Capillary Electrophoresis Based Immunoassay for Monoclonal Antibody with Diode Laser Induced Fluorescence Detection

ABSTRACT

A capillary electrophoresis based immunoassay (CEIA) for monoclonal antibody using diode laser induced fluorescence (LIF) detection was described. A direct assay for monoclonal anti-BSA in mouse serum was used as a model. BSA was labeled with Cy5 and used as the immunoreagent. The 635 nm line of a diode laser was used as the excitation source for LIF detection. The calibration curve for anti-BSA in mouse serum had a linear dynamic range of 4-40 nM. The concentration limit of detection (LOD) was 1.2 nM. Incubation time and CE conditions such as buffer concentration, pH and separation voltage were optimized, and the performances of different lasers as excitation sources were also compared.     

A low-cost light-scattering detector for the flow-injection nephelometric determination of sulfate.

A simple low-cost flow-through light-scattering detector was developed for determining the particle mass concentration in colloidal suspensions. Employing a laser pointer as a light source and a photodiode IC as a light sensor, the detector was shown to have good sensitivity, yet was small and battery operated. The detector was demonstrated to be effective for the flow-injection nephelometric determination of sulfate by precipitation as barium sulfate.     

Effect of ammonia carrier gas on the response of the flame ionization detector

The effect of using ammonia as a carrier gas on the response of the flame ionization detector (FID) has been investigated. It was found that the FID response, calculated as the effective carbon number (ECN), increased for all the compounds studied when ammonia, rather than helium, was used. The change was 0–0. 9 carbon atom for hydrocarbons, one carbon atom for alcohols and diphenyl ether, and 0.4–1 carbon atom for phenols and ketones. The increase in ECN was larger for amines (0. 8–5 carbon atoms), but these numbers also reflected an improvement in chromatographic performance as a result of reduced adsorption on the column. The largest change in signal-to-noise ratio, a six-fold increase, was obtained for octyl-amine; ratios for hexyl methyl ketone, diisobutyl ketone, dihexyl-amine, dibutylamine, and N-methyloctylamine increased by a factor of 2–3 when ammonia was used as carrier gas. To determine the extent to which the effect on detector response was solely attributable to ammonia, a mixture of 5 % ammonia in nitrogen was used as detector make-up gas with helium as carrier gas. Under these conditions the noise in the FID increased but for most of the compounds studied the signal-to-noise ratio also increased.     

离子印迹传感器选择性检测甲基汞离子

以甲基汞离子为模板,8-巯基喹啉为荧光单体,4-乙烯基吡啶为功能单体,乙二醇二甲基丙烯酸酯为交联剂,偶氮二异丁腈为引发剂,在二甲基亚砜溶剂中,以聚偏氟乙烯(PVDF)膜为支撑介质,65℃热引发聚合得到甲基汞离子荧光印迹膜。该荧光印迹膜对甲基汞离子表现出良好的选择性,最佳吸附pH值为7.0,检出限为3.5×10-7mol/L。将其作为吸附材料,应用于河水中甲基汞离子的分离和富集,结果表明,该传感器对甲基汞离子具有良好的选择性和特异性吸附,回收率达93%～104%。     

Understanding the importance of the viscosity contrast between the sample solvent plug and the mobile phase and its potential consequence in two-dimensional high-performance liquid chromatography

The effect of solvent viscosity mismatch on elution performance in reversed-phase HPLC was studied using moment analysis. Two conditions were tested: (1) the mobile phase viscosity was less than the injection plug viscosity, and (2) the mobile phase viscosity was greater than the injection plug viscosity. Under the first condition, retention time and elution performance decreased as the viscosity contrast between the mobile phase and injection plug increased. The effect on performance was more marked as the injection volume increased. A decrease in performance of 12% for compounds with retention factors up to 2.8 was apparent even when the viscosity contrast was only 0.165 cP. In the second set of conditions, elution performance was actually observed to increase, by as much as 25% for a 40 μL injection, as the viscosity contrast between the mobile phase and the solute plug increased. No change in the retention factor was observed. This behaviour was attributed to the shape of an injection plug as it enters into the column, whereby a low viscosity plug permeates away from the wall when the column contains a higher viscosity mobile phase, and vice a versa for a high viscosity plug entering a low viscosity mobile phase. At no stage was either a band splitting or shoulders observed with viscosity contrasts up to 1.283 cP, as could have been expected.     

Molecularly imprinted silica as a selective SPE sorbent for triazine herbicides

A molecularly imprinted organically modified silica was prepared through a simple sol‐gel procedure and evaluated as a specific sorbent for SPE of triazine herbicides. The material proved to be highly selective for the template molecule, atrazine, as well as for other structurally related species such as simazine and propazine. The performance of this material was shown to be comparable with commercial acrylate‐based molecularly imprinted polymers. The molecularly imprinted silica was applied for the determination of trace levels of the target triazine analytes in sugar cane juice (locally called “garapa”).     

Multifunctional flexible and stretchable polyurethane/carbon nanotube strain sensor for human breath monitoring

Flexible and stretchable polyurethane/carbon nanotube composite with strain detection ability was used for human breath monitoring. The composite material consisted of a network of multiwalled carbon nanotubes and thermoplastic high elastic polyurethane. It was found that elongation of the composite led to a macroscopic increase in electrical resistance, which can be used as a principle for applied strain detection. This detection was reversible, durable, and sensitive with gauge factor reaching very promising value, as, for example, ~46 at applied deformation of 8.7%. Further, the composite could be elongated to very large extend of deformation without discontinuity in measured resistance change reaching gauge factor ~ 450 at composite mechanical break at ~300% of strain. Sensor durability was also confirmed by sine wave deformation cycling when any decrease in the sensor properties for more than 10³ cycles was observed. Simultaneously, the prepared composite possessed other utility properties also and was considered as multifunctional when it was tested as an organic solvent vapor sensor, an element for Joule heating and finally as a microstrip antenna.     

A comparison of liquid–liquid porosimetry equations for evaluation of pore size distribution

This paper reviews and numerically tests many of the methods for the determination of pore size distribution of liquid membranes by liquid–liquid porosimetry. The flux through membranes was defined for flow of two immiscible liquids when drops or a liquid jet is formed, as well as the case when the interface is forced out by sufficient pressure. Several methods from literature for the determination of pore size distribution, some variations of these, and one new method are presented with a consistent theoretical basis. Using numerical tests it was found that all methods were very sensitive to measurement noise as low as ±0.1%, and that some form of data smoothing, such as a smoothing spline, was required to obtain a satisfactory distribution. The effects of elastic and permanent membrane compression were tested and a method was proposed to reduce the resulting error. A method based on the ratio of flux liquids with and without a liquid–liquid interface was recommended as it was less sensitive to the effects of compression in some cases and it provides a check when compression is not repeatable.     

Syntheses and characterization of statistical and block fluorinated copolymers with linear and star-like architectures via ATRP

The synthesis of a fluorinated macroinitiator for copper-catalyzed atom transfer radical polymerization (ATRP) is reported, as well as its use for the controlled living polymerization of poly(propylene glycol) methacrylate (PPGM) in MEK at 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer and the molecular weight of the polymer estimated by NMR spectroscopy was in close agreement with the theoretical molecular weight, as expected for controlled processes. The statistical copolymerization of PPGM or methyl ether poly(ethylene glycol) methacrylate (MPEGMA) with a perfluoroalkyl ethyl methacrylate by copper-mediated ATRP was also investigated and led to copolymers with essentially random incorporation of monomers. The syntheses and characterization of star-like homopolymers of MPEGMA or the fluorinated monomer via ATRP are also reported, as well as an amphiphilic star-like block copolymer containing ethyleneglycol units as the core and fluorinated moieties in the shell. The micellar behavior of this copolymer was investigated as a function of the external environment.     

Hazard evaluation for oxidation of cyclic ethers

Ethers are widely used as a solvent for synthesis reactions, however, they are known as hazardous chemicals as they have low flash points and form peroxides under oxidative conditions. In this study, the oxidative reactivity of cyclic ethers was evaluated by thermal analysis. The accelerated test was performed in a pressure vessel under a high oxygen pressure (2 MPa), and DSC was used to detect the products of the reaction. Tetrahydrofuran (THF) and 1,3-dioxolane were used as a sample. The result of the DSC measurement of THF without any antioxidant showed that the DSC curve depended on the exposure time. It was found that this method can be used for the oxidation evaluation. The DSC measurement was also used for the detection of ether peroxides, and this method was faster and simpler than the potassium iodine titration.     

Separation of glycosylated caseinomacropeptide at pilot scale using membrane adsorption in direct-capture mode

A direct-capture anion-exchange membrane adsorption process for the separation of a pure glycosylated (gCMP) fraction of caseinomacropeptide (CMP) was successfully developed at pilot plant scale. The method was evolved using a commercial CMP isolate as feedstock as well as fresh sweet whey from skim milk. The former resulted in a binding capacity (BC) of 0.28 mg gCMP/cm² membrane surface with a purity of 97% while the latter afforded a gCMP fraction with a purity of 91% and a BC of 0.21 mg gCMP/cm² membrane surface. The main difference was a significant fouling of the membrane adsorber module when the whey was applied, which resulted in a loss of 46% BC after at least five loading/elution cycles. This effect was not observed using the pure CMP isolates and indicates a blocking of the ion-exchange ligands. Triglycerides, as detected by lipid analysis, as well as protein aggregates and casein-flocculates, are mainly responsible for the fouling process. The fouling was decreased using microfiltered whey or by increasing the temperature of the adsorption process. Additionally, a method of repeated elution was shown to decrease the volume of the eluate as well as the NaCl consumption of the elution buffer. The process development further included a desalting and concentration step, which was performed by a 10 kDa ultrafiltration/diafiltration (UF/DF). The efficiency of the UF was strongly influenced by the pH of the solutions and showed best performance at pH 4.1 for the eluate. The residual solution had to be adjusted at pH 6.5 as there was a strong decrease of flux at lower pH levels.     

Determination of anabolic steroids with gas chromatography-ion trap mass spectrometry using hydrogen as carrier gas.

Helium is considered to be the ideal carrier gas for gas chromatography/mass spectrometry (GC/MS) in general, and for use with an ion trap in particular. Helium is an inert gas, can be used without special precautions for security and, moreover, it is needed as a damping gas in the trap. A disadvantage of helium is the high viscosity resulting in long GC run times. In this work hydrogen was tested as an alternative carrier gas for GC in performing GC/MS analyses. A hydrogen generator was used as a safe source of hydrogen gas. It is demonstrated that hydrogen can be used as a carrier gas for the gas chromatograph in combination with helium as make-up gas for the trap. The analysis time was thus shortened and the chromatographic performance was optimized. Although hydrogen has proven useful as a carrier gas in gas chromatography coupled to standard detectors such as ECD or FID, its use is not mentioned extensively in the literature concerning gas chromatography-ion trap mass spectrometry. However, it is worth considering as a possibility because of its chromatographic advantages and its advantageous price when using a hydrogen generator.     

调制脉冲电沉积法制备质子交换膜燃料电池铂催化电极

通过调制脉冲电流在质子交换树脂(Nafion)粘接的无催化多孔碳电极(UCE)上电沉积Pt 催化剂, 对所沉积Pt 催化电极性能及负载量用循环伏安法(CV)、X 射线衍射仪(XRD)、透射电镜(TEM)及分光光度法进行了表征. 结果表明, 通过调制电沉积过程的脉冲参数, 能够实现质子交换膜燃料电池(PEMFC)电极Pt催化剂的直接电化学沉积, 能够调控电沉积Pt粒径, 并能有效地缓解电沉积过程中析氢对沉积金属催化剂铂的干扰, 所沉积的Pt 催化剂利用率较传统Nafion 粘接Pt/C催化电极要高. 脉冲导通时间ton 为300 μs、断通时间toff 为1200 μs, 脉冲峰值电流密度jp 为100 mA·cm-2 时, 电沉积120 s制得的电极的Pt 晶粒约5-8 nm, Pt 表面利用率为43.14%, 沉积Pt的电流效率为45%.     

Convenient and Scalable Process for the Preparation of Indole via Raney Nickel–Catalyzed Hydrogenation and Ring Closure

An efficient and practical method for the synthesis of indole as a key starting material for many useful chemicals is described. Using 2-nitrotoluene as starting material, hydroxymethylation with formaldehyde under alkaline conditions gave 2-(2-nitrophenyl)ethanol on a large scale. Raney Ni catalyst was used for both reduction of the nitro group as well as for the indole formation. The overall yield was 78% from 2-nitrotoluene.     

Antibody adsorption and orientation on hydrophobic surfaces

The orientation of a monoclonal, anti-streptavidin human IgG1 antibody on a model hydrophobic, CH(3)-terminated surface (1-dodecanethiol self-assembled monolayer on gold) was studied by monitoring the mechanical coupling between the adsorbed layer and the surface as well as the binding of molecular probes to the antibodies. In this study, the streptavidin antigen was used as a probe for the Fab portions of the antibody, while bacteria-derived Protein G' was used as a probe for the Fc region. Bovine serum albumin (BSA) acted as a blocking protein. Monolayer coverage occurred around 468 ng/cm(2). Below 100 ng/cm(2), antibodies were found to adsorb flat-on, tightly coupled to the surface and unable to capture their antigen, whereas the Fc region was able to bind Protein G'. At half-monolayer coverage, there was a transition in the mechanism of adsorption to allow for vertically oriented antibodies, as evidenced by the binding of both Protein G' and streptavidin as well as looser mechanical coupling with the surface. Monolayer coverage was characterized by a reduced level in probe binding per antibody and an even less rigid coupling to the surface.     

铌酸催化的苯甲醛与甲醇缩合反应

采用铌酸为催化剂,探索了该催化剂对苯甲醛与甲醇缩合反应的影响.优化反应条件是,催化剂用量为反应物质的量的5mol%,甲醇10mL(兼作溶剂),回流状态下反应2h,反应的产率和转化率分别达到94%、98.0%.该催化剂同样适用于其他醛(酮)与甲醇的缩合反应,可得到34%～89%的产率.所述方法操作简单、产率高、选择性好而且对环境友好,反应结束后,催化剂很容易回收,并能有效重复使用.     

A natural component as initiator for photopolymerization of 1,6-hexanedioldiacrylate

1,3-Benzodioxole (BDO) as a simple model compound for the BDO derivatives from natural plant was used as coinitiator for p-chlorobenzophenone (CBP) and initiator for UV photopolymerization of 1,6-hexanedioldiacrylate (HDDA), respectively. The results showed that, BDO was an effective coinitiator for CBP. Although BDO as initiator led to very low rate of polymerization, it was still meaningful for the photocuring field.     

Evaluation of transversal and longitudinal dispersion in a flow injection system by exploiting laser induced fluorescence: influence of flow-cell positioning

A fully mechanized set-up was built for the experimental determination of bi-dimensional dispersion with high spatial resolution (2400 μm²). Gravitational and wall effects in a single stream were evaluated by using time-based sampling and a micro-flow cell. Vertical upward and downward flows as well as horizontal flows were investigated. Ethylene glycol (MEG) and Rhodamine B in MEG were used as carrier and sample solutions, respectively. Longitudinal profiles were obtained by laser induced total fluorescence (LIF) at up to 19 transversal sites and combined to generate high-resolution bi-dimensional profiles. A two frontal maxima pattern was observed for all flows. The volumetric fraction of RB shape was highly stretched for downward flow and there was high asymmetry for horizontal flow. The sensitivity of three dispersion parameters was evaluated: maximum peak value, peak half-width at half-height, and peak area.Data modeling showed that the tanks-in-series was more sensitive to wall effects, had good adjustment with only one tank for upward and horizontal flow and needed two tanks for downward flow which was attributed to the latter having higher dispersion. A black box empirical modeling described better the gravitational effect and allowed to identify a parameter sensitive to upward and downward flow as well as hinting to two inner streams within the horizontal flow. It also pointed to a wall dispersion contribution of twice that of the liquid-liquid dispersion.     

氮磷掺杂碳点荧光探针用于食品中柠檬黄的快速检测

本工作以葡萄糖为碳源,乙二胺、浓磷酸为氮、磷杂原子供体,通过酸碱中和自放热法制备氮磷共掺杂碳量子点(N,P-CDs).基于柠檬黄对N,P-CDs荧光的猝灭效应,构建了一种快速灵敏检测柠檬黄的荧光方法.在最佳实验条件下,N,P-CDs对柠檬黄的检测展现出高选择性和高灵敏度特点,柠檬黄浓度在0.01-10.0μM范围内与N...     

Preparation of uniformly sized molecularly imprinted polymers for phenolic compounds and their application to the assay of bisphenol A in river water.

Uniformly sized molecularly imprinted polymers, which can recognize bisphenol A (BPA), have been prepared by a multi-step swelling and polymerization method using BPA or a structurally related analogue of BPA [p-t-octylphenol (OP) or p-t-butylphenol (BP)] as the template molecule, 4-vinylpyridine as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The BP-imprinted polymer showed higher molecular recognition ability for BPA than the OP-imprinted polymer. The BPA- and BP-imprinted polymers were applied for the assay of a trace amount of BPA in river water using column-switching HPLC with fluorescence detection: A BPA-imprinted polymer was used for removal of BPA from the pretreatment eluent as the trap column, and a BP-imprinted polymer was used for selective pretreatment and enrichment of BPA in river water as the pretreatment column. The calibration graph, constructed from peak area data plotted versus BPA concentration, was linear with a correlation coefficient of >0.999 in the concentration ranges of 25-1000 ppt. The limit of quantitation was 25 ppt with a 5-ml injection. The column-switching HPLC system was successfully applied for the assay of BPA in river water.