脱镁叶绿酸a对金黄色葡萄球菌、大肠杆菌的抑制作用

以叶绿素为提取物，进行化学修饰得到光敏活性剂-脱镁叶绿酸α，其对微生物生长影响的研究表明：在光照条件下，脱镁叶绿酸α对金黄色葡萄球菌的生长和大肠杆菌原生质体的再生有明显的抑制作用；在暗培养条件下，脱镁叶绿酸α的抑制作用减弱。     

EDTA络合滴定石灰石中钙镁含量的实验分析

工业生产和控制中钙镁测定多采用EDTA络合滴定分析,在实际测定中,发现当p H值大于12.5时,加入糊精、三乙醇胺、氢氧化钾及钙羧酸指示剂,用EDTA络合滴定Ca,以及在p H值为10时,加入盐酸羟胺、三乙醇胺、氨性缓冲溶液及酸性铬兰K-萘酚绿B指示剂,用EDTA络合滴定Mg具有广泛的适用性,实验在p H值大于12.5时,只加入三乙醇胺、氢氧化钾及钙羧酸指示剂,用EDTA络合滴定Ca做了初步的实验分析。     

分光光度法测定大麦苗粉中脱镁叶绿酸的含量

以建立测定叶绿素类产品中脱镁叶绿酸含量方法为主要目的,采用85%丙酮和乙醚萃取色素,经17%的盐酸溶液酸化后,用可见分光光度计测定667 nm下样品的吸光值,计算出脱镁叶绿酸的含量.结果表明:脱镁叶绿酸浓度在0.13mg/L～127mg/L范围内具有良好的线性关系,回归方程为Y=0.027 5X+0.002 5,R2=0.999 8.加样平均回收率为90.0%.     

EDTA络合滴定盐样中钙镁含量的探讨

在PH10.8氨性缓冲溶液中,采用乙酰丙酮掩蔽镁.以二甲酚橙(XO)—氯化十六烷基吡啶(CPC)作指示剂,用EDTA溶液滴定,测定盐样中钙镁离子的含量,终点变色敏锐。     

DAAD作为铜的络合滴定指示剂的探讨

DAAD用作铜的络合滴定指示剂的实验结果表明,在pH=4.5时终点变化敏锐,准确度高,选择性好.各种金属离子不干扰测定,但锌、铅、镍、锰允许量较小.该法可用于矿石中铜、锌的连续测定.     

单宁酸络合镁与DNA的作用机制研究

单宁酸(tannic acid,TA)具有抑菌性、抗氧化性性能,镁离子具有重要的生理调节作用,通过络合反应将单宁酸和氯化镁制备成单宁酸络合镁(tannic acid complexing magnesium,T-Mg)。为了进一步了解T-Mg的一些功能,本文利用紫外光谱法、荧光光谱法、黏度法和热变性等方法在体外模拟体内环境研究了单宁酸络合镁与脱氧核糖核酸(DNA)的相互作用方式并进行分析。T-Mg与DNA相互作用后,随着DNA浓度的增加,T-Mg-DNA体系紫外吸收峰呈现先减色效应和微弱的红移,最大减色率为1.82%,后增色效应,增色率为5.2%;采用摩尔比法,在pH=7.4的缓冲溶液中,25℃时,最大吸收波长222nm处,求得T-Mg与DNA结合比为n(T-Mg):n(DNA)=5.88:1,结合常数为6.20×10~7L/mol;由于T-Mg嵌入到DNA碱基对之间,使得T-Mg-DNA体系荧光吸收强度增强,最大增幅为2.14倍。黏度法和热变性法表明,T-Mg可使DNA的黏度降低、热变性温度升高,进一步证实了T-Mg与DNA之间作用方式为以T-Mg部分插入为主导,镁离子促进了T-Mg和DNA之间的作用。     

苦卤脱镁后提取钠盐、钾盐工艺的研究

苦卤脱镁后提取钠盐、钾盐工艺的研究山东轻工业学院化工系苑庆忠关键词苦卤，脱镁，钠盐，钾盐１前言全国海盐苦卤化工面临的主要问题是降低能耗和改变产品结构。在改变产品结构方面国内各盐区做了大量的研究工作，提出多种方案和思路。近几年笔者进行了从苦卤中提取镁盐...     

热脱附-气相色谱/质谱联用分析鲜食玉米香气成分

采用热脱附-气相色谱/质谱联用技术（TD-GC/MS）首次分析了鲜食玉米的香气成分组成,并对普甜和紫糯两种鲜食玉米香气成分进行了比较。在最优实验参数:吸附温度30℃,吸附时间2h,冷阱温度-30℃下,普甜玉米和紫糯玉米共鉴定出香气成分38种,其中普甜玉米34种,紫糯玉米30种;普甜、紫糯玉米共有成分26种,相对含量之和分别为80.223%、90.783%;普甜玉米特有成分8种,相对含量之和为16.042%,紫糯玉米特有成分4种,相对含量之和为7.998%。该法分析鲜食玉米挥发性成分操作简单,浓缩富集效率高,重现性好,绿色环保,真实全面地反映了紫糯玉米和普甜玉米香气成分的构成。      

热脱附-气相色谱/质谱联用分析鲜食玉米香气成分

采用热脱附-气相色谱/质谱联用技术(TD-GC/MS)首次分析了鲜食玉米的香气成分组成,并对普甜和紫糯两种鲜食玉米香气成分进行了比较。在最优实验参数:吸附温度30℃,吸附时间2h,冷阱温度-30℃下,普甜玉米和紫糯玉米共鉴定出香气成分38种,其中普甜玉米34种,紫糯玉米30种;普甜、紫糯玉米共有成分26种,相对含量之和分别为80.223%、90.783%;普甜玉米特有成分8种,相对含量之和为16.042%,紫糯玉米特有成分4种,相对含量之和为7.998%。该法分析鲜食玉米挥发性成分操作简单,浓缩富集效率高,重现性好,绿色环保,真实全面地反映了紫糯玉米和普甜玉米香气成分的构成。     

金枕榴莲果实挥发性成分的热脱附-气相色谱／质谱分析

为了解榴莲异味的来源及果肉、果皮气味的差异,采用热脱附．气相色谱／质谱（TCT—GC／MS）联用技术,对动态顶空密闭循环吸附捕集的果肉、果皮样品挥发物进行分析检测。结果表明,榴莲挥发性成分中富含酯类化合物,尤其在果皮挥发物中占大多数,丙酸乙酯（47．37％）接近果皮挥发物总含量的半数;果肉挥发物中还有部分烷、烯、醇、醚、酮、酰胺等化合物。果肉挥发物中的含硫化合物,主要为二乙基二硫醚（8．03％）、乙基正丙基二硫醚（0．06％）、二乙基三硫醚（2．24％）和3．乙基2,4．二硫代．5-己酮（1．19％）,而在果皮挥发物中则未检出。研究中检测到3-乙基2,4-二硫代-5-己酮,但未检测到3-羟基-2-丁酮以及大量烷烃,显示样品采集技术的不同将导致结论完全各异。     

Prediction of short peptides composition by RP-HPLC coupled to ESI mass spectrometry

The combination of reversed-phase chromatography and electrospray mass spectrometry was used to predict the amino acid composition of low molar weight peptides present in a complex mixture of rapeseed protein hydrolysates. First, amino acid retention times on a hydrophobic stationary phase were evaluated to determine hydrophobicity coefficients for each amino acid and then global hydrophobicity coefficients were established for standard peptides. In this way, a correlation between peptide hydrophobicity coefficients and retention time was established. Then, a C language program was developed to calculate all potential amino acid combinations from the mass of a peptide (molar mass < 1000 Da) and determine theoretical hydrophobicity coefficients corresponding to these combinations. Comparison between the theoretical retention time determined by the model and the experimental retention time resulted in the establishment of a sorted potential composition table. This methodology has been applied to two different rapeseed protein hydrolysates peptides that have been purified and sequenced.     

液相色谱—电感耦合等离子体质谱法分析大米中的砷形态

目的建立液相色谱—电感耦合等离子体质谱法测定大米中砷形态化合物的分析方法。方法样品经硝酸提取,采用Dionex lonPac AS7色谱柱, 5 mmoL/L和10 mmoL/L碳酸铵溶液作为流动相进行梯度洗脱,液相色谱分离,电感耦合等离子体质谱进行定性和定量分析。结果在1.0～100.0μg/L浓度范围内各砷形态线性良好,相关系数r均优于0.999,方法加标回收率为84.5%～112.1%,相对标准偏差5%。结论本研究建立的方法准确、可靠、灵敏度高,适用于大米中砷形态化合物的定量检测。     

Arsenic speciation in fish sauce samples determined by HPLC coupled to inductively coupled plasma mass spectrometry

Fish sauce is a condiment typically used in most East Asian cooking and has recently been considered as an effective route to iron fortification in countries where iron deficiency anaemia is widespread. Current consumption and the increasing awareness of the uniqueness of fish sauce as a condiment necessitate assessment of the health risk that it poses. This study focuses on the analysis of arsenic in fish sauce samples with special emphasis on identification of the species present as a consequence of the fermentation process. Total arsenic concentrations of six different fish sauces from Thailand and Vietnam were in the range of 0.69–2.75 mg l⁻¹. Speciation analyses done on the fish sauce samples showed that most of the arsenic present in the fish sauces were arsenobetaine (82–94%), arsenocholine (4.9–7.7%), trimethylarsine oxide (0.7–7.8%), and trimethylarsenopropionate (0.5–2.1%). Highly toxic arsenic compounds, such as arsenite, arsenate, methylarsonic acid (MA) and dimethylarsinic acid (DMA), were below the detection limit of 0.01 mg l⁻¹.     

Comprehensive analysis of umami compounds by ion-pair liquid chromatography coupled to mass spectrometry

An ion-pair LC-ESI-MS method was developed capable of analyzing various reported umami or umami-enhancing compounds, including glutamic acid and 5'-ribonucleotides. The method was validated using tomato and potato samples and showed overall good analytical performance with respect to selectivity, detection limit, linearity, and repeatability. The method was applied to various tomato samples resulting in concentrations of glutamic acid and 5'-ribonucleotides that were in good comparison with literature. The methodology might also be used for the discovery of new umami (enhancing) compounds in an untargeted mode. This was to a certain extent demonstrated for tomato samples by correlating all peaks observed with the ion-pair liquid chromatography-mass spectrometry (LC-MS) method to sensory properties using multivariate statistics. PRACTICAL APPLICATION: This study describes the development and application of a LC-MS method, which can be used to quantify several known umami (enhancing) compounds in various foods. Furthermore, the method might be useful for the discovery of new umami (enhancing) compounds.     

Analysis of volatile compounds of eucalyptus honey by solid phase extraction followed by gas chromatography coupled to mass spectrometry

Solid-phase extraction (SPE) followed by gas chromatography coupled to mass spectrometry has been used for the analysis of volatile compounds of eucalyptus honey. Different amounts of honey and dichloromethane were employed to optimize solid-phase extraction conditions. The best result was obtained with 20 g of honey eluted with 60 mL of dichloromethane. This method presented a good precision for volatile compounds usually found in honeys and allowed the quantification of 35 volatile compounds (terpenes and derivatives, furan and pyran compounds, ketones, benzene compounds, acids, and norisoprenoids) of eucalyptus honey.     

铜离子络合法测定HBP-NH2溶液含量及其应用

利用铜离子与端氨基超支化合物(HBP-NH2)的络合作用测定HBP-NH2溶液的浓度.试验表明,铜离子与HBP-NH2的络合物在637nm处的吸光度,与HBP-NH2溶液浓度在0.2～1.2g/L范围内,呈良好的线性关系(R=0.9999,n=6),相对标准偏差为1.5%～2.3%,回收率为97.69%～102.86%.应用该法测试棉织物表面HBP-NH2吸附量和接枝量,其测试结果与活性染料无盐染色后K/S值一致.     

毛细管电泳-电感耦合等离子体质谱（CE-ICP-MS）联用测定干海产品中的六种砷形态化合物

采用电感耦合等离子体质谱（ICP-MS）测定了鱿鱼、银鱼、沙丁鱼、虾、牡蛎、蛤蜊、紫菜、羊栖菜、海带、浒苔10种干海产品中的砷总量,建立了毛细管电泳（CE）与ICP-MS联用测定亚砷酸盐As（III）、砷酸盐As（V）、甲基砷酸（MMA）、二甲基砷酸（DMA）、砷甜菜碱（AsB）和砷胆碱（AsC）六种砷形态化合物的分析方法。结果发现除了浒苔其余干海产品中砷总量均超出了无机砷允许限值（GB 2762-2005）,形态分析结果表明干海产品中主要是有机砷,萃取液中无机砷含量仅占砷总量的0¹5.2%。该方法简单方便、快速,样品消耗量少,而且具有较好的准确性,适用于其他生物样品中砷形态化合物的分析。      

液液微萃取结合气相色谱-串联质谱测定饮料酒中挥发性酚类化合物

挥发性酚类化合物对饮料酒的风味具有重要影响,同时还具有一定的生理活性。将液液微萃取法与气相色谱-串联质谱联用技术相结合,建立饮料酒中挥发性酚类化合物的测定方法。将酒样稀释至体积分数为10%,再用乙酸乙酯对目标化合物进行萃取,采用气相色谱-串联质谱在动态多反应监测模式下测定挥发性酚类化合物。该方法可准确测定饮料酒中10种挥发性酚类化合物,且线性关系良好(r²≥0.998),检出限及定量限分别为1.0～10.0μg/L和3.5～35.0μg/L;在高、中、低3个浓度水平下的加标回收率为92.3%～100.7%,相对标准偏差为0.3%～3.7%,通过对比试验发现,该方法的准确度与重复性高于顶空固相微萃取-气相色谱质谱法。该方法具有准确、重复性好、有机溶剂用量少等优点,适用于测定不同类型饮料酒中挥发性酚类化合物,研究同时发现挥发性酚类化合物在不同类型饮料酒中的分布存在显著差异。     

电感耦合等离子体质谱法测定面粉中铝

建立了电感耦合等离子体测定面粉中铝含量的方法。样品经加酸微波消解赶酸后,用电感耦合等离子体质谱仪进行测定。标准曲线线性范围内线性相关性不小于0.999,最低检出限为0.03 mg/kg,加标回收率为87.2%~96.2%,精密度为0.43%~1.01%。本方法操作简单、灵敏度高、回收率好。     

高压液相色谱-等离子体质谱联用技术 测定水产品中的硼酸

目的 建立高效液相色谱-电感耦合等离子体质谱法(HPLC-ICP-MS)分析水产品中的硼酸含量。方法 采用超声提取法对水产品进行前处理,优化蛋白沉淀剂、提取时间和流动相等条件。结果 该方法对硼酸的检出限为0.015 mg/L,加标回收率为85.1%～112.1%,相对标准偏差(RSD)在6.0%～8.2%之间。结论 该方法测定水产品中的硼酸含量准确、可靠,满足外源性硼酸的检测。