Selective solid‐phase extraction of metal for water decontamination

Metal‐contaminated industrial effluent is a major concern for human health. Therefore, the removal of metal is of primary importance. In this study, metals were selectively extracted from water. Selective metal recovery was studied with a crown‐ether‐based polymer, wherein the selectivity was observed for strontium over lead. Parameters influencing the metal recovery, such as the contact time, adsorbent dosage, and metal‐ion concentration, were evaluated. Interestingly, the adsorption rate of strontium was exponentially increased for the initial 4 h, and lead was adsorbed exponentially after 6 h. Notably, 98% strontium adsorption and 64% lead adsorption were obtained in 24 h. The Langmuir adsorption isotherm was in good agreement and demonstrated that the reactive sites of the adsorbent were homogeneous with monolayer metal adsorption with an adsorbent. The Freundlich adsorption isotherm was not obeyed by both metals. The pseudo‐first‐order and pseudo‐second‐order kinetics indicated that strontium was adsorbed by chemisorption and lead was adsorbed by physisorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42849.     

Analysis of fatty acid profile in plasma phospholipids by solid‐phase extraction in combination with GC

Phospholipids are recognised as an important source and transport form for metabolically active fatty acids. Therefore, detailed analysis of fatty acid profiles in plasma phospholipids as marker for dietary habits or interventions gains more and more importance. Appropriate analytical methods described so far are either expensive or susceptible to handling errors. We developed a method to separate plasma phospholipids by acetone fractionation combined with SPE in order to analyse the fatty acid compositions in phospholipid fractions of human plasma by GC analysis. The method has been validated in order to be applied to the routinely performed analysis of the samples of patients who will be participating in a dietary supplement study. The method presented here was successfully validated and is stable, efficient and reproducible. It can be used in a routine fashion to deliver the fatty acid profile [palmitic acid (16:0), heptadecanoic acid (17:0), stearic acid (18:0), oleic acid (18:1n‐9), linoleic acid (18:2n‐6), linolenic acid (18:3n‐3), arachidonic acid (20:4n‐6), eicosapentaenoic acid (20:5n‐3) and docosahexaenoic acid (22:6n‐3)] in plasma phospholipid samples. Using a sample volume of 500 µL, recovery of plasma phospholipids is 92 ± 11%; LOQ is 2.2 µg fatty acid/mL. A set of samples from cancer patients and healthy individuals was analysed and confirmed the applicability of the described method.     

Molecularly imprinted polymer membranes for substance‐selective solid‐phase extraction from aqueous solutions

Thin‐layer molecularly imprinted polymer (MIP) composite membranes for selective binding of monocrotophos (MCP) pesticide from aqueous solutions were developed. The procedure was based on commercially available membrane modules that were rinsed with prepolymerization imprinting mixtures. After the in situ polymerization and generation of MIP films on the membranes within the modules, the membranes were evaluated in terms of affinity toward the target molecule MCP. MIP membranes with different porogens and different monomers on Nylon‐6 membranes were prepared. It was shown that MIP membranes synthesized with methacrylic acid as monomer and toluene as porogens on the Nylon‐6 membranes provided a highly selective binding of MCP from aqueous solutions under the optimized elution conditions. With the novel surface modification technique, the low nonspecific binding properties of the microfiltration membrane could successfully be combined with the receptor properties of molecular imprints, yielding substance‐specific MIP composite membranes. The high affinity of these synthetic membranes to MCP pesticide together with their straightforward and inexpensive preparation could be applied in a fast preconcertration step, solid‐phase extraction, by a simple microfitration for the determination of MCP in water. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4468–4473, 2006     

Molecular imprinted solid‐phase extraction of huperzine A from Huperzia Serrata

On the basis of the non‐covalent interaction between template and monomer, porous molecularly imprinted polymers (MIPs) were synthesized by a thermal‐initiated polymerization method using huperzine A as template, acrylamide, or methacrylic acid as function monomer, ethylene glycol dimethacrylate as cross‐linking agent. The interaction between template and functional monomers was studied by UV spectrophotometry, which showed a formation of huperzine A‐monomer complexes with stoichiometric ratio of 1 : 2 in the pre‐polymerized systems. The resultant MIP particles were tested in the equilibrium binding experiment to analyze their adsorption ability to huperzine A, and were characterized by Fourier Transform Infrared (FTIR) study. The recognition properties of MIP were estimated in solid‐phase extraction by selecting four compounds (isolated from the Chinese herb Huperzia serrata) as substrates, and were compared with and prior to those of the NIP. High affinity and adsorption of MIP1 which was prepared in chloroform with huperzine A as imprinted molecule, and acrylamide (AM) as functional monomer, made an attractive application of MIP1 in separation processes. In final, using MIP1 solid‐phase extraction micro‐column, huperzine A was enriched and separated from the real extraction sample of Huperzia serrata. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Magnetic molecularly imprinted polymer nanoparticles coupled with high performance liquid chromatography for solid‐phase extraction of carvedilol in serum samples

Herein, we report a magnetic molecularly imprinted polymers (m‐MIPs) using Fe₃O₄ as a magnetic component, carvedilol as a template molecule for the solid‐phase extraction (MISPE) as the sample clean‐up technique combined with high‐performance liquid chromatography (HPLC) and for the controlled release of carvedilol at different pH values of 1.0 (simulated gastric fluid), 6.8 (simulated intestinal fluid), and 7.4 (simulated biological fluid). The adsorption kinetics was modeled with the pseudo‐first‐order and pseudo‐second‐order kinetics, and the adsorption isotherms were fitted with Langmuir and Freundlich models. The performance of the m‐MIPs for the controlled release of carvedilol was assessed and results indicated that the magnetic MIPs also have potential applications in controlled drug release. Furthermore, the m‐MIPs were applied to the extraction of carvedilol from human blood plasma samples. Carvedilol can be quantified by this method in the 2–350 μg L^?1 concentration range. The limit of detection and limit of quantification in plasma samples are 0.13 and 0.45 μg L^?1. The results from HPLC showed good precision (3.5% for 50.0 μg L^?1) and recoveries (between 85 and 93) using m‐MIP from human plasma samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41209.     

Solid‐phase extraction in combination with GC/MS for the quantification of free fatty acids in adipocere

Current research investigating the effect of specific aquatic microenvironments on the formation of adipocere using domesticated pigs (Sus scrofa) has demonstrated the need for a fast and reliable method to separate and identify fatty acids present in adipocere. Adipocere is defined as a late‐stage post‐mortem decomposition product consisting of a mixture of free fatty acids (FFA), which have formed under favorable conditions due to the hydrolysis of triglycerides in adipose tissue. Whilst good separations of adipocere lipids have been achieved using TLC, this method is time consuming when processing large numbers of samples. This paper describes a rapid and simple method for the extraction, identification and quantification of FFA commonly found in adipocere, by solid‐phase extraction (SPE) using aminopropyl disposable columns in combination with GC/MS. The recoveries of FFA associated with adipocere were all above 90%, with coefficients of variation below 10%, indicating that the technique was reproducible. The limits of quantification were registered at levels of parts per million. Standard curves were linear over the range of 50–1000 µg/mL, with all correlation coefficient values greater than 0.998. A marked increase in concentration of saturated fatty acids was observed during adipocere formation, ranging from 20 to 55% for palmitic acid, 13 to 23% for stearic acid and 2.8 to 4.1% for myristic acid. These results demonstrate the suitability of aminopropyl disposable SPE columns to efficiently and rapidly isolate FFA from adipocere prior to quantitative GC/MS analysis.     

Mixed templates molecularly imprinted solid‐phase extraction for the detection of sulfonamides in fish farming water

Highly selective molecularly imprinted polymers (MIPs) that absorb sulfonamides (SAs) are prepared using two types of SAs as mixed templates, 2‐vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the crosslinker. The optimum combination of the mixed templates, their adsorption effect and the imprinting mechanism are evaluated based on SPE recoveries of a family of analytes, equilibrium binding, BET surface area analysis and UV. The results indicate that the mixed templates not only optimize the cavities of the MIPs but also improve the MIPs selectivity and adsorption capacity for the target analytes in aqueous solution. Therefore, MIPs are used for the quantitative analysis of SAs in fish farming water using off‐line SPE coupled to HPLC/DAD. The recovery and RSD were 84.16–101.19 and 1.98–7.10%, respectively. Four SAs analytes were detected in four types of water samples in the range of 8.49–74.60 ng L^?1. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41491.     

Effect of absorbent in solid‐phase extraction on quantification of phospholipids in palm‐pressed fiber

Palm‐pressed fiber (PPF) is a by‐product of palm oil milling and it has been found to contain a high percentage of phospholipids (PL). The aim of this work was to evaluate the best solid‐phase extraction (SPE) method to purify PL from PPF. The purified PL were analyzed using high‐performance liquid chromatography (HPLC) with an evaporative light‐scattering detector (ELSD). The oil was extracted from PPF using the Folch method and classes of PL were purified using SPE. Different solvent phases and normal‐phase SPE cartridges [silica (Si), aminopropyl‐bonded silica (NH₂) and diol‐bonded silica (2OH)] at the same ratio of oil to sorbent mass were used to study the separation of PL from the extracted oil. The recovery of each standard PL was performed in a model oil system with the same amount of standard PL being added, and the repeatability of the SPE method was investigated. The isolation of PL by SPE diol cartridge and subsequent analysis by HPLC/ELSD have shown to be an accurate and reproducible analytical method for the determination of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and lysophosphatidylcholine in PPF. This method provided a high yield and rapid separation of PL in PPF with less contamination from other lipid groups.     

Metabolism of trans fatty acids by hepatocytes

The present work was undertaken to study the metabolism of fatty acids with trans double bonds by rat hepatocytes. In liver mitochondria, elaidoyl-CoA was a poorer substrate for carnitine palmitoyltransferase I (CPT-I) than oleoyl-CoA. Likewise, incubation, of hepatocytes with oleic acid produced a more pronounced stimulation of CPT-I than incubation with trans fatty acids. This was not due to a differential effect of cis and trans fatty acids on acetyl-CoA carboxylase (ACC) activity and malonyl-CoA levels. Elaidic acid was metabolized by hepatocytes at a higher rate than oleic acid. Surprisingly, compared to oleic acid, elaidic acid was a better substrate for mitochondrial and, especially, peroxisomal oxidation, but a poorer substrate for cellular and very low density lipoprotein triacylglycerol synthesis. Results thus show that trans fatty acids are preferentially oxidized by hepatic peroxisomes, and that the ACC/malonyl-CoA/CPT-I system for coordinate control of fatty acid metabolism is not responsible for the distinct hepatic utilization of cis and trans fatty acids.     

An improved micro-extraction cell for supercritical fluid extraction and chromatography of fatty acids

An improved supercritical fluid micro-extraction cell of increased reliability was designed for on-line supercritical fluid extraction and chromatography (SFE/SFC) of food and other lipid-related samples. The key components in the modified cell include a Swagelok stainless steel reducing union with a dual ferrule as the cell, with polyetherether-ketone (PEEK) ferrules and nuts to connect the cell to the control valve. The new cell did not leak under all conditions examined (100–500 atmospheres, 40–80°C), even after numerous extractions (>250). The quantitative performance of the cell was evaluated with fatty acid standard solutions, technical grade fatty acid sources and wheat flour. The percent relative error (%RE) for the fatty acid standards and technical-grade fatty acid samples was ≤6.0% for oleic, linoleic and linolenic acid. The %RE for oleic and linoleic acid in the whole-wheat samples was ≤10%. The results demonstrate that the new extraction cell can be used for quantitative extractions and that the sensitivity of the SFE/SFC technique is excellent. Similar SFE/SFC methods could prove useful in studying the interaction of free fatty acids with various food components such as enzymes, amylose and proteins.     

反式脂肪酸测定方法的研究

简要介绍了反式脂肪酸(TFA)的生成途径及主要的食物来源,反式脂肪酸对人体健康的主要危害和影响,综述了反式脂肪酸的分析检测方法如气相色谱法、红外光谱法、Ag离子色谱技术、毛细管电泳法等,并比较了各种方法的优缺点。     

Accurate determination of hexanal in beef bouillons by headspace solid‐phase microextraction gas‐chromatography mass‐spectrometry

Lipid oxidation has great impact on the quality of food products through flavor and taste deterioration, reduction in nutritive value, and potential toxicity of the oxidized food components. Flavor and taste deterioration can be easily perceived and it represents one of the major causes of consumer complaints in the food industry. The deterioration of sensory properties is due to the decomposition products of hydroperoxides that easily isomerize and degrade into volatile compounds. Volatile products are responsible for flavor and taste deterioration. In this study, we present the development of the solid‐phase microextraction gas chromatography‐mass spectrometry (SPME‐GC‐MS) technique to quantify low amounts (μg/g range) of secondary oxidation products, i.e. hexanal. The optimization of SPME parameters is a difficult task because of the possibility of further formation of volatile products during analysis. Different parameters such as type of fiber, exposure time of the fiber to the sample headspace and the optimal temperature of absorption have also been investigated. The complete validation of the method was achieved by the determination of linearity, limits of detection and quantification and repeatability. We demonstrated that the SPME method is a valuable tool for the quantification of low amounts of secondary oxidation products such as hexanal. Therefore, this technique can be used to detect early formation of volatiles.     

Influence of moderate amounts of trans fatty acids on the formation of polyunsaturated fatty acids

The effect of trans fatty acids from partially hydrogenated soybean oil and butterfat on the formation of polyunsaturated fatty acids was investigated. Five groups of rats were fed diets that contained 20 wt% fat. The content of linoleic acid was adjusted to 10 wt% of the dietary fats in all diets, whereas the amount of trans fatty acids from partially hydrogenated soybean oil (PHSBO) was varied from 4.5 to 15 wt% in three of the five diets. The fourth group received trans fatty acids from butterfat (BF), while the control group was fed palm oil without trans fatty acids. Trans fatty acids in the diet were portionally reflected in rat liver and heart phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylinositol, and phosphatidylserine. Incorporation in the sn-1 position was compensated by a decrease in saturated fatty acids. Trans fatty acids were not detected in diphosphatidylglycerol. Compared to the presence in the dietary fats, 8t- and 10t-18:1 were discriminated against in the incorporation in PE and PC from liver and heart, whereas 9t- and 12t-18:1 were preferred. The formation of 20:4n-6 was not influenced by 4.5 wt% trans fatty acids (from PHSBO) but apparently was by 10 wt% in liver. In contrast, even a content of 2.5 wt% trans fatty acids from BF reduced the formation of 20:4n-6. The inhibitory effect of trans isomers on linoleic acid conversion was reflected less in heart than in liver and less for PE than for PC. Groups with trans fatty acids showed increased 22:6n-3 and 22:5n-3 deposition in liver and heart PE and PC.     

Use of dried blood for measurement of trans fatty acids

Background  

Fatty acid measurements especially trans fatty acid has gained interest in recent times. Among the various available biomarkers, adipose tissue is considered to be the best for the long term dietary intake but the invasive nature of tissue aspiration reduces its utility. Phlebotomy is a much less invasive method of sample collection when a large number of participants are involved in the study and therefore is an alternative, most suitable for large population based studies. In the present study fatty acid (with special emphasis on trans fatty acid) extraction from blood spotted and dried on filter paper was carried out to simplify the sample collection procedure and transportation.