柚木石油醚抽提物成分及其对心边材颜色的影响

为探究国产柚木抽提物对心材和边材颜色差异的影响,采用3种沸程的石油醚溶液分别对国产柚木的心材与边材进行抽提处理,利用气相色谱-质谱法分析抽提液的成分和含量,并以差异较大的抽提物溶液处理柚木边材,通过色度学参数表征柚木边材的变色情况,从而验证影响柚木心材和边材颜色的主要抽提物成分。结果表明:在3种沸程的石油醚抽提液中,柚木心材抽提物在成分种类数量和含量上均显著高于边材;不同沸程的石油醚对柚木心、边材中抽提物成分有一定的影响,其中30~60℃(低沸程)和60~90℃(中沸程)石油醚抽提物成分和含量的差异较小,而90~120℃(高沸程)石油醚抽提物的含量较高,约为中、低沸程抽提物含量的2倍;柚木心材抽提液中酚类、醌类、烯烃类物质的含量较多,但这些物质在边材中含量极低;4-叔丁基-2-苯基苯酚、2-甲基蒽醌(柚木醌)、全反式三十碳六烯(角鲨烯)是柚木心、边材抽提物含量差异最明显的物质。经角鲨烯溶液处理后的柚木边材表面颜色变黄,更接近心材颜色,因此,角鲨烯是导致柚木心边材颜色差异的重要抽提物成分。     

顶空固相微萃取气相色谱质谱嗅觉测量联用初探鲢肉的挥发性风味物质

为探明鲢肉挥发性气味特征物质,通过顶空固相微萃取法提取和浓缩了鲢肉中的挥发性物质,并利用气相色谱质谱联用以及气相色谱〖CD*7/9〗嗅觉测量法对气味物质进行了定性分析及气味特征的评价。由8人组成的评价小组通过检测频率法进行嗅觉测量。结果表明,经GCMS分析鉴定得到了29种挥发性气味物质,主要是一些羰基类和醇类化合物,占了总挥发性物质的88%。通过检测频率分析法鉴定出12种化合物具有气味特征,表现为鱼腥、金属、青草、油脂氧化、蘑菇等特征。另外有4种未知物也显示了较强的风味特性,它们协同作用构成了鲢的特殊气味。     

Characterization of hepatic and extrahepatic glutathione S-transferases in rainbow trout (Oncorhynchus mykiss) and their induction by 3,3′,4,4′-tetrachlorobiphenyl

Liver, kidney, gill and olfactory epithelium cytosolic fractions of rainbow trout (Oncorhynchus mykiss) were examined for glutathione S-transferase (GST) contents. Proteins retained on a glutathione (GSH)-affinity matrix were separated as monomers by reversed-phase HPLC and characterized by immunoblotting, mass spectrometry and partial amino acid sequence. For each organ concerned, a specific pattern of these proteins was determined and appeared similar for liver and kidney on one hand, and for gill and olfactory epithelium on the other hand. It was confirmed that the prominent hepatic GST is a class enzyme, also constitutively expressed as a major isoform in the four organs studied. Moreover, a class variant and two new class GST subunits were characterized in minor fractions. An unknown protein, which was found major in gills and olfactory epithelium, exhibited some characteristics of class GSTs. Occurrence of possible GSH-adduct formation observed on two distinct monomers in specific experimental conditions is discussed. These results and methods were used to investigate the effect of 3,3,4,4-tetrachlorobiphenyl (TCB), a polychlorinated biphenyl (PCB), on GST expression in trout liver. From HPLC-profiling, significant co-induction of the major class and the two minor class GST subunits was observed in trout after waterborne exposure to TCB which was followed by a slight increase in 1-chloro-2,4-dinitrobenzene (CDNB) activity. The present work allows qualitative evaluation of the specific detoxification potential of rainbow trout. The use of HPLC-profiling of GSTs as a possible tool for the biomonitoring of polluted aquatic environment is suggested.     

A comparison between X‐ray fluorescence and dissolution methods employing lithium metaborate fusion for elemental analysis of soil clays

Abstract

A method employing fusion of soil clay samples with lithium metaborate (1:5 ratio) in a furnace at 1050°C for 1 hr. subsequent dissolution of the fused sample in 4% HNO₃. and elemental analysis for Si, Al, Fe, Ca, Mg, K, and Ti by atomic absorption spectrometry was compared with the X‐ray fluorescence (XRF) fused disc technique for analysis. Duplicated analyses were performed on 15 clay samples from soils of the southern U.S and three API reference samples. The mean total percent recovery by this method was excellent (100.14 ± 2.85). Elemental oxide quantities in terms of SiO₂. Al₂O₃, Fe₂O₃, MgO, CaO and K₂O determined by atomic absorption/flame emission (AA/FE) spectroscopy were in good agreement with values measured by x‐ray fluorescence (XRF) on the same subsamples (r = 0.89^* to 0.98^**). but somewhat more variable on subsamples seperated from different pretreatments (r = 0.70^* to 0.97^** ). The method, which has also been tested on 36 additional clay samples from a variety of Kentucky soils with total percent recoveries ranging from 96.5 ‐ 103.5%. demonstrated no bias due to mineralogy with respect to mixed, montmorillonitic. and siliceous classes. This technique presents numerous advantages over other elemental analysis techniques utilizing fusion, dissolution, or XRF spectroscopy with respect to time, effort and cost. With the introduction of inductively‐coupled plasma (ICP) emission spectroscopy. efficiency can be additionally improved.     

栀子花化学成分的GC/MS分析

采用超声波提取栀子花提取液,然后对其化学成分进行GC/MS分析。从栀子花中分离确定出27种主要成分,其中萜类物质含量相对较高。     

微波消解-原子荧光法测定竹丝鸡肉中的砷含量

采用微波消解-原子荧光法对广东竹丝鸡肉中有毒有害元素砷的含量进行抽样检测分析。结果表明:该方法检出限为0.067μg/L,回收率为95.7%~101.2%;竹丝鸡肉中砷的检出率为100%,平均残留量为0.041 mg/kg,符合我国无公害畜禽肉中砷的限量标准,并达到了我国绿色食品中砷限量标准。     

液相色谱-离子阱质谱联用技术定性检测渔药中喹诺酮类抗菌素

建立了高效液相色谱-质谱联用技术定性检测渔药中喹诺酮类抗菌素的方法.利用喹诺酮类化合物的质荷比(m/z)和其荧光光谱特性对渔药中恩诺沙星、环丙沙星、诺氟沙星、氧氟沙星四种喹诺酮类化合物进行定性分析,结果表明该方法快速可行,方法检出限分别为1.29 ng、1.23 ng、1.08 ng、1.00 ng,可用于渔药中喹诺酮类抗菌素的监控.     

原子吸收次灵敏线法直接测定土壤中Fe、Mn

用原子吸收次灵敏线法塞曼效应扣除背景测定土壤中Fe、Mn,实验结果表明:此方法有较好的准确度,精密度,操作简单,适合一般土壤中Fe、Mn的测定。     

Amelioration of Aluminum Toxicity by Pretreatment with Phosphate in Aluminum‐Tolerant Rice Cultivar

Abstract

The phytotoxicity of aluminum (Al) in relation to preculture with phosphates was examined in the rice cultivar Arkansas fortuna. In plants precultured with phosphates, Al did not inhibit shoot growth, while Al retarded shoot growth in plants precultured without phosphates. In contrast, Al inhibited root elongation, irrespective of the presence of phosphates in the preculture solution. A large proportion of the Al in roots was in unknown, insoluble forms. In phosphate‐precultured plants, Al deposition was slightly increased, presumably due to the formation of aluminum phosphates in the roots, and phosphorus levels in shoots were markedly increased. Binding with phosphates may ameliorate the toxicity of Al when it enters the shoots and account for the uninhibited shoot growth in the presence of Al in plants precultured with phosphates.     

K均值和分层聚类法在大米产地鉴别中的应用

大米称誉为"五谷之首",是我国的主要粮食作物。大米产地鉴别方法的研究对于保护广大消费者和生产厂家的利益、推动我国大米出口业的发展等都具有重要意义。为此,选取了19个响水大米样品和10个非响水大米样品,使用等离子体原子发射光谱的方法测定了样品中P,B,Zn,Fe,Cu,Mn,Na,K,Mg和Ca等10种微量元素的含量,并利用样品中的微量元素含量数据,使用K-Means聚类法和Hierarchical聚类法对大米样品进行了聚类分析。结果表明,K-Means和Hierarchical聚类法对于样品有聚类趋势。研究结果能够为大米生产厂商与质检部门鉴别大米产地提供参考和借鉴。