Isoprenoid Alcohols are Susceptible to Oxidation with Singlet Oxygen and Hydroxyl Radicals

Isoprenoids, as common constituents of all living cells, are exposed to oxidative agents—reactive oxygen species, for example, singlet oxygen or hydroxyl radicals. Despite this fact, products of oxidation of polyisoprenoids have never been characterized. In this study, chemical oxidation of isoprenoid alcohols (Prenol‐2 and ‐10) was performed using singlet oxygen (generated in the presence of hydrogen peroxide/molybdate or upon photochemical reaction in the presence of porphyrin), oxygen (formed upon hydrogen peroxide dismutation) or hydroxyl radical (generated by the hydrogen peroxide/sonication, UV/titanium dioxide or UV/hydrogen peroxide) systems. The structure of the obtained products, hydroxy‐, peroxy‐ and heterocyclic derivatives, was studied with the aid of mass spectrometry (MS) and nuclear magnetic resonance (NMR) methods. Furthermore, mass spectrometry with electrospray ionization appeared to be a useful analytical tool to detect the products of oxidation of isoprenoids (ESI–MS analysis), as well as to establish their structure on the basis of the fragmentation spectra of selected ions (ESI–MS/MS analysis). Taken together, susceptibility of polyisoprenoid alcohols to various oxidizing agents was shown for the first time.     

Rapid complexing of oxoacylglycerols with amino acids peptides and aminophospholipids

We prepared model Schiff bases from 2-[9-oxo]nonanoyl glycerol (2-MAG-ALD) and various amino compounds. 2-MAG-ALD was obtained by pancreatic lipase hydrolysis of trioleoyl glycerol and reductive ozonolysis of the resulting 2-monooleoyl glycerol. The reaction products were purified by thin-layer chromatography. Schiff bases were synthesized in greater than 50% yield by reacting 2-MAG-ALD with twofold molar excess of valine, Nα-acetyl-l-lysine methyl ester and the tripeptides glycyl-glycyl-glycine, glycyl-glycyl-histidine, and glycyl-histidyl-lysine in aqueous methanol and with 1-palmitoyl-2-stearoyl glycerophosphoethanolamine (PE) in chloroform.methanol for 16 h at room temperature. Prior to analysis the bases were reduced with sodium cyanoborohydride in methanol for 30 min at 4°C. Reaction products were analyzed by high-performance liquid chromatography/electrospray ionization/mass spectrometry (HPLC/ESI/MS). Reduced Schiff bases of 2-MAG-ALD with PF and amino acids were analyzed by normal-phase HPLC/ESI/MS and those with peptides by reversed-phase HPLC/ESI/MS. Single adducts were obtained in all cases and both the α-amino group of valine and the ε-amino group of Nα-acetyl-l-lysine methyl ester were reactive. Molecular ions of reaction products were the only detected ions in the negative ionization mode, whereas in the positive ion mode sodiated molecular ions were also detected. The present study suggests that 2-MAG-ALD may form Schiff base adducts with amino compounds in other aqueous media, such as the intestinal lumen and in the hydrophobic environment of cell membranes.     

凝胶渗透色谱－液相色谱－串联质谱法测定水产品中性激素

建立水产品中性激素的凝胶渗透色谱净化－超高效液相色谱－串联质谱分析方法。采用乙酸乙酯提取样品,经GPC净化后, LC－MS／MS测定,外标法定量。流动相为乙腈和0．1％甲酸水溶液,梯度洗脱,电喷雾正离子多反应模式监测。3种性激素在0．5～20．0μg／L线性范围内,相关系数大于0．998,定量限为0．3μg／kg,回收率为88．6％～96．4％,相对标准偏差为1．84％～6．24％。本方法灵敏度高、重现性好,适用于水产品中性激素的测定。     

Monitoring the Epoxidation of Canola Oil by Non-aqueous Reversed Phase Liquid Chromatography/Mass Spectrometry for Process Optimization and Control

Non-aqueous reversed phase liquid chromatography/electrospray mass spectrometry (NARP-LC/ESI–MS) was used to monitor the epoxidation of canola oil by performic acid. The reaction was sampled at regular intervals over 28?h and analyzed by NARP-LC/ESI–MS in order to observe the formation of partially epoxidized reaction intermediates and the fully epoxidized products. The experiment focused on the transformation of triacylglycerols (TAG) with 54 carbons in the fatty acyl chains and between 2 and 7 double bonds which account for >93?% of the oil. NARP-LC/ESI–MS allowed determination of the time required for full epoxidation of the oil. It was shown that complete epoxidation of TAG with low numbers of double bonds occurs more rapidly than for those with many double bonds. Furthermore, it was observed that epoxidation of multiply unsaturated TAG occurs via a sequential process in which partially epoxidized intermediates are consumed to form other more highly epoxidized compounds as the reaction proceeds. Data obtained by flow-injection ESI–MS was found to be comparable to that obtained from NARP-LC/ESI–MS for monitoring intermediates and products and could be adapted for in-process reaction monitoring.     

Comprehensive Quantitation Using Two Stable Isotopically Labeled Species and Direct Detection of <Emphasis Type="Italic">N</Emphasis>-Acyl Moiety of Sphingomyelin

Sphingomyelin (ceramide‐phosphocholine, CerPCho) is a common sphingolipid in mammalian cells and is composed of phosphorylcholine and ceramide as polar and hydrophobic components, respectively. In this study, a qualitative liquid chromatography‐electrospray ionization tandem mass spectrometry (LC–ESI–MS/MS/MS) analysis is proposed in which CerPCho structures were assigned based on product ion spectra corresponding to sphingosylphosphorylcholine and N‐acyl moieties. From MS/MS/MS analysis of CerPCho, we observed product ion spectra of the N‐acyl fatty acids as [RCO₂]^? ions as well as sphingosylphosphorylcholine. A calibration curve for CerPCho was constructed using two stable isotopically labeled CerPCho species and then used to quantify the CerPCho species in HeLa cells as a proof‐of‐principle study. The present study proposes an accurate method for quantifying and assigning structures to each CerPCho species in crude biologic samples by LC–ESI–MS/MS/MS analysis.     

Synthesis of poly (γ‐benzyl‐L‐glutamate) with well‐defined terminal structures and its block polypeptides with alanine,leucine and phenylalanine

The ring‐opening polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG‐NCA) was initiated by n‐hexylamine in N,N‐dimethyformamide under normal pressure at 0 °C. The products were characterizated by gel permeation chromatography, matrix‐assisted laser desorption/ionization time of flight mass spectroscopy (MALDI‐TOF MS), nuclear magnetic resonance etc. MALDI‐TOF MS gave direct evidence that the side reactions during the polymerization of BLG‐NCA could be greatly reduced by decreasing the reaction temperature, e.g. from room temperature to 0 °C. As a result, over 90% of the products were amino‐terminated poly(γ‐benzyl‐L ‐glutamate) (PBLG) with low polydispersity index when the polymerization was carried out at 0 °C, which could be used to re‐initiate the polymerization of other NCAs. Then several well‐defined PBLG‐containing block copolypeptides were successfully synthesized in a convenient way. Copyright © 2012 Society of Chemical Industry     

加速溶剂萃取-液相色谱-串联质谱法测定电子电气产品中的六溴环十二烷异构体

建立了采用加速溶剂萃取-液相色谱-串联质谱(LC-MS/MS)法测定电子电气产品中六溴环十二烷的检测方法。将粉碎后的样品以甲苯为萃取溶剂进行加速溶剂萃取,萃取液经浓缩后采用LC-MS/MS测定。采用电喷雾离子源,定性离子对为640.5/78.9和640.5/80.9;定量离子对为640.5/78.9。方法检出限:β-六溴环十二烷为0.05 mg/kg,α-、γ-六溴环十二烷为0.1 mg/kg;在0.1～10 mg/kg范围加标回收率为88.8%～104.0%;相对标准偏差为3.0%～6.5%。结果表明:该方法快速、准确灵、敏度高能,满足相关测定要求。     

液相色谱-串联质谱法测定乳制品中的氯霉素

建立了超高效液相色谱-串联质谱/质谱法测定奶粉、凝固型酸奶及液态奶中氯霉素的方法。试样用10%亚铁氰化钾及20%乙酸锌作为沉淀剂,以乙酸乙酯提取,采用电喷雾离子源,负离子扫描,多反应监测(MRM)模式进行检测,外标法定量。结果表明,氯霉素在0.5~100μg/L浓度范围内线性关系良好,空白样品加标回收率均大于80%,相对标准偏差小于6%。氯霉素方法检出限(LOD)均为0.1μg/kg。该方法准确、灵敏、操作相对简便,有效降低基质干扰,适用于奶粉、牛奶中氯霉素的测定。     

中药黄芪中异黄酮苷类化合物的高效液相色谱-串联质谱分析

利用高效液相色谱-大气压化学电离质谱联用技术,建立了黄芪提取物中的有效成分毛蕊异黄酮-7-O-β-D-葡萄糖苷和芒柄花素-7-O-β-D-葡萄糖苷的定性分析方法。这两个化合物在大气压化学电离质谱条件下,质谱裂解行为的研究表明,二者具有相似的特征质谱裂解行为,即在正离子模式下的一级质谱中均产生强的准分子离子[M+H]+峰和苷元离子[M+H-G lu]+峰;且苷元离子经碰撞诱导解离均产生.CH3(15 Da)、CH3OH(32Da)和2CO(56 Da)的中性丢失;同时发生Retro-D iels A lder(RDA)裂解反应,导致在毛蕊异黄酮-7-O-β-D-葡萄糖苷和芒柄花素-7-O-β-D-葡萄糖苷的二级质谱图中分别产生相对分子质量为m/Z148和m/Z133的特征碎片离子峰。这些特征碎片可以作为这两个化合物定性的依据。该方法已成功应用于黄芪注射液中的这两种物质的定性分析。     

Chemistry of archaeological animal fats

Animal fats are preserved at archaeological sites in association with unglazed pottery, human and animal remains, and other deposits or hoards. High-temperature gas chromatography (HT-GC) and combined HT-GC/mass spectrometry (HT-GC/MS) has confirmed the presence of animal fats in lipid extracts of artifacts. Degradation products and pathways have been discerned through the analyses of archaeological finds and the products of laboratory and field-based decay experiments. The origins of preserved fats have been determined through detailed compositional analysis of their component fatty acids by GC, by GC/MS of dimethyl disulfide derivatives of monoenoic components, and by GC-combustion-isotope ratio-MS (GC-C-IRMS), to derive diagenetically robust delta(13)C values. Regiospecific analysis of intact triacylglycerols by high-performance liquid chromatography/MS (HPLC/MS), with atmospheric pressure chemical ionization, provides a further criterion for establishing the origin of fats. Preparative GC has been employed to isolate individual fatty acids from archaeological pottery in sufficient amounts for (14)C dating.     

Fast GC—MS in Supersonic Molecular Beams

The features of supersonic molecular beams (SMB) are used to improve gas chromatography—mass spectrometry (GC–MS) performance and establish a new method of fast GC–MS. In SMB, the sample compounds are vibrationally cooled such that their electron impact mass spectra are characterized by enhanced M⁺ peaks, together with library-searchable fragments. A new ionization method, hyperthermal surface ionization (HSI), provides ultrasensitive ionization coupled with a tunable degree of selectivity for nitrogen-containing drugs. SMB enables the use of very high carrier gas flow rates which, when a short megabore column is used, results in ultra-fast GC–MS having conventional chromatographic peak widths. Thus, fast GC–MS in SMB can be performed with conventional quadrupole analyzers. The slightly reduced GC resolution can, in many cases, be compensated for by the selectivity of hyperthermal surface ionization or by the increased EI selectivity through enhanced M⁺. “Fast”, “very-fast”, and “ultra-fast” GC–MS are defined and demonstrated with drugs, and the ability to analyze underivatized steroids is shown. Practical examples are shown including ultra-fast GC–MS of lidocaine in human plasma extract achieved in a few seconds and screening of other drugs, without any sample preparation or extraction, achieved in less than three minutes. We conclude that GC–SMB–MS exhibits a combination of faster analysis with improved sensitivity and selectivity, a wider range of molecules amenable to GC–MS, improved MS information, and higher a degree of flexibility.     

Application of DNPH Derivatization with LC/MS to the Identification of Polar Carbonyl Disinfection Byproducts in Drinking Water

A qualitative method using 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by analysis with liquid chromatography (LC)/negative ion-electrospray mass spectrometry (MS) was developed for analyzing and identifying highly polar aldehydes and ketones in ozonated drinking water. Using this method, aldehydes could be easily distinguished from ketones by differences in their mass spectra and chromatographic behavior. Results for many polar-substituted aldehyde and ketone standards are presented, as well as the identification of polar disinfection by-products (DBPs) in ozonated drinking water from full-scale plants and laboratory-scale ozonation of humic acid. One polar DBP identified has not been previously reported. This method could also potentially be used as a tool to identify carbonyl-containing DBPs from disinfectants other than ozone. However, the detection limits for the DNPH-LC/MS method are not as low as for the pentafluorobenzylhydroxylamine (PFBHA)-gas chromatography (GC)/MS method (LC/MS is typically not as sensitive as GC/MS). Therefore, it is not recommended that this method replace the PFBHA-GC/MS method, but be used as a supplement to enable the identification of highly polar carbonyl-containing DBPs that would not be possible by GC/MS.     

降糖类中成药中违禁化学成分的定性分析新方法研究

以50%乙腈超声提取样品后,再以乙腈-0.02 mol/L乙酸铵溶液(含0.1%甲酸)为流动相,经C18柱分离后,ESI源离子化,然后采用正离子模式定性判别苯乙双胍、格列吡嗪、格列本脲,据此建立了降糖类中成药中非法添加降糖化学成分的快速液质定性方法。此方法检测快速灵敏、选择性强,适用于大批量样品的定性鉴别。     

陈皮浸膏热裂解产物分析及其在卷烟中的应用

运用快速溶剂萃取提取陈皮,浓缩得陈皮浸膏。采用热裂解-气相色谱/质谱联用技术(Py-GC/MS),在300,450,600,750,900℃下分析其热裂解产物,陈皮浸膏在600℃以下裂解产物主要是醛类、酮类、酯类和呋喃类物质;在600℃以上,检测到对人体有害物质,如对二甲苯。卷烟加香实验表明:陈皮浸膏在烟丝中的添加量适宜控制在0.03%~0.05%,药香与烟香协调性较好,刺激性降低。     

高效液相色谱-电喷雾串联质谱法测定水产品中14种喹诺酮类与磺胺类药物残留

建立了高效液相色谱-电喷雾串联质谱法测定水产品中恩诺沙星、环丙沙星、双氟沙星、沙拉沙星、氟甲喹、喹酸、磺胺嘧啶、磺胺甲唑、磺胺喹啉、磺胺甲基嘧啶、磺胺二甲氧嘧啶、磺胺二甲基嘧啶、磺胺间二甲氧嘧啶、甲氧苄胺嘧啶共14种常用喹诺酮类与磺胺类兽药的残留检测方法。样品制备后,采用1%乙酸-乙腈提取液提取,用正己烷净化处理后,采用LC/MS/MS电喷雾电离(ESI),多反应监测(MRM)正离子模式检测,外标法定量。在0～100μg/kg范围内14种兽药的线性相关系数均>0.99。在添加浓度5～50μg/kg范围内,14种药物的回收率在70.0%～110%,相对标准偏差(RSD)均在12%以内。方法的检出限为0.1～0.5μg/kg。     

Quantification of Phorbol Esters in Jatropha curcas by HPLC‐UV and HPLC‐ToF‐MS with Standard Addition Method

Established analytic methods for the quantification of phorbol esters (PE), which are some toxic components in Jatropha curcas L., include HPLC with UV‐detection with the commercially available phorbol myristate acetate (PMA) as internal standard or HPLC coupled with MS detection with an external calibration, mostly also with PMA. The differences in the fatty acid side chains and connection to the base structure of PMA compared to PE leads to different UV absorption and MS ionization effects and cause problems for exact quantitative measurements. In this paper, a method is presented which combines both detection types and shows differences between both results. For this purpose, an extraction routine is performed on a PE‐containing seed oil to get a PE standard in high purity, which was used for a standard addition method on two real J. curcas oil samples, derived from Ghana and Mexico. Furthermore, a detection window of ±10 ppm for the high accurate ToF‐MS detection is set to eliminate isobaric interferences from co‐eluting material. Method evaluation of inter‐ and intra‐day variance as well as the recovery rate are performed and determined. With this method a limit of detection of 62 ng mL^?1 (UV) and 11 ng mL^?1 (MS) can be achieved. Practical Applications: Due to the good biological and technical properties of Jatropha curcas L., its seed oil seems perfect for the application as biodiesel feedstock. The toxicity on the other hand could cause problems when converting side products from the oil production to products of higher value. With the here described method an accurate and precise analysis procedure for the quantification of the toxic compounds namely, phorbol esters, could be applied for toxicity studies or routine checks in industry which is converting plant material from J. curcas, so that no toxic material is used for example as animal feed. In this paper, an exact and robust analysis method is described for the quantification of phorbol esters (PE) in Jatropha curcas L. seed oil. This method procedure includes the extraction of PE in methanol, chromatographic separation on a reverse phase C18 HPLC column and the quantification by standard addition method. For the standard addition method a highly pure PE standard is used, which is extracted and purified by semi preparative HPLC right before the measurements. The used detector for identification and quantification is UV set at 280 nm and ESI‐ToF‐MS with a ±10 ppm mass difference of the deprotonated and formate adduct pseudo molecular ion of PE.

     

UPLC-ESI-MS/MS法快速测定烟草中几种潜香物质

使用超高效液相色谱-电喷雾串联四级杆质谱(UPLC-ESI-MS/MS)在多反应离子监测(MRM)模式下分离鉴定了烟草中7种潜香物质。烟样经甲醇提取,XAD-2柱分离纯化,选择中性丢失162扫描确定母离子,通过对母离子二级质谱扫描(MS2),并根据193、179、163、134.7、133等特征碎片离子峰分析结果确定了7种潜香型物质,分别为熊果苷、香豆酸-葡萄糖苷、香豆素奎尼酸、绿原酸、隐绿原酸、葡萄糖基阿魏酸、3-氧化紫罗兰醇葡萄糖苷。最后以苯酚-β-D-吡喃葡萄苷为内标,测定了烟叶不同部位的7种潜香型物质的相对含量。该方法快速、简便,适合于不同烟叶中潜香型物质的分析研究。     

气质联用法鉴别ESBR和SSBR

本文介绍了一种通过气质联用法（GC/MS）测定提取液中的松香酸类物质以区分溶液聚合丁苯橡胶（SSBR）和以松香酸皂或混合酸皂为乳化剂的乳液聚合丁苯橡胶（ESBR）的方法,适用于生橡胶、混炼橡胶、硫化橡胶和橡胶制成品。对多个SBR进行GC/MS实验,谱图分析显示ESBR均含有松香酸类物质和脂肪酸类物质,而SSBR则未发现这两类物质。在此基础上开展已知配方硫化橡胶的实验。结果表明：对于生橡胶而言,无论ESBR使用何种乳化剂,均可以通过松香酸类物质和/或脂肪酸类物质完全区分ESBR和SSBR;混炼橡胶、硫化橡胶和橡胶制成品样品在确定含有丁苯橡胶的基础上,通过松香酸类物质的存在即可确认ESBR。     

Quasi-dynamic mode of nanomembranes for time-of-flight mass spectrometry of proteins

Mechanical resonators realized on the nano-scale by now offer applications in mass-sensing of biomolecules with extraordinary sensitivity. The general idea is that perfect mechanical biosensors should be of extremely small size to achieve zeptogram sensitivity in weighing single molecules similar to a balance. However, the small scale and long response time of weighing biomolecules with a cantilever restrict their usefulness as a high-throughput method. Commercial mass spectrometry (MS) such as electro-spray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF)-MS are the gold standards to which nanomechanical resonators have to live up to. These two methods rely on the ionization and acceleration of biomolecules and the following ion detection after a mass selection step, such as time-of-flight (TOF). Hence, the spectrum is typically represented in m/z, i.e. the mass to ionization charge ratio. Here, we describe the feasibility and mass range of detection of a new mechanical approach for ion detection in time-of-flight mass spectrometry, the principle of which is that the impinging ion packets excite mechanical oscillations in a silicon nitride nanomembrane. These mechanical oscillations are henceforth detected via field emission of electrons from the nanomembrane. Ion detection is demonstrated in MALDI-TOF analysis over a broad range with angiotensin, bovine serum albumin (BSA), and an equimolar protein mixture of insulin, BSA, and immunoglobulin G (IgG). We find an unprecedented mass range of operation of the nanomembrane detector.     

Analysis of the polyethylene glycol glucosides and FA esters thereof by atmospheric-pressure ionization MS

Polyethylene glycol (PEG) glucosides (PEGG) and the PEGG esters of lauric acid were analyzed by atmospheric-pressure ionization MS (API-MS) with electrospray ionization. Straightforward mass characterization of the complex mixtures could be achieved without prior chromatographic separation. The constituents were identified on the basis of quasi-molecular ions. Individual components could be observed as protonated molecular ions [M+H]⁺ and/or as their NH₄ ⁺, Na⁺, or K⁺ adducts in positive ion mode. The mass spectrometric investigation showed that mixtures of PEGG consisted of monoglucoside, diglucoside, polyglucoside, and free PEG. The esterification product is a mixture of two types of nonionic surfactants: PEG-laurates and PEGG-laurates. The reasons for distortion of the quasi-molecular ion intensities and the stabilization of adduct ions were discussed. The rapid and highly sensitive API-MS analysis technique proposed here is well suited for direct characterization of complex mixtures and suitable for development as a routine analytical method.