变色酸2C和TAN双显色体系RP-HPLC法分离测定铍(Ⅱ)、铬(Ⅲ)、铜(Ⅱ)、铁(Ⅱ)、镍(Ⅱ)

基于变色酸 2 C和 TAN双显色体系发展了一种同时测定铍 ( )、铬 ( )、铜 ( )、铁 ( )和镍 ( )的新 RP-HPLC法 .在 p H=5 .0的乙酸盐缓冲介质中 ,同时加入变色酸单偶氮试剂变色酸 2 C和噻唑偶氮试剂TAN,它们能与不同金属离子形成有色螯合物 ,以 YWG-ODS柱为固定相 ,含显色剂、溴化四丁铵和乙酸盐缓冲溶液 ( p H=5 .0 )的甲醇 /乙醇 /水 (体积比 35 :5 :60 )溶液为流动相 ,并用分光光度检测器于 5 80 nm处测量 ,用 RP-HPLC可成功地分离和测定 ng/ m L级的铍 ( )、铬 ( )、铜 ( )、铁 ( )和镍 ( )等 5种金属离子 .此方法灵敏度高 ,简便快速 ,用于大米、面粉中上述金属离子的测定 。

浅谈炼钢厂拉矫机液压装置密封改造

拉矫机上拉矫液压缸体温度大约在150°左右,缸体内密封元件老化速度加快产生泄漏,导致拉矫辊对铸坯夹紧力产生波动,影响铸机正常拉钢,采用进口的特种耐高温材料,并利用独特的密封形式,解决了长期困绕拉矫液压缸密封寿命短的问题。

Berry-Esseen bounds and Cramér type large deviations for eigenvalues of random matrices.

We establish Berry-Esseen bounds and Cramér type large deviations for the eigenvalues of Wigner Hermitian matrices in the bulk and at the edge cases. Similar results are also obtained for covariance matrices.

Synthesis of ultra-small mordenite zeolite nanoparticles

The mordenite（MOR） nanoparticles（MNPs）with ultra-small crystallites（~30 nm） were synthesized by using tetraethylammonium bromide（TEAB） as structure directing agent at low temperature（403K）. The formation of MNPs was considered to be due to high concentration of TEAB and occurrence of limiting Ostwald ripening at low temperature. The MNPs exhibited not only higher catalytic activity at low temperature for selective catalytic reduction of NOx but also higher catalytic activity and longer lifetime for disproportionation of toluene than conventional MOR（cMOR） bulk crystals.