Valve On The Lab And Ampere Law Detection Research

The development of sequential injection lab-on-valve (SI-LOV) format provides vast potentials for instrumental miniaturization and on-line detection. It not only allows various experimental operations, but also facilitates in-valve homogenous and heterogeneous physical/chemical/bio-chemical reactions and real-time monitoring. What is more, sample metering, mixing, dilution, reagent addition, incubation, separation, and detection can be executed in any desired sequence in a system consisting of all kinds of channels that are integrated with a multi-purpose flow cell. In addition to the downscaled fluidic manipulation and automatic operation, the LOV manifold is ideal for on-line miniature sample treatment and field speciation analysis. Last but not the least, the novel and unique applications can be conducted based on a variety of detection techniques along with improved efficiency.Chapter1. Lab-on-valve manifold coupled to irreversible biamperometric detection for the on-line monitoring of quercetinThe analytical performance of lab-on-valve (LOV) system using irreversible biamperometry for the determination of quercetin was evaluated. By integrating miniaturized electrochemical flow cell designed and processed which is furnished with two identical polarized platinum electrodes, into the LOV unit, the lab-on-valve system combines sampling with analysis, realizing automated on-line analysis for quercetin in a closed system. The biamperometric detection system was established to record the relationship between oxidation current and time by coupling the irreversible oxidation of quercetin at one pretreated platinum electrode with the irreversible reduction of platinum oxide at the other pretreated platinum electrode. Factors influencing the analytical performance were optimized, including the potential difference, buffer solution and pH, and flow variables in the LOV. A linear calibration curve was obtained within the range of1-100μg mL-1of quercetin with the detection limit (3σ) of0.17μg mL-1. The relative standard deviation (R.S.D.) was3.3%for11successive determinations of25μg mL-1quercetin and the sample throughput was35h-1. The proposed method not only exhibits high selectivity and low sample/reagent consumption, but also achieves on-line analysis.Chapter2. Indirect biamperometric determination of o-phenylenediamine in lab-on-valve format using reversible indicating redox systemThe miniaturized lab-on-valve (LOV) manifold well hyphenated with indirect biamperometry is presented for automated determination of trace level concentrations of organic environmental pollutants by programmable flow. The experimental procedure was carried out by means of taking o-phenylenediamine (OPDA) as a model analyte, relying on Fe (Ⅲ)/Fe (Ⅱ) couple that served as an indicating redox system. The miniaturized electrochemical flow cell (EFC) designed and processed was integrated into the LOV module which is assembled with two identical polarized platinum electrodes between which a small potential difference (AE) was applied, to implement automated on-line analysis in a closed system. Factors affecting analytical performance are discussed, including indicating redox systems, concentration of indicating system, the acidity, the potential difference, and flow variables in the LOV. The calibration curve showed an excellent linearity in the concentration range of5.0×10-7-1.0×10-4mol L-1(R2=0.9993). The limits of detection (LOD) and quantitation (LOQ) for OPDA were found to be1.1×10-7and3.7×10-7mol L-1, respectively. A sampling frequency of40h-1was obtained along with a R.S.D. of2.8%at1.0×10-6mol L-1OPDA (n=11). The proposed procedure was successfully applied to the assay of OPDA in industrial waste water. Chapter3. On-line coupling of lab-on-valve format to amperometry based on polyvinylpyrrolidone doped carbon paste electrode and its application to the analysis of morinThe potential capabilities and analytical performance of lab-on-valve (LOV) manifold as a front end to amperometry have been explored for the on-line determination of morin. Meanwhile, the electrochemical behaviors of morin were investigated based on polyvinylpyrrolidone (PVP) doped carbon paste electrode (CPE), which found that PVP can significantly improve its oxidation peak current. The excellent amperometric current response was achieved when the potential difference (AE) of0.6V was implemented in pH6.5phosphate buffer solution (PBS) that served as the supporting electrolyte. A well-defined oxidation peak has been obtained in studies using PVP as a modifier of CPE based on the oxidation of morin. The present work introduces the LOV technique as a useful tool for amperometric measurement, documents advantages of using programmable flow, and outlines means for miniaturization of assays on the basis of PVP modified CPE.