Quality control procedures for chloride and nitrate ions analysis in plant samples by ion chromatography

This paper describes useful procedures to monitor quality of chloride and nitrate ions analysis in plant samples by ion chromatography. The use of certified reference materials (CRMs) provided an efficient way to verify the accuracy of the method. Data generated by the method of analysis for chloride compared favourably with certified values. The quality system included also the systematic analysis of an internal reference sample in each batch of samples routinely analysed. The performance of the method, including extraction and measurement, over a period of 3 years was reported with control charts. The yearly variation coefficients were less than 6.5% for chloride and nitrate ions. Finally, the analytical method was evaluated through the participation of laboratory to an international proficiency testing scheme. Found results were not significantly different from published medians.     

Active single-drop microextraction for the determination of gaseous diisocyanates

Heterocyclic amines (HAs) were analysed in meat extract samples using a new method based on pressurised liquid extraction (PLE) and liquid chromatography-tandem mass spectrometry. This method combines the use of a pressurised fluid with a triple quadrupole MS/MS system, resulting in benefits from both systems: high extraction efficiency and sensitivity. The effects of solvent type and PLE operational parameters, such as temperature and extraction time, were studied to obtain maximum recovery of the analytes with minimum contamination. HA extraction was best achieved using dichloromethane/acetone (50/50, v/v) at 80 degrees C for 10 min. Recoveries ranged from 45% to 79% with good quality parameters: limit of detection values between 0.02 and 1 ng g(-1), linearity (r(2)>0.997), and run-to-run and day-to-day precisions with relative standard deviations lower than 13% achieved at both low (0.20 microg g(-1)) and medium (1.0 microg g(-1)) concentrations. This method reduces sample manipulation and total extraction time by nearly four-fold compared to conventional solid phase extraction. The optimised method was validated using laboratory reference material based on a meat extract, and was successfully applied to HA analysis in several cooked beef samples.     

超声细胞粉碎萃取结合超高效液相色谱用于六味地黄丸的整体分析（英文）

针对中药复方制剂六味地黄丸的质量控制提出了一种多指标全药材整体分析新策略。从组成六味地黄丸的每一味药材中选取1~2个药效成分,即选取熟地黄中的毛蕊花糖苷、山茱萸中的莫诺苷和马钱苷、牡丹皮中的丹皮酚和芍药苷、山药中的尿囊素、茯苓中的茯苓酸、泽泻中的23-乙酰泽泻醇B作为六味地黄丸的质量控制指标成分,采用快速、简便、高效的超声细胞粉碎提取(UCGE)法对这8个指标成分进行同步提取。用响应曲面分析中的Box-Behnken模式对UCGE提取过程中对提取效率影响较大的料液比、提取时间和提取温度等参数进行了优化。得到最优的提取条件:料液比1∶45(g/mL)、提取时间40 min、提取温度20℃。进一步利用超高效液相色谱-二极管阵列检测(UPLC-PAD)技术实现多指标成分在同一根色谱柱上的同步分离和检测,从而建立六味地黄丸的多指标全药材整体色谱。采用HSS T3色谱柱(50 mm×2.1 mm,1.8μm),以乙腈-水为流动相进行梯度洗脱,基于指标成分的紫外光谱特征选择5个检测波长同时检测,并进行了线性关系、检出限、定量限、精密度、稳定性、重复性、准确性等方法学验证。该研究为六味地黄丸质量标准的建立提供了依据,同时也为中药复方制剂提供了一种质量控制新模式和新理念。     

A rapid fractionation method for heavy metals in soil by continuous-flow sequential extraction assisted by focused microwaves

A microwave-assisted continuous-flow sequential extraction system was developed for rapid fractionation analysis of heavy metals in soil. Insertion of pressure-adjusted air between the extractants provided stable flows of the extractants without mutual mixing and back-pressure influence of a column packed with soil, thereby facilitating reliable continuous-flow extractions. In addition, use of pure water as a pumping solvent removed metal contamination because of direct contact between corrosive extractants and the pump containing metallic materials. Focused microwave irradiation to the soil accelerated the selective extractions of the acid-soluble and reducible fractions of heavy metals in soil in the first and second steps of the sequential extraction conditions, as defined by the Commission of the European Bureau of Reference (BCR). The microwave-assisted continuous-flow extraction provided high correlations in amounts of six heavy metals except Zn in the first step and Cu in the second step extracted from a reference sludge soil, BCR CRM 483, with a conventional batchwise extraction proposed by BCR; continuous-flow extraction assisted by conductive heating provided lower correlations for all the six metals. The proposed method drastically reduced the time required for the sequence extraction to ca. 65 min without losing accuracy and precision of the fractionation analysis of heavy metals in soil, whereas the BCR batchwise method requires ca. 33 h. An erratum to this article can be found at     

Rapid analysis of pseudolaric acids in Cortex Pseudolaricis and related medicinal products by high performance liquid chromatography

A simple, rapid, reverse-phase high performance liquid chromatographic method was developed for the quantitative analysis of pseudolaric acids in Cortex Pseudolaricis and its related medicinal products. With a C₁₈ analytical column (4.6 mm × 150 mm i.d.), five pseudolaric acids, namely pseudolaric acids A-C, pseudolaric acid A-O-β-d-glucopyranoside and pseudolaric acid B-O-β-d-glucopyranoside, were well separated within 7 min. Acetonitrile and 0.10% acetic acid were used as the mobile phase in a gradient program. The UV detection wavelength was set at 260 nm. The detection limits and quantification limits ranged in 8.26-16.66 ng/ml and 27.54-55.53 ng/ml, respectively. The intra- and inter-day variations were less than 1% for all five compounds. The recovery of all spiked pseudolaric acids ranged from 99.1% to 101.9%. Compared to existing analytical methods, this new method not only used two more important chemical markers but also provided a fivefold reduction in analysis time. In addition, the extraction method of herb sample was also modified by an orthogonal array experiment on three variable parameters: extraction time, solvent volume, and extraction cycles. The optimized extraction method was much simpler and could be efficiently used to analyse large set of herbal materials and related medicinal products. Nineteen herb samples collected from different regions of China and five related products were examined with this new analytical method. The results showed that this method is effective in distinguishing adulterants and unqualified products.     

Ultrasonication extraction coupled with magnetic solid-phase clean-up for the determination of polycyclic aromatic hydrocarbons in soils by high-performance liquid chromatography

C18-functionalized magnetic microspheres synthesized in a three-stage system and characterized by Fourier transform infrared (FTIR) spectroscopy and SEM were applied for clean-up and enrichment of polycyclic aromatic hydrocarbons (PAHs) in soil samples combined with ultrasonication extraction. Magnetic solid-phase extraction (MSPE) parameters, such as elution solvents, amounts of sorbents, enrichment time and organic modifier, were optimized together with ultrasonication time and extraction solvents. Under the optimal conditions, the developed method provided spiked recoveries of 63.2-92.8% with RSDs of less than 6.4% and limits of detection were 0.5-1.0 ng/g. This new method provides several advantages, such as high extraction efficiency, convenient extraction procedure and short analysis times. Finally, the method was successfully applied to the determination of polycyclic aromatic hydrocarbons in soil samples.     

Trace analysis of technical nonylphenol,bisphenol A and 17alpha-ethinylestradiol in wastewater using solid-phase microextraction and gas chromatography-mass spectrometry

To enable high sample throughput, an automated solid-phase microextraction (SPME) method coupled with GC-MS for the trace analysis of technical nonylphenol, bisphenol A and 17alpha-ethinylestradiol was developed. The extraction performance of different SPME fibre coatings was examined, with polyacrylate proving most suitable. Although study of the extraction time showed that the analytes have not reached equilibrium after 3 h, as a compromise an extraction time of 1 h was applied in all the experiments with detection limits between 0.04 and 1 microg l(-1) for wastewater effluent. The mean reproducibility of the technique is 8% RSD. Carry-over effects are negligible. The linearity of calibration curves ranges over three orders of magnitude. The method was tested for determining the analytes in influents and effluents of constructed wetland plants and in model wastewater used in laboratory experiments.     

Use of different sample temperatures in a single extraction procedure for the screening of the aroma profile of plant matrices by headspace solid-phase microextraction

This study proposes a new approach to the optimization of the extraction of the volatile fraction of plant matrices using the headspace solid-phase microextraction (HS-SPME) technique. The optimization focused on the extraction time and temperature using a CAR/DVB/PDMS 50/30 μm SPME fiber and 100mg of a mixture of plants as the sample in a 15-mL vial. The extraction time (10-60 min) and temperature (5-60 °C) were optimized by means of a central composite design. The chromatogram was divided into four groups of peaks based on the elution temperature to provide a better understanding of the influence of the extraction parameters on the extraction efficiency considering compounds with different volatilities/polarities. In view of the different optimum extraction time and temperature conditions obtained for each group, a new approach based on the use of two extraction temperatures in the same procedure is proposed. The optimum conditions were achieved by extracting for 30 min with a sample temperature of 60 °C followed by a further 15 min at 5 °C. The proposed method was compared with the optimized conventional method based on a single extraction temperature (45 min of extraction at 50 °C) by submitting five samples to both procedures. The proposed method led to better results in all cases, considering as the response both peak area and the number of identified peaks. The newly proposed optimization approach provided an excellent alternative procedure to extract analytes with quite different volatilities in the same procedure.     

QuEChERS sample preparation followed by ultra-performance liquid chromatography – tandem mass spectrometry for rapid screening of dioctyl sulfosuccinate sodium salt in avian egg tissue

A quantification method was developed for the determination of dioctyl sulfosuccinate sodium salt (DOSS) in avian egg samples based on a QuEChERS extraction technique followed by UPLC-MS/MS analysis. DOSS is an anionic surfactant that is part of the Corexit^® 9500 dispersive mixture that prevents the formation of oil slicks on water bodies. It was extensively used when the Deepwater Horizon rig exploded and a large amount of crude oil was released into the Gulf of Mexico. QuEChERS provided a simple, effective and time saving sample preparation method prior to analysis without reducing analytical sensitivity and became an excellent substitute to lengthy traditional extraction methods. Weak anionic exchange cleanup significantly reduced matrix effects and improved analyte sensitivity. Ultra-performance liquid chromatography provided an effective separation method, while MS/MS provided the necessary selectivity and increased sensitivity. Our method achieved baseline separation of DOSS, surrogate (sodium octyl sulfate – d17) and the internal standard (sodium dioctyl sulfate – d25), with limits of detection (LOD) and limits of quantitation (LOQ) for DOSS being 260 and 500 pg/mL, respectively. Quality control recoveries were 70.5 ± 7.3% (mean ± standard deviation, n = 3) for the laboratory control sample and 72.4 ± 4.9% (n = 3) for the matrix spike. The extraction efficiency was monitored by adding surrogate compound to every sample with recoveries of 104.6 ± 14.1 for SDS-d1 and 81.8 ± 6.8 for SOS-d17. Currently, limited peer reviewed scientific data are reported on the effects of oil dispersants on the environment. Our analytical method for the determination of DOSS in avian egg matrix can be used to provide reliable data on the fate and effects of DOSS in biological systems.     

Analysis of phenoxyalkanoic acid herbicides and their phenolic conversion products in soil by microwave assisted solvent extraction and subsequent analysis of extracts by on-line solid-phase extraction-liquid chromatography

A multiresidue method for the determination of phenoxyalkanoic acid herbicides and their phenolic conversion products in soil was developed. The method was based on microwave-assisted solvent extraction (MASE) of soil samples by an aqueous methanolic mixture and subsequent analysis of extracts by automated solid-phase extraction followed by on-line high-performance liquid chromatography and diode array detection. MASE parameters (extraction temperature and time, composition of the extraction mixture and extraction volume) were optimized with respect to analyte recoveries. The method was validated with two types of soils containing 1.5 and 3.5% organic matter, respectively, both types containing fresh and aged residues of sought analytes. Under the selected analytical conditions when soils with fresh residues were analyzed all target analytes were recovered above 80% from the soil containing 1.5% organic matter, while limits of identification at the level of 20-40 ng/g were achieved. From the soil containing 3.5% organic matter the least polar phenolic analytes exhibited slightly reduced recoveries, while identification limits of 30-50 ng/g were achieved. Samples with aged residues exhibited reduced recoveries for some analytes, the reduction amounting up to 6-12% within 1 month of aging period depending on soil organic matter.     

Combination of ultrasound-assisted ionic liquid dispersive liquid-phase microextraction and high performance liquid chromatography for the sensitive determination of benzoylureas pesticides in environmental water samples

This paper describes a new method for rapid and sensitive determination of diflubenzuron, flufenoxuron, triflumuron and chlorfluazuron in water samples by ultrasound-assisted ionic liquid dispersive liquid-phase microextraction in combination with HPLC. Ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate ([C(6)MIM][PF(6)]) was used as the extraction solvent for the enrichment of four benzoylurea (BU) pesticides. Factors such as volume of [C(6)MIM][PF(6)], sonication time, sample pH, extraction time, centrifuging time and salting-out effect were systematically investigated. Under the optimum conditions, an excellent linear relationship was achieved in the range of 1.0-100?μg/L. The detection limits varied from 0.21 to 0.45?μg/L and the precision of the method was below 6.9% (RSD, n=6). The proposed method was successfully applied for the determination of these BU pesticides in water samples and excellent spiked recoveries were achieved. All these results demonstrated that this procedure provided a new simple, rapid, easy to operate, efficient and sensitive method for the analysis of BU pesticides in aqueous samples.     

保健食品中非法添加物检测的前处理及分析方法研究进展

保健食品作为一种特定的食品种类,能调节人体的机能,适用于特定人群食用.但是在保健食品中添加化学药物和非法添加物的现象也层出不穷,因此迫切需要建立多指标的有效检测方法,为保健食品的质量安全提供技术保障.高效的前处理方法和高灵敏的分析方法为检测非法添加物提供了有效的技术手段.综述了近三年来溶剂萃取和固相萃取样品前处理方法,以及高效液相色谱、实时直接分析质谱、表面增强拉曼光谱及色谱-质谱串联技术等分析方法在微量及痕量非法添加物检测中的应用,为进一步研究建立高效简便的前处理方法和检测新方法、新技术提供理论参考.     

A rapid method for the determination of brominated flame retardant concentrations in plastics and textiles entering the waste stream

Due to new European legislation, products going to waste are subject to ‘low persistent organic pollutant concentration limits’. Concentrations of restricted brominated flame retardants in waste products must be determined. A rapid extraction and clean‐up method was developed for determination of brominated flame retardants in various plastics and textiles. The optimised method used vortexing and ultrasonication in dichloromethane followed by sulfuric acid clean‐up to determine target compounds. Poly‐brominated diphenyl ethers were determined by gas chromatography with mass spectrometry and hexabromocyclododecane by liquid chromatography with tandem mass spectrometry. Good recoveries of target analytes were obtained after three extraction cycles. The method was validated using poly‐propylene and poly‐ethylene certified reference materials as well as previously characterised textiles, expanded and extruded poly‐styrene samples. Measured concentrations of target compounds showed good agreement with the certified values indicating good accuracy and precision. Clean extracts provided low noise levels resulting in low limits of quantification (0.8–1.5 ng/g for poly‐brominated diphenyl ethers and 0.3 ng/g for α‐, β‐ and γ‐hexabromocyclododecane). The developed method was applied successfully to real consumer products entering the waste stream and it provided various advantages over traditional methods, including reduced analysis time, solvent consumption, minimal sample contamination and high sample throughput, which is crucial to comply with the implemented legislation.     

A semi-automated approach for processing and extracting low-level plutonium from soil

A semi-automated approach for processing and extracting plutonium from large soil samples has been developed and implemented in our laboratory. The system approach was designed around basic plutonium techniques already published in the literature. The technique was carried out using modular work stations for the major analytical steps, namely; soil leaching, plutonium extraction and phase evaporation. This allowed the laboratory to operate in a batch mode which improved sample flow and significantly reduced analysis cost and time. The method has been validated and is routinely used in our laboratory. Chemical yield, accuracy and precision were comparable to those obtained from manual procedures. The system was designed with built-in flexibility to accommodate revised or similar procedures and to complement most existing laboratory equipment and resources.     

Determination of 2,4-D and Dicamba in food crops by MEKC

Summary The determination of 2,4-D (2,4-dichlorophenoxyacetic acid) and Dicamba (2-methoxy-3,6-dichlorobenzoic acid) residues in sugar cane, rice and corn was performed by a supercritical fluid extraction (SFE) method using CO₂/acetone as extraction mix and an SFE apparatus developed in our laboratory. The extracts were cleaned up after extraction by both liquid-liquid partition and a Florisil column. Micellar electrokinetic capillary chromatography (MEKC) coupled with ultraviolet on-column detection was used for the analysis of these pesticides. The detection limits were improved by the preparation of a special detection cell with an increased pathlength that gave detection limits of ca. 0.6 pg for 2,4-D and Dicamba. Our results demonstrated that capillary electrophoresis can be a powerful new analytical tool for pesticide residue analysis.     

RP-HPTLC densitometric determination and validation of vanillin and related phenolic compounds in accelerated solvent extract of Vanilla planifolia*

A simple, fast and sensitive RP-HPTLC method is developed for simultaneous quantitative determination of vanillin and related phenolic compounds in ethanolic extracts of Vanilla planifolia pods. In addition to this, the applicability of accelerated solvent extraction (ASE) as an alternative to microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and Soxhlet extraction was also explored for the rapid extraction of phenolic compounds in vanilla pods. Good separation was achieved on aluminium plates precoated with silica gel RP-18 F(254S) in the mobile phase of methanol/water/isopropanol/acetic acid (30:65:2:3, by volume). The method showed good linearity, high precision and good recovery of compounds of interest. ASE showed good extraction efficiency in less time as compared to other techniques for all the phenolic compounds. The present method would be useful for analytical research and for routine analysis of vanilla extracts for their quality control.     

Analysis of Steroid Hormones in Water Using Palmitate-Coated Magnetite Nanoparticles Solid-Phase Extraction and Gas Chromatography–Tandem Mass Spectrometry

A new extractive method based on magnetic solid–phase extraction using palmitate-coated magnetite nanoparticles coupled with gas chromatography-tandem mass spectrometry was developed for the extraction of estrone, androstenedione and progesterone hormones from water. The amount of nanoparticles and extraction time were optimized applying an experimental design to estimate simultaneously their influence on the recoveries. Results showed that the extraction efficiency was highly affected by the addition of salt and acetonitrile was the solvent used to elute the analytes from the nanoparticles. Derivatization via enolization of ketone group was carried out in the extract for the simultaneous derivatization of hydroxyl and ketone groups of steroid hormones previously to their chromatographic analysis. The extraction efficiencies of the nanoparticles were studied spiking at four concentration levels and recoveries from 94.6 to 109.7 % were obtained. The limits of detection ranged from 4 to 8 ng L⁻¹. The developed method provided a preconcentration factor of 100. The present work shows that palmitate-coated magnetite nanoparticles have good applicability for the extraction of natural estrogenic hormones that could be pollutants in real water samples.

     

Accelerated solvent extraction combined with dispersive liquid–liquid microextraction before gas chromatography with mass spectrometry for the sensitive determination of phenols in soil samples

A method combining accelerated solvent extraction with dispersive liquid–liquid microextraction was developed for the first time as a sample pretreatment for the rapid analysis of phenols (including phenol, m‐cresol, 2,4‐dichlorophenol, and 2,4,6‐trichlorophenol) in soil samples. In the accelerated solvent extraction procedure, water was used as an extraction solvent, and phenols were extracted from soil samples into water. The dispersive liquid–liquid microextraction technique was then performed on the obtained aqueous solution. Important accelerated solvent extraction and dispersive liquid–liquid microextraction parameters were investigated and optimized. Under optimized conditions, the new method provided wide linearity (6.1–3080 ng/g), low limits of detection (0.06–1.83 ng/g), and excellent reproducibility (<10%) for phenols. Four real soil samples were analyzed by the proposed method to assess its applicability. Experimental results showed that the soil samples were free of our target compounds, and average recoveries were in the range of 87.9–110%. These findings indicate that accelerated solvent extraction with dispersive liquid–liquid microextraction as a sample pretreatment procedure coupled with gas chromatography and mass spectrometry is an excellent method for the rapid analysis of trace levels of phenols in environmental soil samples.     

Combination of stir bar sorptive extraction–retention time locked gas chromatography–mass spectrometry and automated mass spectral deconvolution for pesticide identification in fruits and vegetables

Fruit and vegetable samples collected at a local market were analyzed using stir bar sorptive extraction (SBSE) followed by thermal desorption, retention time locked (RTL) gas chromatographic separation and full scan mass spectrometric determination. Although the technique is proven to have sufficient extraction efficiency and productivity in pesticide analysis, the full scan chromatograms are loaded with matrix components making qualitative evaluation time consuming and too difficult to be adequate for routine laboratory screening. Identification can be facilitated to a great extent with evaluation methods provided by data evaluation software. Through the comparison of three evaluation methods we found that the mass spectral deconvolution software AMDIS supports most the decision making process, performing best in discovering positive hits and reducing data for supervision, making SBSE suitable for routine applications.