微波消解-原子荧光光谱法测定苹果中的汞

建立了微波消解-原子荧光光谱法测定苹果中汞的方法,采用密闭微波消解苹果样品,优化了微波消解条件和仪器测定条件。方法的检测限为0.00043ng/mL,RSD为2.01%,回收率在98%～104%之间,方法简便、快速、准确,结果令人满意。     

微波消解-等离子体发射光谱法测定腐竹中硼砂

采用正交试验设计优化介质辅助微波消解样品的条件,以电感耦合等离子体发射光谱法(ICP-AES)测定腐竹中硼砂。考察了微波消解功率、混合酸的比例、混合酸用量、试样消解时间4个因素在不同水平条件下对仪器响应值的影响。在优化了微波消解条件下测定实际样品,方法检出限为0.4mg/kg,加标回收率为91.2%～103.9%,相对标准偏差<2%。     

微波消解-原子吸收法快速测定莼菜中铜、锌的含量

应用微波消解制备系统,对莼菜湿样中铜、锌元素进行了微波消解研究,并采用原子吸收法测定其元素的含量。通过L9(34)正交设计,讨论了HNO3/H2O2比、固液比、消解时间、微波功率对微波消解结果的影响。最佳的消解条件为:HNO3/H2O2(V/V)=1:1,固液比(g/ml)=1:12,消解时间为6min,微波功率为700W。在最佳微波消解条件下,进行了精密度实验、回收率实验和金属离子干扰实验。结果表明,所得铜的回收率在97.60%～102.80%之间,RSD为4.61%;锌的回收率在98.40%～101.80%之间,RSD为6.19%。微波消解法处理莼菜湿样,具有快速、简便、节约试剂、消解完全等特点,测定结果的精密度、准确度令人满意。     

微波消解-MPT-AES法测定芦荟中的Ca、Mg、Fe、Zn、Pb

采用微波消解技术消解芦荟,利用微波等离子体炬原子发射光谱法(MPT-AES)测定芦荟中Ca、Mg、Fe、Zn、Pb的含量。考察了分析谱线、载气流量、工作气流量、氧屏蔽气压力等实验参数对元素测定的影响。在最佳实验条件下,方法对Ca、Mg、Fe、Zn、Pb元素的检出限分别为5.62,3.03,78.36,25.41,6ng/mL;线性范围分别为0.05-100,0.01-100,0.2-20,0.1-20,0.02-10μg/mL;相对标准偏差均<5.10%,回收率为99.7%-102.5%。微波消解方法的测定结果与常规干灰化法测定结果相吻合,且具有准确、快速、操作简便等优点,有一定的实际应用价值。     

微波消解-电感耦合等离子体质谱法测定油茶籽油中的5种重金属元素

建立微波消解-电感耦合等离子体质谱法测定油茶籽油中的Pb、Cd、Cr、Cu、As五种重金属元素的方法。优化微波消解条件和仪器测定条件,选择同位素187Re、103Rh、45Sc作为内标元素来校正基体带来的干扰。方法的检出限在0.36～1.64μg/kg,加标回收率在84%～111%之间,精密度RSD在1.6%～7.6%(n=5)之间。采用该方法对茶叶标准样品(GBW10016)和苹果标准样品(GBW10019)进行验证,测定值均在保证值范围内。本方法具有快速、准确、可靠、灵敏度高。     

3种不同方法测定食品中铝残留量比较

目的:观察并分析干灰化、湿法消解、微波消解3种方法对食品中铝残留量的测定情况。方法:干灰化法将样品完全灰化,湿法消解采用电热板加热样品,微波消解法将样品于微波消解炉中消解,消解后分别取1 m L样品消解液测定吸光度并计算铝残留量。分析3种方法测定食品中铝残留量的精确度和准确度。结果:干灰化法的相对标准偏差为8.32%~8.91%,湿法消解的相对标准偏差为6.13%~6.90%,微波消解的相对标准偏差为5.64%~7.62%;干灰化法均值为0.184%,湿法消解均值为0.187%,微波消解均值为0.201%。结论 :干灰化、湿法消解、微波消解在食品铝残留量测定当中具有比较良好的精确度和准确度,每种方法有各自优点,根据具体测定情况选择合适的方法。     

微波消解——ICP—OES测定皮革及其制品中的重金属含量

建立了微波消解-ICP-OES准确、快速测定皮革及其制品中多种重金属元素的分析方法.结果表明,优化微波消解条件和ICP-OES分析条件后,方法检出限(3S/N)为0.02～0.12 mg/kg,3种浓度水平的加标回收率在91.1%～105.8%之间,相对标准偏差小于8.9%.该方法适用于皮革及其制品中重金属元素的日常检测.     

微波消解-FAAS法测定啤酒中钠、钾、钙和镁

结合微波消解技术进行样品前处理,应用火焰原子吸收光谱法测定啤酒中Na、K、Ca和Mg四种元素,同时选择了较佳的微波消解条件.Na、K、Ca和Mg的方法检测限分别为:0.0018、0.0024、0.0030和0.0029μg/mL,相对标准偏差(RSD)小于1.87%,加标回收率均在97.5%～102.5%之间.结果表明,该法具有快速、简便、节省试剂、消解完全、空白值低、污染少等特点,测定结果的精密度和准确度令人满意.     

微波消解-凯式定氮法测定牛奶中蛋白质含量

建立微波消解-凯式定氮法测定牛奶中蛋白质含量的方法,采用密闭微波消解样品,优化微波消解条件.方法的相对标准偏差RSD为1.82%,回收率在98.8%～101.7%之间.     

苹果、脐橙中铅和汞的快速测定的方法研究

研究一种简单快速测定苹果和脐橙中铅和汞的方法。在铁氰化钾-酒石酸体系下,用微波消解-原子荧光光谱法快速测定铅和汞的含量。结果表明:在优化的工作条件下,铅和汞的线性范围分别为0~100μg/L和0~2.00μg/mL,检出限分别为0.37μg/L和4.64×10-3μg/L,加标回收率为98.5%和97.1%,相对标准偏差均小于5%(n=11)。该方法具有操作简便、快速、灵敏度高的优点,可作为苹果和脐橙中微量铅和汞快速测定的方法。     

Natural pigments: carotenoids, anthocyanins, and betalains--characteristics, biosynthesis, processing, and stability

Pigments are present in all living matter and provide attractive colors and play basic roles in the development of organisms. Human beings, like most animals, come in contact with their surroundings through color, and things can or cannot be acceptable based on their color characteristics. This review presents the basic information about pigments focusing attention on the natural ones; it emphasizes the principal plant pigments: carotenoids, anthocyanins, and betalains. Special considerations are given to their salient characteristics; to their biosynthesis, taking into account the biochemical and molecular biology information generated in their elucidation; and to the processing and stability properties of these compounds as food colorants.     

Hormones, metabolites, and reproduction in Holsteins, Jerseys, and their crosses

Holsteins (HH), Jerseys (JJ), and their crosses in first (n=157) and second (n=107) lactation were used to determine if reproduction, progesterone (P4), insulin-like growth factor 1 (IGF-1), insulin, nonesterified fatty acids (NEFA), and milk production differed between genetic groups. Thirty-four cows were Holstein-Jersey (HJ) crosses, 46 were Jersey-Holstein (JH) crosses, 48 were purebred Holsteins (HH), and 29 were purebred Jerseys (JJ) in first lactation, whereas the second-lactation animals included 23 HJ, 35 JH, 35 HH, and 14 JJ. Blood samples were collected weekly for the first 10 wk postpartum. Analyses were conducted using the MIXED, chi-square, and GLIMMIX procedures (SAS Institute Inc., Cary, NC). Seasons of calving were cold (November to May) and hot (June to October) and were combined with year to form 8 year-seasons. Days open and number of services were affected by genetic group. The HH were open 169±8 d, which was greater than HJ (143±9 d), JJ (132±10 d), and JH (127±8 d). The HH had 2.4±0.1 services per pregnancy, which was greater than JH (1.9±0.1), but not different from HJ (2.1±0.2) or JJ (2.1±0.2). Concentrations of NEFA were greater in lactation 2 (0.52±0.02 mEq/L) than in lactation 1 (0.45±0.02 mEq/L) and decreased over the 10-wk period. Concentrations of NEFA were greater in the cold season except in yr 3. Insulin in lactation 1 (0.81±0.03 ng/mL) was greater than in lactation 2 (0.72±0.03 ng/mL); insulin decreased to wk 2 then gradually increased. The HJ had the greatest insulin concentrations (0.87±0.04 ng/mL) and the JJ had the lowest (0.66±0.04 ng/mL), and IGF-1 gradually increased over the 10-wk period. Milk production (actual yield in the first 305 d, not adjusted for fat and protein) was affected by genetic group, lactation number, year-season, and wk 1 insulin. The HH produced 10,348±207 kg of milk, which was greater than the HJ (9,129±230 kg), the JH (9,384±190 kg), and the JJ (7,080±240 kg). Milk production in lactation 2 (9,676±163 kg) was greater than that in lactation 1 (8,294±160 kg). The JJ (10.3±4.7%) had the highest frequency of mastitis. The chance of getting mastitis for HH (1.1±0.9%) differed from that for HJ (9.4±4.1%), JH (8.1±3.4%), and JJ (10.3±4.7%). Genetic group affected hormones and metabolites, which may partially explain differences in reproductive measures and milk yield.     

Capsicum--production, technology, chemistry, and quality. Part V. Impact on physiology, pharmacology, nutrition, and metabolism; structure, pungency, pain, and desensitization sequences

The spice Capsicum is the fruit of the cultivated species of the genus Capsicum (family, Solanaceae), C. annuum principally, and C. frutescens L. to a lesser extent. A third variety of C. annuum var. annuum fruits, the large-sized, fleshy bell capsicum is used as a fresh vegetable and valued for its aroma, color, and crisp texture, but with no pungency. This variety is not considered in this series of reviews covering primary processing, production, international trade, chemistry, and biochemistry of functional components--the red keto carotenoids, the aromatic volatiles and the pungent capsaicinoids in Parts I to III. The valid qualitative aspects correlating the specific components of capsicum and their sensory responses are critically covered in Part IV. In this the concluding part of the series of reviews, the significant preference of the spice for initially evoking an aversive response, its potent physiological and pharmacological effects, and the aspects of structure-activity relationships of the pungent stimuli of the capsaicinoids are reviewed. The beneficial effects particularly associated with long usage by some ethnic groups and its safe consumption levels, with a critical review of the studies on the gastrointestinal tract, the cardiovascular system, the sensory system, thermoregulation, nutritional impacts, and an overview of the five series is also detailed.     

卷烟中锂、铬、镍、铜、砷、硒、钼、镉、铊和铅含量分析

采用微波消解-电感耦合等离子体质谱法测定了41个牌号烤烟型卷烟和雪茄烟样品烟丝中的锂、铬、镍、铜、砷、硒、钼、镉、铊和铅含量,并按照类型和价位对卷烟中这10种有害元素含量进行了统计分析。结果发现:①卷烟中锂和铜的含量较高,铊的含量很低,铬、镍、镉、铅、砷、硒和钼7种元素的平均含量为0.55～4.42μg/g;②雪茄烟中铬、镍、砷、钼、镉、铊和铅的含量一般高于烤烟型卷烟,而硒元素的含量则相反,但差别较小;烤烟型卷烟中锂和铜的含量与雪茄烟没有显著差异;③高档卷烟中的锂、镍、镉、铊和铬含量较低,而砷、铅的含量较高;不同价位卷烟的铜、硒和钼含量差异不显著。     

Simultaneous and Direct Determination of As, Bi, Pb, Sb, and Se and Co, Cr, Cu, Fe, and Mn in Milk by Electrothermal Atomic Absorption Spectrometry

Tungsten permanent modifier with coinjection of Pd(NO₃)₂ and W–Ru permanent modifiers are proposed for the direct and simultaneous determination of As, Bi, Pb, Sb, and Se (group 1) and Co, Cr, Cu, Fe, and Mn (group 2), respectively, in milk by graphite furnace atomic absorption spectrometry. The performance of modifiers was evaluated by means of thermal behavior of analytes, sensitivity, atomic signal profile, repeatability, graphite tube lifetime, and background intensity. An air-assisted pyrolysis step was necessary to quantitative elimination of the organic matter. After methods optimization, 14 commercial milk samples were analyzed. The found concentrations of As, Bi, Pb, Sb, Se, Co, and Cr were lower than their limit of detection (2.13, 2.21, 1.49, 1.63, 2.05, 1.0, and 1.2 μg L⁻¹, respectively). Concentrations of Cu, Fe, and Mn were in the 1.58–5.74 μg L⁻¹, 9.79–49.3 μg L⁻¹, and 2.25–4.08 μg L⁻¹ intervals, respectively. The limits of detection for Cu, Fe, and Mn were 1.7, 5.3, and 2.0 μg L⁻¹, respectively. The accuracy of methods was checked after analysis of two milk standard materials. Results for Cr, Cu, Fe, Mn, Pb, and Mn were in agreement with certified values of SRMs at the 95% confidence level. Accuracy was also evaluated by addition–recovery tests and recoveries in the 86–127% range were obtained for all elements. The use of pretreat platform of graphite tubes with W or W–Ru allowed enlarging the lifetime of atomizer in 750 heating cycles.     

Polyphenols, Anthocyanins, Ascorbic Acid, and Radical Scavenging Activity of Rubus, Ribes, and Aronia

ABSTRACT: Total polyphenols, total anthocyanins, and reduced ascorbic acid were evaluated in berries belonging to the genera Rubus, Ribes, and Aronia by means of spectrophotometric and high-performance liquid chromatography (HPLC) techniques. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of the fruit extracts was tested. Total polyphenols ranged from 140.6 to 888.5 mg/100 g fresh weight (FW), total anthocyanins ranged from 22.0 to 460.5 mg/100 g FW, and reduced ascorbic acid ranged from 12.4 to 153.8 mg/ 100 g FW. The average EC50 values for Aronia melanocarpa, Ribes nigrum, Ribes rubrum, Rubus fruticosus, and Rubus idaeus were 1.8, 2.8, 5.3, 6.4, and 8.2 mg FW, respectively. The results indicate that the fruits tested are good sources of natural antioxidants.     

Tyrosinase, Laccase, and Peroxidase in Mushrooms (Agaricus, Crimini, Oyster, and Shiitake)

Enzyme assays and electrophoresis were used to monitor the activity of tyrosinase, laccase, and peroxidase in Agaricus bisporus (common cultivated button mushrooms and Crimini mushrooms), Oyster, and Shiitake mushrooms. The three enzymes could be differentiated using specific substrates and inhibitors. Tyrosinase seemed to be the major phenol oxidase in the Agaricus strains, while Oyster and Shiitake mushrooms had much lower levels. Peroxidase activity was low or undetectable in all types examined. Control of enzymatic browning in different mushroom types may depend upon the distribution of different oxidases within any given type.