世界采样大会的由来与Pierre Gy采样理论的发展

简单介绍了世界采样大会的由来与Pierre Gy采样理论的产生与发展。重点阐述了Pierre Gy公式和采样理论的涵义与应用,以及化学计量学对采样理论发展的推动和促进作用。同时,采样理论的发展也推动了过程分析技术的应用以及各类先进采样、制样和混样设备的研制和应用。中国作为全球最大的大宗商品进口国和消费国,对采样理论和实践应用有着迫切的需求,将第九届世界采样与混样大会引入中国,必将促进和提升我国采样理论的研究和实践水平,使其更好地为我国大宗商品交易和检验检测市场服务。     

在线采样技术在中国的发展

在线采样技术能实时采样,满足在线监测的采样要求。按照采样进样介质的不同分为气体、液体、固体三类。对气体中有毒气体、大气颗粒物、VOCs,液体中水样、原油,固体中煤的机械化采样技术进行了概述,旨在帮助了解在线采样技术在国内矿业、环境行业的发展和应用。随着5G时代的到来,在线采样技术一定会发挥越来越重要的作用。     

在线采样技术在中国的发展

在线采样技术能实时采样,满足在线监测的采样要求。按照采样进样介质的不同分为气体、液体、固体三类。对气体中有毒气体、大气颗粒物、VOCs,液体中水样、原油,固体中煤的机械化采样技术进行了概述,旨在帮助了解在线采样技术在国内矿业、环境行业的发展和应用。随着5G时代的到来,在线采样技术一定会发挥越来越重要的作用。     

重要性采样方法与自由能计算

分子动力学模拟与自由能计算已经在化学、生物学与材料学等领域得到广泛的应用。然而,由于在传统分子动力学模拟的时间尺度内,体系很难跨越较高的自由能能垒,在相空间内的采样大大受限,采样困难使自由能计算难以收敛。增强采样是解决这一问题的有效途径,重要性采样方法就是其中一类。本文综述了四种广泛应用的重要性采样方法--伞状采样方法、metadynamics方法、自适应偏置力方法和温度加速分子动力学方法的原理和进展,其中重点概述了自适应偏置力方法的最新发展--扩展自适应偏置力方法和扩展广义自适应偏置力方法,并对这四种重要性采样方法的优缺点进行了比较。最后,讨论和展望了重要性采样与自由能计算方法面临的挑战和前景,并提出了对自适应偏置力方法可能的改进,如与加速分子动力学（aMD）或弦方法结合以提高在高维度空间中的采样效率。     

挥发性有机物在3种采样装置中的稳定性

详细研究了50种挥发性有机物在Summa采样罐、Teldar采样袋和铝箔采样袋中的稳定性。Summa采样罐适合采集所有50种有机化合物；Teldar采样袋适合采集沸点低于150℃的有机物；铝箔采样袋适合采集沸点低于60℃的有机物。3种采样装置对有机物的吸附能力与有机物的沸点呈线性负相关。铝箔采样袋的吸附方程斜率的绝对值最大；其次是Teldar采样袋；最少是Summa采样罐。     

挥发性有机物在3种采样装置中的稳定性

详细研究了50种挥发性有机物在Summa采样罐、Teldar采样袋和铝箔采样袋中的稳定性.Summa采样罐适合采集所有50种有机化合物;Teldar采样袋适合采集沸点低于150℃的有机物;铝箔采样袋适合采集沸点低于60℃的有机物.3种采样装置对有机物的吸附能力与有机物的沸点呈线性负相关.铝箔采样袋的吸附方程斜率的绝对值最大;其次是Teldar采样袋;最少是Summa采样罐.     

固相微萃取现场流动采样装置

为了满足固相微萃取（SPME）方法现场采样的要求，设计了一套流动采样装置，并采用直接萃取法来研究苯系物（BTEX）的萃取过程，以对该装置进行性能评估。结果表明：非平衡点流动采样方法的灵敏度与国家环保局规定的顶空法相当，BTEX的LOD值均在μg/L水平。该方法具有很好的精密度和准确度，BTEX的相对标准偏差均小于5％；加标回收率均在95．2％－100．9％之间。实际应用研究结果表明，这套流动采样装置可用于实际的现场采样测定。     

微量甲醛污染物的液滴采样装置及应用

依据气体分子扩散理论,采用自制模拟风洞液滴采样装置,并结合乙酰丙酮荧光分光光度法,探讨了液滴采样的最优化条件.实验结果表明:自制模拟风洞液滴采样装置在泵选样速度为0.1 mL/min,进样管内径为5 mm,风扇电压为9V的强制气体流动的条件下,采样效果理想,有较高的灵敏度和重现性.     

原位被动采样技术*

本文介绍了近些年来环境监测中三种新的原位被动采样技术-透析装置（Dialysis peepers）法、薄膜扩散平衡 (DET) 技术和薄膜扩散梯度 (DGT) 技术。综述了三种技术的原理、装置和特点。着重论述了三种技术在环境中的应用研究,包括透析装置以及DET 技术和DGT联用技术测量水体和沉积物孔隙水中可溶性金属的浓度;DGT技术可以作为一种预测重金属生物可利用性的新方法。DGT技术与其他技术（如DET、高离子选择电极、配体交换法、HPLC-ICP-MS等）联用可以更好地测量环境中重金属的形态。最后展望了原位被动采样技术未来的发展。     

增量取样量接近分析试样量时的取样——理论修正与结果

化学分析取样几乎总是一个多步骤过程,所有的步骤都会导致分析结果的总体不确定性。样品采取之后,不论后续采样过程如何精细,前期采样阶段的误差都无法在后续采样过程中更正。第一次取样是最重要的,通常其方差远远超过实验室测量的方差。但这不意味着在最终实验室分析试样制备阶段可以忽略采样理论的原理。现代分析仪器旨在处理小样本(从毫克到几克)。在这种情况下,如果样品是包含少量分析物的混合颗粒,则物料的不均匀性可能会很大以至于破坏整个分析过程。不均匀性计算和样品制备过程中基本采样误差方差的估计对于开发适用的分析程序至关重要。在样本制备的最后步骤中,新的增量本是父增量本的重要组成部分,在估算样本方差时必须考虑到这种影响。TOS提供了用于处理这些情况的工具。通过两个案例阐明了不均匀性计算的应用。在第一个例子中,评估了鸡饲料中低含量添加剂的成分不均匀性,在第二个例子中,对样品制备进行了优化,以校正用于分析硅灰石精矿中矿物杂质含量的红外仪器。在处理颗粒混合物和评估混样效率时,不均匀性评估也很重要。     

Sampling and sampling strategies for environmental analysis

Sampling errors are generally believed to dominate the errors of analytical measurement during the entire environmental data acquisition process. Unfortunately, environmental sampling errors are hardly quantified and documented even though analytical errors are frequently yet improperly reported to the third decimal point in environmental analysis. There is a significant discrepancy in directly applying traditional sampling theories (such as those developed for the binary particle systems) to trace levels of contaminants in complex environmental matrices with various spatial and temporal heterogeneities. The purpose of this critical review is to address several key issues in the development of an optimal sampling strategy with a primary goal of sample representativeness while minimizing the total number of samples and sampling frequencies, hence the cost for sampling and analysis. Several biased and statistically based sampling approaches commonly employed in environmental sampling (e.g. judgmental sampling and haphazard sampling vs. statistically based approaches such as simple random, systematic random, and stratified random sampling) are examined with respect to their pros and cons for the acquisition of scientifically reliable and legally defensible data. The effects of sample size, sample frequency and the use of compositing are addressed to illustrate the strategies for a cost reduction as well as an improved representativeness of sampling from spatially and temporally varied environmental systems. The discussions are accompanied with some recent advances and examples in the formulation of sampling strategies for the chemical or biological analysis of air, surface water, drinking water, groundwater, soil, and hazardous waste sites.     

Comparison of direct solid sampling and slurry sampling for the determination of cadmium in wheat flour by electrothermal atomic absorption spectrometry

Two analytical methods for the determination of cadmium in wheat flour by electrothermal atomic absorption spectrometry without prior sample digestion have been compared: direct solid sampling analysis (SS) and slurry sampling (SlS). Besides the conventional modifier mixture of palladium and magnesium nitrates (10 μg Pd + 3 μg Mg), 0.05% (v/v) Triton X-100 has been added to improve the penetration of the modifier solution into the solid sample, and 0.1% H₂O₂ in order to promote an in situ digestion for SS. For SlS, 30 μg Pd, 12 μg Mg and 0.05% (v/v) Triton X-100 have been used as the modifier mixture. Under these conditions, and using a pyrolysis temperature of 800 °C, essentially no background absorption was observed with an atomization temperature of 1600 °C. About 2 mg of sample have been typically used for SS, although as much as 3-5 mg could have been introduced. In the case of SlS multiple injections had to be used to achieve the sensitivity required for this determination. Calibration against aqueous standards was feasible for both methods. The characteristic mass obtained with SS was 0.6 pg, and that with SlS was 1.0 pg. The limits of detection were 0.4 and 0.7 ng g⁻¹, the limits of quantification were 1.3 and 2.3 ng g⁻¹ and the relative standard deviation (n = 5) was 6-16% and 9-23% for SS and SlS, respectively. The accuracy was confirmed by the analysis of certified reference materials. The two methods were applied for the determination of cadmium in six wheat flour samples acquired in supermarkets of different Brazilian cities. The cadmium content varied between 8.9 ± 0.5 and 13 ± 2 ng g⁻¹ (n = 5). Direct SS gave results similar to those obtained with SlS using multi-injections; the values of both techniques showed no statistically significant difference at the 95% confidence level. Direct SS was finally adopted as the method of choice, due to its greater simplicity, the faster speed of analysis and the better figures of merit.     

A novel technique for the sampling and gas chromatographic analysis of vapours

Summary A conventional pyrolysis gas chromatography system has been adapted to the analysis of vapours. A Curie point pyrolysis wire is used as a holder for granular active carbon on which the sample can be adsorbed. Desorption is achieved in the pyrolysis unit, but no pyrolysis occurs. The present study reports on the completeness of adsorption by the sampler and on the degree of release of adsorbate from it.     

Efficacy of independence sampling in replica exchange simulations of ordered and disordered proteins

Recasting temperature replica exchange (T‐RE) as a special case of Gibbs sampling has led to a simple and efficient scheme for enhanced mixing (Chodera and Shirts, J. Chem. Phys., 2011, 135, 194110). To critically examine if T‐RE with independence sampling (T‐REis) improves conformational sampling, we performed T‐RE and T‐REis simulations of ordered and disordered proteins using coarse‐grained and atomistic models. The results demonstrate that T‐REis effectively increase the replica mobility in temperatures space with minimal computational overhead, especially for folded proteins. However, enhanced mixing does not translate well into improved conformational sampling. The convergences of thermodynamic properties interested are similar, with slight improvements for T‐REis of ordered systems. The study re‐affirms the efficiency of T‐RE does not appear to be limited by temperature diffusion, but by the inherent rates of spontaneous large‐scale conformational re‐arrangements. Due to its simplicity and efficacy of enhanced mixing, T‐REis is expected to be more effective when incorporated with various Hamiltonian‐RE protocols. © 2017 Wiley Periodicals, Inc.     

固体进样直接测定法测定铜精矿中汞

建立了固体进样直接测定法测定铜精矿中汞含量的方法。铜精矿样品在测汞仪的分解炉中经300℃干燥和750℃高温热分解后,汞被催化分解为汞原子,于850℃齐化成金汞齐。汞蒸气被氧气流带入单波长光学吸收池,在波长253.7 nm处测量汞的吸光度,采用标准曲线法计算汞量。方法的线性范围分别为0~1.00,0~100μg/mL,线性相关系数为0.9999,检出限分别为0.10,0.04 ng/g。5个汞含量不同的铜精矿样品测定结果的相对标准偏差为2.14%~4.35%(n=11),样品加标回收率为92.00%~104.02%。采用该方法分别对2个铜精矿样品和铜精矿国际标准物质进行测定,测定结果与标准分析方法测定值和标准物质标示值基本一致。该方法简便、快速、准确,可以作为标准方法推广使用。     

Textile-based sampling for potentiometric determination of ions

Potentiometric sensing utilizing textile-based micro-volume sampling was applied and evaluated for the determination of clinically (Na⁺, K⁺, Cl^–) and environmentally (Cd²⁺, Pb²⁺ and pH) relevant analytes. In this technological design, calibration solutions and samples were absorbed into textiles while the potentiometric cells (ion-selective electrodes and reference electrode) were pressed against the textile. Once the liquid, by wicking action, reached the place where the potentiometric cell was pressed onto the textile, hence closing the electric circuit, the potentiometric response was obtained. Cotton, polyamide, polyester and their blends with elastane were applied for micro-volume sampling. The textiles were found to influence the determination of pH in environmental samples with pH close to neutral and Pb²⁺ at low analyte concentrations. On the other hand, textile-based micro-volume sampling was successfully applied in measurements of Na⁺ using solid-contact sodium-selective electrodes utilizing all the investigated textiles for sampling. It was found that in order to extend the application of textile-based sampling toward environmental analysis of ions it will be necessary to tailor the physio-chemical properties of the textile materials. In general, textile-based sampling opens new possibilities for direct chemical analysis of small-volume samples and provide a simple and low-cost method to screen various textiles for their effects on samples to identify which textiles are the most suitable for on-body sensing.     

Development and validation of a new direct sampling method for coarse mono- and mixed waste fractions bound in bales

Sampling of coarse waste materials is considered to be a particularly challenging task and is at the same time the most crucial step in the overall data acquisition process. Despite this fact, research work on new sampling methods or new scientific approaches to sampling has been rather limited over the last decades. This paper focuses on a completely new sampling procedure for coarse two-dimensional materials similar to municipal solid waste or packaging plastics. The developed method is especially suitable for materials with particle sizes >100 mm and is based on the ‘press-and-drill method’ introduced by researchers from Fachhochschule Nordhausen. The basic idea is to sample the material in its compressed form (e.g. as bales) with a drilling tool in order to gain increments. The study presented in this paper shows the results of two extensive test series applying this new sampling technique to a middle-calorific fraction produced from packaging material (mainly plastics, textiles and paper). In parallel, the state-of-the-art approach was also applied on the same materials to gain valuable reference data. Results from both approaches are used for the extensive validation of the new sampling method. The verification of accuracy was realised by doping the material with defined pieces of foil containing molybdenum sulphide (MoS₂) which acted as a tracer in the bale. The results obtained by the new direct bale sampling showed not only good accordance with the actual tracer content in each bale but also with results derived from the state-of-the-art approach. In this study, homogeneously distributed parameters (e.g. loss of ignition) were included just as inhomogeneously distributed elements (i.e. Cu). It is shown that sufficient representativeness for coarse materials (d₉₅ > 300 mm) is obtained despite relatively small sample amounts and without previous comminution of the material.     

Air sampling of organophosphate triesters using SPME under non-equilibrium conditions

Solid phase micro-extraction (SPME) was used to collect air samples of semi-volatile organophosphate triesters, a group of compounds that are commonly used as flame retardants/plasticisers and have therefore become ubiquitous indoor air pollutants. SPME is a simple sampling technique with several major advantages, including time-efficiency and low solvent consumption. Analyte losses also tend to be relatively low. In quantitative SPME, measurements are normally taken after the analyte has reached partitioning equilibrium between the fibre and the sample matrix. However, equilibrium sampling of semi-volatile compounds in air with SPME often takes several hours. Clearly, time-weighted average (TWA) sampling using SPME under non-equilibrium conditions could be considerably faster. So, in this study, the possibility of sampling organophosphate triesters under non-equilibrium conditions was tested. The most important variables proved to be the fibre coating and the air velocity during sampling. The highest uptake rate was obtained with polydimethylsiloxane (PDMS, 100 m). The rate for this fibre was 150-fold higher than obtained with PDMS/DVB and Carbowax/DVB, both 65 m. Contrary to theoretical expectations, the uptake rate appeared to be constant for all tested air velocities over the fibre surface >7 cm/s. These findings suggest that the uptake rate for non-equilibrium SPME sampling is independent of the sampling flow above this flow rate, which would considerably enhance the robustness and flexibility of the method. Applying this method for TWA sampling, with sampling periods of 1 h, detection limits lower than 2 ng/m³ for individual organophosphate esters were obtained.     

Method for fractional solid-waste sampling and chemical analysis

Chemical characterization of solid waste is a demanding task due to the heterogeneity of the waste. This article describes how 45 material fractions hand-sorted from Danish household waste were subsampled and prepared for chemical analysis of 61 substances. All material fractions were subject to repeated particle-size reduction, mixing, and mass reduction until a sufficiently small but representative sample was obtained for digestion prior to chemical analysis. The waste-fraction samples were digested according to their properties for maximum recognition of all the studied substances. By combining four subsampling methods and five digestion methods, paying attention to the heterogeneity and the material characteristics of the waste fractions, it was possible to determine 61 substances with low detection limits, reasonable variance, and high accuracy. For most of the substances of environmental concern, the waste-sample concentrations were above the detection limit (e.g. Cd?>?0.001?mg?kg^?1, Cr?>?0.01?mg?kg^?1, Hg?>?0.002?mg?kg^?1, Pb?>?0.005?mg?kg^?1). The variance was in the range of 5–100%, depending on material fraction and substance as documented by repeated sampling of two highly different material fractions (‘Vegetable food’ and ‘Shoes, leather, etc.’). Statistical analysis showed for the ‘Vegetable food’ that the variance could not be attributed to a single step in the procedure, whereas in the case of ‘Shoes, leather, etc.’, the first coarse shredding was the main source of variance (20–85% of the overall variation). Only by increasing the sample size significantly can this variance be reduced. The accuracy and short-term reproducibility of the chemical characterization were good, as determined by the analysis of several relevant certified reference materials. Typically, six to eight different certified reference materials representing a range of concentrations levels and matrix characteristics were included. Based on the documentation provided, the methods introduced were considered satisfactory for characterization of the chemical composition of waste-material fractions.