采用LC/MS/MS测定侧流卷烟烟气中挥发性羰基化合物的方法研究

挥发性羰基化合物是卷烟烟气中的一类重要有害物质,准确测定卷烟烟气中,特别是侧流卷烟烟气中的挥发性羰基化合物还有许多问题有待解决。实验中采用2,4-二硝基苯肼（DNPH）酸性溶液捕集侧流烟气中的羰基化合物,乙腈水溶液稀释后,以对羟基苯甲酸丁酯为内标物,用带有负离子电喷雾的LC/MS/MS定量分析侧流烟气中8种挥发性羰基化合物。实验证明,此方法有较好的重复性:对8种羰基化合物测定的相对标准偏差在6%以下;具有较高的灵敏度:8种挥发性羰基化合物的检出限均低于2.8 ng/ cig;较高的准确性:8种挥发性羰基化合物的回收率在87.2%～104.7%之间。与以往的分析方法相比,该方法具有更高的选择性,实现了烟气中巴豆醛、2-丁酮的DNPH衍生物的同分异构体的分离,对巴豆醛、2-丁酮定量更为准确,分析方法的灵敏度也明显提高。      

塑料包装材料中邻苯二甲酸酯的LC/MS/MS测定方法研究

建立了LC/MS/MS测定塑料包装材料中邻苯二甲酸酯含量的分析方法.将塑料包装材料粉碎后索氏提取,经LC/MS/MS分析在50μg/L～400μg/L范围内呈现良好的线性关系(R2＞0.9985),方法检测限小于35μg,/kg;在50μg/kg、200μ g/kg、400μg/kg三个样品加标水平,PAEs的回收率在91.42％～99.90％之间;方法精密度实验的相对准偏差在5％之内.结果表明该方法准确可靠,精密度较高.     

Detection of melamine and cyanuric acid in vegetable protein products used in food production

The multitude of food recalls in 2007 clearly demonstrated that total nitrogen-content (ΣN) determination by means of near-infrared spectroscopy (NIRS) and Kjeldahl-based measurements can be deceived, and should no longer be regarded as a complete quality assurance program for nutritive-protein evaluations. Furthermore, contemporary Canadian-employed analytical tools are precariously limited in their ability to effectively assure a product where there is no a priori knowledge of the environmental toxin(s) involved. In light of these challenges, this study explored a number of analytical techniques used to assess and furthermore assure the quality of vegetable protein products (VPPs). Using liquid chromatography with tandem mass spectrometry (LC/MS/MS) technologies, a combination of VPP-based samples was analyzed for the presence of nitrogen-bearing environmental toxicants. Of the 52 samples tested, involving an assortment of matrices, melamine and cyanuric acid were positively identified (>1 ng/mL) in 22 and 17 samples, respectively. Subsequent high pressure liquid chromatography with ultraviolet/visible (HPLC-UV) amino acid profiling further confirmed the adulteration of those materials contaminated with melamine and melamine-related compounds. Based on the evidence presented herein, LC/MS/MS in combination with HPLC-UV provides for a reliable food safety detection system as applied to VPPs. Moreover, HPLC-UV is indispensable as a stand-alone 1st level of screening to assess the integrity of a VPP or any nutritive protein-based sample.     

Covalent interactions between amino acid side chains and oxidation products of caffeoylquinic acid (chlorogenic acid)

BACKGROUND: Physicochemical properties and digestibility of proteins can be modified by covalent interactions with oxidized phenolic compounds, i.e., quinones. In order to control these interactions in food products, the covalent interactions between quinones from caffeoylquinic acid (CQA) and amino acid side chains were studied with mass spectrometry using N‐terminally protected amino acids. RESULTS: The addition of two molecules of CQA, presumably in the form of a pre‐formed dimer, was observed for lysine, tyrosine, histidine and tryptophan. A monomer of CQA seemed to be able to react with histidine and tryptophan, whereas no interaction with a CQA monomer was observed for lysine and tyrosine. Serine and threonine showed no covalent interactions with CQA. Cross‐linking between CQA and the side chains of two molecules of lysine is likely to occur also in proteins. The results show that protein cross‐linking may also be expected to occur via two tyrosine residues in the absence of other phenolic substrates. The side chains of lysine and tyrosine are more reactive than that of histidine and tryptophan. CONCLUSIONS: These results show that covalent protein modification by oxidized phenolics occurs preferentially via an initial dimerization and encompasses not only lysine and cysteine residues. Copyright © 2008 Society of Chemical Industry     

液质联用技术测定茶叶中多菌灵残留

建立茶叶中多菌灵残留的高效液相色谱-串联四极杆质谱联用测定方法。该方法中样品经0.2 mol/L盐酸甲醇溶液(1∶1,υ/υ)超声提取,MCX固相萃取柱净化,以ZORBAX Eclipse XDB-C18色谱柱(3.0 mm×50 mm,1.8μm)分离,流动相为0.1%甲酸水和乙腈(梯度洗脱),电喷雾正离子MRM模式检测。该方法的检出限为1.0μg/kg,线性范围0.5μg/L～3 000μg/L,加标回收率为85.0%～96.0%,相对标准偏差为3.71%。     

水果中噻虫嗪农药残留LC/MS/MS测定

目的建立一种简单、快速、灵敏的水果中噻虫嗪农药残留的液相色谱-串联质谱(liquid chromatography-mass spectrometry/mass spectrometry,LC-MS/MS)分析方法。方法称取水果样品5 g,加入乙腈20 m L在超声波振荡条件下提取,提取液使用20 mg石墨化炭黑(Carb)和60 mg N-丙基乙二胺(PSA)粉末进行分散固相萃取净化,经液相色谱质谱联用仪检测,外标法定量。结果噻虫嗪农药残留的色谱图分离效果良好,方法的检出限为0.3μg/kg,线性相关系数为0.9999,噻虫嗪在苹果、梨、桃中的添加水平为0.01、0.05、0.10 mg/kg,回收试验表明该方法平均回收率为88.9%~100.3%(n=6),相对标准偏差为1.98%~4.53%。结论该方法简单、快速、灵敏、净化效果好、回收率高,适合水果中噻虫嗪农药残留的检测和安全监控。     

液相色谱-串联质谱法测定肠衣中克伦特罗残留量不确定度分析

对液相色谱-串联质谱法测定肠衣中克伦特罗残留量的不确定度进行分析,建立数学模型,找出影响测量不确定度的各种因素,对各个不确定度分量进行评估和计算合成。给出了液相色谱-串联质谱法测定肠衣中克伦特罗残留量的相对合成标准不确定度urel=0.034及扩展不确定度U(X)=0.03μg/kg。     

液相色谱-串联质谱法测定猪肉及组织中沙丁胺醇的含量不确定度评定

目的分析液相色谱一串联质谱法检测猪肉及组织中沙丁胺醇的不确定度,探讨各因素对检验结果的影响。方法依据JJG1059.1-2012《测量不确定度评定与表示》和CNAS-GL06《化学分析中不确定度的评估指南》规定的方法和程序,分析影响测量不确定的来源,并对各不确定度分量进行了评估。结果合成各变量的不确定度,最终得到测定结果的扩展不确定度:(11.05±0.77)μg/kg(k=2)。结论影响检测结果不确定度的主要因素为回收率和标准曲线拟合,在实际测量过程严格控制实验条件可提高检测的准确性和可靠性。     

QuEChERS—UPLC/MS/MS快速测定茶叶中的草甘膦和氨甲基磷酸

采用QuEChERS—超高效液相色谱—串联质谱技术同时测定茶叶中的草甘膦和氨甲基磷酸农药残留。茶叶样品用纯水提取,经分散固相萃取净化,以乙腈和0.1%氨水溶液为流动相进行梯度洗脱,采用CORTECSTM UPLC~C_(18+)色谱柱分离,电喷雾—负离子多反应模式监测,内标法定量。草甘膦和氨甲基磷酸农药在5~500μg/L内线性关系良好,相关系数均大于0.999,该方法的检出限为10μg/kg,定量限为30μg/kg。分别添加30,100,500μg/kg 3个浓度水平的草甘膦和氨甲基磷酸农药,草甘膦的回收率为90.5%~93.5%,相对标准偏差为4.1%~7.2%;氨甲基磷酸的回收率为99.2%~102.4%,相对标准偏差为3.4%~8.3%。该方法前处理简便、分析速度快、方法稳定,适用于茶叶中草甘膦和氨甲基磷酸农药残留的同时测定。     

高效液相色谱-质谱联用测定乳制品中6种四环素类抗生素

建立了乳制品中6种四环素类抗生素残留的高效液相色谱-电喷雾离子阱质谱联用测定方法。该方法采用多反应监测正离子模式，可一次对6种四环素类抗生素进行定性和定量分析。该方法的检出限0．5-4．0μg/L，测定低限牛奶0．6-4.5μ/L，乳粉为6．0-45．0μg/kg，线性范围4．0-100．0μg／L，加标回收率56．1％-104．9％，相对标准偏差为2．5％-15．0％。该法具有样品预处理简单，灵敏度高，分析时间短等优点。     

Fast analysis of glufosinate,glyphosate and its main metabolite,aminomethylphosphonic acid,in edible oils,by liquid chromatographycoupled with electrospray tandem mass spectrometry

ABSTRACT

A method has been developed for the rapid, specific, accurate, precise and sensitive determination of glufosinate, glyphosate and its major metabolite, aminomethylphosphonic acid, in edible oils, by liquid chromatography coupled to tandem mass spectrometry. Oils were extracted with acidified water (1% formic acid), and the extracts were directly injected into an LC using a Hypercarb column as the stationary phase. The analytes were eluted by a mobile phase of methanol and water containing 1% acetic acid, and they were ionised by electrospray ionisation in negative ion mode. The method was validated and limits of quantification ranged from 5 μg kg^?1 (aminomethylphosphonic acid) to 10 μg kg^?1 (glyphosate and glufosinate). Three concentrations (10, 50 and 100 μg kg^?1) were selected to perform recovery studies. Mean recoveries ranged from 81.4% to 119.4%. Intra and inter-day precision were lower than 19%. Different edible oils were analysed, and no residues of the studied herbicides were detected above limits of quantification.     

Transglucosylation of caffeic acid by a recombinant sucrose phosphorylase in aqueous buffer and aqueous-supercritical CO2 media

Polyphenolic compounds, such as caffeic acid, offer many health benefits, but their industrial applications are limited because of their low solubility in water and instability under UV light or heat. In this study, we enzymatically produced caffeic acid glucosides, in both aqueous buffer and aqueous-supercritical carbon dioxide (SC-CO₂) media, using a recombinant sucrose phosphorylase (SPase) from Bifidobacterium longum. By using LC/MS/MS analysis, we verified that the enzymatic reaction products were caffeic acid monoglucosides and diglucosides. Under SC-CO₂, the amounts of the reaction products from the enzyme reaction were smaller than those in the aqueous reaction medium. However, this is the first report of the transglucosylation of caffeic acid by SPase, and also the first enzymatic reaction with phenolic compounds conducted in a SC-CO₂ phase.     

风干牦牛肉氨基酸与脂肪酸组成分析评价

通过对风干牦牛肉原料及成品中氨基酸与脂肪酸的含量进行测定,分析其组成变化,并对风干牦牛肉的营养价值进行评价。结果显示:原料肉和风干牦牛肉均含有十八种氨基酸和十四种脂肪酸,且风干牦牛肉的氨基酸和脂肪酸总量分别高于原料肉1.34g/100g干物质和0.62%（p<0.05）。风干牦牛肉的氨基酸总量为81.14g/100g干物质,EAA/TAA为39.45%,EAA/NEAA为65.15%。脂肪酸总量为97.97%,P:S为0.32,接近理想模式,n-6:n-3为1.4,处于理想范围。因此可以判断风干牦牛肉是一种具有独特风味的优质蛋白质来源,也是具有均衡脂肪酸的高营养价值的肉制品。      

质谱技术的研究进展

本文为质谱技术的研究现状作一综述,着重介绍了ESI、MADLI两种关键的电离技术以及色谱/质谱联用技术,并对未来予以展望。     

Determination and quantification of the kokumi peptide, γ-glutamyl-valyl-glycine,in commercial soy sauces

Recent studies have demonstrated that kokumi substances, such as glutathione, are perceived through the calcium-sensing receptor (CaSR), and screening by CaSR assay and sensory evaluation has shown that γ-glutamyl-valyl-glycine (γ-Glu-Val-Gly) is a potent kokumi peptide. In this study, the contents of γ-Glu-Val-Gly in six commercial brands of dark-coloured soy sauces, two brands of light-coloured soy sauce, and one brand of white soy sauce, were investigated by high performance liquid chromatography–tandem mass spectrometry (LC/MS/MS), followed by derivatization with 6-aminoquinoyl-N-hydroxysuccinimidyl-carbamate (AQC). The analyses indicated that γ-Glu-Val-Gly was present in all investigated soy sauces at concentrations ranging from 0.15 to 0.61 mg/dl, demonstrating that it is widely distributed in soy sauces.     

Determination of polyadipates migrating from lid gaskets of glass jars. Hydrolysis to adipic acid and measurement by LC–MS/MS

Polyadipate plasticizers can be present in the polyvinylchloride (PVC) gaskets used to seal the lids of glass jars. As the gaskets can come into direct contact with the foodstuffs inside the jar, the potential exists for polyadipate migration into the food. The procedure and performance characteristics of a test method for the analysis of polyadipates in food simulants (3% aqueous acetic acid and 10% aqueous ethanol) and the volatile test media used in substitute fat tests (isooctane and 95% aqueous ethanol) are described. The PVC gaskets were exposed to the food simulants or their substitutes under standard test conditions. Studies were initially carried out using direct measurement of the polyadipate oligomers by liquid chromatography with time-of-flight mass spectrometric detection (LC-TOF-MS) but this was not practical due to the number of peaks detected. Instead, the migrating polyadipates were hydrolysed to adipic acid and measured by liquid chromatography with tandem mass spectrometric detection (LC–MS/MS). The amount of polyadipate that this measurement of adipic acid represents was then calculated. Method performance was assessed by analysis of gaskets from two types of jar lids by single-laboratory validation. Linearity, sensitivity, repeatability, intermediate reproducibility and recovery were determined to be suitable for checking compliance with the 30 mg/kg specific migration limits for polyesters of 1,2-propane diol and/or 1,3- and/or 1,4-butanediol and/or polypropylene-glycol with adipic acid, which may be end-capped with acetic acid or fatty acids C₁₂–C₁₈ or n-octanol and/or n-decanol. The method was found to be much quicker than previous methods involving extraction, clean-up, hydrolysis, esterification, derivatisation and GC measurement, consequently saving time and money.     

Fast detection of cyclopiazonic acid in cheese using Fourier transform mid-infrared ATR spectroscopy

A simple and rapid Fourier transform mid-infrared spectroscopic method with attenuated total reflection was developed for the detection of cyclopiazonic acid in ewe's cheese samples. A partial least-squares calibration model for the prediction of cyclopiazonic acid content in ewe medium-ripened cheese, based on spectra data, revealed to be the best approach. The PLS model was tested by cross-validation in order to minimize standard error of the model and the relevant RMSECV (root of mean-squared error in cross-validation) was calculated to be 0.05 μg/g. In parallel experiments, cyclopiazonic acid content was estimated using the developed SPME-HPLC/UV method and different cheese samples were analysed using both techniques. The method appears to be useful for a qualitative and semi-quantitative screening of a large number of cheese samples, important in food contaminants monitoring. Since no sample pretreatment is required at all, the analysis times are dramatically shortened in comparison with any chromatographic procedure.     

A preliminary study of presence of resveratrol in skins and pulps of European and Japanese plum cultivars

BACKGROUND: Resveratrol is a polyphenol with health properties being mainly present in the skins of several foods. However, any study has been carried out to analyze the presence of this stilbene in the plum fruit from the genus Prunus in European and Japanese cultivars. RESULTS: The analysis of resveratrol from the skin in different cultivars of plums from Spanish markets with liquid chromatography coupled to ultraviolet (LC‐UV) detector with subsequent confirmation by LC‐MS/MS has been demonstrated that contents of this compound in plums ranged from 0.1 to 6.2 µg/g. CONCLUSIONS: Values of resveratrol in European plum cultivars is higher than in Japanese cultivars. Copyright © 2012 Society of Chemical Industry     

A novel approach to simultaneous screening and confirmation of regulated pharmaceutical compounds in dietary supplements by LC/MS/MS with an information-dependent acquisition method

The commercial success of synthetic phosphodiesterase-5 (PDE-5) inhibitors (viz. sildenafil, vardenafil and tadalafil) for erectile dysfunction (ED) has led to their widespread use as adulterants in dietary supplements (DSs). Reports on adulteration by ED drugs or their analogues in DSs suggest they may cause a serious threat to human health. The problem is becoming more complex as hidden and structurally modified analogues are continuously being reported. To analyse known drugs and their analogues, three commonly used PDE-5 inhibitors, naturally existing icariin and yohimbin, and their 19 analogues were analyzed in this study. They were identified using ion-spray liquid chromatography/tandem mass spectrometry (LC/MS/MS) using multiple reaction monitoring (MRM). This MRM procedure gave a limit of detection of less than 0.02?ng?ml^?1 for the 24 compounds, selectivity of fragmentation using MRM for 2.5?–?8.5?min in a single run and peak height repeatability of coefficient of variation of 3.9?–?31.8%. An IDA method using the MRM scans to detect the presence of known analytes was set up and added to a built-in library for screening for PDE-5 inhibitors. These MRM experiments were used to trigger product ion scans using a hybrid quadrupole-linear ion trap instrument. The product ion scan was compared and confirmed by a library search of MS/MS spectra acquired from a reference standard. To search for new analogues of PDE-5 inhibitors, a precursor ion scan of an expected ion m/z 283, which was one of the mass fragments from the analogues of sildenafil or vardenafil, was performed and fragmentation of the precursor ion, by combining a precursor ion scan with automatic confirmation using EPI spectra, was acquired. Of the 37 DSs tested, two were eventually found to be adulterated with yohimbin and vardenafil, respectively. The approach proposed in this study would be valuable in characterizing chemical constituents of drug residues and their analogues with identical chemical substructures from complex natural and synthetic sources in DSs using an information-dependent acquisition-enhanced product ion (IDA–EPI) scan.     

A thermostable lectin from the rhizomes of Kaempferia parviflora

BACKGROUND: Kaempferia parviflora, or black galingale (Kra‐Chai‐Dam), belongs to the Zingiberaceae family and is used as both a food ingredient and a medicinal plant. There are diverse reports on the biological activities of compounds extracted from the plant, such as antimalarial, antifungal and an effective sexual‐enhancing role, but not on the lectins. RESULTS: A lectin was isolated from the rhizomes of Kaempferia parviflora using affinity chromatography on Concanavalin A followed by gel filtration chromatography on Sephacryl S‐100. The molecular weight of the purified lectin was about 41.7 kDa. This lectin showed haemagglutinating activity against erythrocytes from several sources, with the highest level being against those from rabbits. Moreover, the lectin was thermostable, with significant haemagglutinating activity detectable up to 75 °C. The results of trypsin digestion and liquid chromatography/tandem mass spectrometry analysis suggested that this protein could be a member of the lectin/endochitnase1 family. CONCLUSION: A lectin that showed thermotolerant haemagglutinating activity against erythrocytes from several sources was successfully purified from K. paviflora rhizomes. Peptide sequence analysis indicated that this lectin is similar to lectin/endochitinase 1 (Urtica dioica) or Hevein‐like protein (Hevea brasiliensis). Copyright © 2010 Society of Chemical Industry