A new sample preparation technique for organochlorines in cod liver oil combining SPE and NP-HPLC with HRGC-ECD

The analysis of semivolatile organochlorines (polychlorinated biphenyls and chlorinated pesticides) in less polluted biomaterials requires specific strategies in controlling the blank in sample preparation. The procedure described here allows to decrease significantly the level of contamination during the clean-up step of fish oil. Solid-phase-extraction (SPE) on LiChrolut EN and normal phase HPLC in the normal- and the backflush-mode were used to reduce the amount of solvents needed and the analysis time compared to established clean-up procedures. With a certified reference material (BCR-CRM 349; Cod Liver Oil) the precision and effectiveness of the new method were validated. Recovery rates of the Internal Standards (PCB 103 and TCN) lay between 75% and 90% at the microg/kg lipid level. The quantitative analyses were carried out by high resolution gas chromatography with electron capture detector (HRGC-ECD).     

Multiresidue determination of organochlorines in fish oil by GC-MS: A new strategy in the sample preparation

A rapid, economic and environmentally friendly analytical methodology has been implemented for the determination of α-, β-, γ- and δ-HCH, p,p′-DDT, p,p′-DDD and p,p′-DDE, PCBs congeners #28, #52, #101, #153, #138 and #180 and Hexachlorobenzene in fish oil. 1,2,3,4-Tetrachloronaphtalene was used as internal standard. The sample preparation, consisting of a single step of clean-up and fractionation, took place in a column filled with different layers of neutral and sulphuric acid modified silica. The analytes were eluted by vacuum with of hexane. Significant reduction in terms of solvents, sorbents, and analysis time was achieved in comparison with literature.Gas chromatography coupled to mass spectrometry was used for the separation and determination of the analytes. The instrumental limits of detection were from 0.1 to 1.3 ng mL⁻¹ and the response of the detector was linear up to 200 ng mL⁻¹. The separation proved to be precise (RSD < 3.7% in peak area) and robust in terms of peak area, peak efficacy and resolution. The methodology was validated with two certified reference materials of cod liver oil, BCR 598 and BCR 349, obtaining no statistically significant differences between the concentrations found and certified. For the analytes that were not certified, aliquots of the reference materials were spiked and the recoveries obtained were satisfactory. These results were consistent with those found previously for DDTs by gas chromatography with an electron-capture detector.The methodology was applied to the analysis of three fish oil pills sold in Spain as a dietary supplement of vitamins and omega-3 fatty acids. The sum of the analytes studied was from 64 to 80 ng g⁻¹. The most abundant compounds are PCBs, followed by DDTs in all samples.     

A membrane separation technique for optimizing sample preparation of MALDI-TOF MS detection

Here, we report a new method based on the combination of membrane separation technology and nanomaterial to rapid detection of peptides and protein with MALDI-TOF MS. This method shows advantages as it can inhibit the heterogeneous of sample spot and enhance the target molecular signal intensity.     

imFASP: An integrated approach combining in-situ filter-aided sample pretreatment with microwave-assisted protein digestion for fast and efficient proteome sample preparation

An integrated sample preparation method, termed “imFASP”, which combined in-situ filter-aided sample pretreatment and microwave-assisted trypsin digestion, was developed for preparation of microgram and even nanogram amounts of complex protein samples with high efficiency in 1 h. For imFASP method, proteins dissolved in 8 M urea were loaded onto a filter device with molecular weight cut off (MWCO) as 10 kDa, followed by in-situ protein preconcentration, denaturation, reduction, alkylation, and microwave-assisted tryptic digestion. Compared with traditional in-solution sample preparation method, imFASP method generated more protein and peptide identifications (IDs) from preparation of 45 μg Escherichia coli protein sample due to the higher efficiency, and the sample preparation throughput was significantly improved by 14 times (1 h vs. 15 h). More importantly, when the starting amounts of E. coli cell lysate decreased to nanogram level (50–500 ng), the protein and peptide identified by imFASP method were improved at least 30% and 44%, compared with traditional in-solution preparation method, suggesting dramatically higher peptide recovery of imFASP method for trace amounts of complex proteome samples. All these results demonstrate that the imFASP method developed here is of high potential for high efficient and high throughput preparation of trace amounts of complex proteome samples.     

Solid-phase microextraction: a promising technique for sample preparation in environmental analysis

Solid-phase microextraction (SPME) is a simple and effective adsorption and desorption technique, which eliminates the need for solvents or complicated apparatus, for concentrating volatile or nonvolatile compounds in liquid samples or headspace. SPME is compatible with analyte separation and detection by gas chromatography and high-performance liquid chromatography, and provides linear results for wide concentrations of analytes. By controlling the polarity and thickness of the coating on the fibre, maintaining consistent sampling time, and adjusting other extraction parameters, an analyst can ensure highly consistent, quantifiable results for low concentration analytes. To date, about 400 articles on SPME have been published in different fields, including environment (water, soil, air), food, natural products, pharmaceuticals, biology, toxicology, forensics and theory. As the scope of SPME grew, new improvements were made with the appearance of new coatings that allowed an increase in the specificity of this extraction technique. The key part of the SPME fibre is of course the fibre coating. At the moment, 27 variations of fibre coating and size are available. Among the newest are a fibre assembly with a dual coating of divinylbenzene and Carboxen suspended in poly(dimethylsiloxane), and a series of 23 gauge fibres intended for specific septumless injection system. The growth of SPME is also reflected in the expanding number of the accessories that make the technology even easier to use Also available is a portable field sampler which is a self-contained unit that stores the SPME fibre after sampling and during the shipment to the laboratory. Several scientific publications show the results obtained in inter-laboratory validation studies in which SPME was applied to determine the presence of different organic compounds at ppt levels, which demonstrates the reliability of this extraction technique for quantitative analysis.     

Novel sample preparation technique with needle-type micro-extraction device for volatile organic compounds in indoor air samples

A novel needle-type sample preparation device was developed for the effective preconcentration of volatile organic compounds (VOCs) in indoor air before gas chromatography–mass spectrometry (GC–MS) analysis. To develop a device for extracting a wide range of VOCs typically found in indoor air, several types of particulate sorbents were tested as the extraction medium in the needle-type extraction device. To determine the content of these VOCs, air samples were collected for 30 min with the packed sorbent(s) in the extraction needle, and the extracted VOCs were thermally desorbed in a GC injection port by the direct insertion of the needle. A double-bed sorbent consisting of a needle packed with divinylbenzene and activated carbon particles exhibited excellent extraction and desorption performance and adequate extraction capacity for all the investigated VOCs. The results also clearly demonstrated that the proposed sample preparation method is a more rapid, simpler extraction/desorption technique than traditional sample preparation methods.     

High-performance liquid chromatographic separation of the fat-soluble vitamins in cod liver oil and feeds

A MicroPak-CN column with a methylene chloride—chloroforms-n-hexane (3:2:15) mobile phase separates the fat-soluble vitamins in cod liver oil and formulated feed. Powdered feed samples are dissolved in n-hexane—chloroform—ethanol (6:3.5:0.5) and centrifuged before injection. The oil is dissolved in the extraction solvent or mobile phase before injection. The naturally occurring vitamins are identified from their absorption spectra by stopped-flow spanning of the individual vitamins.     

A new approach for development of rugged sample preparation of metabolites of albendazole in cow milk

Sample preparation is the critical step in analysis of residues in biological samples. The development of a ragged method is time-consuming, because a huge number of parameters must be checked. To reduce the number of experiments Taguchi's method was applied in the sample preparation of metabolites of albendazole. During the experiments 11 controllable and 7 noise factors were investigated. From the influence of controllable and noise factors on recovery and standard deviation, conditions for the sample preparation and recovery could be concluded with high accuracy and reliability.     

Automated sample clean-up and fractionation of organochlorine pesticides and polychlorinated biphenyls in human milk using NP-HPLC with column-switching

A method has been developed for the automated sample pretreatment of organochlorine pesticides (OCP's) and polychlorinated biphenyls (PCB's) in extracts of human milk. This work was part of a regular monitoring program presently carried out at our institute. In this program several hundreds of human milk samples have to be analyzed for the occurrence of PCB's and OCP's. With a normal bore straight phase HPLC system, utilizing column switching we are able to separate the fat from the compounds of interest and, moreover, complete separation of the PCB fraction from the OCP's can be achieved. Under the conditions used to separate the PCB fraction from intefering OCP's column-switching is essential since the retention times for the OCP's vary from 4 minutes for hexachlorobenzene (HCB) to more than 2 hours for dieldrin. 1 ml of an extract containing 45 mg of fat is injected on the first (pre)column, the fat is retained on this column and the early eluting HCB, the PCB fraction, and the DDT complex are transferred to the second (analytical) column. Compounds eluting later than p,p′-DDT are collected directly from the precolumn. Meanwhile, the PCB fraction is separated from the rest of the OCP's on the analytical column. Contrary to conventional gravity-controlled chromatography or solid phase extraction the clean-up process can be monitored on-line by UV-detection, thus rendering a fast and reliable optimization of the system. The OCP-fractions collected from the LC are pooled before they are transferred to a high resolution gas chromatograph equipped with a large volume option. The PCB-fraction is injected directly in a HRGC equipped with a concurrent solvent evaporation injection device. The limits of detection for the OCP's (HCB, α-,β- and γ-HCH, β-Hepo (heptachlorepoxide), dieldrin, p,p′-DDE, o,p′-DDT p,p′-DDT and TDE) and the PCB's investigated are at sub-ppb level (fat basis); the recoveries vary from 80 to 100%.     

Ultrasound: A subexploited tool for sample preparation in metabolomics

Metabolomics, one of the most recently emerged “omics”, has taken advantage of ultrasound (US) to improve sample preparation (SP) steps. The metabolomics–US assisted SP step binomial has experienced a dissimilar development that has depended on the area (vegetal or animal) and the SP step. Thus, vegetal metabolomics and US assisted leaching has received the greater attention (encompassing subdisciplines such as metallomics, xenometabolomics and, mainly, lipidomics), but also liquid–liquid extraction and (bio)chemical reactions in metabolomics have taken advantage of US energy. Also clinical and animal samples have benefited from US assisted SP in metabolomics studies but in a lesser extension. The main effects of US have been shortening of the time required for the given step, and/or increase of its efficiency or availability for automation; nevertheless, attention paid to potential degradation caused by US has been scant or nil. Achievements and weak points of the metabolomics–US assisted SP step binomial are discussed and possible solutions to the present shortcomings are exposed.     

Molecularly imprinted SPE and MEKC with in-capillary sample preconcentration for the determination of digoxin in human urine

Molecularly imprinted solid-phase extraction (MISPE) combined with MEKC was used for clean-up, preconcentration and determination of digoxin in the presence of its aglycon digoxin (digoxigenin) in human urine samples. In addition, the use of an in-capillary sample concentration electrophoretic technique by sweeping was investigated to enhance the concentration sensitivity in MEKC. The highly selective, fast and effective sample pretreatment by MISPE along with the preconcentration by sweeping could overcome the low sensitivity of the highly efficient capillary electrophoresis separation with UV detection. The optimization of the variables affecting the separation as well as MISPE conditions procedure was carried out to select the best conditions of selectivity and sensitivity to determine digoxin at low concentration levels in urine. To demonstrate the suitability of the developed method several analytical characteristics (selectivity, linearity, accuracy, precision, and LOD) were evaluated. Satisfactory results were obtained in terms of linearity (r > 0.99), recovery (95.4-96.5% with RSD from 1.3% to 2.6%), precision (RSD from 0.3% to 1.7% for migration times and from 2.1% to 7.3% for corrected peak areas), and sensitivity (LODs of 6 μg/L with 5 mL of sample or 1.2 μg/L with 25 mL). The proposed MISPE-MEKC method was satisfactorily applied to the analysis of spiked human urine samples achieving a concentration factor up to 7500-fold.     

Determination of 25‐hydroxyvitamin D3 in human plasma using HPLC with UV detection based on SPE sample preparation

Interest in the metabolism and physiological action of vitamin D is increased exponentially. The most important metabolites of vitamin D are 25‐hydroxyvitamin and 1,25‐dihydroxyvitamin D₃. The aim of the study was to develop a rapid and simple HPLC method for the measurement of 25‐hydroxyvitamin D₃ in human plasma. A method for the measurement of 25‐hydroxyvitamin D₃ using HPLC with UV detection and investigation into the extraction techniques with regard to stability and recovery are described. For the separation, RP column LiChroCart 125‐4, Purospher RP‐18e, 5 μm, was used. The mixture of methanol and deionized water (95:5 v/v) was used as mobile phase. The analytical performance of this method is satisfactory: the intra‐ and inter‐assay coefficients of variation were below 10%. Quantitative recoveries from spiked plasma samples were between 92.0–103.2%. The LOD was 10 nmol/L. The preliminary reference range of 25‐hydroxyvitamin D₃ in a group of blood donors is 62 ± 26 nmol/L.     

Miniaturized solid-phase extraction as a sample preparation technique for the determination of phthalates in water

Miniaturized solid-phase extraction (SPE) has been developed and successfully employed for the determination of organic species in water samples by liquid chromatography (LC). The method is based on the concept of a microscale extraction technique using a fused-silica capillary column for gas chromatography (GC), so-called in-tube solid-phase microextraction (SPME). The extraction conditions, such as the extraction time and flow-rate for the extraction and desorption process, were investigated as well as the effect of the internal structure of the extraction capillary on the efficiency. By inserting a stainless steel wire into the extraction capillary to reduce the internal volume of the capillary with the same surface area of the coating, an improved extraction and pre-concentration effects were obtained. Further pre-concentration was accomplished by the extraction device with a novel fiber-in-tube configuration. The direct coupling of the extraction method with a LC system has made it possible to determine low levels of phthalates in water samples without high consumption of organic solvents. The system developed must have potential applications for the analysis of environmental and biological samples in aqueous sample matrices.     

Solutions and challenges in sample preparation for chromatography

Sample preparation as practiced today in analytical laboratories is a complex combination of classical and modern techniques. In this review, the progress made in the last few years in sample preparation for chromatography is examined and discussed in comparison with previous achievements in the field. Discovery and development of new materials is seen as one of the main sources of progress, but finding better ways of using the old principles and the improvements in technology are also major contributing factors for advancement. Practical demands for analysis of pharmaceutical products, the environmental studies, and life science are the main driving forces for development in sample preparation for chromatography.     

Molecularly imprinted polymers for sample preparation: A review

In spite of the huge development of analytical instrumentation during last two decades, sample preparation is still nowadays considered the bottleneck of the whole analytical process. In this regard, efforts have been conducted towards the improvement of the selectivity during extraction and/or subsequent clean-up of sample extracts. Molecularly imprinted polymers (MIPs) are stable polymers with molecular recognition abilities, provided by the presence of a template during their synthesis and thus are excellent materials to provide selectivity to sample preparation. In the present review, the use of MIPs in solid-phase extraction and solid-phase microextraction as well as its recent incorporation to other extraction techniques such as matrix-solid phase dispersion and stir bar sorptive extraction, among others, is described. The advantages and drawbacks of each methodology as well as the future expected trends are discussed.     

X射线荧光光谱法测定除尘灰中砷、铅含量

以熔融制样法,采用X射线荧光光谱对除尘灰中的有害元素：砷、铅含量进行了测定。对样品的烧失温度进行了讨论,发现在950℃灼烧温度下灼烧2h时除碳完全。砷和铅的相对标准偏差为0.15 %和0.20 %。测试结果与化学分析法、原子吸收光谱法等相吻合。该方法制作工艺简单,分析速度快,样品可长期保存,还能满足其他元素的日常分析。     

A new preparation technique of catalysts characterized by small metal crystallites

The present study reports a new and original technique for obtaining nickel catalysts characterized by small metal crystallites. The catalysts were prepared on -Al₂O₃. The total surface of the carrier was 37.5 m²/g. The preservation of the appropriate procedure and conditions of preparation allow a large expansion of active nickel surface (mean crystallite size 2.0–3.0 nm) in spite of the quite hard conditions of reduction (773 K and 3 h).

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, . -Al₂O₃. 37,5 ²/. ( 2,0–3,0 ) (3 773 ).

     

Phase separation and extraction with acetonitrile for sample preparation in HPLC analysis

Summary Acetonitrile can be salted-out from aqueous solution by adding tetrabutylammonium perchlorate. This phase separation method has been used for the extraction of the Fe(III)-4,7-diphenylphenanthroline complex into acetonitrile followed by direct injection onto an ODS column. The Fe complex is separated by using 9:1 acetonitrile/water as a mobile phase. The proposed reversed-phase high-performance liquid chromatography has been applied to the determination of Fe in serum.