苯胺柱前衍生麦芽糊精的高效液相色谱-电喷雾质谱分析

研究苯胺柱前衍生寡糖混合物麦芽糊精的高效液相色谱-电喷雾质谱分析方法。优化色谱及质谱分析的条件,采用反相C18色谱柱(4.6mm×250mm,5μm);乙腈和乙酸铵溶液(pH4.5、10mmol/L)为流动相进行梯度洗脱;在239nm波长处检测,并采用高效液相色谱-电喷雾质谱联用技术对寡糖衍生物进行分析,建立苯胺衍生寡糖的高效液相色谱(HPLC)分离分析、电喷雾质谱(ESI-MS)及液相色谱-电喷雾质谱联用(LC-ESI-MS)组分分析方法。在液质联用条件下,麦芽糊精衍生物分离效果良好。该方法衍生化产物稳定,后处理简单,在食品体系寡糖混合物分离分析方面有潜在的应用前景。     

高效液相色谱—串联质谱法快速测定胶原蛋白粉中呋喃类代谢物

目的简化测定胶原蛋白粉中呋喃类代谢物残留的实验过程,缩短实验的检测时间。方法在GB/T21311-2007的基础上,对其进行方法改进,建立高效液相色谱-串联质谱法(HPLC-MS/MS)测定胶原蛋白粉中呋喃西林(SEM)、呋喃妥因(AHD)、呋喃唑酮(AOZ)、呋喃它酮(AMOZ)等4种呋喃代谢物的快速检测方法。采用55℃衍生化,对衍生品按照离心、调p H值、离心的步骤进行处理,使得调节p H值更容易,同时避免传统试验方法中使用分液漏斗时样品乳化成胶状体而不能达到液液分离的目的的现象。结果实验结果表明,本方法与《GB/T21311-2007动物源性食品中硝基呋喃类药物代谢物残留量检测方法高效液相色谱串联质谱法》相比,结果并无很大的差异,但是大大缩短了实验的检测时间、简化了实验过程。结论本实验方法更加适合大批量样品的试验检测。     

高效液相色谱法测定奶粉中卵磷脂的质量分数

建立了奶粉中卵磷脂(PC)的高效液相色谱-蒸发光散射检测的测定方法,奶粉经去蛋白-液液萃取-富集浓缩超滤后进高效液相色谱仪,采用硅胶色谱柱,正己烷-异丙醇-水(体积比31∶62︰7)流动相体系,等度洗脱能够快速有效地分离奶粉中的卵磷脂。线性范围为0.020～1.60 g/L,相关系数为0.9996,检出限为15 mg/L,加标回收率为95.2%～96.8%。该方法用于实际样品的测定,结果令人满意。     

高效液相色谱测定烟用香精及料液中保润剂方法的改进

用高效液相色谱建立了一种便捷、可靠、清洁环保的分析烟用香精及料液中的主要保润剂的方法.样品用超纯水溶解提取,在Varian Metacarb 67C色谱柱上以超纯水作为流动相等梯度洗脱对山梨醇、1,2-丙二醇和丙三醇进行色谱分离.山梨醇、1,2-丙二醇和丙三醇的检测限(S/N=3)和定量限(S/N=10)分别为0.30...     

超高效液相色谱串联质谱法快速测定乳及乳制品中三聚氰胺

建立快速、经济测定乳及乳制品中三聚氰胺的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法。乳及乳制品样品中加入乙腈-水溶液,通过超声波提取和二氯甲烷液液萃取除去蛋白质、脂肪等杂质,进一步稀释后直接进样。经超高效液相色谱(UPLC)快速分离,采用电喷雾正离子(ESI+)多反应监测模式(MRM),实现对三聚氰胺的定性和外标法定量。乳及乳制品样品在1.2 min内完成分析,且具有良好的线性关系(r=0.999 1);方法检出限和定量限(LOQ)分别为0.005 mg/kg、0.017 mg/kg;在0.5～100μg/L的基质添加浓度范围内,平均回收率为91.3%～97.1%,相对标准偏差(RSD)小于9.03%。     

QuEChERS前处理结合高效液相色谱法及高效液相色谱-串联质谱法检测葡萄酒中3种赭曲霉毒素

目的建立QuEChERS净化技术结合高效液相色谱法及高效液相色谱-串联质谱法检测葡萄酒中赭曲霉毒素A(OTA)、赭曲霉毒素B(OTB)和赭曲霉毒素C(OTC)3种赭曲霉毒素的方法。方法对QuEChERS净化条件和高效液相色谱及高效液相色谱-串联质谱检测条件进行优化,葡萄酒样品先用乙腈-冰乙酸(90∶10,V/V)进行酸化稀释,离心后取上清液经C_(18)+SiO_2+MgSO_4净化剂组合净化过滤,待测样液经液相色谱C_(18)柱(4.6 mm×250 mm,5μm)梯度洗脱分离后,分别采用荧光检测器和串联质谱电喷雾技术,在多反应监测(MRM)模式下,实现同时对葡萄酒中OTA、OTB和OTC三种赭曲霉毒素的定性和定量分析。结果方法最低定量限(LOQ)均为2.0μg/kg,相对标准偏差(RSD)为2.01%～7.52%(n=6)。结论该方法操作方便、灵敏度高、重现性好,适用于日常监管工作中对葡萄酒中赭曲霉毒素的检测。     

GPC-UPLC-MS/MS法测定食用油中壬基酚和双酚A

建立食用油中壬基酚和双酚A的凝胶渗透色谱(GPC)-超高效液相色谱-质谱联用(UPLC-MS/MS)分析检测方法。食用油样品经乙酸乙酯-环己烷溶解,GPC净化后,采用超高效液相色谱-串联质谱法分析测定。仪器使用WATERS ACQUITY UPLC BEH C18色谱柱,以甲醇-0.1%氨水为流动相,梯度洗脱分离后,串联四极杆质谱多反应监测方式检测,采用内标法定量。分析结果表明,目标物检出限为1.0μg/kg,在1.0μg/kg~5.0×10~2μg/kg的范围内呈良好的线性关系(R~20.99),试验中平均添加回收率85.1%~112.5%,相对标准偏差2.57%~6.08%。     

超高效液相色谱-串联质谱法测定猪肉中肾上腺素残留量

建立了猪肉中肾上腺素残留量的超高效液相色谱-串联质谱(UPLC-MS/MS)的检测方法。样品经乙腈+甲醇(95+5)提取,C_(18)色谱柱分离,超高效液相色谱-串联质谱仪检测。本方法定量限为10μg/kg,线性范围为5～500ng/mL。样品加标回收率为75%～98%,相对标准偏差为4.8%～7.9%,方法简便快速、灵敏度高,为猪肉中肾上腺素残留量测定提供了新的方法。     

超高效液相色谱-串联质谱法测定茶叶中的百草枯

文章建立了一种利用超高效液相色谱-串联质谱法测定茶叶中百苹枯含量的方法.茶叶样品使用甲醇-0.1 mol/L盐酸溶液(3:7,V/V)提取,经Poly-sery MCX柱净化后用超高效液相液相色谱-串联质谱进行测定.在5～100μg/L浓度范围内,百草枯的线性良好(R2=0.9991),方法定量限为0.01 mg/kg...     

高效液相色谱-质谱法测定聚碳酸酯水杯中双酚A迁移量

目的 建立高效液相色谱-质谱法(high performance liquid chromatography-mass spectrometry, HPLC-MS)测定聚碳酸酯(polycarbonate, PC)水杯中双酚A迁移量的方法。方法 选用水、4%乙酸溶液、10%乙醇和异辛烷溶液作为食品模拟液, 准确量取迁移试验中得到的食品模拟液1 mL, 通过0.22 μm微孔滤膜后, 用高效液相色谱-质谱联用仪对双酚A进行分离测定。结果 该方法相对标准偏差不大于3.24%(n=6), 回收率在87.7%~105.0%之间; 检出限为 1 μg/L。结论 该方法样品前处理方法简便, 检出限高, 操作简单, 线性关系好, 适合于PC水杯及不同塑料制品中迁移双酚A的检测分析。     

采用高效液相色谱法鉴别啤酒中异构化α-酸的种类

采用高效液相色谱法(HPLC)分析异构化α-酸,给出同一色谱条件下异α-酸、二氢、四氢和六氢异α-酸的HPLC谱图和各组分的紫外光谱。用该方法分析未知啤酒样品,将其与标准品进行对照,从而鉴别出样品中异构化α-酸的种类。     

ESTIMATION OF α-, β- AND ISO-α-ACIDS IN HOPS,HOP PRODUCTS AND BEER USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

Methods are described in which high performance liquid chromatography (HPLC) is used to estimate α-, β- and iso-α-acids in hops, hop products and beer. The chromatography relies on an isocratic elution of components from a polythene ‘cartridge’ column, and the method is calibrated with the pure substances as primary standards. Using such a column over 1000 analyses have been carried out without any significant loss in resolution or precision. The procedures are sufficiently rapid for use in commercial transactions and for quality control purposes. For hops and hop extracts coefficients of variation (%) of 2·5 and 0·8 were obtained respectively for α-acids. Values of 0·9 and 0·3 were obtained for iso-α-acids in isomerised extracts and beers respectively. For some isomerised extracts it has been observed that peaks in addition to those given by the iso-α-acids are present on the chromatogram. The current method recommended by the EBC over estimates the iso-α-acid content since these other constituents are included in the analysis.     

The impact of different hop compounds on the growth of selected beer spoilage bacteria in beer

Beer spoiling lactic acid bacteria are a major reason for quality complaints in breweries around the world. Spoilage by a variety of these bacteria can result in haze, sediment, slime, off-flavours and acidity. As these bacteria occur frequently in the brewing environment, using certain hop products that inhibit the growth of these spoilers could be a solution to prevent problems. To investigate the impact of seven different hop compounds (α-acids, iso-α-acids, tetrahydro-iso-α-acids, rho-iso-α-acids, xanthohumol, iso-xanthohumol and humulinones) on the growth of six major beer spoilage bacteria (Lactobacillus brevis. L. backi, L. coryniformis, L. lindneri, L. buchneri, Pediococcus damnosous), two concentrations (10 and 25 mg/L) of each hop substance were added to unhopped beer. The potential growth of the spoilage bacteria was investigated over 56 consecutive days. A comparison of the results shows a strong inhibition of growth of all spoilage bacteria at 25 mg/L of tetrahydro-iso-α-acids closely followed by α-acids as the second most inhibitory substance. The results showed a high resistance of L. brevis to all hop compounds as well as an inhibition of L. coryniformis and L. buchneri at low concentrations of most hop components. In comparison with the control sample, L. lindneri showed increased growth in the presence of some hop compounds (rho-iso-α-acids, xanthohumol, iso-xanthohumol, humulinones). © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling     

HOP RESIN ANALYSIS BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY ON MICROPARTICULATE SILICA

A high-performance liquid chromatographic separation of hop resins on a commercially available microparticulate silica has been developed. The chromatography involves a new mechanism in hop resin separation. A solvent containing di-n-butylammonium acetate is used. The method gives good separation of α-acid, iso-α-acid, β-acid and humulinic acid, and has been used for the quantitative analysis of α-acid and iso-α-acid in hop extracts and isomerised hop extracts.     

CHROMATOGRAPHIC STUDY OF THE INFLUENCE OF LINOLEIC ACID AND ISO-α-ACIDS IN THE FORMATION OF CARBONYLS IN BEER

The influence of the concentration of linoleic acid, iso-α-acids and metabisulphite in the formation of volatile carbonyls in beer has been studied. The ageing of the beer is effected by means of a 1.5 hour reflux at pH=2 and the carbonyl compounds are determined by high pressure (HPLC) liquid chromatography of the corresponding 2.4 dinitrophenylhydrazones (DNPS). It has been shown that carbonyls with more than 5 carbon atoms mainly come from the autoxidation of linoleic acid. The inhibiting action of metabisulphite has also been confirmed     

异构酒花浸膏中异α-酸氢化工艺优化

采用单因素筛选试验考察了氢化温度、pH值、氢气压力、氢化时间、催化剂用量、浸膏中异α-酸浓度对异α-酸氢化的影响。再利用Plackett-Burman设计研究了各因素对异α-酸氢化的影响。结果表明,底物异α-酸浓度、氢气压力和pH对异α-酸酒花浸膏氢化效果影响显著;在此基础上,采用L9(34)正交设计法对影响异α-酸酒花浸膏氢化的3个主要因素异α-酸浓度、氢气压力、pH进行了参数优化试验。结果表明,影响异α-酸酒花浸膏氢化的主次因素顺序为异α-酸浓度>氢气压力>pH值,异α-酸氢化的最佳工艺参数为:异α-酸的浓度55mg/mL,氢气压力0.2 MPa,pH值10,催化剂Pb/C用量3%,氢化时间4h。浸膏中四氢异α-酸的浓度达到58.89%,异α-酸氢化转化率达到89.73%。     

OXIDATION PRODUCTS OF ISOHUMULONES

A complex mixture of oxidation products is formed from iso-α-acids during wort boiling. These substances are already present in hops and persist to beer. Seven major constituents of such a mixture, obtained from pure humulone, were isolated by countercurrent distribution and their structures were elucidated, mainly by mass spectroscopy. The bitterness of the new beer substances was evaluated against trans isohumulone as a reference standard. These oxidation products of iso-α-acids are not extracted with iso-octane and they therefore escape the usual beer bitterness assay.     

Analysis of hop acids by capillary electrophoresis

Micellar electrokinetic chromatography (MEKC) was used to separate components of hop extracts. The separation of a sample of iso-α-acids by MEKC was better and faster than by an established HPLC method, giving <0.8% RSD on migration times and 5–10% RSD on peak areas. MEKC was also successfully used to separate the oxidation products of the α- and β-acids and thus to monitor the stability of hop products containing them. Furthermore, MEKC distinguished among samples of reduced iso-α-acids (rho-, tetrahydro- and hexahydro- derivatives).     

Hop bitter acids inhibit carbohydrate metabolism,enhance biogenic amine metabolism and alter L-malic acid,glutamic acid and arginine metabolism of Lactobacillus brevis 49

Beer contains only limited amounts of readily fermentable carbohydrates and amino acids. Beer spoilage lactic acid bacteria have to come up with metabolic strategies in order to deal with selective nutrient content. The research was performed to investigate the influence of iso-α-acids on the metabolism of organic acids, biogenic amines (BAs), off-flavour compounds, carbohydrates and amino acids of Lactobacillus brevis 49. Only glyoxylic acid and ethyl formate in de man, rogosa, sharpe broth was consumed, and multiple organic acids, BAs and off-flavour compounds were produced. By supplementing a series of concentrations of hop iso-α-acids, consumption of L-malic acid, glutamic acid and arginine and generation of BAs were found benefit for bacteria to develop hop-resistance. In the metabolism of carbohydrates, glucose was preferred over maltose and maltriose, and hops significantly inhibited the utilisation of carbohydrates. The results provide comprehensive information of metabolites of L. brevis 49 under various concentrations of hop stress.     

Detection of selected stimulants as contaminants in solid nutritional supplements by liquid chromatography–mass spectrometry

Nutritional supplements are frequently used by athletes and can contain substances banned by the World Anti Doping Agency (WADA). The aim of this study was to develop a screening method for the detection of selected stimulants in solid nutritional supplements. Analysis of the samples was performed on an LCQ-Deca^® instrument after an acidic wash with n-pentane and an alkaline liquid/liquid extraction with diethylether. The mass spectrometer was operated in full scan MS² using positive ionisation. Detection limits (LODs) were equal or below 50 ng/g for all compounds except strychnine (100 ng/g). The suitability of the method for routine application was illustrated by the analysis of two suspicious samples.