超声萃取- 气相色谱法测定扇贝中30 种脂肪酸

研究扇贝中脂肪酸测定的前处理技术,建立扇贝中30种脂肪酸(包括饱和脂肪酸、不饱和脂肪酸)的同时测定分析方法。样品经冷冻干燥、超声提取、硫酸-甲醇法甲脂化后,采用气相色谱分析,内标法定量测定扇贝中脂肪酸的含量。正交试验显示,脂肪酸的最佳提取工艺为：溶剂比例为甲醇-二氯甲烷溶液(1:3,V/V)、料液比1:140(mg/mL)、提取3次、每次15min,其中提取次数与溶剂比例对结果影响显著(P＜0.05)。30种不同的脂肪酸在5.0～80.0μg/mL范围内,线性良好,相关系数均大于0.999;不同水平下的加标回收率分别为84%～91%、86%～99%;相对标准偏差(n＝5)分别为1.3%～3.5%、0.9%～3.1%;方法的检出限(RSN＝ 3)为1.94～2.57mg/kg。该方法操作简便、迅速、灵敏、准确度高,可满足扇贝以及类似性质的生物体脂肪酸的检测需要。     

油菜蜂花粉酚类化合物的初步分离和抗氧化性研究

采用甲醇提取油菜蜂花粉,提取物再经正丁醇萃取后,用聚酰胺层析得到各分离组分,并对各分离组分进行抗氧化性指标测定,并进行TLC、HPLC 分析。结果表明：甲醇提取物酚类化合物含量为3.69%,正丁醇萃取物为6.32%,聚酰胺层析中80% 和100% 乙醇洗脱组分酚类化合物含量分别为15.92% 和16.87%。同时,测定蜂花粉中各分离组分在浓度为1mg/ml 时的还原力和DPPH·清除率,甲醇提取物还原力为26μgVC/mg,正丁醇萃取物为84μgVC/mg,80%和100%乙醇洗脱组分提高到154μgVC/mg 和104μgVC/mg;甲醇提取物DPPH·清除率为83.45%,正丁醇萃取物为88.66%,聚酰胺层析中80% 和100% 乙醇洗脱组分DPPH·清除率分别为97.20% 和94.34%。实验表明：蜂花粉经过甲醇提取、正丁醇萃取和聚酰胺层析后,80% 乙醇和100% 乙醇分离组分酚类化合物含量和抗氧化活性均显著性提高。     

婴幼儿配方食品和乳粉中核苷酸的测定方法

采用碱性磷酸酶先将样品中的核苷酸酶解为核苷,然后用高效液相色谱法测定婴幼儿配方食品和乳粉中核苷酸总量。试样经水提取,通过调pH值沉淀蛋白质,样液中的核苷酸经碱性磷酸酶水解生成核苷,再通过快速加热的方式终止酶解反应,同时进一步去除杂质,用磷酸二氢钾及甲醇作流动相,用普通C18色谱柱,采用梯度洗脱的模式对5种核苷进行有效分离。本方法回收率在92.4%～103.7%之间,相对标准差2.0%～8.0%。核苷酸各组分定量限:CMP为0.6 mg/100g,UMP为0.7 mg/100g,IMP+AMP为0.5 mg/100 g,GMP为0.4 mg/100 g(均为质量分数)。该方法简便、快速、准确,完全能满足婴幼儿配方食品中核苷酸总量测定的要求。为核苷酸检测开辟了全新的途径。     

棉籽油脂肪酸甲酯化的方法及其脂肪酸含量分析

以新陆早39号以及新陆早50号的棉籽为材料,利用索氏提取仪提取其总油脂,分别采用三种常用的脂肪酸甲酯化方法:KOH-甲醇法,H₂SO₄-甲醇,14% BF₃-甲醇法进行甲酯化后,GC-MS上机分析;通过37种脂肪酸甲酯混标制定标准曲线,用外标法进行定量。结果表明:KOH-甲醇法甲酯化的脂肪酸GC-MS上机分析能检测到10种脂肪酸组分;H₂SO₄-甲醇与14% BF₃-甲醇法只能检测到6种。用KOH-甲醇法甲酯化后GC-MS测定表明,棉籽油脂肪酸以多不饱和脂肪酸的亚油酸为主,其次是饱和脂肪酸的棕榈酸以及单不饱和脂肪酸的油酸。在新陆早39号以及新陆早50号中,每克棉籽中亚油酸的含量分别达147.29 mg与163.2 mg,分别占其油脂含量的60.12%与60.83%;棕榈酸含量分别为65.05 mg与62.28 mg,分别占其油脂含量的26.55%与23.24%。油酸含量分别为24.79 mg与22.19 mg,分别占其油脂含量的10.12%和8.28%。结论:三种常用的脂肪酸甲酯化方法中,KOH-甲醇法更方便,快速,检测种类多,适用于棉籽脂肪酸的甲酯化。     

高效液相色谱法测定食品中的辣椒素、二氢辣椒素

采用高效液相色谱法测定食品中的辣椒素、二氢辣椒素.超声波辅助甲醇-四氢呋喃(1 1)提取样品中的辣椒素、二氢辣椒素,荧光检测器对其进行检测(Ex=229nm、Em=320nm).结果表明,辣椒素含量在0.13～160mg/L之间,二氢辣椒素含量在0.04～160mg/L之间;峰面积与待测物浓度呈良好的线性关系,相关系数为1;RSD为1.36%～4.79%,回收率在70.50%～100.07%之间.     

大豆脂肪酸含量的快速测定

建立了一步提取测定大豆中脂肪酸的检测方法。金属钠与甲醇反应得到的甲醇-钠试剂,使试样中的脂肪和游离脂肪酸甲酯化,用正己烷提取后,氢火焰离子化检测器检测,保留时间定性,面积归一化法测定脂肪酸相对百分含量。该方法测定脂肪酸取样量少,操作方便、快速,百分含量相对标准偏差RSD0.68%~2.68%,可满足大豆中脂肪酸测定的要求。     

芝麻油中芝麻素、芝麻林素和细辛素检测方法优化

采用有机溶剂甲醇提取、HPLC同时分析芝麻油中芝麻素、芝麻林素和细辛素含量。为提高分析质量与准确性,优化甲醇提取溶剂用量和超声辅助提取的时间,并对检测方法进行方法学考察。结果表明：最佳提取条件为甲醇用量10 mL（芝麻油0.1 g）,超声时间2 min;芝麻素、芝麻林素和细辛素线性范围分别为4～100 mg/L、4～100 mg/L和1～40 mg/L,线性关系良好,相关系数分别为0999 5、0.999 6和0.999 2;芝麻素、芝麻林素和细辛素的检出限分别为0.03、0.02 mg/g和0.02 mg/g,定量限分别为0.06、0.06 mg/g和0.04 mg/g,加标回收率分别为87.17%～92.59%、9271%～102.24%和95.66%～108.93%,加标回收率的相对标准偏差均小于5%,方法的稳定性、准确性和精密度均符合检测要求。该方法操作简单、耗时短(完成一次分析只需30 min)、成本低、稳定性高,能有效应用于芝麻油中3种木脂素组分的分析检测。     

高效液相色谱- 串联质谱法测定猪肉中10 种类固醇类激素残留

建立猪肉中类固醇类激素残留高效液相色谱- 串联质谱(LC-MS/MS)分析方法。样品经甲醇提取,固相萃取柱净化后采用LC-MS/MS 进行检测分析;并对样品前处理条件和质谱参数进行研究。结果表明：这些激素物质的线性范围均为0.5～100μg/kg;低、中、高3 种加标水平的加标回收率为71%～89%;最低检出限为0.2～2μg/kg。本方法快速简便、灵敏度高、选择性好、测定结果令人满意,可在各食品检测机构推广应用。     

液质法测定猪肉中八种糖皮质激素残留

建立猪肉中糖皮质激素多残留的液相色谱串联质谱(LC-MS/MS)分析方法。样品经甲醇提取,固相萃取柱净化后采用LC-MS/MS 进行检测分析。对样品前处理条件和质谱参数进行研究,这些激素的物质的线性范围均为0.5～100μg/kg。低、中、高3 种质量浓度加标回收率均为78%～101%;最低检出限为0.2～2μg/kg。该方法快速简便,灵敏度高,选择性好,测定结果令人满意,可在各食品检测机构推广应用。     

火焰光度检测器-气相色谱法测定食品中3-乙酰基-2,5-二甲基噻吩的含量

目的建立火焰光度检测器-气相色谱法检测食品中3-乙酰基-2,5-二甲基噻吩(3-acetyl-2,5-dimethylthiophene,ADP)的分析方法。方法含油脂食品经甲醇提取后冷冻过滤、不含油脂食品经正己烷提取后离心,以气相色谱仪-火焰光度检测器为检测手段,外标法定量。结果 ADP在0.005～1.000μg/mL浓度范围内二次曲线线性良好,相关系数为0.9999;ADP在不同基质中的检出限均可达到0.015 mg/kg,定量限达到0.05 mg/kg;在不同基质及不同加标浓度下,平均加标回收率为86.3%～108.7%,相对标准偏差(relative standard deviations,RSDs)为4.50%～6.97%(n=6)。结论该方法前处理操作简便、技术难度低,准确度和灵敏度高,抗干扰能力强,适用于定量准确并快速地测定食品中ADP的含量。     

Exclusive quantification of methyl-branched fatty acids and minor 18:1-isomers in foodstuff by GC/MS in the SIM mode using 10,11-dichloroundecanoic acid and fatty acid ethyl esters as internal standards

Minor fatty acids (iso- and anteiso-fatty acids, vaccenic acid, elaidic acid) in foodstuff (seafood, milk, and dairy products) were analyzed by gas chromatography with electron ionisation mass spectrometry in the selected ion monitoring mode (GC/EI-MS-SIM). For this purpose, lipids were obtained by accelerated solvent extraction (ASE) and the fatty acid constituents were converted into methyl esters. Instead of the determination of the relative contribution of the minor fatty acids to the sum of all fatty acids detected (the so-called 100% method), we exclusively quantified the minor fatty acids, which was possible by using two types of internal standards (IS-1 and IS-2). For recovery checks during the extraction and/or the transesterification step we added the novel 10,11-dichloroundecanoic acid (DC-11:0) as IS-1. DC-11:0, which has never been detected in foodstuff, was synthesized by electrophilic addition of chlorine to 10-undecenoic acid (11:1n-10). The novel IS eluted in the range of 23:0 from the polar GC column used and showed the same properties as fatty acids in foodstuff during sample preparation. Recovery rate of DC-11:0 was generally >96% in the various samples analyzed. Ethyl esters (FAEE) of a12:0, a14:0, a15:0, a16:0, a17:0, and a18:0 (IS-2) were added to both the external standard (a quantitative mixture of methyl esters of methyl-branched fatty acids and 18:1n-9trans) in order to determine their response factors relative to FAEE and to the food samples. With this technique, (only) methyl-branched fatty acids (MBFAs) as well as vaccenic acid (18:1n-7) and elaidic acid (18:1n-9trans) were quantified in a range of dairy products (including twelve cheeses) and seafood. All samples were analyzed in triplicates, and good standard deviations (concentrations 0.002–5 g/100 g; standard deviations 0.00–0.03) were obtained in all cases. MBFAs were detected in all samples analyzed. The highest content of MBFAs (3.0 g/100 g) was determined in red-smear of romadur cheese. In all except two cheeses, i17:0 was the most abundant MBFA. The highest amount of 18:1n-9trans was found in feta (2.84 g/100 g) whereas 0.03 g/100 g in big eye snapper (Pricanthus tayenus) marked the lowest record of this minor fatty acid. Seal oil contained the highest amount of 18:1n-7 with 5.00 g/100 g, whereas emmental cheese was the sample with the lowest content of this monoenoic fatty acid. The combination of suitable IS and a sensitive GC/EI-MS-SIM method proved to be well suited for the quantification of minor fatty acids in foodstuff. When only a set of fatty acids is going to be analyzed, this method is less time consuming compared to “100% methods” and less prone to false results due to the higher selectivity of GC/MS compared to GC in combination with flame ionisation detection (GC/FID).     

白果油的提取及脂肪酸组成分析

以白果为原料,用索氏提取和超临界萃取(SFE)两种方法从中提油,比较了不同提取方法对油得率的影响,测定了索氏提取油的理化特性,用气相色谱法和高效液相色谱法分别测定两种方法提取油的脂肪酸组成和VE的含量。结果表明,与常规植物油脂理化指标相比,白果油比重偏高,碘值较大,说明白果油不饱和程度较高;气相色谱分析结果表明两种方法提取的白果油中均含有多种不饱和脂肪酸,且不饱和脂肪酸含量均大于91%,而其中亚油酸和油酸的总含量均大于75%,索氏提取和超临界萃取的油中VE的含量分别为670 mg/kg和610 mg/kg。     

气相色谱法测定食品中反式脂肪酸的研究进展

气相色谱法(GC)是测定食品中反式脂肪酸(TFAs)的常用方法,该方法灵敏度高、准确度好。然而,由于来源于反刍动物的天然TFAs(n-TFAs)与部分氢化油的工业TFAs(IP-TFAs)的组成不同,以及不同食品中不饱和脂肪酸的组成差异,无法利用一种固定操作程序完全分离并准确分析各类食品中的TFAs组成。本文通过分析食品中TFAs的来源与组成,系统综述了GC法分析TFAs的原理和操作步骤,包括样品前处理方法、甲酯化衍生方法、Ag+预分离法,色谱条件(如色谱柱、柱长、柱温、进样口温度和检测器温度等)的选择和优化,以及常见的定性、定量分析方法。同时介绍了目前国内外标准方法的适用范围和特点,以便帮助分析人员依据实际样品以及所在实验室条件选择适合的分析方法。     

两种不同酯化方法分析荞麦中脂肪酸成分

采用索氏提取法对荞麦油进行了提取,分别采用两种方法进行甲酯化处理,以气相色谱-质谱联用仪进行了分析,对脂肪酸组成和含量进行了比较。结果表明:两种酯化方法分别鉴定出8种脂肪酸,占荞麦油总量的98.64%和99.97%;方法1鉴定出的主要脂肪酸为:棕榈酸占脂肪酸总量的15.92%,亚油酸占脂肪酸总量的30.37%,油酸占脂肪酸总量的35.32%;方法2鉴定出的棕榈酸占脂肪酸总量的35.66%,亚油酸占脂肪酸总量的11.75%,油酸占脂肪酸总量的33.26%。     

Use of focused open vessel microwave-assisted extraction as prelude for the determination of the fatty acid profile of fish – a comparison with results obtained after liquid-liquid extraction according to Bligh and Dyer

 A method based on microwave-assisted extraction (MAE) was developed to extract lipids from fish for the determination of the fatty acid composition. Microwave-assisted extraction was performed with an open-vessel extraction apparatus similar to the system of Soxhlet. The solvent was an equivolume mixture of ethyl acetate and cyclohexane. The solvent forms a ternary azeotrope with water, and water is separated after re-condensation in a water trap. With this technique, extraction can be performed without pre-drying of fish tissues. After lipid extraction, the esterification was performed with trimethylsulfonium hydroxide (TMSH) and the fatty acid methyl esters (FAMEs) were determined by GC/FID. The results were compared with those obtained after liquid-liquid extraction according to Bligh and Dyer. Fillets of mackerel (Scomber scombrus) and livers of cod (Gadus morhua) were used as the sample material. The water content (n=7) of the cod livers was 36.2±1.6% and that of mackerel fillets was 74.5±0.5%. The lipid contents (n=5) using the MAE method were 5.6±0.4% and 62.6±3.1% in mackerel and cod liver, respectively. Relative levels of 58 fatty acids (two co-eluted) were determined with GC/FID on two capillary columns with different polarity. These were 10 saturated, 24 unsaturated, and 24 unidentified peaks which are most likely unsaturated or branched-chain fatty acids. After MAE the composition of the 57 peaks was virtually the same as that obtained with the Bligh and Dyer method. The advantages are, however, that MAE is faster, requires less solvent, and avoids the use of chlorinated solvents and so is more environmentally friendly. Our results confirm that MAE is a well-suited alternative to the Bligh and Dyer method for the extraction of lipids followed by determination of the fatty acid profile. Received: 1 March 2000 / Revised version: 23 May 2000     

上海地区部分市售食品中反式脂肪酸含量与组成分析

目的了解上海地区部分市售食品中的反式脂肪酸(trans-fatty acids,TFAs)含量以及异构体组成,为开展TFAs的风险评估和食品选择提供参考。方法于2011年1～6月在上海市超市、面包店或快餐店中抽取具有代表性的9大类共106种市售食品,包括植物油、乳及乳制品、休闲食品、方便食品、快餐食品、饮料、小吃甜饼、调味品和畜禽肉及制品,采用银离子固相萃取(Ag+-SPE)结合气相色谱方法检测TFAs含量。结果抽检样品中的TFAs以反式油酸(t C18∶1)为主,反式多不饱和脂肪酸含量较少。除黑咖啡外,其余105种食品均检测到TFAs,其中,巧克力派的TFAs含量最高(1 711.58 mg/100 g)。反刍动物食品和含乳及乳制品的食品中11t C18∶1异构体含量较高(占总TFAs的53.9%～100.0%)。富含氢化油的休闲食品中9t C18∶1异构体含量较高(占总TFAs的14.3%～87.7%)。猪肉和牛肉经加工后TFAs含量有不同程度降低。结论市售食品中普遍检测到TFAs,食物成分和加工过程不同总TFAs含量及异构体组成存在较大差异,预包装休闲食品和西式甜饼店食品含有较多的TFAs。     

气相色谱法同时测定食品中的胆固醇和植物甾醇

建立气相色谱法同时测定食品中植物甾醇和胆固醇含量的分析方法,测定植物甾醇含量较高的常见植物油和同时含有胆固醇及植物甾醇的样品。采用5α-胆甾烷为内标参照物,样品经皂化后提取,浓缩后正庚烷定容上机进样分析。胆固醇和植物甾醇在0.001～2.5 mg/mL质量浓度范围内线性良好,线性相关系数R2均大于0.99。方法的检出限为0.3 mg/100 g,定量限为1.0 mg/100 g,该方法相较于液相色谱法能有效将胆固醇和植物甾醇进行分离,具有步骤简单、重复性好、准确度和灵敏度高等特点。     

微波辅助甲酯化-快速GC法测定烟草中的多元酸和高级脂肪酸

建立了同时检测烟草中多元酸(草酸、丙二酸、反丁烯二酸、琥珀酸、苹果酸和柠檬酸)和高级脂肪酸(棕榈酸、硬脂酸和亚油酸)的微波辅助甲酯化-快速气相色谱(GC)分析方法,并测定了烤烟及雪茄烟各10个烟叶样品中的多元酸和高级脂肪酸含量(质量分数)。结果表明:①最优前处理条件为衍生化试剂10%硫酸-甲醇溶液,微波功率以20 W/s的速率升高至1200 W(保持1 min),萃取剂二氯甲烷。②快速GC分析时间为8.81 min,目标化合物标准曲线线性良好(r2>0.99),加标回收率在83.18%~114.17%之间,精密度(RSD)小于5%。③烤烟烟叶和雪茄烟烟叶中有机酸含量差异较大,其中烤烟烟叶中多元酸(除苹果酸外)含量低于雪茄烟烟叶,高级脂肪酸(除硬脂酸外)含量高于雪茄烟烟叶。该方法快速、准确,适用于测定烟草中的多元酸和高级脂肪酸含量。      

中空纤维支撑液膜结合气相色谱测定肉中挥发性脂肪酸

利用中空纤维支撑液膜萃取结合气相色谱测定肉中的挥发性脂肪酸,并建立和验证此方法。中空纤维支撑液膜能够对已酸化的肉浆上清液进行选择性富集。中空纤维管中的萃取物,经盐酸酸化后可直接进行气相色谱分析。此方法线性相关好(r≥0.9261),检测限较低(0.03～0.16μmol/L),回收率可接受(71.0%～123.1%),日内精密度(7.82%～10.28%)和日间精密度(10.01%～15.96%)良好。畜肉中的挥发性脂肪酸含量(725.30～845.23mg/kg)明显高于禽肉中(192.82～282.39mg/kg)。猪肉中总挥发性脂肪酸含量与其pH值呈负相关(r=0.7592),与挥发性盐基氮负相关良好(r=0.7890),此结果表明总的挥发性脂肪酸有可能作为肉新鲜度的检测指标。