Separation, concentration and determination of chloramphenicol in environment and food using an ionic liquid/salt aqueous two-phase flotation system coupled with high-performance liquid chromatography

Ionic liquid–salt aqueous two-phase flotation (ILATPF) is a novel, green, non-toxic and sensitive samples pretreatment technique. ILATPF coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of chloramphenicol, which combines ionic liquid aqueous two-phase system (ILATPS) based on imidazolium ionic liquid (1-butyl-3-methylimidazolium chloride, [C₄mim]Cl) and inorganic salt (K₂HPO₄) with solvent sublation. In ILATPF systems, phase behaviors of the ILATPF were studied for different types of ionic liquids and salts. The sublation efficiency of chloramphenicol in [C₄mim]Cl–K₂HPO₄ ILATPF was influenced by the types of salts, concentration of K₂HPO₄ in aqueous solution, solution pH, nitrogen flow rate, sublation time and the amount of [C₄mim]Cl. Under the optimum conditions, the average sublation efficiency is up to 98.5%. The mechanism of ILATPF contains two principal processes. One is the mechanism of IL–salt ILATPS formation, the other is solvent sublation. This method was practical when applied to the analysis of chloramphenicol in lake water, feed water, milk, and honey samples with the linear range of 0.5–500 ng mL⁻¹. The method yielded limit of detection (LOD) of 0.1 ng mL⁻¹ and limit of quantification (LOQ) of 0.3 ng mL⁻¹. The recovery of CAP was 97.1–101.9% from aqueous samples of environmental and food samples by the proposed method. Compared with liquid–liquid extraction, solvent sublation and ionic liquid aqueous two-phase extraction, ILATPF can not only separate and concentrate chloramphenicol with high sublation efficiency, but also efficiently reduce the wastage of IL. This novel technique is much simpler and more environmentally friendly and is suggested to have important applications for the concentration and separation of other small biomolecules.     

Synchronized separation,concentration and determination of trace chloramphenicol,thiamphenicol and florfenicol in food by using polyoxyethylene cetyl ether-salt aqueous two-phase system coupled with high-performance liquid chromatography

As a novel and green pretreatment technique to trace samples, polyoxyethylene cetyl ether (POELE20)–(NH₄)₂SO₄ aqueous two-phase extraction system was coupled with high-performance liquid chromatography to analyse synchronously chloramphenicol (CAP), thiamphenicol (TAP) and florfenicol (FF) in chicken and pork samples. It was found that the extraction efficiency (E%) and enrichment factor (F) of the three antibiotics were influenced by the types of salts, the concentration of salt, the concentration of POELE20, system temperature and pH. The final optimal condition was as following: the phase-forming salt is (NH₄)₂SO₄, the concentration of (NH₄)₂SO₄ is 0.141 g mL^?1, the concentration of POELE20 is 0.03 g mL^?1, the temperature is 298.15 K, and the system pH is 4.5. This POELE20–(NH₄)₂SO₄ ATPS was applied to separate and enrich three antibiotics in real sample under the optimal conditions, and it was found that the recovery was 97.20–102.00 % with a RSD of 0.61–4.85 %. The limit of detection for CAP, TAP and FF were 0.10, 0.50 and 0.50 μg kg^?1, and the limit of quantitation for CAP, TAP and FF was 0.15, 1.50 and 1.50 μg kg^?1. Seven times the experiments were used to verify the repeatability and veracity of this method, and the RSD for the intra-day and inter-day were 1.13–3.22 and 1.74–4.72 %.     

Optimization of partitioning process parameters of chloramphenicol in ionic liquid aqueous two-phase flotation using response surface methodology

Ionic liquid aqueous two-phase flotation (ILATPF) is a green and effective separation and purification method, which combines solvent sublation and ionic liquid aqueous two-phase extraction system. This investigation attempts to study and optimize the partitioning conditions of chloramphenicol (CAP) in ILATPF. An experimental design of response surface methodology (RSM) was used to evaluate the influence of the variables, including the type of ionic liquid (IL), K₂HPO₄ concentration, flotation time and gas flow rate on CAP flotation. Quadratic polynomial models were adjusted to the data to predict the behavior of two responses, namely the partition coefficient (K) and sublation efficiency (E) of CAP. The optimal flotation conditions were found using [C₆mim]Cl, 0.74 g/mL K₂HPO₄, 50 min flotation time and 50 mL/min gas flow rate, which ensured K = 405.71 and E = 93.16 %. It was observed that the effect of the four factors on K and E of CAP was flotation time > gas flow rate > the type of IL > K₂HPO₄ concentration. The ILATPF was proved effective for CAP separation in aqueous phase, and RSM was revealed to be an appropriate and powerful tool for experimental design of CAP separation by ILATPF.     

Extraction and determination of chloramphenicol in feed water,milk, and honey samples using an ionic liquid/sodium citrate aqueous two-phase system coupled with high-performance liquid chromatography

A green, simple, non-toxic, and sensitive sample pretreatment procedure coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of chloramphenicol (CAP) that exploits an aqueous two-phase system based on imidazolium ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, [Bmim]BF₄) and organic salt (Na₃C₆H₅O₇) using a liquid–liquid extraction technique. The influence factors on partition behaviors of CAP were studied, including the type and amount of salts, the pH value, the volume of [Bmim]BF₄, and the extraction temperature. Extraction efficiency of the CAP was found to increase with increasing temperature and the volume of [Bmim]BF₄. Thermodynamic studies indicated that hydrophobic interactions were the main driving force, although electrostatic interactions and salting-out effects were also important for the transfer of the CAP. Under the optimal conditions, 90.1% of the CAP could be extracted into the ionic liquid-rich phase in a single-step extraction. This method was practical when applied to the analysis of CAP in feed water, milk, and honey samples with a linear range of 2~1,000 ng mL⁻¹. The method yielded a limit of detection of 0.3 ng mL⁻¹ and a limit of quantification of 1.0 ng mL⁻¹. The recovery of CAP was 90.4–102.7% from aqueous samples of real feed water, milk, and honey samples by the proposed method. This novel process is much simpler and more environmentally friendly and is suggested to have important applications for the separation of antibiotics.     

Ionic liquid-salt aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of sulfonamides in water and food

Ionic liquid-salt aqueous two-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection was developed for the determination of sulfonamides in water and food samples. In the procedure, the analytes were extracted from the aqueous samples into the ionic liquid top phase in one step. Three sulfonamides, sulfamerazine, sulfamethoxazole, and sulfamethizole were selected here as model compounds for developing and evaluating the method. The effects of various experimental parameters in extraction step were studied using two optimization methods, one variable at a time and Box–Behnken design. The results showed that the amount of sulfonamides did not have effect on the extraction efficiency. Therefore, a three-level Box–Behnken experimental design with three factors, which combined the response surface modeling, was used to optimize sulfonamides extraction. Under the most favorable extraction parameters, the detection limits (S/N?=?3) and quantification limits (S/N?=?10) of the proposed method for the target compounds were achieved within the range of 0.15–0.3 ng/mL and 0.5–1.0 ng/mL from spiked samples, respectively, which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Finally, the proposed method was successfully applied to the determination of sulfonamide compounds in different water and food samples and satisfactory recoveries of spiked target compounds in real samples were obtained.     

Extraction and determination of morphine in compound liquorice using an aqueous two-phase system of poly(ethylene glycol)/K2HPO4 coupled with HPLC

An aqueous two-phase system (ATPS) of poly(ethylene glycol) (PEG)/K₂HPO₄ coupled with high performance liquid chromatography (HPLC) method was developed for the separation and determination of morphine in compound liquorice. Morphine and its analogs were used as model compounds to investigate influence of various factors on extraction behaviors of ATPS, such as the types and concentrations of salts, PEG molecular mass, temperature and pH. It was observed that the types of salt had much influence on extraction efficiencies of morphine and its analogs. The results indicated that hydrophobic force cooperating with hydrogen bond interaction between analytes and phases played important role in extraction process. In the optimal system of containing 0.5 g PEG2000 and 1.5 g K₂HPO₄, the recoveries of the spiked standards for the analytes were all 91.7-100.3% with relative standard deviation of 1.0-3.0%. Morphine in compound liquorice was determined by the proposed method and the results were consistent with those of LC-MS method. Compared with conventional liquid-liquid extraction or solid-phase extraction, this extraction method can be completed in one operation and is low-cost. Since the entire extraction process is organic solvent-free, this new technique is environmental friendly.     

在线自动化柱前衍生-高效液相色谱法测定食品中组胺的研究

建立了在线自动化柱前衍生.高效液相色谱法测定食品中组胺的新方法.通过对测定过程中各个影响因素进行优化,如自动化衍生程序的设定,衍生试剂的用量,衍生体系pH影响等,确立了适宜的测定条件.在该条件下,对于组胺的检出限为0.01 μg/mL,在0.05～100 λg/mL范围内,线性关系良好(r2＞0.999).通过对样品基质进行加标,检出限为0.20 mg/kg.将所建立的方法应用于金枪鱼罐头,烟熏鲣鱼,冻鲭鱼等样品中组胺的测定,测得的组胺含量为0.59～167 mg/kg,加标回收率均大于97%,测定值的相对标准偏差均小于5%.所建立的方法适用于大量样品的常规分析测定.     

HPLC法快速测定食品添加剂的检测条件研究

建立一种HPLC法快速测定食品中苯甲酸、山梨酸和糖精钠的分析方法.采用C18反向高效液相色谱柱,以甲醇和乙酸铵溶液为流动相洗脱,用紫外检测器于230nm波长处检测.当流动相甲醇与乙酸铵的比例(V/V)为39∶61时,各组分均得到较好的分离,色谱峰分离度达到3.0以上,色谱峰型尖锐,保留时间较短.色谱峰面积和保留时间的RSD均小于1%,表明该方法具有很好的准确度和精密度.在该色谱条件下,分别对饮料、调料等实际样品进行检测,结果表明该色谱条件的HPLC法快速、准确,重现性好,可作为食品中防腐剂和甜味剂的定性定量的参考方法.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Selective separation and enrichment of proteins in aqueous two-phase extraction system

A simple aqueous two-phase extraction system(ATPS) of PEG/phosphate was proposed for selective separation and enrichment of proteins.The combination of ATPE with HPLC was applied to identify the partition of proteins in two phases.Five proteins (bovine serum albumin,Cytochrome C,lysozyme,myoglobin,and trypsin) were used as model proteins to study the effect of phosphate concentration and pH on proteins partition.The PEG/phosphate system was firstly applied to real human saliva and plasma samples,some pro...     

Reversibly soluble macroaffinity ligand in aqueous two-phase separation of enzymes

Use of alginate as a free bioligand incorporated in an aqueous two-phase system of polyethylene glycol 6000-salt resulted in considerable purification of wheat germ alpha-amylase and sweet potato beta-amylase from their crude extracts. The elution of the enzyme from the free bioligand was facilitated by exploiting the fact that alginate can be reversibly precipitated in the presence of Ca2+. alpha-Amylase could be purified 42-fold with 92% activity recovery. beta-Amylase on the other hand could be purified 43-fold with 90% recovery. Both purified enzymes showed a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis.     

Selective separation and determination of quercetin from red wine by molecularly imprinted nanoparticles coupled with HPLC and ultraviolet detection

In this study, a highly sensitive and selective sample pretreatment procedure using molecularly imprinted silica nanoparticles was developed for the extraction and determination of quercetin in red wine samples coupled with high‐performance liquid chromatography with ultraviolet detection. The imprinted silica nanoparticles were prepared in the presence of N‐acryoyl‐l ‐aspartic acid (functional monomer), quercetin (template), azobisisobutyronitrile (initiator) and methylene bisacrylamide (cross‐linker) and methanol/water (porogen) via surface‐initiated reversible addition‐fragmentation chain transfer polymerization. Surface characterization was performed and several imprinting parameters were investigated, and the results indicated that adsorption of quercetin on the imprinted silica nanoparticles followed a pseudo‐first‐order adsorption isotherm with a maximum adsorption capacity at 26.4 mg/g within 60 min. The imprinted silica nanoparticles also showed satisfactory selectivity towards quercetin as compared with its structural analogues. Moreover, the imprinted nanoparticles preserved their recognition ability even after five adsorption–desorption cycles. Meanwhile, the nanoparticles were successfully applied to selective extraction of quercetin from red wine with a high recovery (99.7–100.4%). The limit of detection was calculated to be 0.058 μg/mL with a correlation coefficient 0.9996 in the range of 0.2–50 μg/mL. As a result, the developed selective extraction method using molecular imprinting technology simplifies the sample pretreatment procedure before determination of quercetin in real samples.     

Simultaneous extraction and determination of sulfadiazine and sulfamethoxazole in water samples and aquaculture products using [Bmim]BF4/(NH4)3C6H5O7 aqueous two-phase system coupled with HPLC

An ionic liquid aqueous two-phase system (ILATPS) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄)/ammonium citrate ((NH₄)₃C₆H₅O₇) coupled with high-performance liquid chromatography was developed for the separation and determination of sulfadiazine (SD) and sulfamethoxazole (SMX) in water samples as well as aquaculture products. The effect of such parameters as the types and concentrations of salts, temperature, the concentrations of SD and SMX and the extraction time on the partitioning behavior expressed in terms of extraction efficiency has been evaluated. Under the optimal conditions, this extraction method has been successfully applied to the analysis of SD and SMX in water samples and aquaculture products with the recoveries of 98.29–99.55 % (SD) and 92.09–99.82 % (SMX). The detection limits for two analytes were 0.9 ng mL^?1 (SD) and 1.8 ng mL^?1 (SMX). In comparison with the traditional solvent extraction, ILATPS is much simpler and more environmentally friendly for the separation and enrichment of the sulfonamides antibiotics.     

Preparation and characterization of magnetic chitosan microsphere sorbent for separation and determination of environmental estrogens through SPE coupled with HPLC

In this paper, a new separation sorbent of magnetic chitosan microsphere was prepared by means of suspension process using magnetic-Fe(3)O(4) nanoparticles as magnetic material and glutaraldehyde as the cross-linker. The morphology and properties of magnetic chitosan microspheres were characterized by FT-IR, SEM and adsorption test, and the results showed that they had good recognition, high selective ability and fast adsorption-desorption dynamics for estriol (E3), 17β-estradiol (E2) and diethylstilbestrol (DES). Applying this material as SPE sorbent, a method for separation, enrichment and analysis of estrogens in samples coupled with HPLC was developed. Under the optimized condition, the detection limit (S/N=3) for three estrogens was 3.2-20.1 ng/L, and the RSD for five replicate extractions of 50 μg/L E3, E2 and DES was 4.6-8.3%. The blank river water spiked with E3, E2 and DES at 0.05 and 0.2 mg/L levels were extracted and determined by the developed method with good recoveries ranging from 85.5 to 103.7%.     

Separation of endo-polygalacturonase using aqueous two-phase partitioning

The partitioning of endo-polygalacturonase (endo-PG) in polyethylene glycol (PEG)-polyvinyl alcohol (PVA10000) and PEG-hydroxypropyl starch (Reppal PES100) aqueous two-phase systems was studied, and revealed the possibility of using aqueous two-phase extraction to purify and concentrate endo-PG from its clarified fermentation broth. For the PEG8000-PVA10000 system, endo-PG presented in the fermentation broth (at concentration that is more than 40% of total protein) mainly dominates in the top phase with a partitioning coefficient of 6, while total protein concentrates in the bottom phase. A separation scheme consisting of two consecutive aqueous two-phase extraction steps was proposed: a first extraction in polyethylene glycol (PEG8000)-polyvinyl alcohol system, followed by a second extraction in PEG8000-(NH4)2SO4 system. This allowed the separation of endo-PG from polymer and the recycling of PEG polymer, since endo-PG was very strongly partitioned into the bottom phase of the PEG8000-(NH4)2SO4 system. Laboratory-scale experiments were performed to test the efficiency of this scheme. It was found that enzyme recovery was up to 91% with a total purification factor of about 1.9 and a concentration factor of more than 5. About 90% of the total PEG added into the systems can be recovered, and no reduction was obtained in the purification factor using recycled PEG.     

原子吸收光谱法研究双水相体系对铬的选择性萃取分离效率

研究了乙醇-硫酸铵双水相体系对Cr(Ⅵ)的选择性萃取分离效率及其原子吸收光谱法(AAS)分析. 配制乙醇-硫酸铵双水相体系, 并考察不同种类盐, 盐用量, 酸度和时间对体系萃取分离效率的影响, 用AAS法测定体系对以重铬酸根形式存在的Cr(Ⅵ)的选择性萃取分离效率, 通过乙醇和水相的AAS法测定选择了最佳萃取分离条件, 在pH为4的酸性介质中把水相中的Cr(Ⅵ)萃取到乙醇相而Cr(Ⅲ)留在水相中, 使两种形态的铬彼此分离, 通过对醇相Cr(Ⅵ)和水相Cr(Ⅲ)的 AAS测定, 得到最佳测定条件及体系对Cr(Ⅵ)的萃取率为: 双水相体系的体积为10.0 mL, V(EtOH)∶V(H2O)=2∶3, (NH4)2SO4的质量为1.7 g, pH 4, Cr(Ⅵ)萃取率为90% 以上, Cr(Ⅲ)回收率为98%～108%. 本法可用于铬的形态分析.     

Simultaneous determination of 3-monochloropropane-1,2-diol and acrylamide in food by gas chromatography-triple quadrupole mass spectrometry with coupled column separation

Both 3-monochloropropane-1,2-diol (3-MCPD) and acrylamide are contaminants found in heat-processed foods and their related products. A quantitative method was developed for the simultaneous determination of both contaminants in food by gas chromatography-triple quadrupole mass spectrometry (GC–MS/MS). The analytes were purified and extracted by the matrix solid-phase dispersion extraction (MSPDE) technique with Extrelut NT. A coupled column (a 3 m Innowax combined with a 30 m DB-5 ms) was developed to separate both compounds efficiently without derivatization. Triple quadrupole mass spectrometry in multiple reaction monitoring mode (MRM) was applied to suppress matrix interference and obtain good sensitivity in the determination of both analytes. The limit of detection (LOD) in the sample matrix was 5 μg kg⁻¹ for 3-MCPD or acrylamide. The average recoveries for 3-MCPD and acrylamide in different food matrices were 90.5–107% and 81.9–95.7%, respectively, with the intraday relative standard deviations (RSDs) of 5.6–13.5% and 5.3–13.4%, respectively. The interday RSDs were 6.1–12.6% for 3-MCPD and were 5.0–12.8% for acrylamide. Both contaminants were found in samples of bread, fried chips, fried instant noodles, soy sauce, and instant noodle flavoring. Neither 3-MCPD nor acrylamide was detected in the samples of dairy products (solid or liquid samples) and non-fried instant noodles.     

Selective separation of protein and saccharides by ionic liquids aqueous two-phase systems

In the present work, it was found that aqueous solution of a hydrophilic ionic liquid (IL), 1-butyl-3-methylimidazolium dicyanamide ([C₄mim][N(CN)₂]), could be separated into an aqueous two-phase system (ATPS) by inorganic salts such as K₂HPO₄ and K₃PO₄. The top phase is IL-rich, while the bottom phase is phosphate-rich. It was shown that 82.7%–100% bovine serum albumin (BSA) could be enriched into the top phase and almost quantitative saccharides (arabinose, glucose, sucrose, raffinose or dextran) were preferentially extracted into the bottom phase in a single-step extraction by [C₄mim][N(CN)₂] + K₂HPO₄ ATPS. The extraction efficiency of BSA from the aqueous saccharide solutions was influenced by the molecular structure of saccharides. The conductivity, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were combined to investigate the microstructure of the IL-rich top phase and the possible mechanism for the selective separation. It is suggested that the formation of the IL aggregate and the IL aggregate-BSA complex plays a significant role in the separation of BSA from aqueous saccharide solutions. This is the first example for the selective separation by ILs-based ATPSs. It is expected that these findings would have potential applications in bio-analysis, separation, and IL recycle.