Combined uncertainty estimation for the determination of the dissolved iron amount content in seawater using flow injection with chemiluminescence detection.
Combined uncertainty estimation for the determination of the dissolved iron amount content in seawater using flow injection with chemiluminescence detection.
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DOI：
10.1002/lom3.10057
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发表时间：
2015-12
期刊：
影响因子：
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通讯作者：
Quétel CR
中科院分区：
文献类型：
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作者：
Floor GH;Clough R;Lohan MC;Ussher SJ;Worsfold PJ;Quétel CR
本工作评估了与通过流动注射化学发光（FI-CL）测量<0.2 μm过滤和酸化海水样品中Fe含量相关的组合不确定度预算的组成部分。通过差示称重，以重量分析法测定上样标准品溶液和样品的量。在测量过程中，观察到负载质量的变化高达5%，这与在恒定负载时间条件下操作时所做的通常假设相矛盾。因此，将信号强度（V）归一化为负载质量，并使用平均归一化强度（以V kg−1计）与添加到“低水平”铁海水基质中的Fe含量值（以nmol kg−1计）的曲线来产生校准图。实施的测量程序和开发的不确定度估计过程进行了验证，从与三个SAFe和GEOTRACES标准物质（D2，GS和GD）的共识值获得的协议。基于峰高和峰面积的结果的相对扩展不确定度估计分别约为12%和10%（覆盖因子k = 2）。最重要的影响因素是敏感系数的不确定性（即，校准斜率）和序列内稳定性（即，在几个小时的操作中的信号稳定性;这里是32小时）。对于GD，使用峰高测量，这些因素分别占69.7%和21.6%，而短期重复性仅占7.9%。因此，仅基于强度重复性的不确定度估计（如FI‐CL研究中经常进行的那样）并不是对程序总体不确定度的现实估计。
This work assesses the components contributing to the combined uncertainty budget associated with the measurement of the Fe amount content by flow injection chemiluminescence (FI‐CL) in <0.2 μm filtered and acidified seawater samples. Amounts of loaded standard solutions and samples were determined gravimetrically by differential weighing. Up to 5% variations in the loaded masses were observed during measurements, in contradiction to the usual assumptions made when operating under constant loading time conditions. Hence signal intensities (V) were normalised to the loaded mass and plots of average normalised intensities (in V kg−1) vs. values of the Fe amount content (in nmol kg−1) added to a “low level” iron seawater matrix were used to produce the calibration graphs. The measurement procedure implemented and the uncertainty estimation process developed were validated from the agreement obtained with consensus values for three SAFe and GEOTRACES reference materials (D2, GS, and GD). Relative expanded uncertainties for peak height and peak area based results were estimated to be around 12% and 10% (coverage factor k = 2), respectively. The most important contributory factors were the uncertainty on the sensitivity coefficient (i.e., calibration slope) and the within‐sequence‐stability (i.e., the signal stability over several hours of operation; here 32 h). For GD, using peak height measurements, these factors contributed respectively 69.7% and 21.6% while the short‐term repeatability accounted for only 7.9%. Therefore, an uncertainty estimation based on the intensity repeatability alone, as is often done in FI‐CL studies, is not a realistic estimation of the overall uncertainty of the procedure.