Analysis of Nereistoxin Using HPLC And Electrochemical Detection

Abstract

Nereistoxin blocks nicotinic cholinergic transmission, but the exact mechanism by which this dithiolane blocks nicotinic acetylcholine receptors is not clear. One possibility is that nereistoxin is reduced in vivo and the resulting product, dihydronereistoxin, reduces a disulfide bond in the region of the receptor where acetylcholine binds. Other possibilities include that nereistoxin oxalate as supplied is not pure and contains dihydronereistoxin, or that nereistoxin acts as a simple competitive antagonist. We report here a method for simultaneous detection of both nereistoxin and dihydronereistoxin using π reversed-phase, ion-pair high-performance liquid chromatography with electrochemical detection. The standard curve for nereistoxin is linear to 400 pmol, and the detection limit is 10 pmol. The working electrode response is stable for up to 60 injections. Reduction of nereistoxin to dihydronereistoxin by NaBH₄ was 92% complete under the conditions reported here, but reoxidation occurs slowly upon standing at room temperature. No dihydronereistoxin was detected in commercial samples of nereistoxin oxalate.     

HPLC Determination of Iodide in Scrum Using Paired Ion Chromatography with Electrochemical Detection

Abstract

HPLC utilizing paired ion chromatography with electrochemical detection is used for the determination of iodide in serum. Serum samples are prepared by precipitation of protein, centrifugation and removal of Interfering substances with a bonded phase column. The resulting sample is then analyzed. The method has successfully been applied to human serum and gives data that agrees well with values obtained by other methods. The method is accurate precise, and time conservative when compared to more classical methods.     

Selective Separation of Polar Compounds Using an Electric Field Coupled Normal Phase HPLC Column

Abstract

An electric field coupled method for separation of polar compounds using normal phase high performance liquid chromatography is described. The method, which is not based on electrophoresis or electrochromatography, selectively changes the column capacity for polar analytes. The use of different columns showed improved column efficiency and up to a 62% increase in the number of theoretical plates. The theory for the improvement is presented. The significance and utility of the method for selective analysis of polar fractions in environmental samples is discussed.     

High-speed LC Analysis Using Electrochemical Detection

Abstract

The chromatographic performance of an electrochemical detector incorporating a flowcell with improved dispersive charac- teristics has been evaluated for use in high-speed liquid chroma- tography. High-speed C18/3 um columns, 100 × 4.6 mn, i.d. were found to be well matched to this detector with respect to extra- column contributions to band broadening. The capabilities of this high-speed LC-EC system are demonstrated by a 3-minute separation of phenols and a 4-minute separation of catecholamines and ace- t ominophen.     

超声提取正相高效液相色谱法测定大豆及大豆油中的磷酸甘油酯

建立了超声提取-固相萃取纯化/正相高效液相色谱测定大豆及大豆油中磷脂酰胆碱(PC)、磷脂酰乙醇胺(PE)、磷脂酰肌醇(PI)的方法。考察了提取溶剂、超声功率、超声时间、提取温度及净化方式的影响,并研究了不同色谱固定相对磷酸甘油酯分离效果的影响。优化的实验条件为:以氯仿-甲醇(2∶1,体积比)为提取溶剂,1 500 W功率超声提取30 min;氨基固相萃取柱为纯化小柱;正己烷-异丙醇-1%HAc(8∶8∶1,体积比)为流动相。在该条件下,PC、PE、PI的线性范围分别为0.08～8.00、0.15～15.00、0.30～20.00 g.L-1,定量下限分别为0.021、0.050、0.060 g.L-1,检出限在8～23 mg.L-1之间,其在大豆和大豆油中的回收率为85%～108%。日内与日间精密度分别不大于4.7%和8.6%。     

Electrochemical DNA Hybridization Detection Using DNA Cleavage

We report the new method for detection of DNA hybridization using enzymatic cleavage. The strategy is based on that S1 nuclease is able to specifically cleave only single strand DNA, but not double strand DNA. The capture probe DNA, thiolated single strand DNA labeled with electroactive ferrocene group, was immobilized on a gold electrode. After hybridization of target DNA of complementary and noncomplementary sequences, nonhybridized single strand DNA was cleaved using S1 nuclease. The difference of enzymatic cleavage on the modified gold electrode was characterized by cyclic voltammetry and differential pulse voltammetry. We successfully applied this method to the sequence‐selective discrimination between perfectly matched and mismatched target DNA including a single‐base mismatched target DNA. Our method does not require either hybridization indicators or other exogenous signaling molecules which most of the electrochemical hybridization detection systems require.     

高效液相色谱电化学检测法测定阿奇霉素及相关组分

提出了用高效液相色谱电化学检测法同时测定阿奇霉素颗粒中阿奇霉素(AZMC)及相关组分(即脱糖氧胺阿奇霉素、阿奇霉素A及N-去甲基阿奇霉素)含量的方法.采用Thermo C18柱(150 mm×4.6 mm,5μm)作固定相分离上述4组分.以20 mmol·L-1磷酸二氢钾(用1 mol·L-1氢氧化钾溶液调pH为7.37)-甲醇(47+53)为流动相,流量为1.0 mL·min-1,电化学检测电位为1.05 V,柱温为35℃.阿奇霉素及相关组分的峰面积值与相应浓度之间的线性范围依次为37.06～593.00,2.63～84.00,9.20～294.50,6.69～107.00 mg·L-1,检出限(3S/N)分别为9.28,1.32,4.60,3.35 mg·L-1.用标准加入法作回收试验,测得平均回收率分别为99.9%,100.6%,99.9%,99.8%.     

Determination of Zearalenol and Zearalenone Using Electrochemical Detection

Abstract

A method is described for the determination of zearalenol and zearalenone in corn using electrochemical detection. the sample is extracted with chloroform, and the extract is cleaned up by liquid-liquid partition. Zearalenol and zearalenone are resolved by liquid chromatography (LC), using a C₁₈ column and a mobile phase consisting of 35 + 25 + 40 CH₃ CN + MeOH + H₂O and 0.02 mole/L sodium acetate buffered at pH 6.5. Zearalenol and zearalenone were detected with an electrochemical detector at an applied potential of +0.95V vs Ag/AgCl. Average recoveries of zearalenol and zearalenone in corn samples spiked at levels of 25–1000 ng/g were 104,2 and 97.5%, respectively. the coefficients of variation for the proposed method were 10.8% for zearalenol and 8.8% for zearalenone.     

应用纳米磁性球电化学检测特定序列DNA

采用分散聚合法制备纳米磁性羧基球,利用化学偶联法将末端修饰氨基的寡聚核苷酸固定在纳米磁性球表面,制成新型核酸探针,该探针可特异性结合目标单链寡聚核苷酸.在磁场作用下,将纳米磁珠与本体溶液分离并富集在电极表面,以中性红为嵌合指示剂,用示差脉冲伏安法测定杂交结果.经过条件优化,本法测定DNA的浓度线性范围为1.0×10^-6～5.0×10^-9mol/L,检出限为8.6×10^-10mol/L.     

Trace Enrichment and HPLC Analysis of Chlorophenols in Environmental Samples,Using Precolumn Sample Preconcentration and Electrochemical Detection

Abstract

A HPLC method has been developed for trace analysis of chlorophenols in the 0.2–2 ppb range from spiked water samples. Simple liquid-liquid extraction followed by on-line preconcentration of total mono- and dichlorophenols has been performed using a divinylbenzene-styrene copolymeric sorbent (PRP₁) as packing material for the precolumn. The chlorophenols have been eluted from the precolumn on an analytical column (5μm LiChrosorb RP-18, 12.5 cm × 4 mm) by use of a switching valve system followed by separation. Detection was carried out with an electrochemical detector. The linearity of the detector response has been proved over two orders of magnitude. The detection limit of chlorophenols by means of the electrochemical method is in the lower picogram range. The recoveries of the isomeric chlorophenols from spiked river water samples having initial concentrations of 2ppb are usually 70–90%. The procedure has been applied to drinking water and river water.     

适配体电化学传感器检测汞离子进展

适配体是一小段经体外筛选得到的寡核苷酸序列。适配体中的胸腺嘧啶(T)碱基可与Hg~(2+)形成比双链DNA更加稳定的T-Hg~(2+)-T结构。利用该性质结合电化学测量方法可制作检测Hg~(2+)的特异性强、灵敏度高的适配体电化学传感器,并建立微量Hg~(2+)的检测方法。该文对近年来发展的检测Hg~(2+)的适配体电化学传感器进行了综述和总结,对文献报道的几类传感器的构建过程和检测机理进行了详述,对检测方法的优缺点进行了分析。最后,对此类传感器今后的发展方向提出了展望,引用文献83篇。     

Electrochemical Detection of 2,4,6-Trinitrotoluene Using Interdigitated Array Electrodes

Abstract

We describe the use of interdigitated array gold electrodes (IDAs) for the electrochemical detection of 2,4,6-trinitrotoluene (TNT). Our protocol generates a reversible redox couple (hydroxylamine/nitroso) from the initial reduction of TNT, which can be amplified using redox cycling at IDA electrodes. The IDA electrodes give a limit of detection for TNT at ～6 ng/mL with a linear response (r² = 0.998) between 10 and 10,000 ng/mL for static conditions and between 5 and 200 ng/mL for flow conditions (r² = 0.999).     

Electrochemical Detection of Schistosoma Japonicum Antibody Using Biocatalytic Deposition

Abstract

An ultrasensitive electrochemical immunoassay based on biocatalytic deposition has been proposed for the detection of Schistosoma japonicum antibody (SjAb) in infected rabbit serum. Schistosoma japonicum antigen (SjAg) was immobilized on the gold electrode surface via glutaraldehyde crosslink and then incubated with infected rabbit serum containing SjAb; finally, the goat anti-rabbit IgG labeled with alkaline phosphatase was sandwiched to form the immunocomplex on the gold electrode surface. The alkaline phosphatase converted nonelectroactive substrate into the reducing agent and the latter, in turn, reduced metal ions to form electroactive metallic product on the electrode surface. Linear sweep voltammetry (LSV) was used to quantify the amount of the deposited silver and give the analytical signal for SjAb. Assay conditions such as the antigen concentration and enzymatic silver deposition time were optimized. The electrochemical immunosensor was able to realize a reliable determination of SjAb in the dilution range from 1:5000 to 1:100 with a detection limit of 1:6457 of dilution ratio. The feasibility of the proposed immunosensor for possible clinical applications was also investigated by analyzing real serum samples.     

液相色谱电化学检测抗结核药物—异烟肼

本文讨论了以无有机溶剂存在的水溶液为流动相异烟肼的液相色谱一薄层安培检测法。在所选定的实验条件下,检测限达2ng。应用本法分析了片剂中异烟肼的含量     

Chiral Separation of Carboprost Isomers by Normal Phase LC Using Amylose Chiral Stationary Phase

LC separation of carboprost diastereomers in bulk drug was developed and validated using normal-phase amylose stationary phase Chiralpak AD-H. The effect of the organic modifiers, namely 2-propanol and ethanol in the mobile phase was optimized in order to obtain the best separation. The retention time of (R)-carboprost and (S)-carboprost were 15.3 and 17.1 min, respectively. Calibration curves were linear over the range of 0.2–1.0%, with the regression coefficient (R ²) of 0.9997. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.07 and 0.2%, respectively. The method was accurate, precise and suitable to use for the purpose of controlling unwanted (R)-isomer in the carboprost active pharmaceutical ingredient. This method can be successfully applied to the analysis of chiral purity of carboprost in pharmaceutical bulk drug samples.     

Immobilized Polysaccharide-Based Stationary Phases for Enantioseparation in Normal Versus Reversed Phase HPLC

A set of 31 structurally different chiral pharmaceutical compounds was used as model analytes for investigation of the enantioselective potential of two immobilized polysaccharide-based chiral stationary phases under normal and reversed phase separation conditions. These chiral stationary phases differed in the polymeric backbone, amylose or cellulose, but possessed the same derivatization functionality. The results showed that the tris(3,5-dimethylphenylcarbamate) of amylose and cellulose have very broad, and often complementary, enantiorecognition abilities. In general, normal phase separation mode seemed to be more advantageous for separation of the majority of studied pharmaceuticals no matter if amylose- or cellulose-based columns were used. However, in certain cases the reversed phase separation system yielded better results. The combination of these two immobilized chiral stationary phases offers a powerful tool for enantioseparation of different types of pharmaceuticals in the normal and/or reversed phase mode.

     

正反相模式下键合纤维素手性固定相对手性化合物的拆分

在自行合成的键合型纤维素-(3,5-二甲基苯基氨基甲酸酯)(CDMPC-CSP)手性固定相上,在正相模式下对苯偶姻和甲霜灵外消旋体进行了拆分,考察了流动相中醇以及温度在手性识别中对手性分离的影响。同时考察了反相模式下外消旋体的拆分。     

Detection of Aflatoxins in Capsicum Spice Using an Electrochemical Immunosensor

Abstract

Electrochemical immunosensor based on immobilized aflatoxin B1 (AFB)–albumin conjugate and polyclonal antibody against AFB1 was performed for a competitive assay of AFB1 in capsicum spice. Spiked samples were used for construction of calibration curve. The proved limit of detection was 2.4 ppb. Immunosensor long-term stability was also estimated. Decrease of immunosensor sensitivity was less than 10% when stored in a refrigerator and approximately 22% for the immunosensor preserved at laboratory temperature for two weeks. Consequent performance of immunosensors for assay of real capsicum spice samples with proven aflatoxins presence produced good correlation with the data from valid method (high-performance liquid chromatography with fluorescence detector).     

Normal Phase TLC Separation of Enantiomers Using Chiral Ion Interaction Agents

Abstract

A method for the thin layer chromatographic (TLC) separation of enantiomers and diastereomers involving the use of chiral ion interaction agents is described. Several aromatic amino alcohols were resolved by TLC on diol and/or high performance silica gel plates using a mobile phase containing (1R)-(-)- ammonium-10-camphorsulfonate or N-benzoxycarbonyl-glycyl-L-proline (ZGP). Many of these chiral aromatic amino alcohols are of pharmacological importance as α- and β-adrenergic blockers, adrenergic compounds, and anti-glaucoma agents. A comparison was made between various N-CBZ-amino acid derivatives as chiral counter ions/chiral mobile phase additives (CMAs). These separations could not be achieved on other normal phase TLC stationary phases including microcrystalline cellulose, alumina and ordinary silica gel plates.