茶叶中锰、铁、锌、铬等10种微量元素的快速测定

茶叶样品经粉碎干燥后,以硝酸-高氯酸混合液进行消解处理,火焰原子吸收分光光度法测定了K、Ca、Na、Mg、Fe、Mn、Cu、Zn、Ni、Cr的含量。结果表明,回收率在89.30%～103.20%之间,相对标准偏差小于10%。方法简单、快速、经济,结果可靠。     

石墨炉原子吸收法测定灵芝孢子粉中的痕量硒与锗

有机硒、锗具有抗癌，提高人体免疫的功能，已引起许多研究者的关注。灵芝孢子粉含有丰富的营养成分，如灵芝多糖，灵芝酸，腺苷，18种氨基酸及牛黄酸和特有的矿物元素等均起着奇特的功效，这些营养成分在人体中的功效同样引起许多研究者的重视^[1,2]。本文利用日立Z－8000型原子吸收光谱仪，采用石墨炉法测定有机硒、有机锗。     

红外光谱法测定尿素生产中脱氢催化剂的 S(Ⅵ)含量

本文介绍一个用红外光谱法测定尿素生产装置内使用过的脱氢催化剂中S(Ⅵ)的含量(以SO_4~-形式存在)。取Al_2(SO_4)_3作标样,溴化钾压片法制备13mm样片,用补偿法测定1120cm~(-1)SO_4~(2-)吸收峰的光密度,绘制A_(1120)～S(Ⅵ)标准曲线。样片中SO_4~(2-)含量在1mg以内符合朗伯—比尔定律。当脱氢催化剂中S(Ⅵ)含量在20％以内,方法准确度为3％,平均偏差最大为0.20。文中并介绍了操作误差的来源及克服办法。     

Symmetry role on the preedge X—ray absorption fine structure at the metal K edge

The preedge features in a system with “even”symmetry,apart from quadrupolar transition contribution,are mainly dipolar in character,associated with the existence of unoccupied states made up of mixed cation-4p with higher-neighboring cation-3d orbitals,and reflect the density of states due to the medium-range order of the system.In “odd“symmetry materials these preedge features ate the result of a transition from the ls to a final density of states of p symmetry due to an unsymmetrical mixing of the ligand wave functions with the central cation 3d orbitals,similar to atetrahedral configuration.These results are validated for Fe as a photoabsorber by comparing XAS spectra of Fe2SiO4(fayalite) to ab initio full multiple scattering calculations at the fe K edge,but pertain to all systems containing sixfold-coordinated cations.