Measurement uncertainty from physical sample preparation: estimation including systematic error.

OVERVIEW OF STANDARDS FOR COAL AND COKE SAMPLING © N.M. Нolik (State Enterprise “Ukrainian State Research Institute for Carbochemistry (UKHIN)”, 7 Vesnina str., Kharkiv, 61023, Ukraine), D.V. Miroshnichenko, Doctor of Technical Sciences (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine (NTU “KhPI”) The article discusses the main stages of testing solid fuels, in particular hard coal and coke, including sample collection, preparation and examination. The importance of obtaining a representative sample that corresponds to the average composition of the entire fuel and is sufficient in weight for accurate measurements is emphasised. It is determined that the heterogeneity of the composition of solid fuels complicates the process of taking a representative sample, which is critical for the accuracy of research. The main stages of obtaining an analytical sample used to determine the chemical and physical characteristics of fuel are described. Special attention is paid to the importance of compliance with the requirements of standards during sample collection and preparation. An overview of the main national and international regulations on sampling and preparation of solid fuels is provided, as well as the scope and key provisions of each standard. The aspects of the importance of the stage of sampling and preparation of solid fuel samples that affect the accuracy of the results of studies of its properties are considered. The main types of samples are listed; requirements for samples, covering the mass and number of spot samples; sampling methods; general requirements for the design of mechanical samplers and sample preparation equipment. The author analyses a number of current Ukrainian regulatory documents and points out the need for their harmonisation with international standards to improve the accuracy of the sampling process. The aspects of the importance of the stage of sampling and preparation of solid fuel samples that affect the accuracy of the results of studies of its properties are considered. The article considers the requirements for determining the systematic error of testing hard coal, anthracite or coke, the sequence of testing and calculation and the criteria for evaluating the test results are presented. The necessity of checking mechanical samplers to determine the presence or absence of a systematic sampling error is noted. The importance of participating in international standardisation is highlighted, which allows for continuous improvement of sampling and sample preparation methods. Keywords: sampling, sample preparation, solid fuel, coal, coal coke, point sample, mechanical sampler, systematic error. Corresponding author N.M. Golik, e-mail: aisim@ukhin.org.ua

Recent advances in sampling and sample preparation for effect-directed environmental analysis

Capillary electrophoresis-mass spectrometry (CE-MS) employing a sheathless porous tip interface has become a strong analytical tool for the efficient profiling of highly polar and charged metabolites in volume/material-restricted biological samples. As more and more metabolomics studies are (intrinsically) dealing with low numbers of mammalian cells, it would be important to use an additional performance metric to effectively evaluate the sampling and sample preparation procedure, in particular quenching. An established parameter to assess the sampling and sample preparation quality when working with cell cultures is the adenylate energy charge (AEC), which represents an index of the energy state of a cell. In this protocol, a CE-MS strategy is proposed for the reliable determination of the adenylate energy charge (AEC) in metabolomics studies dealing with low numbers of mammalian cells.

Sample preparation is considered as the most significant, time-consuming, tedious, error-prone and yet inevitable step in forensic chemical analysis workflow. Trace and ultra-trace level concentration of the analyte(s) of interest, the presence of a wide variety of matrix interferents and the limited availability of the forensic sample often pose formidable challenges to forensic analytical chemists. Due to the phenomenal improvement of analytical instruments in recent years in terms of sensitivity, ruggedness, portability and automation, dependence on chemical evidence in forensic investigations is on a continuous rise with robust demand for simple, fast and sensitive sample preparation techniques capable of preparing the sample with minimal effort and cost. Due to the wide variety of forensic samples and the availability of a large number of existing and emerging analytical instruments for their analysis, it is impractical to standardize forensic sample preparation process. Based on the type, nature and the origin of the forensic samples, different sample preparation techniques have emerged over the last couple of decades. The current chapter classifies forensic samples into different classes such as trace evidence, environmental pollutants, gunshot residues, etc. and briefly discusses about the current best practices in sample preparation for each class of the forensic sample. Due to space limitations, only the most important sample preparation techniques have been highlighted. For comprehensive information, the readers are encouraged to consult with the review articles cited in each section.

Evaluation of an automatic sample preparer in the development and validation of an analytical method for vial wall sorptive extraction

The application of deep eutectic solvent-based magnetic nanofluid in analytical sample preparation

The exposome is the measure of total environmental exposures and has a significant impact on human health outcomes. Exposomics research typically examines complex biological samples and assesses 100s to 1,000s of small molecules associated with chemical exposure events. To acquire robust and comprehensive datasets encompassing a broad range of multi-class biomarkers of chemical exposures, high-resolution and tandem mass spectrometry have emerged as the preferred analytical tools in the field. Due to matrix effects and interferences associated with complex biological samples together with the presence of very low abundance analytes, sensitivity and reproducibility have plagued exposomic studies. This is especially true for large sample sets where adequate robustness is frequently lacking. A possible solution to this problem is the development of non-discriminatory sample preparation methods which can reduce interferences while increasing sensitivity and reproducibility. However, sample preparation techniques intrinsically result in a discrete loss of analytes leading to the outstanding analytical challenge of finding a proper balance. Therefore, approaches which decrease matrix interferences while preserving broad chemical coverage need to be developed. In this review, sample preparation procedures currently applied in exposome research and related fields are summarized and critically evaluated. This includes a comparison of advantages and limitations between different techniques such as solid-phase extraction, liquid extraction, QuEChERS, filters and dilute and shoot with a liquid chromatography-mass spectrometry analysis focus. Based on this evaluation, recommendations promoting balanced strategies for sample preparation in future exposome research applications are provided.

Development and characterisation of a method for determining N-terminal heterogeneity in the human recombinant follitropin β-subunit.

Supercritical fluid extraction (SFE) of fruits and vegetables poses unique sample preparation considerations because the sample size is small (1–3 g) and the analyte is distributed in a moist solid matrix. The goal of this research was to develop practical sample preparation procedures for SFE of pesticide residues in produce so that acceptable accuracy and precision are maintained. In this study, 130 extractions of potato, fortified with up to 40 pesticides, were performed with 2 commercial SFE instruments. Extracts were analyzed by gas chromatography with ion trap mass spectrometry or electron capture detection. Four sample preparation procedures were tested and Hydromatrix was used to control the amount of water in the sample. The highest recoveries and lowest standard deviations were obtained when 20–50 g samples were blended with an equal amount of Hydromatrix and dry ice was added to keep the samples frozen. The dry ice helped produce a homogeneous flowable powder and greatly reduced the degradation or vaporization of several pesticides. Recoveries of most pesticides from subsamples of <4 g with this procedure were 90–105%, with relative standard deviations of 1–6%. Only diphenylamine and disulfo-ton gave reduced recoveries with this procedure. When samples were extracted sequentially with an autosampler, certain pesticides were degraded in the extraction vessels over a period of several hours. To avoid losses of these pesticides, the sample in the extraction vessel was either purged with CO2 to remove oxygen or kept frozen until extracted. Peach and orange check samples were analyzed with the method, and results were comparable with those from traditional analyses.

The microstructure evolution during preparation of thin Si(111) samples for surface sensitive imaging has been studied using ultra-high vacuum (UHV) transmission electron microscopy (TEM). The effects of ion beam sputtering and electron annealing have been investigated. A unique and routine sample preparation method for surface sensitive TEM imaging that combines TEM sample preparations with surface science sample preparation was developed. The microstructure evolution during the sample preparation process was studied in detail.

Liquid–phase microextraction: A review of reviews

The gamma-ray burst location algorithm used to produce the BATSE burst locations in the 3B catalog data is described. The software algorithm and data processing procedures have been improved to minimize the effect of systematic errors on burst locations. Our current estimate of the RMS systematic error for the 3B catalog, based on IPN and COMPTEL located bursts, is approximately 1.6°, as opposed to 4° for the 2B catalog. The improvements in the 3B algorithm remove many of the outliers from the burst location error distribution. The differences between the 2B and 3B location algorithms are discussed to explain changes in burst locations between the two catalogs. Estimates of the systematic errors on burst locations are presented.

Pesticides have been worldwide used for the protection of food crops against pests and diseases. It is common that residues of these pesticides occur in food products, especially agricultural commodities. Adverse effects on human health of pesticides residues remaining in food after they are applied to food crops are generally known. Possible health risk due to pesticide residues in the diet has deeply modified the strategy for the crop protection, with emphasis on food quality and safety. The widespread concern for the health of society led to the strict regulation of maximum residue limits (MRLs) of pesticide residues in food commodities. There are various organizations that set maximum residue limits (MRLs), such as European Commission (EC), Codex Alimentarius or national governments in Australia, Canada, Japan, USA, etc. Individual limits for different active substance per food commodity combinations are being set by EC within the range of 0.0008-50 mg.kg-1 (Directive 91/414/EEC). Newly discovered ecotoxicological problems, particularly the knowledge on endocrine disrupting effects (Colborn et al., 1993; Lintelmann et al., 2003) related also to pesticide residues, emphasise the acute requirement of analytical methods development with increased sensitivity and reliability for monitoring, confirmation and quantification of lower residue levels. Analysis close to these levels corresponds to the ultratrace analysis. This calls for urgent attention in two areas: (a) legislative requirements continuously decreasing the maximum acceptable concentration levels in food, and (b) the apparent importance of methods development in the area of pesticide residues analysis. The urgent requirement for low-level analyses promotes also contribution to the science – in the field of separation methods for ultra-trace analysis of organic pollutants in complex mixtures. The method development heads to speeding up the analysis (what leads to reduction of financial demands) while preserving the efficiency of conventional approaches or getting even better efficiency. In pesticide residues analysis additionally there is ever increasing interest to analyse as many analytes as possible in a single analysis. In the case of semivolatile pesticide residues analysis gas chromatography (GC) still plays an important role. Scientifically valid methods for the analysis at low concentration levels are currently still often very close to limits of detections (LODs). The most efficient approach to pesticide analysis involves the use of multiclass, multiresidue methods (MRMs). The sample preparation procedure should be taken into consideration together with the chromatographic analysis and detection in many aspects, mainly in limit of quantifications (LOQs) and selectivity. In multiresidue pesticides analysis used for an inspection of the

Developing Green Sorbents Derived from Natural Materials for Microextraction and Determination of Emerging Contaminants

Traditionally, boron (B) isotope ratios have been determined using thermal ionization mass spectrometry (TIMS) and, to some extent, secondary ion mass spectrometry (SIMS). Both TIMS and SIMS use a high-resolution mass analyzer, but differ in analyte ionization methods. TIMS uses electrons from a hot filament, whereas SIMS employs an energetic primary ion beam of Ga+, Cs+, or O- for analyte ionization. TIMS can be used in negative or positive ion modes with high sensitivity and precision of B isotope ratio determination. However, isobaric interferences may be a problem, if the sample is not well purified and/or memory of the previous sample is not removed. Time-consuming sample preparation, analyte (B) purification, and sample determination processes limit the applications of TIMS for routine analyses. SIMS can determine B and its isotope ratio in intact solid samples without destroying them, but has poorer resolution and sensitivity than TIMS, and is difficult to standardize for biological samples. Development of plasma-source mass spectrometry (MS) enabled the determination of B concentration and isotope ratio without requiring sample purification. Commonly used plasma-source MS uses an Ar inductively coupled plasma (ICP) as an ionization device interfaced to a low-resolution quadrupole mass analyzer. The quadrupole ICP-MS is less precise than TIMS and SIMS, but is a popular method for B isotope ratio determination because of its speed and convenience. B determination by ICP-MS suffers no spectroscopic interferences. However, sample matrices, memory effects, and some instrument parameters may affect the accuracy and precision of B isotope ratio determination if adequate precautions are not taken. New generations of plasma-source MS instruments using high-resolution mass analyzers provide better sensitivity and precision than the currently used quadrupole ICP-MS. Because of the convenience and high sample throughput, the high-resolution ICP-MS is expected to be the method of choice for B isotope ratio determination. The current state of instrumental capabilities is adequate for B isotope determination. However, precision and accuracy are primarily limited by sample preparation, introduction, and analytical methodology, including 1. Analyte loss and isotope fractionation during sample preparation. 2. The precision of B isotope determination in small samples, especially those containing low concentrations. 3. Difficult matrices. 4. Memory effects. Sample preparation by alkali fusion allows rapid and complete decomposition of hard-to-digest samples, but high-salt environments of the fused materials require extensive sample purification for B ratio determination. The alternative wet-ashing sample decomposition with HF also results in B loss and isotopic fractionation owing to the high volatility of BF3. Open-vessel dry- or wet-ashing methods usually do not work well for animal samples, and are also prone to B loss and contamination. Closed-vessel microwave digestion overcomes these problems, but the digests of biological materials have high C contents, which cause spectral interference on 11B and affect 11B/10B ratios. Exchange separation/preconcentration of B using exchange (cation or anion exchange, B-specific resin, e.g., Amberlite IRA-743) tend to cause B isotope fractionation, and C eluting from these resin columns may interfere with B isotope ratio determination. Memory effects of B that occur during sample determination may cause serious errors in B isotope ratio determination, especially when samples varying in B concentrations and/or isotope composition are analyzed together. Although the utilization of high-resolution plasma-source MS will undoubtedly improve analytical precision, it is the sample preparation, sample introduction, and analytical methodology that represent the primary limitation to accurate and precise B isotope ratio determination.