Improvement of mineral oil saturated and aromatic hydrocarbons determination in edible oil by liquid–liquid–gas chromatography with dual detection

Mineral oils, which are mainly composed of saturated hydrocarbons and aromatic hydrocarbons, are widespread food contaminants. Liquid chromatography coupled to gas chromatography with flame ionization detection represents the method of choice to determine these two families. However, despite the high selectivity of this technique, the presence of olefins (particularly squalene and its isomers) in some samples as in olive oils, does not allow the correct quantification of the mineral oil aromatic hydrocarbons fraction, requiring additional off‐line tools to eliminate them. In the present research, a novel on‐line liquid chromatography coupled to gas chromatography method is described for the determination of hydrocarbon contamination in edible oils. Two different liquid chromatography columns, namely a silica one (to retain the bulk of the matrix) and a silver‐ion one (which better retains the olefins), were coupled in series to obtain the mineral oil aromatic hydrocarbons hump free of interfering peaks. Furthermore, the use of a simultaneous dual detection, flame ionization detector and triple quadrupole mass spectrometer allowed us not only to quantify the mineral oil contamination, but also to evaluate the presence of specific markers (i.e. hopanes) to confirm the petrogenic origin of the contamination.     

Detailed elucidation of hydrocarbon contamination in food products by using solid-phase extraction and comprehensive gas chromatography with dual detection

The present work is focused on the development/optimization of a comprehensive two-dimensional gas chromatography method, with dual detection [flame ionization (FID) and mass spectrometric], for the simultaneous identification and quantification of mineral-oil contaminants in a variety of food products. The two main classes of contaminants, namely saturated and aromatic hydrocarbons, were previously fractionated on a manually-packed silver silica solid-phase extraction (SPE) cartridge. The quantitative results were compared with those obtained by performing a large volume injection, in a GC-FID system, after the same SPE process and by an on-line liquid–gas chromatography method, with very similar results observed. The presence of a series of unknown compounds, that appeared when using the off-line methods, was investigated using the mass spectrometric data, and were tentatively-identified as esterified fatty acids, most probably derived from vegetable oil based ink.     

LC-GC analysis of the aromatics in a mineral oil fraction: Batching oil for jute bags

Aromatics of a C₁₅? C₃₀ mineral oil fraction, the “batching oil” used for producing jute fabrics, were analyzed for estimating the toxicity of oil transferred from jute bags to foods. Group-type pre-separation according to ring systems occurred on a LC NH₂ column with pentane and small additions of methanol as eluent. LC fractions were characterized by LC-GC-MS and quantitated by LC-GC-FID. The oil contained 23% aromatics and 1% “polars”; some 99.5% of the aromatics were alkylated.     

Development of an improved analytical method for the determination of carcinogenic polycyclic aromatic hydrocarbons in transformer oil

Polynuclear aromatic hydrocarbons (PAHs) are natural constituents of transformer oils and are essential in prolonging transformer in-service lifetime. Issues concerning PAH carcinogenicity demand methods that provide qualitative and quantitative information on the PAH composition of new and in-service oils to allow informed operational decisions to be made. However, current analytical methods focus on PAH fingerprinting, as opposed to quantitative analysis and are also cumbersome, relying on the use of large (>100 ml) volumes of organic solvents, some of which are hazardous. This paper reports a method for the improved quantification of carcinogenic PAHs in transformer oils that is both simple and repeatable. The method uses commercially available solid-phase extraction columns and millilitre volumes of relatively non-hazardous solvents. Extraction efficiencies of > or =74% were obtained for the Environmental Protection Agency priority PAHs. The method has potential for automation and high-throughput analysis and thus is of interest to industries that use transformer oils.     

Feasibility studies for the preparation and certification of reference materials Part II: mineral oil contaminated waste materials

The 2-year international joint project HYCREF (Contract-No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogenous and stable water-, soil- and waste reference materials contaminated with mineral oil hydrocarbons and to test certify the mineral oil content by gas chromatographic methods. As mineral oil products are important sources for environmental contaminations, appropriate reference materials certified by using the new gas chromatographic methods (soil: ISO/FDIS 16703, waste: prEN 14039 and KW/04, water: ISO 9377-2) are highly needed. Additional to the HYCREF-results presented in part I–mineral contaminated soils–this second paper gives an overview of the feasibility study for the preparation and test certification of three waste reference materials (offshore marine sediment, building material and industrial waste). The following specifications, which had been defined in the project work plan, were reached successfully: uncertainty of the mineral oil content resulting from the certification exercise ≤5% and a between-bottle inhomogeneity of ≤3%. All three materials have been evaluated for long- and short term stability. They contain different levels and types of mineral oil and cover the full application range of ISO/FDIS 16703 and prEN 14039 (100–10,000 mg/kg). The expanded uncertainties U _cert of the three materials are about 6%. In this way, they are comparable to ERM^®-CC015a (U _cert=7.1%, mineral oil in a river sediment) and are suited to close the present gap of commercially available CRM for mineral oil determination in waste.     

Development of a DSC method for determination of certain technological parameters of margarine and mixed-fat spread

Nutritional-physiological research of near past decades had established the real nutritional value of fats and oils. In the former theory the nutritional value of fats and oils is influenced mainly by the rate of saturated/unsaturated fats. It was ruled out, and positive, inert or risk physiological effect of every single fatty acid had been established. The health-care effect of omega-3 fatty acid mainly by the favourable (<3:1) rate of omega-6/omega-3 was established, as inert was concerned the saturated C₁₆ fatty acid and the maximal amount of trans-fatty acids carrying health risk in fats was legally regulated in some countries. These nutritional-physiological requirements were mainly fulfilled by margarine producers and the elementary fats were selected in such a way that they should meet these requirements. Our method helps to the producers to quickly determine the amount of the liquid and solid fat at certain temperature and/or to adjust the technological temperature parameters. The main steps of our method are: a./ determination of cooling rate (K min^–1) of the crystallizer device; b./ determination of the rate of liquid/solid fat at 10°C temperature. This value is used for the determination of the rate of fats and oils as a function of technology and required consistency firmness (spread ability); c./ determination of the temperature from the cooling curve where the crystallization of most part of the fat has finished. This value is used for the determination of outlet temperature parameter of product coming out from the crystallizer device for margarines or mixed-fat spreads with water-in-oil system.     

重油中含硫芳烃二维液相色谱分离平台开发及应用

基于氯化钯配位交换色谱柱和氨基键合正相色谱柱，利用自动阀切换系统，构建了在线二维液相色谱分离平台。通过优化液相色谱分离条件，实现减压蜡油样品中含硫芳烃的在线富集与多环芳烃的环数分离。利用傅里叶变换离子回旋共振质谱对分离后的含硫芳烃和芳烃组分进行分子水平表征，得到更为详细的化合物类型与碳数分布信息。根据计算得到的平均结构信息，可以提供分离后组分典型的分子结构式，并对芳环结构和侧链位置进行了推测。建立的分析表征方法可以加深对重馏分油中含硫芳烃化合物的分子水平认识，为重油加工过程的原料选择与工艺条件优化提供技术支持。     

Development of an improved method for the determination of polycyclic aromatic hydrocarbons in mainstream tobacco smoke

A gas chromatograph/mass-selective detection (GC/MS) method has been developed and validated for the quantitation of 16 polycyclic aromatic hydrocarbons found in mainstream tobacco smoke condensate. The utilization of two types of solid-phase extraction media combined with capillary column technology removed matrix interferences, afforded a significant reduction in analysis run time, and increased accuracy. Also, the addition of a chilled impinger was used to trap semi-volatile polycyclic aromatic hydrocarbons and to provide more accurate data. This was done without sacrificing the repeatability, reproducibility, and precision obtained in previously published methods. The development and validation studies discussed in this paper resulted in an improved, robust analytical method capable of increasing laboratory capacity and reducing sample reporting time.     

Application of counter-current chromatography as a new pretreatment method for the determination of polycyclic aromatic hydrocarbons in environmental water

Counter‐current chromatography (CCC) was investigated as a new sample pretreatment method for the determination of trace polycyclic aromatic hydrocarbons (PAHs) in water environmental samples. The experiment was performed with a non‐aqueous binary two‐phase solvent system composed of n‐heptane and acetonitrile. The CCC column was first filled with the upper stationary phase, and then a large volume of water sample was pumped into the column while the CCC column was rotated at 1600 rpm. Finally, the trace amounts of PAHs extracted and enriched in the stationary phase were eluted out by the lower mobile phase and determined by gas chromatography–flame ionization detector (GC‐FID) or gas chromatography–mass spectrometry (GC‐MS). The enrichment and cleanup of PAHs can be fulfilled online by this method with high recoveries (84.1–103.2%) and good reproducibility (RSDs: 4.9–12.2%) for 16 EPA PAHs under the optimized CCC pretreatment conditions. This method has been successfully applied to determine PAHs in lake water where 8 PAHs were detected in the concentration of 40.9–89.9 ng/L. The present method is extremely suitable for the preparation of large volume of environmental water sample for the determination of trace amounts of organic pollutants including PAHs as studied in this paper.     

土壤中多环芳烃和酞酸酯类有机污染物气相色谱-质谱测定方法中的质量控制与质量保证

建立了气相色谱-质谱(GC-MS)测定土壤中多环芳烃(PAHs)和酞酸酯类(PAEs)有机污染物的方法。样品经加速溶剂萃取和超声萃取处理后,通过固相萃取或凝胶渗透色谱法进行净化,在选择离子监测模式下进行定量。通过全程序空白、空白加标回收、清洁土壤基质加标回收及有证标准参考物质比对等方式,对所建立的方法进行严格的质量控制和保证。16种PAHs和7种PAEs的方法检出限分别为0.13～2.2 μg/kg和0.19～0.52 μg/kg,平均加标回收率分别为41.5%～116.9%和90.7%~107.1%。本研究所建立的土壤中PAHs和PAEs的GC-MS快速分析方法及其质量控制措施可以为全国性土壤污染状况调查数据的科学性和准确性提供技术保障。     

Development of a matrix solid-phase dispersion method for the determination of polycyclic aromatic hydrocarbons in sewage sludge samples

A new, single-step extraction and purification method based on matrix solid-phase dispersion (MSPD) was developed to determine 17 polycyclic aromatic hydrocarbons (PAHs) in sewage sludge samples. The MSPD method consists of sample homogenisation, exhaustive extraction and clean-up by a single process. The different operational parameters of the method, such as the type of dispersant, type and amount of additives, clean-up co-sorbent and extractive solvent were evaluated. Reversed-phase (C18) and polymeric (Oasis HLB and Oasis MAX) materials, as well as normal phase sorbents (Florisil, silica, neutral alumina) and an inert support (sand) were tested to assess the sorbents effect on the yield and selectivity of the MSPD process. Analysis of extracts was performed by high performance liquid chromatography (HPLC) coupled with fluorescence detection.Quantification limits obtained for all of these considered compounds (between 0.0001 and 0.005 μg g⁻¹ dry mass) were well below of the limits recommended in the EU. The extraction yields for the different compounds obtained by MSPD ranged from 76.3% to 103.6%. On the other hand, the extraction efficiency of the optimised method is compared with that achieved by microwave-assisted extraction and the method was applied to the analysis of real sewage sludge samples. A certified reference material (sewage sludge (BCR 088)) and a reference material (sewage sludge (RTC-CNS312-04)) were used to validate the proposed method.     

A new approach based on a combination of direct and headspace cold-fiber solid-phase microextraction modes in the same procedure for the determination of polycyclic aromatic hydrocarbons and phthalate esters in soil samples

This study describes a new approach to cold-fiber solid-phase microextraction (CF-SPME) based on a combination of different extraction modes in the same extraction procedure. Also, the high quantity of water required to facilitate both the desorption of analytes from the matrix and their transport to the fiber coating is reported. The extraction mode was changed from the direct to the headspace mode in a single extraction while manipulating the extraction times and coating temperature to improve the extraction of compounds with different volatilities. Compounds with low volatility were better extracted in the direct mode, while the headspace mode was more appropriate for volatile compounds. Polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PEs) in sand or soil samples were used as model compounds and matrices in this study. The optimized conditions were: sample pH in the range of 4-7, addition of 12 mL of 194 g L(-1) aqueous NaCl solution in a 15 mL vial, and 80 min total extraction time with a sample temperature of 90°C (50 min in direct mode with coating at 90°C followed by 30 min in headspace mode with coating at 30°C). The proposed procedure was compared with conventional CF-SPME (with and without addition of water) and was found to be more effective for all the analytes, since it is capable of extracting both heavier and lighter compounds from soil samples in a single extraction procedure. The use of an excess of water and a combination of extraction modes in the same CF-SPME procedure are the main factors responsible for this enhancement. The proposed method was applied to the extraction of PAHs and PEs in spiked soil samples and excellent results were obtained for most of the compounds evaluated.     

Optimization and validation of a low temperature microwave-assisted extraction method for analysis of polycyclic aromatic hydrocarbons in airborne particulate matter

A low temperature microwave-assisted extraction method (MAE) is reported for the analysis of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter (PM). The main parameters affecting the extraction efficiency (choice of extractants, microwave power, and extraction time) were investigated and optimized. The optimized procedure requires a 20 ml mixture of acetone:n-hexane (1:1) for extraction of PAHs in PM at 150 W of microwave energy (20 min extraction time). Clean-up of MAE extracts was not found to be necessary. The optimized method was validated using two different SRM (1648-urban particulate matter and 1649a, urban dust). The results obtained are in good agreement with certified values. PAHs recoveries for both reference materials were between 79 and 122% with relative standard deviation ranging from 3 to 21%. Detection limits were determined based on blank determination using two kinds of quartz filter substrates (n = 10), which ranged from 0.001 (0.03) ng m⁻³ (pg/μg) for B(k)Ft to 1.119 (37.3) for Naph in ng m⁻³ (pg/μg), respectively. The repeatability and day-to-day reproducibility obtained in this study were in the range of 4-16 and 3-25% for spiked standards and SRM 1649, respectively. The optimized and validated MAE technique was applied to the extraction of PAHs from a set of real world PM samples collected in Singapore. The sum of particulate-bound PAHs in outdoor PM ranged from 1.05 to 3.45 ng m⁻³ while that in indoor PM (cooking emissions) ranged from 27.6 to 75.7 ng m⁻³, respectively.     

超高效液相色谱-串联质谱法同时测定食品级聚苯乙烯和聚乙烯色母粒中33种初级芳香胺

建立了超高效液相色谱-三重四极杆质谱(UPLC-MS/MS)同时测定食品级聚苯乙烯(PS)和聚乙烯(PE)色母粒中33种初级芳香胺(PAAs)的检测方法。PS色母粒用二氯甲烷溶解,超声提取后加入甲醇沉淀,并将提取液过石墨化碳固相萃取柱净化;PE色母粒用二氯甲烷超声溶胀提取;将PS色母粒过柱液和PE色母粒提取液浓缩,浓缩液用甲醇-水(1:9, v/v)定容至2 mL, 0.22 μm膜过滤后上机检测。采用BEH Phenyl色谱柱(100 mm×2.1 mm, 1.7 μm),以0.07%(v/v)甲酸甲醇溶液-水(1:9, v/v)为流动相,梯度洗脱分离,UPLC-MS/MS多反应监测(MRM)模式检测,同位素内标法定量。优化了色谱分离条件、质谱碎裂电压、碰撞能量等,并考察了提取时间、提取溶剂、浓缩方式等对回收率的影响。33种PAAs的方法检出限为6~10 μg/kg,定量限为20~30 μg/kg, 2种不同基质样品在20、100、200 μg/kg等3个添加水平的平均回收率为61.3%~119.8%,相对标准偏差(RSD)为1.4%~14.8%。本方法操作简便、快速、准确、灵敏度高,能满足相关测定要求。     

应用二极管阵列串联荧光检测-高效液相色谱技术快速测定玩具材料中蒽油的4种成分

采用二极管阵列串联荧光检测-高效液相色谱法对玩具材料中蒽油的4种主要成分蒽、菲、芘、荧蒽进行了检测。样品用正己烷-丙酮溶液超声提取,硅胶小柱净化。方法的荧光检测线性范围为0.5～1000 μg/L,二极管阵列检测线性范围为0.5～1000 mg/L。加标回收、精密度试验表明4种成分的回收率为70.0%～120%,精密度为0.7%～8.8%。蒽、菲、芘、荧蒽的检出限分别为0.1、0.1、0.2、0.3 μg/L,定量限分别为0.4、0.2、0.5、0.8 μg/L。方法具有灵敏度高、检出限低的特点,适用于玩具材料中蒽油4种成分的快速定性、定量检测。     

紫草油有效成分的高效液相色谱测定法及其在超临界流体萃取制备紫草油中的应用

紫草提取制备成的紫草油能够预防及治疗婴儿尿布疹、皮肤溃烂、湿疹等多种皮肤疾患,临床应用非常广泛,超临界流体萃取是紫草有效成分提取的优选方法.该文建立了紫草油有效成分的高效液相色谱(HPLC)测定方法,并以紫草油所含的有效成分含量为评价指标,采用三因素三水平正交试验法对紫草超临界流体萃取制备过程中的几个重要因素(萃取压力...     

Ultra-high performance liquid chromatographic method for the determination of polycyclic aromatic hydrocarbons in a passive environmental sampler

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous compounds released in the environment by different sources. The aim of the present work was to validate a solid‐phase extraction (SPE) and a rapid ultra‐high performance liquid chromatographic (UHPLC) method for the analysis of PAHs in a passive environmental sampler, namely a Dacron® (the commercial name of a synthetic fiber based on polyethylene terephthalate) textile. The elution temperature was optimized to improve the resolution of early‐eluted compounds, namely acenaphthene (Ac) and fluorene (F). The UHPLC method lasts about 10 min and showed good linearity for all the 16 PAHs considered, with regression coefficients over 0.99. Recoveries, limits of detection (LODs), and limits of quantification (LOQs) of the SPE method were well within the performance criteria fixed by the Regulation n. 836/2011, namely 0.3 and 0.9 μg/kg, respectively.     

Development and validation of a LC method for the separation and determination of the anticancer‐active FeIII(4‐methoxy‐salophene) using the new second‐generation monolith

LC method with the newly introduced second‐generation monolithic silica RP‐18e column has been developed for the separation of Fe^III(salophene) and four methoxy‐substituted Fe^III(salophene) complexes. The method has been validated for the quantitation of Fe^III(4‐OMe‐salophene), a highly active anticancer substance in vitro, bound to serum albumin. Our routinely used high‐resolution continuum‐source atomic absorption spectroscopy method based on the determination of the central iron atom was unsuitable in this case because serum originally contains significant amounts of iron as revealed by a blank sample of serum albumin. The developed LC method depends on detecting the whole complex rather than the bound iron. Two morphologically different first‐ and second‐generation HPLC monolithic columns have been compared for this purpose. The newly introduced second‐generation monolithic silica column Chromolith® HighResolution RP‐18e column (100 × 4.6 mm, Merck) separated the mixture successful within 13 min. A mobile phase consisting of 25 mM phosphate buffer pH 3/methanol (60:40, v/v) was used at a flow rate of 1 mL/min. The dynamic linear working range of the calibration curve for Fe^III(4‐OMe‐salophene) was found to be between 1 and 200 μg/mL. Detection and quantitation limits were 0.3 and 1 μg/mL, respectively.     

Development of a method for the rapid determination of pentachlorophenol in leather using supercritical fluid extraction with in situ derivatization

Pentachlorophenol (PCP) was extracted from leather with supercritical carbon dioxide and in situ acetylated under static SFE conditions in the presence of triethylamine. During the dynamic extraction step, the derivatives were removed from the matrix and collected with either a pure liquid (light petroleum) or a liquid-solid (light petroleum-solid sorbent (C18, alumina, Florisil or Celite)) trap. To prevent restrictor plugging, a suitable restrictor was designed. The clean-up of the extracts was optimized in this study. Different internal standards were tested and it was shown that not all of them were usable. The SFE results were compared with those obtained by Soxhlet extraction with methanol. With SFE instead of conventional Soxhlet extraction, the overall time required for determination of PCP in leather can be reduced from about 2 days to approx. 3 hours.     

Development and validation of a hydrophilic interaction liquid chromatographic method for determination of aromatic amines in environmental water

A simple, precise, and accurate hydrophilic interaction liquid chromatographic (HILIC) method has been developed for the determination of five aromatic amines in environmental water samples. Chromatography was carried out on a bare silica column, using a mixture of acetonitrile and a buffer of NaH₂PO₄–H₃PO₄ (pH 1.5, containing 10 mM NaH₂PO₄) (85:15, v/v) as a mobile phase at a flow rate of 1 mL min⁻¹. Aromatic amines were detected by UV absorbance at 254 nm. The linear range of amines was good (r² > 0.998) and limit of detection (LOD) within 0.02–0.2 mg L⁻¹ (S/N = 3). The retention mechanism for the analytes under the optimum conditions was determined to be a combination of adsorption, partition and ionic interactions. The proposed method was applied to the environmental water samples. Aromatic amines were isolated from aqueous samples using solid-phase extraction (SPE) with Oasis HLB cartridges. Recoveries of greater than 75% with precision (RSD) less than 12% were obtained at amine concentrations of 5–50 μg L⁻¹ from 100 mL river water and influents from a wastewater treatment plant (WWTP). The present HILIC technique proved to be a viable method for the analysis of aromatic amines in the environmental water samples.