固相萃取-高效液相色谱法同时测定啤酒中的4种异构化α-酸

建立了固相萃取-高效液相色谱同时测定啤酒中4种异构化α-酸的方法。采用Sep-Pak C18萃取柱,系统研究了啤酒中异构化α-酸的最佳固相萃取条件。选择以2 mL酸化甲醇为洗脱溶剂,萃取前调啤酒样品的pH至2.5。该方法准确可靠,重现性好,4种异构化α-酸的回收率为90.6%～96.4%,相对标准偏差小于4%。异α-酸、二氢异α-酸、四氢异α-酸和六氢异α-酸的最低检测限依次为0.14,0.36,0.33和0.53 mg/L。     

反相高效液相色谱法同时测定啤酒中的4种异构化α-酸

1引言啤酒的苦味主要来自于酒花制品形成的异α-酸,为进一步提高质量,一系列具有特殊功效且稳定性较高的还原异构化α-酸(二氢、四氢和六氢异α-酸)受到广泛应用。异构化α-酸多采用HPLC方法进行分析。有离子对和离子抑制分离模式。国外多采用前者,围绕着色谱柱选择、不同类型异构化α-酸的分离条件及样品处理等方面展开。由于结构相似,不同类型异α-酸的组分之间易重叠,难以定性。目前尚鲜见HPLC同时分离啤酒中4种异构化α-酸的相关报道。本实验采用离子抑制机理同时分离啤酒中的异α-酸、二氢、四氢和六氢异α-酸。本方法无需离子对试…     

反相高效液相色谱法(RP-HPLC)测定酒花浸膏中的异构化α-酸

建立了一种利用反相高效液相色谱法(RP-HPLC)测定酒花浸膏中4种异构化α-酸的方法。异α-酸、二氢异α-酸、四氢异α-酸和六氢异α-酸在色谱柱EC250/4 Nuclesoil,100-5 C18(4.0 mmi.d.×250 mm,5μm),保护柱CC 8/4Nuclesoil 100-5 C18,流动相为V(甲醇)∶V(水)∶V(85%H3PO4)∶V(0.2 mol/LEDTA二钠盐)=770∶210∶5∶1,等梯度洗脱,流速为1.2 mL/min,270 nm紫外检测,加标回收率在93.5%~97.0%之间,RSD<2%。该方法可测定酒花浸膏中异构化α-酸。     

RP-HPLC法同时测定酒花中α-酸、β-酸和异α-酸

建立了RP-HPLC法同时检测酒花中α-酸、β-酸和异α-酸的主要异构体的方法。色谱柱为:EC 250/4 Nucleosil 100-5 C18,保护柱:CC 8/4 Nucleosil 100-5 C18,流动相A:水溶液(H3PO4 0.1%,0.2 mmol/L EDTANa2);流动相B:乙腈。流速为1.0 mL/min,双波长检测UV270 nm和UV315 nm,柱温30℃,进样体积10μL。方法加标回收率在90.0%～105.0%之间。方法可将酒花中α-酸、β-酸6种主要异构体和异α-酸3种主要异构体共9种物质一次性分离。     

紫外分光光度法测定啤酒中α-酸的含量

采用紫外分光光度法测定了8种不同品牌啤酒中α-酸的含量。实验考察了不同有机溶剂、介质酸度对α-酸紫外吸收的影响。结果表明:α-酸在279nm处有较强的吸收,方法线性范围在10～50μg/mL,检出限2.6μg/mL,相对标准偏差2.01%。8种不同品牌啤酒中α-酸的含量(μg/mL)为:百威啤酒(392.07)蓝带啤酒(383.82)崂山啤酒(373.72)雪花啤酒(238.26)司陶特黑啤酒(99.49)燕京啤酒(55.16)青岛啤酒(54.91)哈尔滨啤酒(35.05),平均偏差小于5%。用标准加入法测定其回收率,样品回收率范围在93.81%～105.15%之间。     

啤酒花α-酸中顺反异共葎草酮的分离

啤酒花主要成分~([1])包括α-酸和β-酸,由于每种酸的酰基中饱和烃侧链不同,分别含有3种不同的异构体组分:律草酮(Humulone)、共葎草酮(Cohumulone)和近葎草酮(Adhumulone).在啤酒生产的发酵过程中,加入的α-酸发生异构化反应,经过分子内重排,形成两个系列的五元环化合物,trans-iso-α-酸,cis-iso-α-酸.     

超高效液相色谱-三重四极杆质谱法同时测定化妆品中13种α-羟基酸的含量

提出了超高效液相色谱-三重四极杆质谱法(UHPLC-MS/MS)同时测定化妆品中13种α-羟基酸含量的方法。样品0.2 g经水超声提取30 min(不易分散样品经异丙醇分散均匀后用水超声提取),提取液经离心过滤后采用UHPLC-MS/MS分析，13种目标物在Agilent Zorbax RRHD SB-Aq C₁₈色谱柱上分离，以不同体积比的0.1%(体积分数)甲酸溶液和乙腈混合液为流动相进行梯度洗脱，质谱分析采用电喷雾离子源，负离子、多反应监测模式采集。结果表明：13种α-羟基酸的质量浓度在一定范围内与对应的峰面积呈线性关系，羟基辛酸、二苯乙醇酸、α-羟基癸酸的检出限(3S/N)为0.030μg·g^-1,羟基乙酸、乳酸的检出限(3S/N)为3.0μg·g^-1,其余8种α-羟基酸的检出限均为0.30μg·g^-1。按照标准加入法进行回收试验，回收率为85.1%～114%,测定值的相对标准偏差(n=6)均小于10%。方法用于分析20批样品，α-羟基酸检出总量为20～6 800 mg/100 g,仅有1批...     

高效液相色谱法同时测定异α-酸与四氢异α-酸

1引言啤酒花深加工产品异α-酸与四氢异α-酸近年来已被全国各大啤酒厂广泛使用，但并无统一检测手段。文献报道的方法用乙腈和水作为流动相，单独测定四氢异α-酸。乙腈价格较高，用此方法进行产品质量控制成本高，本法采用甲醇代替乙腈，大大降低成本。分离效果好，并可同时测定异α-酸与四氢异α-酸。2实验部分2．1仪器与试剂P200Ⅱ型高压恒流泵，UV200Ⅱ型紫外可变波长检测器（大连伊力特科学仪器有限公司）。HepersilBDSC185μm柱（150×4.6mmi．d．）。甲醇，85％磷酸，四丁基羟胺10％水溶液，均为分析纯。水为双蒸水。2．2色谱条…     

直接提取-超高效液相色谱-串联质谱法测定玉米酸汤子中米酵菌酸和异米酵菌酸

建立了直接提取-超高效液相色谱-串联质谱法测定玉米酸汤子中的米酵菌酸和异米酵菌酸的方法。样品经体积分数为5%的乙酸-乙腈溶液直接提取、离心、过滤后,采用Waters UPLC CSH C18色谱柱（100 mm×2.1 mm,1.7μm）分离,以体积分数为0.1%的甲酸-2 mmol/L甲酸铵水溶液作为流动相A,乙腈作为流动相B进行梯度洗脱,在电喷雾离子源负离子模式,多反应监测模式下进行扫描检测,以色谱峰面积外标法定量。结果表明,米酵菌酸和异米酵菌酸几乎无明显基质效应,且分别在质量浓度为1～100μg/L、0.1～10μg/L范围内与色谱峰面积线性关系良好,相关系数均不小于0.998,方法检出限分别为0.5、0.1μg/kg,米酵菌酸和异米酵菌酸的样品加标回收率分别为84.96%～92.87%、89.81%～104.77%,测定结果的相对标准偏差均小于10%(n=6)。该方法简单快速、灵敏度高、准确度好,具有较高的重现性,可作为玉米酸汤子中米酵菌酸和异米酵菌酸的定量测定方法。     

高效液相色谱法测定啤酒花及其制品中的α-酸、β-酸和异α-酸

1引言a-酸、B-酸及异a-酸是啤酒苦味酸的主要成分，它们的分析是啤酒花及其制品质量评价及控制的主要内容，国内主要使用光度法和电导滴定法分析，这两种方法因存在许多问题而影响测定结果，因此，国外近年已逐渐用高效液相色谱法（HPIn）分析啤酒、啤酒花及各种啤酒花制品的a一酸、卢一酸及异o一酸。我们在研究啤酒花制品时需要同时分析a一酸、卢·酸及异a一酸，但是已有的HPIn法仅可以同时测定a·酸和公酸，而异a一酸是单独分析的，只有在梯度洗脱和较高的柱温时可以同时测定三者，这就限制了它的推广应用。本文建立了室温下同时测定它…     

Simultaneous determination of E-2-nonenal and beta-damascenone in beer by reversed-phase liquid chromatography with UV detection

A method for the simultaneous determination of E-2-nonenal and beta-damascenone in beer by reversed-phase liquid chromatography using UV detection is presented. The method consists of beer steam distillation, followed by an extraction/concentration step using Sep-Pak Plus C18 RP cartridges and determination by HPLC at 226 nm UV-absorption maximum. The identity of the compounds was confirmed by GC analysis with MS detection of the isolated fractions. A recovery factor of approximately 80% was obtained for beta-damascenone with a R.S.D. of 3%. E-2-Nonenal and beta-damascenone were monitored in a comparative study of fresh and either naturally and forced aged beer. The results obtained show that both compounds have a similar behaviour through an extended storage of beer and consequently can be used as good analytical markers of beer ageing. Nevertheless, the use of beta-damascenone seems to be more convenient because this compound appears in beer in higher concentrations than E-2-nonenal, thus making it easier to measure.     

离子色谱法同时分析啤酒中的有机酸和无机阴离子

建立了以NaOH-甲醇混合淋洗液,离子交换色谱柱,电导检测器检测,分离啤酒中有机酸和无机阴离子的离子色谱法.结果表明：在20 min内分离出啤酒中的11种主要有机酸与无机阴离子,方法回收率和相对标准偏差分别为96.30%～104.8%和0.02%～4.0%.     

Separation and quantification of beer carbohydrates by high-performance liquid chromatography with evaporative light scattering detection

An HPLC method with an evaporative light scattering detector was optimized and validated for quantification of carbohydrates in beer. The chromatographic separation was achieved using a Spherisorb NH2, 5 microm chromatographic column and gradient elution with acetonitrile/water. The determinations were performed in the linear range of 0.05-5.0 g/L for fructose, 0.05-5.0 g/L for glucose, 0.05-15.0 g/L for maltose, 0.05-10.0 g/L for maltotriose, and 0.05-5.0 g/L for maltotetraose. The detection limits were 0.005 g/L for fructose, 0.008 g/L for glucose, and 0.01 g/L for maltose, maltotriose, and maltotetraose. The reliability of the method in terms of precision and accuracy was evaluated in three beer matrices, low alcohol beer, 6% alcohol beer, and beer made with part of adjuncts (4.5% alcohol). Relative standard deviations (RSDs) ranged between 1.59 and 5.95% (n = 10), and recoveries ranged between 94 and 98.4%.     

Preparation of novel solid-phase microextraction fibers by sol-gel technology for headspace solid-phase microextraction-gas chromatographic analysis of aroma compounds in beer

3-(Trimethoxysilyl)propyl methacrylate (TMSPMA) was first used as precursor as well as selective stationary phase to prepare the sol-gel-derived TMSPMA-hydroxyl-terminated silicone oil (TMSPMA-OH-TSO) solid-phase mircroextraction (SPME) fibers for the analysis of aroma compounds in beer. TMSPMA-OH-TSO was a medium polarity coating, and was found to be very effective in carrying out simultaneous extraction of both polar alcohols and fatty acids and nonpolar esters in beer. The extraction temperature, extraction time, and ionic strength of the sample matrix were modified to allow for maximium sorption of the analytes onto the fiber. Desorption temperature and time were optimized to avoid the carryover effects. To check the matrix effects, several different matrices, including distilled water, 4% ethanol/water (v/v) solution, a concentrated synthetic beer, a "volatile-free" beer and a real beer were investigated. Matrix effects were compensated for by using 4-methyl-2-pentanol as internal standard and selecting the "volatile-free" beer as working standard. The method proposed in this study showed satisfactory linearity, precision and detection limits and accuracy. The established headspace SPME-gas chromatography (GC) method was then used for determination of volatile compounds in four beer varieties. The recoveries obtained ranged from 92.8 to 105.8%. The relative standard deviations (RSD, n = 5) for all analytes were below 10%. The major aroma contributing substances of each variety were identified via aroma indexes.     

Magnetic mixed hemimicelles solid-phase extraction of xanthohumol in beer coupled with high-performance liquid chromatography determination

In this study, silica-coated magnetic nanoparticles (Fe(3)O(4)/SiO(2) NPs) modified by cetyltrimethylammonium bromide (CTAB) were synthesized. They were successfully applied for extraction of xanthohumol in beer based on magnetic mixed hemimicelles solid-phase extraction (MMHSPE) coupled with high-performance liquid chromatography-ultraviolet determination. The main factors influencing the extraction efficiency including the surfactant amount, the beer pH, the extraction time, the desorption condition and the maximum extraction beer volume were optimized. Under the optimized conditions, a concentration factor of 60 was achieved by extracting 120 mL beer sample using MMHSPE and the detection limit of xanthohumol is 0.0006 mg/L. The proposed method was successfully applied for determination of xanthohumol in various beer samples with the xanthohumol contents in the range of 0.031-0.567 mg/L. The satisfactory recoveries (90-103%) were obtained in analyzing spiked beer samples.     

气相色谱-质谱法分析啤酒中酒花香气成分

利用顶空固相微萃取-气相色谱质谱技术(HS-SPME/GC-MS)建立了定量分析啤酒中19种源自酒花的微量香气成分的方法。研究了不同萃取头、萃取时间、萃取温度对萃取效果的影响,最终确定HS-SPME最佳萃取条件为采用PDMS萃取头对啤酒样品在50℃下萃取60 min。在最佳萃取条件下,采用啤酒为基体以减少基体干扰,建立标准曲线,随后在SIM模式下以萜品烯-4-醇为内标定量测定了啤酒中酒花香气物质的含量。19种物质的回收率在81.2%～116.8%之间,相对标准偏差(RSD)低于9.8%,在5个加标浓度下,R2大于0.99。相比于传统方法,本方法所需样品量少、灵敏度高、操作过程简便,能准确的检测出啤酒中酒花香气物质的含量。     

Spectrophotometric determination of tannins in tea and beer samples with iron(III) and 1,10-phenanthroline as reagents

A simple and accurate spectrophotometric method is proposed for the determination of tannins in tea and beer samples based on the reduction of iron(III) to iron(II) by tannins at 80 degrees C for 20 min. The iron(II) was then reacted with 1,10-phenanthroline at pH 4.4 to form a coloured complex. Background correction could be effected by precipitating the tannins in the sample solution twice with gelatin and kaolin. Absorbance measurements were made at 540 nm and the calibration graph was linear from 0 to 5.5 micrograms ml-1 of tannic acid with a slope of 0.213 A p.p.m.-1. The precision for the determination of tannins in a tea sample containing 9.45% of tannins was 1.8%. Most of the ingredients commonly found in tea and beer samples do not interfere with the determination. Several tea and beer samples were analysed for their tannin content using the proposed method.     

Direct determination of the estrogenic compounds 8-prenylnaringenin, zearalenone, alpha- and beta-zearalenol in beer by liquid chromatography-mass spectrometry

A novel LC-ESI-MS method for the simultaneous determination of four of the most significant estrogenic compounds naturally occurring in beer, 8-prenylnaringenin (8-PN), zearalenone (ZON), alpha-zearalenol (alpha-ZOL) and beta-zearalenol (beta-ZOL) which requires minimal sample preparation was developed using a chemometric approach. Experimental design was applied to assess the effects of the LC-ESI-MS parameters (mobile phase flow rate, drying gas flow, nebuliser pressure and capillary potential) on the obtained signal and to optimize the values in order to provide maximum sensitivity and detectability. The proposed method is simple, consisting only of degassing the beer and diluting with water (1:1, v/v) before injection. Comparison between the two internal standards used, zearalanone (ZAN) and 4,2'-dihydroxychalcone (4,2'-DHC), showed that ZAN performs better as internal standard not only for the mycotoxins but for 8-PN as well, giving lower % RSDs. Under inter-day conditions mean recoveries were 107% for ZON, 87.8% for alpha-ZOL, 72.8% for beta-ZOL, and 77.5% for 8-PN. The corresponding % RSDs ranged between 5.0 and 8.0. The method limits of detection were 1.3, 1.4, 1.0 and 0.8 ng mL(-1) for ZON, alpha-ZOL, beta-ZOL and 8-PN, respectively. The method was applied to 15 beer samples obtained from local supermarkets and the concentration of the phytoestrogen 8-PN in beer ranged between <0.8 and 38.6 ng mL(-1), while neither ZON nor its metabolites, alpha-ZOL and beta-ZOL, were detected.     

Determination of ochratoxin A in beer marketed in Spain by liquid chromatography with fluorescence detection using lead hydroxyacetate as a clean-up agent

A new sample treatment for liquid chromatographic analysis of ochratoxin A (OTA) in beer is proposed. Degassed beer is mixed with lead hydroxyacetate, which precipitates some bulk components but does not remove OTA. The precipitate is separated and the acidified liquid is extracted with chloroform. The solvent is evaporated and the residue is dissolved in mobile phase (acetonitrile-water, 40:60, v/v; acidified at pH 3.0 with phosphoric acid) and separated by liquid chromatography using fluorescence detection. The limit of detection was 0.005 ng/ml. The average recovery rate and the average RSD of recovery in the spiking level range 0.01-0.5 ng/ml were 95.5% and about 5%, respectively. The method is cheaper that other alternative ones using immunoaffinity columns or other solid-phase extraction cleanup:The separation was optimised with regard to composition and flow of the mobile phase and no interference from the matrix was found. The method was applied to 88 samples of beer (domestic and imported) marketed in Spain. OTA was detected in 82.9% of them. The range for positive samples was 0.007-0.204 ng of OTA/ml.