邻苯二胺分光光度法测定茶汤中的咖啡因

提出了采用邻苯二胺分光光度法测定茶汤中的咖啡因。它是基于咖啡因在加热以及酸性条件下,能与邻苯二胺反应生成浅橙黄色苯并杂环类物质,此物质在488 nm处有最大吸收。该方法线性范围为4.0~25.0μg/mL,表观摩尔吸收系数ε=6.19×104L.mol-1.cm-1,相对标准偏差RSD=1.2%,回收率为100%~105%。已用于茶汤中咖啡因的测定。     

茶叶中3类主要组分的近红外光谱分析作为茶叶质量的快速评定方法

应用近红外光谱法测定了与茶叶品质密切相关的茶多酚、氨基酸及咖啡碱三类化合物。用PLS计算法建立了表示上述组分的二阶导数近红外光谱与其含量间关系的分析模型。根据相关分析模型计算所得的组分含量的结果与用国家标准方法测得的对应组分的含量达到一致。所提出的方法可作为评定茶叶品质的快速方法。     

Atomic absorption spectrophotometric determination of trace copper in waters, aluminium foil and tea samples after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572

An atomic absorption spectrophotometric method for the determination of trace copper after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been developed. This chelate is adsorbed on the adsorbent in the pH range 1–8. The copper chelate is eluted with 5 ml of 0.1 mol l⁻¹ potassium cyanide and determined by flame atomic absorption spectrometry (FAAS). The selectivity of the proposed procedure was also evaluated. Results show that iron(III), zinc(II), manganese(II) and cobalt(II) at the 50 μg l⁻¹ level and sodium(I), potassium(I), magnesium(II), calcium(II) and aluminium(III) at the 1000 μg l⁻¹ level did not interfere. A high enrichment factor, 200, was obtained. The detection limit (3σ) of copper was 0.34 μg l⁻¹. The precision of the method, evaluated by seven replicate analyses of solutions containing 5 μg of copper was satisfactory and the relative standard deviation was 1.7%. The adsorption of copper onto Ambersorb 572 can formally be described by a Langmuir equation with a maximum adsorption capacity of 14.3 mg g⁻¹ and a binding constant of 0.00444 l mg⁻¹. The accuracy of the method is confirmed by analysing tomatoes leaves (NIST 1573a) and lead base alloy (NBS 53e). The results demonstrated good agreement with the certified values. This procedure was applied to the determination of copper in waters (tap, river and thermal waters), aluminium foil and tea samples.     

纳米纤维在分析菊酯类农药残留中的应用

以电纺聚苯乙烯纳米纤维作固相萃取材料,对茶叶样品中的拟除虫菊酯农药进行分离富集,用气相色谱-电子捕获器进行检测,并对影响纤维萃取效率的因素进行优化,联苯菊酯、氯菊酯、氰戊菊酯、溴氰菊酯和甲氰菊酯在纳米纤维柱上的最大吸附量分别为7.8、7.5、7.2、6.6、7.0μg/mg,5种农药的3种标准混合液通过纳米纤维小柱后回收率为65.5%～89.0%,RSD为1.2%～3.0%。测定喷洒5种农药后的茶叶样品添加回收率为61.3%～87.1%,RSD为0.9%～2.8%,方法的测定下限为1.0×10-4～1.0×10-2mg/kg。该方法可以满足茶叶中拟除虫菊酯类农药残留检测的要求。     

茶叶中噻嗪酮残留量的GC-MS测定

采用样品处理的微量化学法和固相萃取技术,建立了茶叶中噻嗪酮残留量的GC -MS测定方法 ;用丙酮 -正己烷 (体积比1∶1)萃取 ,活性碳和中性氧化铝小柱净化 ,净化液用GC -MS测定,外标法定量 ;方法回收率在88%～109 %之间,相对标准偏差为2 %～4 %,测定限为0.010×10-6(w);该法快速、灵敏、准确 ,各项技术指标均满足残留量检测的要求。     

Separation of flavonoids and phenolic acids from propolis by capillary zone electrophoresis

The simultaneous determination of twelve different flavonoids, pinocembrin, acacetin, chrysin, rutin, catechin, naringenin, galangin, luteolin, kaempferol, apigenin, myricetin, and quercetin, two phenolic acids, cinnamic acid and caffeic acid, and one stilbene derivative, resveratrol, in propolis extracts used in medicine has been investigated by capillary zone electrophoresis (CZE). With a buffer constituted by sodium tetraborate 30 mM, pH 9.0, and 15 kV applied voltage, the 15 polyphenols were separated on an uncoated fused-silica capillary within 40 min using normal polarity. Under the experimental conditions used, a linear relationship was calculated between the CZE migration times and the molecular weight of polyphenols' expression of the increasing amount of their hydroxyl groups and polarity. Regression equations revealed a linear relationship (correlation coefficients > 0.97) between the peak area of each polyphenol species and their concentration, from 6 to 120 ng. The levels of analytes in three different propolis extracts, ethanolic, aqueous-ethanolic and aqueous-glycolic, used to prepare various commercial medicinal products, were determined. The aqueous-ethanolic propolis extract showed a great percentage of caffeic acid, galangin, quercetin, and chrysin, whilst the ethanolic preparation was composed of a great amount of resveratrol, chrysin, and caffeic acid. On the contrary, the aqueous-glycolic propolis preparation was composed of approx. 11% of caffeic acid and a low amount of the other identified flavonoids due to the presence of approx. 85% of nonidentified compounds. CZE represents a valuable method for the qualitative and quantitative assay of the most relevant polyphenol components of propolis, representing an alternative to obtain typical fingerprints of propolis and a reliable identification of a large number of propolis polyphenolic species.     

Diamond paste based electrodes for the determination of Pb(II) at trace concentration levels

Three types of monocrystalline diamond: natural diamond 1 μm, synthetic diamond 50 μm (synthetic-1), and synthetic diamond 1 μm (synthetic-2) were used for electrodes’ construction. The linear concentration ranges recorded for Pb(II), when natural diamond, synthetic-1 and synthetic-2 based electrodes were used were between 10⁻⁹ and 10⁻⁶; 10⁻¹⁰ and 10⁻⁷; and between 10⁻¹⁰ and 10⁻⁸ mol l⁻¹, respectively. Low detection limits which lie between 10 and 100 pmol l⁻¹ proves the sensitivity of the electrodes. It was found that Pb(II) yielded a peak at about +0.3±0.02 V (versus Ag/AgCl) for all the electrodes. Lead was determine with high reliability from water and tea samples at trace concentration levels using the proposed diamond paste based electrodes.     

反相高效液相色谱法测定可乐、茶叶中的咖啡因

研究了反相高效液相色谱法（RP－HPLC）直接测定茶叶水提取物、可乐饮料中的咖啡因的新方法，采用PE－C18柱，以CH3OH－H2O－HAc(30:69.92:0.08)溶液作流动相，紫外检测波长为260nm。可在8min内将咖啡因与基体分离，咖啡因含量与峰面积在10μg/mL－100μg/mL范围呈线性关系，回归方程为：Y＝33567c(μg/mL)-126421,r=0.9997.该法可用于可乐饮料，茶叶产品质量的监控及产品真伪的辨别。     

Aluminium in tea—concentrations, speciation and bioavailability

Tea (Camellia sinensis) is one of a few plants accumulating aluminium (Al), making tea a major source of dietary Al intake. This paper reviews published studies on the concentrations, speciation and bioavailability of Al in tea. With very few exceptions, the total concentration of Al in tea infusions is in the range 1-6 mg l⁻¹. Probably more than 90% of this Al is bound to organic matter, but the nature of the organic species is unclear. Three studies using size exclusion chromatography provide evidence for Al species in the molecular mass (MM) range 4000-8500 Da, probably polyphenolic complexes. Two ultrafiltration studies indicate the presence of Al species with MMs above 10,000. The relative amount of the different organic Al species in tea infusions is unclear, and even the identity of any of these has not been demonstrated with certainty. A possible exception is Al trioxalate, which may be an important species based on evidence from two ²⁷Al-NMR studies. It seems fairly well established that drinking tea leads to measurable, but moderate increases in urinary Al excretion. However, the Al present in tea does not seem to be much more bioavailable than that from other dietary sources. Even so, it cannot be dismissed that tea infusions may contain particularly bioavailable and neurotoxic compounds such as Al maltolate, but this is at present speculative.     

直接电喷雾离子阱质谱法快速表征烟叶

建立了一种快速、简单的同时检测烟叶中多酚类和非挥发性有机酸的电喷雾离子阱质谱方法。该方法采用水溶液萃取烟叶,萃取液无需色谱柱分离提纯,直接进入质谱检测,得到烟草质谱轮廓图。采用该方法对25种不同产地、不同等级的烟叶样品进行了测量,并结合模式识别的方法,对这25种烟叶进行了聚类分析,其结果基本符合烟草专家的等级划分。最后对各类烟叶进行了统计分析,得到了表征各类烟叶的平均质谱轮廓和各特征组分对区分烟叶贡献大小。表明该方法可以用于辅助烟叶等级划分及卷烟配方设计。