexus cells, Drosophila melanogaster, Bombyx mori, Apis mellifera, and Tribolium castaneum are presented.     

水中全氟烷基醚类羧酸的超高效液相色谱-串联质谱检测方法研究

电喷雾离子源条件下全氟烷基醚类羧酸(PFECA)发生源内裂解和CO2中性丢失,导致其准分子离子峰的丰度降低,影响该类化合物的检测灵敏度.该文选择[CF3(CF2)nO]或[M-H-CO2]作为母离子,其他次级氟化烷氧基和烷基片段作为子离子,可将全氟烷基醚类羧酸的质谱响应最大提高4个数量级.结合液液萃取,对水样中4种全氟...     

Simultaneous Determination of Trimethoprim, Sulfadiazine, Florfenicol and Oxolinic Acid in Surface Water by Liquid Chromatography Tandem Mass Spectrometry

A liquid chromatographic/tandem mass spectrometric method using atmospheric pressure chemical ionisation (LC-APCI-MS-MS) was developed for simultaneous determination of trimethoprim, sulfadiazine, florfenicol and oxolinic acid in surface water. The compounds were extracted by solid phase extraction on a polymeric sorbent. Two transition products were monitored for each compound. The detection capabilities related to the transition products of lowest abundance were 1 ng L^–1 for trimethoprim, sulfadiazine and florfenicol and 2 ng L^–1 for oxolinic acid. The mean recoveries were 84%, 83%, 96% and 78% at a level of 10 ng L^–1. The relative repeatability standard deviations were less than 11% at a level of 10 ng L^–1.     

Determination of thermodynamic properties of aqueous mixtures of MgCl2 and Mg(NO3)2 by the potentiometric method at T = 298.15

In this research, thermodynamic properties of the ternary electrolyte system (MgCl₂ + Mg(NO₃)₂ + H₂O) were investigated using a potentiometric method. The galvanic cell used had no liquid junction of type: Mg-ISE|MgCl₂ (m_A), Mg(NO₃)₂ (m_B), H₂O|Ag/AgCl. The measurements were performed at T = 298.15 K and at total ionic strengths from 0.001 to 8.000 mol/kg for different series of salt ratios r=mMgCl₂/mMg₂(NO₃) =1.00, 2.50, 5.00, 7.50, 10.00 and 15.00. The PVC based magnesium ion-selective electrode (Mg-ISE) and the Ag/AgCl electrode used in this work were prepared in our laboratory and showed a reasonably good Nernst response. The Pitzer ion interaction model and Harned rule were used to illustrate the ternary electrolyte system investigated. The experimental results showed that both Pitzer model and Harned rule were suitable to be used satisfactorily to describe this ternary system.