从氨氮的能力验证可疑结果看实验室管理

目的通过对水中氨氮的检测能力验证,提高检测人员技术水平和实验室管理水平。方法 2016年重庆市质量技术监督局组织了水质(氨氮、铅)检测能力验证活动,本实验室参加了氨氮的能力验证,测试方法分别为HJ 535-2009《水质氨氮的测定纳氏试剂分光光度法》和GB/T 5750.5-2006《生活饮用水标准检验方法无机非金属指标水杨酸盐分光光度法》。以Z比分值来评价和判定检测结果。结果氨氮理论值为0.44mg/L,本实验室上报值为0.506 mg/L,2|Z|3。氨氮数据为可疑,通过分析原因,采取相应纠正措施,最终获得满意结果。结论采用标准样品进行实验室内部质量控制,提高检测人员操作技能、数据分析能力,可获得满意结果。通过能力验证可疑结果的应用实例描述实验室管理,体现能力验证结果的应用价值。     

A computer simulation of the structure of ZSM-18

The zeolite ZSM-18, whose structure has recently been elucidated and found to contain three-rings, has been investigated using atomistic simulation techniques. Agreement between the calculated and distance least-squares refined structure is very close, including reproducing the geometry of the strained three-ring. Both the site preferences for aluminum substitution and protonation are predicted, the most stable Brönsted acid site being located at the three-ring, despite aluminum being most readily accommodated in the seven-ring. Although the T1-O1-T1 is predicted to be linear for the purely siliceous zeolite, the presence of defects results in a distribution of oxygen positions around the c-axis.     

FTIR study of low-temperature CO adsorption on Cu/silicalite-1

Adsorption of CO on Cu/silicalite reveals the existence of Cu⁺ sites similar in properties to the Cu⁺ cations exchanged in Cu–ZSM-5. In both cases Cu⁺(CO)₂ dicarbonyls are formed at ambient temperature and under CO equilibrium pressure. These species are converted into monocarbonyls after evacuation. At low temperature, as with Cu–ZSM-5, tricarbonyls are formed on part of the Cu⁺ sites on Cu/silicalite-1. However, the polycarbonyls on the Cu/silicalite-1 sample are less stable as compared to Cu–ZSM-5. In addition, a fraction of Cu⁺ sites rather typical for oxide-supported copper is found with Cu/silicalite-1. The location of the different copper cations in Cu/silicalite-1 is discussed.