Determination of 1-nitropyrene in herbs after selective enrichment by a sol-gel-generated immunoaffinity column

Using the determination of 1-nitropyrene as an example the paper demonstrates the advantages of including a highly selective sol–gel-generated immunoaffinity column in the sequence of clean-up steps necessary to determine haptens in complex matrices. The sol–gel method to immobilise antibodies enlarges the variety of immunoaffinity columns available and leads to mechanically stable columns with constant retention characteristics. The sample preparation scheme proposed combines acetonitrile extraction, size-exclusion and immunoaffinity chromatography. 1-Nitropyrene is then separated by reversed-phase HPLC from interfering compounds and determined after catalytic on-line reduction to the corresponding amine by spectrofluorimetry. Concentrations in the range from 0.1 to 1.4 μg/kg 1-nitropyrene were detected in herbs.     

Simplified quantitative determination of plasma phenytoin: on-line pre-column high-performance liquid immunoaffinity chromatography with sample pre-purification

A method for on-line high-performance liquid immunoaffinity chromatographic analysis of 5,5-diphenylhydantoin (phenytoin) in human plasma is described. The technique is simple and does not require sample preparation or addition of an internal standard, and the phenytoin is eluted from the columns in 12 min. A phenytoin-specific polyclonal immunoglobulin was attached to an organic silane derivative on silica. The immunosorbent was packed into a short liquid chromatography column and installed in a modified high-performance liquid chromatography system for on-line sample pre-purification. Standard curve linearity of plasma phenytoin was obtained at concentrations up to 160 mumol/l. When compared to conventional high-performance liquid chromatography, plasma phenytoin levels gave a correlation coefficient of 0.993. The phenytoin is highly bound to plasma proteins (ca. 87%). When plasma is injected onto the pre-column, a dissociation and partition of phenytoin from plasma proteins to a complete association with on-column insolubilized antibodies results.     

Sol-gel immunoaffinity chromatography for the clean up of ochratoxin A contaminated grains

This paper describes the application of sol-gel immunoaffinity columns for clean up of ochratoxin A contaminated cereal crops. Monoclonal antibodies selective for OTA have been entrapped into the pores of a sol-gel matrix in order to prepare immunoaffinity columns. Different parameters such as amount of entrapped antibodies and loading conditions were optimized to obtain highest possible recoveries of OTA. The method has been found to be a suitable tool in sample preparation prior to HPLC-FLD determination and as selective as conventional commercially available immunoaffinity columns. In the clean up of different cereals mean recoveries of 82±5%, 90±6% and 91±3%, were obtained for wheat, barley and rye, respectively, with sol-gel columns containing 1mg of anti-OTA antibodies. The detection limit (signal-to-noise ratio, 3) was 0.5 μg/kg and the limit of quantification (signal-to-noise ratio, 10) determined to be 1 μg/kg. Sol-gel columns can be reused 7 times without significant loss of recovery. After 10 applications the recovery decreased to approx. 50%.     

Ternary-column system for high-throughput direct-injection bioanalysis by liquid chromatography/tandem mass spectrometry

As a continuation of our efforts to improve our high-flow on-line bioanalytical approach for high-throughput quantitation of drugs and metabolites in biological matrices by high-performance liquid chromatography (LC) and tandem mass spectrometry (MS/MS), we have developed a ternary-column on-line LC/MS/MS system with dual extraction columns used in parallel for purification and an analytical column for analysis. The advantage of the dual extraction column system is that sample analysis can take place in one of the extraction columns while the other column is being equilibrated. Thus, the equilibration time does not add to the run time, hence shortening the injection cycle time and increasing the sample throughput. Moreover, the use of two extraction columns in parallel increases the number of samples that can be injected before the system fails due to an overused extraction column. Such a system has successfully been used to develop and validate a positive ion electrospray LC/MS/MS bioanalytical method for the quantitative determination of a guanidine-containing drug candidate in rat plasma. The system used for this work utilized two Oasis HLB extraction columns (1 x 50 mm, 30 microm), one C18 analytical column (3.9 x 50 mm, 5 microm), a ten-port switching value and a tandem mass spectrometer. The on-line analysis was accomplished by the direct injection of 10 microL of the sample, obtained by mixing a rat plasma sample 1:1 with an aqueous internal standard solution. Selected reaction monitoring (SRM) was utilized for the detection of the analyte and internal standard. The standard curve range was 1.00-200 ng/mL. The intra- and inter-day precision and accuracy were within 6.6%. The on-line purification step lasted for only 0.3 min and total run time was only 1.6 min.     

Determination of four fluoroquinolones in milk by on-line immunoaffinity capture coupled with reversed-phase liquid chromatography.

An automated, on-line immunoaffinity extraction method was developed for the analysis of 4 fluoroquinolones in milk: ciprofloxacin, difloxacin, enrofloxacin, and sarafloxacin. This method involves analyte extraction using an immunoaffinity capture column containing anti-fluoroquinolone antibodies coupled on-line with reversed-phase column chromatography. Liquid chromatographic analyses were performed by isocratic elution using a mobile phase of 2% acetic acid-acetonitrile (85 + 15) and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 444 nm, respectively. No significant interferences from the sample matrix were observed, indicating good selectivity with the immunoaffinity column. Recoveries from fortified raw milk samples (5-50 ppb of each fluoroquinolone) ranged from 72 to 90%, with standard deviations of < or = 8%.     

Monoclonal antibody-mediated clean-up procedure for the high-performance liquid chromatographic analysis of chloramphenicol in milk and eggs

A simple, rapid and specific sample preparation method based on antibody-mediated clean-up for the determination of chloramphenicol (CAP) in milk and eggs was developed. Skimmed milk and centrifuged egg homogenates were filtered and directly applied to immunoaffinity columns which were prepared by coupling monoclonal antibodies against CAP to a carbonyldiimidazole-activated support. Using a 0.2 M glycine, 0.5 M NaCl (pH 2.8) solution as an eluent, the immunoaffinity columns can be used more than 30 times without a decrease in column capacity. In subsequent high-performance liquid chromatographic analysis, no matrix interferences were observed. Good recoveries were obtained at spiking levels of 1-100 micrograms kg-1. Due to the high specificity of the clean-up procedure, the limit of detection can be lowered by increasing the test portion. Concerning milk, the limit of detection was successfully lowered to 20 ng kg-1 by increasing the test portion to 11 (recovery 99%). The method was applied to eggs produced by hens treated with CAP. The results are compared with those obtained by solid-phase extraction using silica gel.     

On-line immunoaffinity column-liquid chromatography-tandem mass spectrometry method for trace analysis of diuron in wastewater treatment plant effluent sample

An on-line immunoaffinity column with liquid chromatography/tandem mass spectrometry (IAC-LC-MS/MS) method for the determination of diuron in water matrices was described. This method used a sol-gel immunoaffinity column (20 mm x 4 mm I.D.) for on-line sample cleanup and enrichment, a monolithic analytical column (100 mm x 4.6 mm I.D.) for separation, and a triple quadrupole mass spectrometer for quantitation. The major challenges for the on-line set-up were discussed. The optimized on-line protocol was emphasized by the fact that low limit of quantitation (LOQ) of 1.0 ng/L was achieved with only 2.5-mL sample. In addition, a satisfactory accuracy ( approximately 90% of recovery) and precision (<6% of relative standard deviation) at 50 ng/L concentration were also obtained. Due to the ability of the sol-gel immunoaffinity column to eliminate matrix effect, the on-line IAC-LC-MS/MS analysis method can reliably determine diuron in wastewater treatment plant effluent sample.     

适用于质谱分析的在线固相萃取除盐方法

建立了一个简单、快速、有效的适用于质谱或液相色谱-质谱联用的在线固相萃取(SPE)高通量除盐方法。方法分为单柱和双柱模式,借助于包含双梯度泵(上样泵/分析泵)、自动进样器和配有十通切换阀的柱温箱的高效液相色谱系统,完成样品的自动化在线除盐。单柱模式通过上样泵实现在SPE柱上进样和除盐,被分析物则保留在SPE柱上;除盐完成后,通过阀切换利用分析泵洗脱富集在SPE柱上的被分析物。双柱模式则在单柱模式基础上增加了1根SPE柱,在色谱管理软件控制下2根SPE柱轮流工作,高效率完成样品的在线除盐。该方法在结合质谱分析蛋白质、多肽等领域具有较好的应用前景。     

免疫亲和柱在兽药残留检测应用中的研究进展

免疫亲和柱(IAC)是一种有效的兽药残留检测净化技术,可以简化样品净化过程并且提高待测物的提取效率,近几年在兽药残留检测中得到广泛应用,并表现出良好的发展前景。本文简要叙述了IAC的原理、制备过程以及在各种抗微生物类兽药检测中的应用,就IAC对目前已研制出的抗微生物药的残留检测及净化效果进行综述,并展望了IAC在未来兽药残留检测应用中的发展趋势,为研究者提供参考和研发思路。     

Development of immunoaffinity columns for pyraclostrobin extraction from fruit juices and analysis by liquid chromatography with UV detection

Pyraclostrobin belongs to a new generation of fungicides widely used to preserve high valuable crops. In the present study, three monoclonal antibodies with different affinities to this modern strobilurin have been evaluated for their usefulness in the production of immunoaffinity columns suitable for the solid-phase extraction, concentration, and clean-up of residues from food commodities. Different immunosorbents were produced and characterized in terms of antibody immobilization efficiency, immunosorbent binding capacity, optimum elution conditions, and reusability. Covalent coupling of the antibodies to Sepharose-CNBr gel took place with high yield (over 90%), whereas the immunosorbent efficacy to retain the analyte (from 28 to 68%) was shown to depend on the amount and type of antibody immobilized on the support. As a matter of fact, columns prepared with the monoclonal antibody PYs5#14 were able to selectively bound up to 53 μg of pyraclostrobin per gram of beads. Acetonitrile solutions were preferred over methanolic ones for analyte elution, and some immunosorbents could be reused at least 4-6 times provided that the amount of pyraclostrobin and the volume of sample did not overload the column. Effectiveness of the selected immunoaffinity column was evidenced by the development of an extraction procedure for pyraclostrobin residues from fruit juices and further determination by high-performance liquid chromatography with UV detection. A concentration factor of 50 times was achieved with the developed immunoaffinity column, which eventually resulted in a limit of quantification of 0.01 mg L(-1). Finally, quantitative recoveries were obtained on apple juice and red grape must samples spiked with pyraclostrobin from 0.01 to 1 mg L(-1).     

Immuno-based sample preparation for trace analysis

Immuno-based sample preparation techniques are based upon molecular recognition. Thanks to the high affinity and high selectivity of the antigen–antibody interaction, they have been shown to be a unique tool in the sampling area. Immuno-based sample preparation methods include the widely encountered immunoaffinity extraction sorbents, so-called immunosorbents, as well as membrane-based or ultrafiltration techniques. This review describes the new developments and applications that have occurred in recent years with emphasis on (i) the antigen–antibody interactions, (ii) and their importance for the properties and use of immunosorbents, (iii) multiresidue extractions, (iv) the on-line coupling to chromatographic or electrophoretic separations, and (v) the high potential for improving MS detection. The recent use of artificial antibodies for sample pretreatment, so-called molecularly imprinted polymers, is also described.     

A novel on-line solid-phase extraction approach integrated with a monolithic column and tandem mass spectrometry for direct plasma analysis of multiple drugs and metabolites

An on-line solid-phase extraction liquid chromatography/tandem mass spectrometry (SPE LC/MS/MS) assay using a newly developed SPE column and a monolithic column was developed and validated for direct analysis of plasma samples containing multiple analytes. This assay was developed in an effort to increase bioanalysis throughput and reduce the complexity of on-line SPE LC/MS/MS systems. A simple column-switching configuration that requires only one six-port valve and one HPLC pumping system was employed for on-line plasma sample preparation and subsequent gradient chromatographic separation. The resulting analytical method couples the desired sensitivity with ease of use. The method was found to perform satisfactorily for direct plasma analysis with respect to assay linearity, specificity, sensitivity, precision, accuracy, carryover, and short-term stability of an eight-analyte mixture in plasma. A gradient LC condition was applied to separate the eight analytes that cannot be distinctly differentiated by MS/MS. With a run time for every injection of 2.8 min, a minimum of 300 direct plasma injections were made on one on-line SPE column without noticeable changes in system performance. Due to the ruggedness and simplicity of this system, generic methods can be easily developed and applied to analyze a wide variety of compounds in a high-throughput manner without laborious off-line sample preparation.     

采用自动前处理LC/MS进行血浆中药物的快速分析

药物研究的发展对高通量的样品处理分析提出了越来越高的要求,减少样品制备时间和分析时间是解决问题的关键。我们新近发展了一种具有在线稀释旁路和新的样品预处理柱的Shim-Pack MAYI-ODS自动柱切换HPLC和LC／MS系统,该系统无需样品前处理,可直接进样进行血浆、血清中的药物分析。本文利用自动样品前处理LC／MS系统,用ODS整体柱实现了血浆中药物的快速分析。包括样品预处理,整个分析仅需1．2min完成。     

On-line coupling of high performance gel filtration chromatography with imaged capillary isoelectric focusing using a membrane interface

A high performance liquid chromatography system, a sample preparation device, and an imaged capillary IEF (CIEF) instrument are integrated and multiplexed on-line. The system is equivalent to two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), by transferring the principle of 2-D separation to the capillary format. High performance liquid chromatography (HPLC) provides protein separation based on size using a gel filtration chromatography (GFC) column. Each eluted protein is sampled and directed to a novel microdialysis hollow fiber membrane device, where simultaneous desalting and carrier ampholyte mixing occurs. The sample is then driven to the separation column in an on-line fashion, where CIEF takes place. The fluidic technology used by our 2-D system leads to natural automation. The coupling of the two techniques is simple. This is attributed to high speed and efficiency of the sample preparation device that acts as an interface between the two systems, as well as the speed and simplicity of our whole column absorption imaged CIEF instrument. To demonstrate the feasibility of this approach, the separation of a mixture of two model proteins is studied. Sample preparation and CIEF were complete in just 4-5 min, for each of the eluted proteins. Total analysis time is about 24 min. Three-dimensional data representations are constructed. Challenges and methods to further improve our instrument are discussed, and the design of an improved horseshoe-shaped sample preparation sample loop membrane interface is presented and characterized.     

On-line immunoaffinity capillary electrophoresis based on magnetic beads for the determination of alpha-1 acid glycoprotein isoforms profile to facilitate its use as biomarker

An immunoaffinity purification method coupled on-line to capillary electrophoresis (IACE) which allows the determination of several isoforms of intact alpha-1 acid glycoprotein (AGP) in serum samples using UV detection is developed. The immunoaffinity step is based on anti-AGP antibodies (Abs) covalently bound to magnetic beads (MBs) which are captured at the inlet end of the capillary using permanent magnets placed inside the cartridge of the CE instrument. The on-line method includes injection of the MBs with the Ab bound (MBs–Ab) and their trapping by the magnets at the entrance of the separation column, injection of serum sample and capture of AGP by the Abs, release of captured AGP, focus of desorbed protein, separation of AGP isoforms, and removal of MBs–Ab. The optimization of the different factors involved in each step allowed purification, separation and detection of AGP isoforms in a single electrophoretic analysis in about 1 h. Automation, sample and reagents consumption as well as analysis time was improved compared to off-line alternatives which use purification of AGP in an immunochromatographic column and CE separation of AGP isoforms in two independent operations. The analytical methodology developed allows the separation of 10 AGP isoforms in serum samples from a healthy donor. For a serum sample, precision (expressed as relative standard deviation) in terms of corrected area percentage was better than 0.5% for each peak accounting for more than 10% of total AGP and it was better than 4.0% in terms of relative migration time of each AGP isoform considering the whole process.     

Application of totally automated on-line sample clean up for prostanoid extraction and HPLC separation

Summary The aim of this study has been the evaluation of an automated system for on-line sample preparation using solid phase extraction and HPLC purification for the measurement of prostanoids in urine. We have established the optimum precolumn and column conditions for this analysis. The manual extraction —HPLC procedure furnishes lower recoveries and higher coefficients of variation than those obtained by the automated on-line procedure. The automated system has been applied to prostanoid analysis of human urine samples from subjects exposed to lead.     

Auto-regeneration of anion-trap columns for improved determination of silica by ion chromatography

The goal of this project was to develop an automated method to regenerate the ATC-3 trap columns that are used on the DX-800 on-line ion chromatography silica systems. The old method of regenerating the ATC-3 trap columns was to physically remove the trap columns from the silica system once every 2 weeks and manual regenerate them. A new automated regeneration method was developed by re-plumbing the silica system to allow 300 mM NaOH to run as the eluent. This regenerates the trap column automatically once every 24 h. The data have shown that regenerating the ATC-3 trap columns once per day improves the R.S.D. values for 250 ng/l silica analysis from 26.0 to 8.7%. The length of useful lifetime for the silica concentrator column was increased by an average of 9 months.     

Multidimensional capillary array liquid chromatography and matrix-assisted laser desorption/ionization tandem mass spectrometry for high-throughput proteomic analysis

A two-dimensional capillary array liquid chromatography system coupled with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) was developed for high-throughput comprehensive proteomic analysis, in which one strong cation-exchange (SCX) capillary chromatographic column was used as the first separation dimension and 10 parallel reversed-phase liquid chromatographic (RPLC) capillary columns were used as the second separation dimension. A novel multi-channel interface was designed and fabricated for on-line coupling of the SCX to RPLC column array system. Besides the high resolution based on the combination of SCX and RPLC separation, the developed new system provided the most rapid two-dimensional liquid chromatography (2D-LC) separation. Ten three-way micro-splitter valves used as stop-and-flow switches in transferring SCX fractions onto RPLC columns. In addition, the three-way valves also acted as mixing chambers of RPLC effluent with matrix. The system enables on-line mixing of the LC array effluents with matrix solution during the elution and directly depositing the analyte/matrix mixtures on MALDI plates from the tenplexed channels in parallel through an array of capillary tips. With the novel system, thousands of peptides were well separated and deposited on MALDI plates only in 150min for a complex proteome sample. Compared with common 2D-LC system, the parallel 2D-LC system showed about 10-times faster analytical procedure. In combination with a high throughput tandem time of flight mass spectrometry, the system was proven to be very effective for proteome analysis by analyzing a complicated sample, soluble proteins extracted from a liver cancer tissue, in which over 1202 proteins were identified.     

Sample preparation including sol-gel immunoaffinity chromatography for determination of bisphenol A in canned beverages, fruits and vegetables

The paper describes the development of a very simple method to prepare samples of canned food (beverages, fruits and vegetables) for the determination of bisphenol A by isocratic HPLC with fluorescence detection. The new sample preparation method makes use of the selectivity of bisphenol A antibodies immobilized in a silica matrix by an inexpensive and simple sol-gel technique. In spite of applying highly complex food matrices, immunoaffinity columns could be used for clean-up of at least 15 real samples. Limits of detection (S/N=3) ranged from 0.1 ng/ml for beverages to 4.3 ng/g for vegetables.     

Improvement of the performance of an immunoaffinity extraction method via region-specific immobilization of IgG

Using papaverine as a model target, an immunoaffinity column of high selectivity and binding capacity was prepared by utilizing covalent linkage between the Fc portion of IgG and the surface of Sepharose 4B support. Compared with the commonly used random coupling method, the binding capacity of the region-specific immobilized antibodies was increased from 0.04 to 0.2 mol of antigens/mol of antibodies and a much larger concentration factor was thus achieved. The obtained immunoaffinity column has been successfully used in pretreatment of pericarpium papaveris samples. The method offers an improved approach to immunoaffinity extraction that should be useful for purification and concentration of other targeted compounds in highly complex mixture.