Pretreatment Column Research Articles

Evaluation of the performance of heat pump-assisted distillation of an ethanol–water mixture

ABSTRACTThe process of separation of an ethanol–water mixture was simulated. A heat pump system was then implemented on the distillation column with the highest energy requirements in the process. Complete elimination of hot and cold utilities of the pretreatment column was obtained through an improved system by application of a heat pump at a compressor work of 406.6 kW. Installation of the heat pump system on the pretreatment column of the system results in a reduction of 10.7% of annual operating costs and 6.6% of the total annual costs (TAC). However, the capital costs of the process will enhance by 22.6%.

The use of a temperature-responsive column for the direct analysis of drugs in serum by two-dimensional heart-cutting liquid chromatography.

A novel pretreatment method, which was performed using a two-dimensional high-performance liquid chromatography (2D-HPLC) system, was proposed for the direct analysis of drugs in human serum. A temperature-responsive column was used as a pretreatment column. The stationary phase of the temperature-responsive column exhibits temperature-regulated hydrophilic/hydrophobic characteristics. Controlling the ionic strength of the eluent enables human serum albumin (HSA) to pass through the column without retention. When serum samples containing barbiturates or benzodiazepines were injected into the temperature-responsive column using 10mM of ammonium acetate (pH 6.5) as the mobile phase and in the temperature range of 10-40°C, HSA was eluted from the column near the dead time, followed by the individual drugs. When the column temperature was changed, the retention times of the drugs were altered owing to surface property changes within the pretreatment column. These closely eluted compounds were subsequently introduced into the analytical column using a column-switching valve, with a minimal gap time to avoid foreign substance contamination. This new 2D-HPLC method afforded high-quality chromatograms of multiple drugs without unwanted peaks from foreign substances. The present technique could be an attractive choice in selecting the analytical method for drug analysis.

A Chemiluminescent Protein Microarray Method for Determining the Seroglycoid Fucosylation Index.

The Lens culinaris agglutinin-reactive fraction of AFP (AFP-L3) is widely used to screen for hepatocellular carcinoma (HCC) in Japan and China. We developed a chemiluminescent protein microarray for determining the AFP-L3/AFP index (the ratio of AFP-L3 to total AFP, AFP-L3%) by fixing AFP-specific antibodies and Lens culinaris lectin on aldehyde-coated glass slides. Serum samples were tested for AFP using an enzyme-linked immunosorbent assay (ELISA) to validate the microarray. AFP-L3 was detected using Hotgen Biotech glycosyl capture spin column pretreatment technology and ELISA. When the AFP cut-off value was set to 20 ng/ml, the protein microarray displayed 89.74% sensitivity and 100% specificity for HCC diagnosis, and the ELISA displayed 87.17% sensitivity and 100% specificity. When the AFP-L3% cut-off value was set to 0.1, the protein microarray displayed 56.41% sensitivity and 100% specificity for HCC diagnosis, and the ELISA displayed 53.84% sensitivity and 100% specificity. The ROC curve for the HCC diagnosis showed that the AFP area under the ROC curve (AUC = 0.996; 95% CI: 0.986–1.005) was much higher than that of AFP-L3 (AUC = 0.857; 95% CI: 0.769–0.94) and AFP-L3% (AUC = 0.827; CI: 0.730–0.924). The microarray assay used in this study is a highly sensitive, accurate, and efficient assay for the determination of the AFP-L3%.

Separation performance of polydopamine-based cucurbit[7]uril stationary phase for capillary gas chromatography

Abstract Polydopamine (PDA) coating, a nature-inspired polymer, has attracted great attention in many areas due to its high adhesion strength and stability on almost all types of substrate surfaces. This work presents the first example of using PDA coating as a column pretreatment method in capillary gas chromatography (GC) and its employment in the column fabrication of cucurbit[7]uril (CB7) stationary phase. The fabricated PDA-CB7 column exhibited weakly polar nature and had advantages over CB7 column without PDA for the separations of some critical analytes in GC. This work demonstrates the advantage and potential of using PDA as a facile column pretreatment method in capillary GC column fabrication.

Simple column-switching ion chromatography method for determining eight monosaccharides and oligosaccharides in honeydew and nectar

Honeydew is excreted by aphids as a sweet waste and nectar is floral honey. Honeydew and nectar are complicated samples which consist of various sugars and amino acids. In this work, a simple ion chromatography with column-switching method was developed for the simultaneous analysis of 8 monosaccharides and oligosaccharides in honeydew and nectar. A reversed-phase column was used as a pretreatment column to eliminate organics on-line and sugars were eluted from a collection loop to analytical column by using column-switching technique. This method showed good linearity (r⩾0.9994) and afforded low limits of detection ranging from 1.55 to 10.17μgL−1 for all the analytes. Recoveries ranged from 95% to 105% and repeatability results were acceptable with relative standard deviation of less than 3.21% (n=6). This method was successfully applied to quantification of these sugars in honeydew and nectar. These results showed honeydew had much more oligosaccharides than nectar.

Pilot‐scale evaluation of concentrated piperazine for CO2 capture at an Australian coal‐fired power station: duration experiments

AbstractDuration operation was completed as the final stage of evaluating concentrated piperazine as a CO2 capture solvent at the Tarong pilot plant. For the duration tests, a single operating set‐point was maintained for an extended period of time. The purpose of the duration tests was to monitor the formation of degradation products and the robustness of the solvent. Two duration tests were conducted that differed only in the regeneration temperature used (125 or 155 °C). Four hundred twenty‐five hours of operation were achieved on the solvent with a regeneration temperature of 125 °C. This was followed by a further 421 h of operation with a regeneration temperature of 155 °C, giving a total operating time on the solvent of 1700 h by the end of the project. For the duration experiments, roughly 500 tonnes of flue gas was treated, and approximately 70 tonnes of CO2 captured. The heat stable salt (HSS) measured in highest concentration was formate, with the rate of formation increasing with regeneration temperature. The effect of pre‐treatment could be seen with sulfate concentration in the solvent increasing sharply when caustic supply to the pre‐treatment column was interrupted. Despite the formation of degradation products in the solvent regeneration energy requirements were not notably effected. For operation up to 1700 h on a real coal flue gas, no loss of plant performance was observed. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd

Enhancing biological treatment of dye wastewater with zero-valent iron

Pretreatment of authentic industrial dye wastewater with zero-valent iron (ZVI) was evaluated using a bench-scale integrated anaerobic-aerobic (ZVI-AO) biological treatment system. Average ADMI (American Dye Manufacturers’ Institute) value of dye wastewater was reduced from 245 to 107 units with ZVI column pretreatment. Subsequent treatment of ZVI column effluent by a continuous AO process further reduced the ADMI values to 18-39, resulting in overall decolorization efficiency of 78-89%. A control AO system without ZVI pretreatment, which was operated in parallel, achieved just 44-69% of ADMI removal efficiency. In addition, the ZVI integrated system yielded effluents with much lower COD and BOD concentrations than the control system. The aerobic batch respiration tests confirmed that ZVI treatment transformed the recalcitrant dye compounds to slowly biodegradable fractions, thus enhancing the overall biodegradability of dye wastewater.

A flexible ion chromatography column-switching system with a switching time window (STW) calibration program for the determination of myo-inositol in infant formula by pulsed amperometric detection

The column-switching system allows for convenient determination and calibration of STW parameters.

Quantitative Analysis of Chloramphenicol in Royal Jelly by Column-switching LC-MS/MS Using a Pretreatment Column with a Higher-pressure Capability.

An on-line pretreatment liquid chromatography-tandem mass spectrometry (LC-MS/MS) system was developed for the analysis of chloramphenicol (CAP) in royal jelly. A novel methylcellulose-immobilized restricted access media column with a higher-pressure capability of 60 MPa (MC-ODS HP) was developed for the effective removal of proteins and other compounds in the sample matrix. CAP in a sample solution was extracted in 2 min by the column-switching LC-MS/MS system. The system provides a minimum sample pretreatment along with highly sensitive and reproducible analysis. As a result, the limit of quantitation of CAP was 10 pg/mL (= 0.1 μg/kg royal jelly) and the linear dynamic range was between 10 and 10000 pg/mL (correlation coefficient greater than 0.999). The proposed method meets the requirements of regulations in EU (0.3 μg/kg). The inter-day precision and accuracy of CAP at 100 pg/mL over 3 days were 4.5 and 95.4%, respectively. Compared with the conventional method with a pressure of below 25 MPa, the peak separation in the MRM chromatogram was improved by using smaller particles (1.6 μm) for the analytical ODS column. The LC-MS/MS system with an MC-ODS HP expanded the applicability of the automated pretreatment.

Untargeted metabolomic analysis using liquid chromatography quadrupole time-of-flight mass spectrometry for non-volatile profiling of wines

The current study presents a method for comprehensive untargeted metabolomic fingerprinting of the non-volatile profile of the Graciano Vitis vinifera wine variety, using liquid chromatography/electrospray ionization time of flight mass spectrometry (LC–ESI-QTOF). Pre-treatment of samples, chromatographic columns, mobile phases, elution gradients and ionization sources, were evaluated for the extraction of the maximum number of metabolites in red wine. Putative compounds were extracted from the raw data using the extraction algorithm, molecular feature extractor (MFE). For the metabolite identification the WinMet database was designed based on electronic databases and literature research and includes only the putative metabolites reported to be present in oenological matrices. The results from WinMet were compared with those in the METLIN database to evaluate how much the databases overlap for performing identifications. The reproducibility of the analysis was assessed using manual processing following replicate injections of Vitis vinifera cv. Graciano wine spiked with external standards. In the present work, 411 different metabolites in Graciano Vitis vinifera red wine were identified, including primary wine metabolites such as sugars (4%), amino acids (23%), biogenic amines (4%), fatty acids (2%), and organic acids (32%) and secondary metabolites such as phenols (27%) and esters (8%). Significant differences between varieties Tempranillo and Graciano were related to the presence of fifteen specific compounds.

Suppression of peak tailing of phosphate prodrugs in reversed-phase liquid chromatography

Peak tailing of phosphate prodrugs in acidic mobile phases was thoroughly investigated. The results indicated that both metal–phosphate interactions and silanophilic interactions contributed to the observed peak tailing. Column pretreatment with phosphate buffers was demonstrated to be an effective and robust approach in suppressing metal–phosphate interaction. Silanophilic interactions, such as hydrogen bonding interactions between protonated isolated silanol groups and partially deprotonated phosphate groups were mobile phase pH dependent. The combination of column pretreatment and volatile low pH mobile phase buffers can be used to mitigate peak tailing issues in developing MS compatible RPLC methods for phosphate prodrugs. The use of non-endcapped columns should be avoided in RPLC analysis for phosphate prodrugs due to large amount of residual silanol groups in the stationary phases.

Determination of fructooligosaccharides in milk powder using high performance anion-exchange chromatography coupled with pulsed amperometric detection

Fructooligosaccharides (FOS) are usually added in milk powder as a kind of prebiotic. Thus, quantitative analysis of the FOS is very important for the quality control of milk powder. In this study, a simple method for the simultaneous determination of three FOS components with degrees of polymerization (DP) 3-5 in milk powder was developed by high performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). The samples were extracted with 50% (v/v) ethanol aqueous solution and defatted by an On Guard RP pretreatment column. The separation was performed on a CarboPac PA200 column by gradient elution using deionized water, 0. 2 mol/L NaOH solution and 0. 4 mol/L NaAc solution as the mobile phases. The flow rate was 0. 4 mL/min. The column temperature was 30 °C; and the injection volume was 25 µL. Good linear response was observed in the concentration range of 0.05-10 mg/L (r2 >0. 9993). The limits of quantification were 0. 02, 0. 005 and 0. 02 mg/L for 1-kestose, nystose and fructofuranosyl-nystose, respectively. The mean recoveries varied from 86. 0% to 114. 0% at three spiked levels of 0. 5, 1. 0 and 5. 0 mg/L. The short-chain fructooligosaccharides from inulooligosaccharides (IOS) were successfully separated by the developed HPAEC-PAD method. The method is simple, accurate, sensitive, and helpful for the quality control of milk powder.

Preparation and application of internal surface reversed-phase restricted-access material

A new convenient synthetic method was developed for the preparation of restricted-access material belonging to the group of the internal surface reversed-phase supports, which can be used for the direct injection and analysis of complex biological samples such as plasma samples. The supports, owning the function of reversed-phase chromatography, have an alkyl-chain only to the internal surfaces of the porous silica. Polyvinyl alcoholic groups chemically bound to the external surfaces of the porous silica that has the ability of hydrophilicity. Its structure was characterized by elemental analysis and electron microscope observation. The reversed-phase chromatographic performance was evaluated by using different solute probes, including propranolol, atenolol, phenobarbital and carbamazepine. Meanwhile, the comparative study with Merck Company' s ADS columns was carried out to prove capability of removing protein. At the same time, the plasma sample of propranolol was applied for the determination by direct injections. The results showed that the new internal surface reversed-phase restricted-access material owned the capabilities of protein exclusion and reversed-phase stationary, which could come true the double functions of excluding biomacromolecules and enriching micromolecule analysis. It can be used as a pretreatment column, which has the ability of online and fast analyzing biological specimen by direct probe inlet.

Iron oxide nanoparticle-impregnated powder-activated carbon (IPAC) for NOM removal in MF membrane water treatment system

A novel powder-activated carbon (PAC) by surface modification with iron oxide nanoparticles was applied to microfilter (MF) membrane system for stable operation and removal of natural organic matter (NOM) in water. Two types of PAC (wood-based and coal-based) were used for the preparation of the iron oxide nanoparticle-impregnated PAC (IPAC). The impregnation of the iron oxide nanoparticles played a role to increase the pHPZC of the PACs which means that the IPAC has higher basicity and larger adsorption capacity than the virgin PAC. From the experimental results of size exclusion chromatography (SEC) and SUVA254, there was no specific selectivity in adsorption of NOM on the IPAC. The saturated magnetization value of the IPAC was in the range of 6.75–8.04 emu/g that was enough to separate the IPAC particle from aqueous solution by magnetic force. An IPAC column followed by MF membrane system was operated to investigate NOM removal and membrane fouling control. A magnetic ring on the column above the IPAC bed surface could effectively hold the overflowing discrete IPAC particles. The system performance was compared with other similar MF membrane systems (PAC column-MF, high concentration PAC-MF (HCPAC-MF),and single MF) in terms of trans-membrane pressure (TMP) increase and NOM removal. For a 30-day operation, TMP of the MF membrane system could be maintained stably at 13 kPa with the IPAC column pretreatment, while the TMP of other membrane systems increased to the operation limit (40 kPa). Dissolved organic compound (DOC) and UV254 removal by the IPAC-MF system were 85.3 and 79.6%, respectively. And the removal efficiency of turbidity was more than 80%. With similar removal efficiency of DOC and UV254, the IPAC-MF process showed much more stable operation for longer periods compared to the other hybrid MF membrane systems (HCPAC-MF and PAC column-MF).

Analysis of hexavalent chromium in Colla corii asini with on-line sample pretreatment valve-switching ion chromatography

An ion chromatography (IC) system with on-line sample pretreatment using valve-switching technique was developed for the determination of hexavalent chromium (Cr(VI)) in Colla corii asini. Colla corii asini is a complicated sample with organics as main matrix. In this work, a polymer-based reversed-phase column was used as a pretreatment column. Via valve-switching technique, sample solution with target ions were eluted from a collection loop to analytical columns, with matrix eliminated on-line. Under the optimized separation conditions, the method showed good linearity (r=0.9998) in the range of 0.004–1.0mg/L and satisfactory repeatability (RSD<3%, n=6). The limit of detection (LOD) was 1.4μg/L (S/N=3). The average spiked recoveries of Cr(VI) were 93.4–102.0%. The result showed that the on-line sample pretreatment IC system was convenient and practical for the determination of trace Cr(VI) in Colla corii asini samples

HPLC column-switching technique for sample preparation and fluorescence determination of propranolol in urine using fused-core columns in both dimensions

A new and fast high-performance liquid chromatography (HPLC) column-switching method using fused-core columns in both dimensions for sample preconcentration and determination of propranolol in human urine has been developed. On-line sample pretreatment and propranolol preconcentration were performed on an Ascentis Express RP-C-18 guard column (5 × 4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water (5:95, v/v) at a flow rate of 2.0 mL min(-1) and at a temperature of 50 °C. Valve switch from pretreatment column to analytical column was set at 4.0 min in a back-flush mode. Separation of propranolol from other endogenous urine compounds was achieved on the fused-core column Ascentis Express RP-Amide (100 × 4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water solution of 0.5% triethylamine, pH adjusted to 4.5 by means of glacial acetic acid (25:75, v/v), at a flow rate of 1.0 mL min(-1) and at a temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 229/338 nm. A volume of 1,500 μL of filtered urine sample solution was injected directly into the column-switching HPLC system. The total analysis time including on-line sample pretreatment was less than 8 min. The experimentally determined limit of detection of the method was found to be 0.015 ng mL(-1).

Trace level determination of polycyclic aromatic hydrocarbons in river water with automated pretreatment HPLC

A novel on-line pretreatment pump-injection HPLC system for polycyclic aromatic hydrocarbons is proposed. We report novel pump-injection HPLC-based on-line SPE with a specially designed pretreatment column for the determination of trace amounts of chemical substances in surface water. Polycyclic aromatic hydrocarbons are well known for strong carcinogenicity and thus a severe concentration control is required for drinking water and/or river water, which is the main resource of tap water. We found it possible to detect ng/L levels of polycyclic aromatic hydrocarbons by using pump-injection column switching HPLC with fluorescence detection. To avoid the phenomenon, in which polycyclic aromatic hydrocarbons can be often adsorbed on the surface of flow lines of HPLC by their highly hydrophobicity especially resin-made parts in sample delivery pump, we employed "autodilution" device that provides reliable recovery and repeatability. Additionally, real water samples were collected and then the spiked polycyclic aromatic hydrocarbons were determined at ng/L levels.

Simultaneous Determination of Nitrite and Nitrate in Vegetables by Improved Pretreatment Ion Chromatography

Modified Mn-Al2O3 was prepared by impregnating neutral Al2O3 in Mn( NO3)2 solution for 4 h at a constant temperature of 40 ℃ under stirring condition and then roasting for 2 h at 800 ℃.The prepared modified Mn-Al2O3 was composited with activated carbon powder to form the pretreatment column for the filtration and purification of vegetable samples.A novel ion chromatographic method was developed for the simultaneous determination of nitrite and nitrate in vegetables by using this pretreatment column.Good linear relations for the determination NO "2 and NO" 3 in the range of 0.2-10 mg/L were observed.The relative standard deviations were less than 0.35%.Recoveries of NO "2and NO" 3 were found to be ranged from 94% to 103%.Among the eleven kinds of vegetables which were sold on the market,the levels of nitrites in rape were the most,measuring 4.53 mg/kg.The garland chrysanthemum has the highest levels of nitrates,measuring 539 mg/kg.

Determination of alendronate in low volumes of plasma by column-switching high-performance liquid chromatography method and its application to pharmacokinetic studies in human plasma

A sensitive and simple column-switching high-performance liquid chromatographic (HPLC) method with fluorescence detection was developed for the determination of alendronate in human plasma. Alendronate and pamidronate (internal standard, IS) in plasma including Na(2)EDTA were precipitated with sodium hydroxide and calcium chloride after deproteinization using 10% trichloroacetic acid solution. The precipitated alendronate and IS were reconstituted by sodium citrate and citric acid and then derivatized with 9-fluorenylmethyl chloroformate. The resulting solution was injected onto an HPLC system consisting of a pretreatment column and an analytical column, which were connected with a six-port switching valve. The assay was linear in the concentration range of 2-100 ng/mL in 1 mL of plasma with high precision and accuracy, and the limit of detection was 0.5 ng/mL. It was successfully applied to evaluate the pharmacokinetic parameters of alendronate in human volunteers following single oral administration. The mean value of maximum alendronate plasma concentration (C(max)) was 37.69 ng/mL, and the mean time to reach the C(max) (T(max)) was 1.08 h. The area under the plasma concentration-time curve (AUC) and elimination half-life (T(1/2)) were 106.48 ng/mL/h and 1.66 h, respectively.

Determination of bisphenol A with effective pretreatment medium using automated column‐switching HPLC with fluorescence detection

A practical way for reducing contaminants, such as humic acids, and solving column-clogging problem in environmental water analysis with liquid chromatography is proposed. Detection interference by contamination is one of the most important issues of the environmental analyses. Moreover, due to the recent smaller diameter and fine particle size of an analytical column for HPLC system, a column-clogging problem is another practical difficulty as well. We found it possible to solve these problems by employing column-switching HPLC, which consists of a pretreatment column containing surface-modified polymer particles and flow changeover valves for cleaning the remaining matrices in the pretreatment column prior to analysis. This method was successfully applied to actual HPLC-fluorescence detection of bisphenol A. Limit of detection (LOD) in real sample was <0.7 ng/L. Repeatability was around 1.4% and recovery was around 97% or more. A particular pressure increase was not observed in 150 repeated analyses of real river water samples.