A combined method of sample preparation for the determination of the total element composition of oils

A comprehensive approach to the determination of the elemental composition of oils (including those with a viscosity of 5000 mm²/s) is proposed. It ensures the determination of the most elements present in oils using two versions of sample preparation, autoclave decomposition of oil samples and extraction preconcentration of elements from oil into an aqueous solution on rotating coiled columns (RCCs). The application of RCCs in the elemental analysis of oil ensures the preconcentration of a number of trace elements from oil (including rare-earth elements) and the determination of their concentrations at a level of ng/kg. The preconcentration factor of trace elements from oil using an RCC depends on the volume of oil sample pumped through a constant volume of the stationary phase (acid solution) retained in the column and on the speciation of elements in the oil.     

Microwave assisted sample preparation for determining water-soluble fraction of trace elements in urban airborne particulate matter: evaluation of bioavailability

The feasibility of using two different microwave-based sample preparation methods was investigated to determine the total and water-soluble trace metal fraction in airborne particulate matter. The extraction techniques were then applied to urban particulate matter of different sizes in order to evaluate their bioavailability of associated trace metals. While a combination of HNO₃-HF-H₂O₂ was used for the total trace metal fraction of particulate matter, water was employed for the microwave-assisted extraction of water-soluble trace metal fractions. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for the analysis of trace elements. The experimental protocol for the microwave assisted digestion was established using two different SRMs (1648, urban particulate matter and 1649a, urban dust). In the case of water-soluble trace metal fraction, the quantities extracted from the SRMs were compared between ultrasonic and microwave-assisted extractions, and there was a good agreement between the two extraction methods. Blanks values and limits of detection (LODs) for total and water-soluble trace metal concentrations were determined for three different filter substrates (Teflon, Zeflour, and Quartz). Subsequently, the proposed digestion method was evaluated for its extraction efficiency with these filter substrates. Finally, the real-world application of the proposed microwave-based sample preparation methods was demonstrated by analyzing trace elements in airborne particulate samples collected from different outdoor environments in Singapore. The solubility of 11 trace elements detected in the particulate samples is quantified.     

Sample Preparation Techniques—An Important Part in Trace Element Analysis for Environmental Research and Monitoring

Abstract

For the determination of minute amounts of elements in environmental samples combined analytical procedures are frequently employed. The combination of suitable sample preparation techniques with adequate detection methods lead to powerful analytical procedures. Decomposition methods are an important part of combined procedures for the determination of trace elements in solid samples. After a short summary of the potential sources for systematic errors two new decomposition methods are described that are suitable for the ashing of organic environmental samples. In one method the organic sample is ashed in a high-frequency excited oxygen plasma. The second method is a high pressure decomposition that permits mineralization of the sample in sealed quartz vessels with nitric acid at temperatures up to 320°C.

For both methods the ratio of sample weight to decomposition reagents is comparatively high. This makes these methods in combination with adequate detection methods suitable for the determination of elements at very low concentrations.

X-ray fluorescence spectrometry combined with adequate preconcentration methods is very well suited for the simultaneous determination of trace elements. Following a critical evaluation of various preconcentration techniques the analytical characteristics of filter paper with immobilized complexing agents are described. Particular emphasis is given to filter papers with dithiocarbamates as chelating group.     

Sample preparation methods for subsequent determination of metals and non-metals in crude oil—A review

In this review sample preparation strategies used for crude oil digestion in last ten years are discussed focusing on further metals and non-metals determination. One of the main challenges of proposed methods has been to overcome the difficulty to bring crude oil samples into solution, which should be compatible with analytical techniques used for element determination. On this aspect, this review summarizes the sample preparation methods for metals and non metals determination in crude oil including those based on wet digestion, combustion, emulsification, extraction, sample dilution with organic solvents, among others. Conventional methods related to wet digestion with concentrated acids or combustion are also covered, with special emphasis to closed systems. Trends in sample digestion, such as microwave-assisted digestion using diluted acids combined with high-efficiency decomposition systems are discussed. On the other hand, strategies based on sample dilution in organic solvents and procedures recommended for speciation analysis are reported as well as the use of direct analysis in view of the recent importance for crude oil field. A compilation concerning sample preparation for crude oil provided by official methods as well as certified reference materials available for accuracy evaluation is also presented and discussed.     

Application of PLE for the determination of essential oil components from Thymus vulgaris L

Essential plants, due to their long presence in human history, their status in culinary arts, their use in medicine and perfume manufacture, belong to frequently examined stock materials in scientific and industrial laboratories. Because of a large number of freshly cut, dried or frozen plant samples requiring the determination of essential oil amount and composition, a fast, safe, simple, efficient and highly automatic sample preparation method is needed.Five sample preparation methods (steam distillation, extraction in the Soxhlet apparatus, supercritical fluid extraction, solid phase microextraction and pressurized liquid extraction) used for the isolation of aroma-active components from Thymus vulgaris L. are compared in the paper. The methods are mainly discussed with regard to the recovery of components which typically exist in essential oil isolated by steam distillation.According to the obtained data, PLE is the most efficient sample preparation method in determining the essential oil from the thyme herb. Although co-extraction of non-volatile ingredients is the main drawback of this method, it is characterized by the highest yield of essential oil components and the shortest extraction time required. Moreover, the relative peak amounts of essential components revealed by PLE are comparable with those obtained by steam distillation, which is recognized as standard sample preparation method for the analysis of essential oils in aromatic plants.     

Sample preparation techniques for the determination of trace residues and contaminants in foods

The determination of trace residues and contaminants in complex matrices, such as food, often requires extensive sample extraction and preparation prior to instrumental analysis. Sample preparation is often the bottleneck in analysis and there is a need to minimise the number of steps to reduce both time and sources of error. There is also a move towards more environmentally friendly techniques, which use less solvent and smaller sample sizes. Smaller sample size becomes important when dealing with real life problems, such as consumer complaints and alleged chemical contamination. Optimal sample preparation can reduce analysis time, sources of error, enhance sensitivity and enable unequivocal identification, confirmation and quantification. This review considers all aspects of sample preparation, covering general extraction techniques, such as Soxhlet and pressurised liquid extraction, microextraction techniques such as liquid phase microextraction (LPME) and more selective techniques, such as solid phase extraction (SPE), solid phase microextraction (SPME) and stir bar sorptive extraction (SBSE). The applicability of each technique in food analysis, particularly for the determination of trace organic contaminants in foods is discussed.     

Speciation of trace elements in biological materials: trends and problems.

In the determination of trace elements in biological materials, speciation is of particular importance as the essential effects or toxicity of an element and its metabolic behaviour depend to a large extent on the chemical forms in which it is present in the organism. Speciation is relatively easy if a property of a particular compound can be measured directly in the sample without interference from the other components of the material, e.g., the enzymic activities of the metallo-enzymes. Another possibility for speciation is immunoassay, which likewise allows direct determination of a particular trace element. At present, however, with most trace elements both fractionation methods and analytical procedures have to be combined and speciation has to be carried out by determining the elemental content in the separated fractions. The methods and apparatus used in taking, storing and preparing the samples can, therefore, not be selected solely according to the requirements of trace element determination, but it is also essential to ensure that the biological structures of the components to be separated remain intact. In this work the need for speciation in the investigation of the toxic and essential effects of trace elements is shown with the help of some examples, and the problems that can occur in the various steps of sampling, storage and sample preparation are discussed.     

临床样品微量元素分析过程中样品制备技术的进展

对临床样品微量元素分析过程中的样品制备技术的最近进展进行了评述,主要从直接稀释、湿法消解、干式灰化及微量元素形态分析的样品预处理技术等几方面进行了分别介绍。     

The analysis of solid and liquid high-purity substances

This paper reviews the problems of atomic-spectrometry, mass-spectrometry and activation methods in elemental analysis of high-purity substances. The specific techniques of sample preparation, preconcentration of impurities and the determination of gas-forming trace elements are discussed.     

Capillary microextraction (CME) and its application to trace elements analysis and their speciation

As a solvent-free miniaturized sample preparation technique, capillary microextraction (CME) has been hyphenated with different analytical instruments for trace elements analysis of environmental, biological, food and pharmaceutical samples. This review discusses the fundamentals and recent development of CME, including the theoretical basis, extraction modes (packed, open-tubular and monolithic CME) and capillary materials for CME. The emphasis is placed on the application of CME to trace/ultra-trace elements analysis and their speciation. Existing coating/monolithic materials used for CME are summarized together with a detailed overview of their preparation methods.     

Cloud point extraction utilizable for separation and preconcentration of (ultra)trace elements in biological fluids before their determination by spectrometric methods: a brief review

This review summarizes and discusses applications related to the determination of (ultra)trace elements in biological fluids using cloud point extraction as sample pretreatment technique. Biological fluids, such as urine, whole blood, serum or plasma, are the most often analyzed biological materials in these applications. Spectrometric methods, such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry, are commonly used for quantification of elements preconcentrated by the extraction technique. Optimized extraction procedures lead to the high extraction recoveries of the target analytes. High enrichment factors achieved lead to the lowering of quantification limits. All these achievements illustrate the great potential of extractions for reliable quantification of (ultra)trace elements in complex biological matrix what is documented in this review of a number of works published on this topic.     

高纯四氯化锗测试样品的采集和制备方法研究

针对光纤级高纯四氯化锗(99.999999%)中痕量含氢杂质吸收峰红外透过率检测(FTIR)用试样的采集,以及痕量金属杂质的电感耦合等离子体质谱法(ICP-MS)测定用试样的制备方法进行了系统研究。设计开发了用于检测痕量含氢杂质吸收峰红外透过率的样品采集实验装置,实现了含氢杂质(如—OH、—CH、HCl等)吸收峰的红外透过率在线连续测试,试样采集过程全密闭进行,避免了采样过程的二次污染,采样过程流程简短,操作简便;实验优选了在制备ICP-MS法测定痕量金属杂质用的试样过程中消除四氯化锗基体干扰、防止砷等易挥发杂质损失以及防止样品处理过程污染试样的制样方法,实现了试样制备过程二次污染源的有效控制,制样过程试剂消耗量少,制备时间短,待测元素无损失。     

基于色谱-质谱联用的脂质分析样品前处理技术研究进展

脂质作为细胞膜和亚细胞膜的主要结构成分,在能量来源、细胞信号传导等多种生物学过程中发挥着重要作用。近年来,脂质分析受到越来越多的关注,其中色谱-质谱联用技术在脂质分析中占据主导地位。由于样品基质复杂,样品前处理有富集痕量物质和减少基质干扰的作用,成为脂质分析中的一个关键步骤。该文综述了近年来基于色谱-质谱联用技术的脂质分析中样品前处理技术的研究进展和应用,对各种样品前处理技术进行了阐述和总结。基于液相的萃取方法有液-液萃取和单一有机溶剂萃取。基于固相的萃取方法包括固相萃取和固相微萃取。场辅助萃取方法包括超临界流体萃取、加压流体萃取、微波辅助萃取和超声辅助萃取。此外,还介绍了在线联用样品前处理方法和用于活体分析的样品前处理方法。最后,对基于色谱-质谱联用的脂质分析样品前处理技术存在的问题及发展趋势进行了探讨。样品前处理技术的发展将提高脂质分析的灵敏度、选择性和分析速度。     

Determination of trace elements in olive oil by ICP-AES and ETA-AAS: A pilot study on the geographical characterization

The determination of trace elements in edible oils is important because of both the metabolic role of metals and possibilities for adulteration detection and oil characterization.The most commonly used techniques for the determination of metals in oil samples are inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS). For this study, a microwave assisted decomposition of the olive oil in closed vessels using a mixture of nitric acid and hydrogen peroxide was applied as sample preparation.The low achievable LODs enable the determination by ICP-AES of even very low concentrations of most elements of interest. The proposed ICP-AES method permits the determination of Ca, Fe, Mg, Na, and Zn in olive oils. Elements present in small amounts (Al, Co, Cu, K, Mn, Ni) were measured by ETA-AAS in the same sample digest. The concentrations of Al, Co, Cu, K, Mn, and Ni were in the range from 0.15 to 1.5 μg/g and differ according to the geographical origin of the oils. For the amounts of Fe, Mg, Na, and Zn in the samples, no significant differences according to the geographical origin of the oils could be observed, the mean concentrations being 15.31, 3.26, 33.10, and 3.39 μg/g, respectively. The Ca content varies in the range of 1.3 to 9.0 μg/g.The dependency of the trace elemental content of olive oils on their geographical origin can be used for their local characterization.     

Certification for trace elements and methyl mercury mass fractions in IAEA-452 scallop (Pecten Maximus) sample

A marine certified reference material (CRM), IAEA-452, prepared with scallop (Pecten maximus) sample was recently produced by the International Atomic Energy Agency (IAEA) and certified for trace elements and methyl mercury (MeHg). The Scallop (Pecten maximus) sample is commonly found and consumed seafood and is also used as bio-indicators for trace metal contamination in marine pollution studies. This paper presents the sample preparation methodology, material homogeneity and stability studies, evaluation of certification campaign results, the assignment of property values and their associated uncertainty. The reference values and associated expanded uncertainty for 9 trace elements (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) and MeHg in scallop sample are established. The informative value for one more element (Ni) is also given. The new CRM can be used for the development and validation of analytical methods for determination of trace elements and methyl mercury in seafood and also for quality assurance/quality control purposes.     

Solid-phase microextraction of hop volatiles. Potential use for determination and verification of hop varieties

The composition of hop essential oil is an important tool for evaluation of hop quality. As each hop variety has a typical essential oil pattern (fingerprint), hop oil analyses can be used to distinguish between hop varieties. The headspace solid-phase microextraction (SPME) method as described in this contribution is a simple sample preparation technique and represents an alternative procedure for essential oil fingerprint determination. Different SPME parameters (extraction temperature, extraction time and sample mass) were studied and the results were compared with those obtained by the routine distillation method. It is shown that SPME results can be used for determination and verification of varieties grown in Slovenia by means of principal components analysis.     

Food safety assurance using methods of chemical analysis

A review of state-of-the-art methods of sample preparation and chemical analysis for the control of contaminants in foodstuffs and food raw materials is presented. The main achievements and performance characteristics of methods for the determination of pesticides and veterinary drugs, their metabolites, natural toxins, trace amounts of chemical elements, first of all toxic, allergens, food additives, and contaminants from packaging materials in foodstuffs and for the identification of falsifications by methods of chemical analysis are considered.     

电感耦合等离子体发射光谱法测定地质样品中K、Ca等常量元素的前处理方法对比

通过以标准物质玄武岩为试验对象,分别使用酸溶法和碱熔法进行样品前处理,采用电感耦合等离子体发射光谱法（ICP-OES）测定,二者均取得了良好的结果.其中,酸溶法对样品的消解更为彻底,元素的提取更为完全,与标准物质元素推荐值之间的误差更小.但碱熔法流程更为简单,所需时间短,且不影响样品Si元素的测定.总体来说,碱熔法适合用于常规地质样品常量元素的前处理,酸溶法适合于较难溶解的地质样品常量和痕量元素的测定.二者均对试验细节有较高的要求.实际应用中,需不断改进试验方法,严谨试验细节,以获得更简便的方法和更准确的结果.     

固相萃取技术在食品痕量残留和污染分析中的应用

食品痕量残留和污染分析中,样品的前处理极为重要,也是其难点所在。由于食品和农产品样品的多样性和复杂性,目前还没有一种前处理技术能够适合所有情况下的所有样品。本文对近年来发展起来的新型固相萃取技术如固相微萃取、搅拌棒吸附萃取、基质固相分散萃取、分子印迹固相萃取、免疫亲和固相萃取、整体柱固相萃取、碳纳米管固相萃取等在食品痕量残留和污染分析中的应用进行了综述,对未来的发展前景作了展望。     

Polycyclic aromatic hydrocarbons in edible fats and oils: occurrence and analytical methods

This review deals with analytical methods for polycyclic aromatic hydrocarbon (PAH) determination in oils and fats. The data reported in the introduction deal with PAH dietary intake from this group of food and contamination levels recently found by some authors in different vegetable oils, stressing the importance of establishing a method suitable for routine analyses. Traditional sample preparation relies on tedious, time-consuming procedures. They generally consist of an extraction step (liquid-liquid partition, caffeine complexation, saponification) followed by one or more purification procedures (column chromatography, thin-layer chromatography, solid-phase extraction). The analytical determination is usually carried out by HPLC and spectrofluorometric detection, or through high-resolution capillary GC coupled to flame ionisation detection or mass spectrometry. LC is a valid alternative to the traditional sample preparation, and off-line LC-LC allows performing an accurate PAH analysis in less than 2 h. Also supercritical fluid extraction, allowing performing both extraction and clean-up in one combined step, is a promising technique. Hyphenated techniques such as LC-GC and LC-LC-GC seem to be very promising. A completely on-line method for alkylated PAH determination in oils or lipidic extracts contaminated with mineral oil involves a two-dimensional LC-step with intermediate eluent evaporation and GC transfer through a vaporiser/overflow interface.