In situ measurements are made without the removal of a physical sample and have many advantages over traditional ex situ measurements, made on a removed sample usually in a remote laboratory. The quality of ex situ measurements is usually expressed primarily in terms of their measurement uncertainty, including that arising during the sampling process. However, estimates of uncertainty for in situ measurement values have not usually included this uncertainty from sampling (UfS). It is argued that the making of an in situ measurement inevitably includes the taking of an ‘undisturbed sample’ that generates UfS, which should be included in the estimate of measurement uncertainty. Because undisturbed samples are not prepared or mixed, as is usual for removed samples, the heterogeneity of the analyte concentration in the sampling target is the primary source of UfS. Existing methods for estimating UfS for ex situ measurements can broadly be applied to in situ measurements. However, four extra challenges that limit the design and uptake of uncertainty estimation for in situ methods are identified, and possible solutions and actions required are discussed. Examples of in situ measurements considered include Pb in top soil by hand-held PXRF, 137Cs at a nuclear site by portable gamma-ray spectrometry, and bilirubin in new-born infants by hand-held reflectance photometry.

中文翻译：

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现场测量不确定度估计的挑战

原位测量无需移除物理样品，与传统的非原位测量相比具有许多优势，传统的非原位测量通常在远程实验室中对移除的样品进行。异地测量的质量通常主要用测量不确定度来表示，包括在采样过程中产生的不确定度。然而，原位测量值的不确定性估计通常不包括来自抽样 (UfS) 的这种不确定性。有人认为，进行原位测量不可避免地包括获取产生 UfS 的“未受干扰的样本”，这应该包括在测量不确定度的估计中。因为未制备或混合未受干扰的样品，就像通常去除的样品一样，采样目标中分析物浓度的异质性是 UfS 的主要来源。用于估计非原位测量的 UfS 的现有方法可以广泛应用于原位测量。然而，确定了限制原位方法不确定性估计的设计和采用的四个额外挑战，并讨论了可能的解决方案和所需的行动。所考虑的原位测量示例包括通过手持式 PXRF 测量表层土壤中的铅、通过便携式伽马射线光谱法测量核场地中的 137C，以及通过手持式反射光度法测量新生婴儿的胆红素。并讨论了可能的解决方案和所需的行动。所考虑的原位测量示例包括通过手持式 PXRF 测量表层土壤中的铅、通过便携式伽马射线光谱法测量核场地中的 137C，以及通过手持式反射光度法测量新生婴儿的胆红素。并讨论了可能的解决方案和所需的行动。所考虑的原位测量示例包括通过手持式 PXRF 测量表层土壤中的铅、通过便携式伽马射线光谱法测量核场地中的 137C，以及通过手持式反射光度法测量新生婴儿的胆红素。