土壤铵态氮中氮稳定同位素比值测定前处理方法优化研究

土壤氮素在土壤养分供给和植物生长发育中起着重要作用。利用氮稳定同位素自然丰度或富集标记技术,开展土壤氮循环转化、化肥利用效率和生物有效性等方面的研究,涉及NH4+-N稳定同位素比值的精准测定。本研究在前人基础上,开发了一种快速高通量的铵态氮蒸馏分离方法,并使用次氯酸盐替代了次溴酸盐优化了铵态氮化学转化条件,将转化效率由原方法的25%左右,提高至60%以上。利用新建立的前处理方法结合气体预浓缩装置与稳定同位素质谱仪（PreCon-IRMS）联用系统,分析了不同浓度条件下自然丰度、15N富集和标记的NH4+-N标准溶液中的氮稳定同位素比值。结果表明,新的反应体系下,当铵态氮浓度为0.5 μmol /mL以上时,所有NH4+-N标准样品均能获得较理想的分析精度,其中自然丰度和15N富集参比溶液的NH4+-N的δ15N的精度可控制在0.5‰以内,而15N标记的标准溶液的15N atom%测试精度为0.001~0.006 atom%（CV在0.1~0.3%之间）。所有NH4+-N标准样品的15N测定值与参考值一致,无分馏现象发生。将该方法应用于两种不同土地类型的旱地和稻田土壤浸提液中NH4+-N稳定同位素丰度的测定,也可获得较好的重现性（CV<0.5%）,与原方法测定结果基本一致,且精度更优。优化后的前处理方法操作简单,耗时短,重复性好,适用于土壤溶液铵态氮15N丰度测定的快速、批量前处理。     

2,4,6-三硝基-2,4,6-三氮杂环己酮生成历程的~(15)N NMR研究

由DPT与脲或硝基脲在硝化剂中反应可以合成2,4,6-三硝基-2,4,6-三氮杂环己酮。本文用~(15)N示踪原子对DPT分子中不同位置的氮原子分别进行标记,用~(15)N NMR谱图来考察~(15)N标记的反应物和产物分子中标记原子的位置及丰度。结果表明,与脲或硝基脲缩合的DPT硝解碎片为非硝基取代的N,N-二羟甲基胺,硝基脲上硝基与硝化剂之间存在着交换反应。     

83N系列氮-15参考样品的复测

83N系列氮-15参考样品已于1984年提供给农口有关单位使用,以作为质谱及光谱法分析中仪器固有偏差的校正。原测定中对83N8样品中~(15)N丰度的确定,是采用内插以它为原始物质配制的~(19)N丰度与它靠近的83N7样品定出K值后计算而得;由于83N8的丰度只有12.5原子％~(15)N,质谱测量值与真值的偏离可能对计算结果引入较大误差,故实际只能准至±0.1原子％~(15)N。本工作采用标准样品法,精确测得83N8的丰度为12.48±0.03原子％~(13)N,并对83N系列氮-15参考样品的丰度值作了修正。     

C75N+位置异构体的电子结构和光谱研究

杂原子的介入可改变纯碳笼的电子结构, 使其在超导、光电子器件及有机铁磁体等方面得到应用, 还可改善其氧化还原性能, 提高反应活性, 因而引起人们的研究兴趣[1～3]. Averdung[1]研究了C59N+与H的反应, 用质谱检测到C59NH和C59NH+2, 并用AM1方法优化其结构; Lamparth[2]以双氮杂富勒烯为前体, 合成了C59N+和C69N+, 测定中间体的 1H NMR谱、 UV谱及产物的FAB质谱, 并用 15N标记法证实了最强的碎片峰是N原子进入母体碳笼骨架所致. Diederich[3]观察到C76氮化物的FAB质谱信号, 但未给出进一步信息. 本文用INDO系列方法对氮杂富勒烯C75N+位置异构体的结构和稳定性进行理论研究, 找出最稳定的异构体, 计算其电子吸收光谱, 为实验室合成分离提供理论依据.     

新氮杂冠醚衍生物稀土硝酸盐配合物的制备、表征及荧光性质

通过N3O2大环化合物1，12，15-三氮杂-3，4：9，10-二苯-5，8-二氧杂环十七烷(以下简称为L)与乙酸酐、苯甲酰氯、邻苯二甲酸酐在吡啶介质中反应，合成了N，N’，N”-三乙酰(L^1)、N，N’，N”-三(2-羧基)苯甲酰(L2)、N，N’，N”-三苯甲酰(L3)N3O2大环配体，并制备了L^1的Sm，Eu，Tb，Dy稀土硝酸盐的配合物。通过元素分析、摩尔电导、热分析、红外的测定对配合物进行了表征。结果表明，L^1母体环上的醚氧、酰胺氮均没有参与对稀土离子的配位，并推测了配合物的可能组成。室温下研究了配合物的固体荧光光谱，固态时的配合物(除Sm^3 配合物外)均有较强荧光，其中Tb^3 配合物的荧光强度最高，表明配体三重态的能量与Tb^3 的振动能级更为匹配。在Eu^3 的配合物中，强度比η(^5Do→^7F2/Do→^7F1)=3．7，表明Eu^3 处于一非对称配位环境中。     

杂氮硅三环类化合物15N NMR研究

本文对杂氮硅三环类化合物作了15N核磁共振研究,并用CNDO/II方法对部分化合物进行了量子化学计算。导出了15N化学位移随硅上取代基R的Taft极性取代常数σ和氮原子净电荷密度线性变化的规律。从实验和理论两方面进一步证实了杂氮硅三环类化合物分子中存在着Si←N配位键。     

N-苯乙基甘氨酸和β苯乙胺衍生物的~(15)N、~1H-NMR与电荷密度和结构的关系

测定了九种苯乙基甘氨酸和β苯乙氨衍生物天然丰度的~(15)N及1HNMR参数,结合量子化学计算结果和X射线衍射结构分析对NMR实验结果进行了研究,氮原子净电荷与~(15)N化学位移趋势相一致;对氨基保护基磷酰基定域氮孤对电子的作用优于乙酰基、磺酰基作了理论分析;1J15N-31P研究结果与单晶结构的结论一致。     

利用能力验证结果评价参加实验室的整体检测能力

能力验证是利用实验室间比对确定实验室检测能力的活动,其评价结果多用于评估单个实验室的检测能力。行业监管部门期望掌握实验室整体能力和检测方法的相关信息,为分析参加实验室的整体检测能力和不同测试方法的差异,分析了3年航空煤油检测能力验证结果,采用满意结果百分比、|Z|值平均值随参加能力验证次数的变动情况,证实了能力验证对整体检测能力的改进作用;利用异方差t检验,比较不同测试方法结果的一致性和精密度差异;通过比较能力验证评价标准差和检测标准的精密度要求,评价参加实验室整体检测能力是否符合检测标准要求。研究表明,能力验证数据能够用于定量分析参加实验室的整体检测能力,为行业实验室监管和检测方法间比对提供依据。     

铕—N，N—二（N—亚甲基琥珀酰亚胺）甘氨酸—1，10—二氮杂菲三元配合物的

合成了N,N－二（N－亚甲基琥珀酰亚胺）甘氨酸,并以元素分析、IR、^1H NMR和质谱进行表征,实现中发现铕（Ⅲ）与N,N－二（N－亚甲基琥珀酰亚胺）甘氨酸和1,10二氮杂菲形成的配合物具有光致变色的性质。在铕变色物种里,铕离子与N,N－二（N－亚甲基琥珀酰亚胺）甘氨酸中的羧基,1,10－二氮杂菲中的氮原子相结合,同时也可能与水分子和羟基基团结合。     

实验室间比对在确保结果有效性中的应用

<正>实验室间比对是指按照预先规定的条件,由两个或多个实验室对同一或相似物品进行测量或检测的组织、实施和评价。实验室间比对和能力验证是确保检测结果准确可靠的重要手段,并且可以发现与其他实验室间的差距。申请认可、资质认定或已获认可、资质认定的检验检测机构应尽可能参加实验室间的比对试验和能力验证活动。中国合格评定国家认可委员会(CNAS)在2018年发布的CNAS-CL01:2018《检测和校准实验室能力认可准则》[1]中要求,     

水中易释放氰化物能力验证样品的研制及应用

根据国家地表水环境质量监测网监测任务要求和环境监测的实际需要,制备了水中易释放氰化物能力验证样品。通过均匀性、稳定性检验以及量值一致性评价,研制的样品均匀性良好,在3℃~6℃冷藏避光保存条件下1年内稳定,样品配制值与多家实验室协作测定结果一致。探讨了样品在能力验证活动中的应用,共有来自全国11个省的32家实验室参加了水中易释放氰化物的能力验证计划,实验室满意率在80%以上,实验室结果出现有问题或不满意主要是由于样品前处理以及检测过程质量控制不当导致的。经检测及实验室反馈的数据验证,该能力验证样品能够应用于能力验证活动。     

Proficiency testing in food microbiology “Aqua”: enumeration of Staphylococcus aureus

In 1999 the Food Microbiology laboratory of the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe) started an interlaboratory comparison program for food microbiological tests, known as “Aqua, interlaboratory comparisons for quality assurance”. Aqua produces the test samples, applies statistical methods to estimate homogeneity and stability, processes and evaluates the results. The proficiency testing results allow to evaluate the performance of the laboratories, to identify possible differences and non-conformity, to demonstrate the competence and the quality of results, in order to take suitable corrective and/or preventive action after the individuation of the causes. Moreover, elaborating the results of several proficiency testing by using the control chart method, it is possible to evaluate the trend of the laboratory and to verify that the results are in statistical quality control.     

氧指数检测能力验证结果分析

为了解氧指数检测实验室的能力水平,中国合格评定国家认可委员会(CNAS)开展了"塑料燃烧性能试验(氧指数法)"能力验证计划。通过对氧指数能力验证计划的结果进行统计分析,评价了氧指数检测实验室的整体水平,指出了氧指数检测实验室普遍存在的几类问题并提出了相应的建议。     

稳健统计技术及其在实验室能力验证数据处理中的应用

介绍了传统统计方法存在的问题及稳健统计技术的发展历史、稳健统计技术的属性、基本假设模型、稳健统计量及在实验室能力验证数据处理中的具体应用,提出了实验室能力验证的评价标准。     

Proficiency testing in analytical laboratories: how to make it work

 This paper covers the role of proficiency testing schemes in providing an occasional but objective means of assessing and documenting the reliability of the data produced by a laboratory, and in encouraging the production of data that are "fit-for-purpose". A number of aspects of proficiency testing are examined in order to highlight features critical for their successful implementation. Aspects that are considered are: accreditation, the economics and scope of proficiency testing schemes, methods of scoring, assigned values, the target value of standard deviation σ_p, the homogeneity of the distributed material, proficiency testing in relation to other quality assurance measures and whether proficiency testing is effective. Stress is placed on the importance of any proficiency testing scheme adhering to a protocol that is recognised, preferably internationally. It is also important that the results from the scheme are transparent to both participating laboratory and its "customer". Received: 03 November 1995 Accepted: 20 November 1995     

An error model for evaluation and interpretation of proficiency testing

Data from proficiency testing can be used to increase our knowledge of the performance of populations of laboratories, individual laboratories and different measurement methods. To support the evaluation and interpretation of results from proficiency testing an error model containing different random and systematic components is presented. From a single round of a proficiency testing scheme the total variation in a population of laboratories can be estimated. With results from several rounds the random variation can be separated into a laboratory and time component and for individual laboratories it is then also possible to evaluate stability and bias in relation to the population mean. By comparing results from laboratories using different methods systematic differences between methods may be indicated. By using results from several rounds a systematic difference can be partitioned into two components: a common systematic difference, possibly depending on the level, and a sample-specific component. It is essential to distinguish between these two components as the former may be eliminated by a correction while the latter must be treated as a random component in the evaluation of uncertainty. Received: 20 November 2000 Accepted: 3 January 2001     

Quality issues in proficiency testing

 Proficiency testing is a means of assessing the ability of laboratories to competently perform specific tests and/or measurements. It supplements a laboratory's own internal quality control procedure by providing an additional external audit of their testing capability and provides laboratories with a sound basis for continuous improvement. It is also a means towards achieving comparability of measurement between laboratories. Participation is one of the few ways in which a laboratory can compare its performance with that of other laboratories. Good performance in proficiency testing schemes provides independent evidence and hence reassurance to the laboratory and its clients that its procedures, test methods and other laboratory operations are under control. For test results to have any credibility, they must be traceable to a standard of measurement, preferably in terms of SI units, and must be accompanied by a statement of uncertainty. Analytical chemists are coming to realise that this is just as true in their field as it is for physical measurements, and applies equally to proficiency testing results and laboratory test reports. Recent approaches toward ensuring the quality and comparability of proficiency testing schemes and the means of evaluating proficiency test results are described. These have led to the drafting of guidelines and subsequently to the development of international requirements for the competence of scheme providers. Received: 2 January 1999 · Accepted: 7 April 1999     

实验室熟练水平测试方案简介

介绍了实验室熟练水平测试方案(LPTS)的目的,类型,以及实验室熟练水平测试的组织、基本运行程序和实施的具体步骤。     

土壤中重金属元素检测的质量认证

探讨了土壤中重金属检测能力验证的质量控制措施,为确保能力验证结果的准确性及不断提高实验室的检测技术水平提供参考.     

Comparative analysis of laboratory accreditation in Bulgaria, Lithuania, Slovakia and Serbia and Montenegro

The development of an internationally recognized laboratory accreditation process, accompanied by a mutual recognition agreement (MRA), is an issue of great interest in Central and Eastern European countries. This paper presents a comparative analysis of laboratory accreditation in Bulgaria, Lithuania, Slovakia and Serbia and Montenegro. The basic analysis technique was preliminary laboratory accreditation assessment (PLAA). The analysis data were obtained via a questionnaire issued from January to June 2004, with the participation of accreditation bodies. Results from the study are presented in four sections: accreditation body standards, accreditation body organization, assessors and proficiency testing, and inter-laboratory comparisons. Research results for the countries were accessed using PLAA techniques and conformity/non conformity statements. The analysis verified that PLAA can provide low cost, rapid assessment of the key influencing factors in laboratory accreditation bodies.