All-in-One Flow Injection Spectrophotometric System for Field Testing

To date one of the most significant innovative trends in chemical analysis is to develop analytical instruments that have processed to analyze on-site. Such an apparatus should minimize problems related to sample transports, sample handlings and sample storages. Currently, a traditional wet analysis in laboratories has been replaced with a portable device designed to minimize problems from sending samples to the lab. One of the practical chemical methods which can be developed as the mobile device is flow injection analysis (FIA) because the scaled-down FIA manifolds have been already presented. Regarding the detection, the rapid progress in material science and electronic technology consents the construction of portable detection devices, particularly light-emitting-diodes (LEDs) based-spectrometers. In this work, the FIA analyzer integrated with a built-in detector was designed for on-site chemical testing. A double syringes pump was assembled for transporting of the reagent carrier which were merged at the first mixing coil. A plug of a sample solution was inserted automatically by using a six-port-valve and was mixed with the carrier stream at the second mixing coil before directed to the detector. The heart of the developed analyzer is the built-in spectrophotometric sensor, made of the LEDs as a light source and a photodiode as a detector. The continuous stream of the final product was pushed into a quartz flow-through cuvette and then was exposed to the LED light. Finally, the absorbance of the product solution was calculated according to the Beer-Lambert law.

Flow-injection spectrophotometric determination of dipyrone in pharmaceutical formulations using a solid-phase reactor with copper(II) phosphate

In this work, a flow-injection spectrophotometric method for dipyrone determination in pharmaceutical formulations was developed. Dipyrone sample solutions were injected into a carrier stream of deionized water and the reaction was carried out in a solid-phase reactor (12 cm, 2.0 mm i.d.) packed with Cu3(PO4)2(s) entrapped in a matrix of polyester resin. The Cu(II) ions were released from the solid phase reactor by the formation of Cu(II)-(dipyrone)n complex. When the complex is released, it reacts with 0.02% m/v alizarin red S in deionized water to produce a Cu(VABO3)3 complex whose absorbance was monitored at 540 nm. The calibration graph was linear over the range 5.0×10−5–4.0×10−4 mol L−1 with a detection limit of 2.0×10−5 mol L−1 and relative standard deviation for 10 successive determinations of 1.5% (2.0×10−4 mol L−1 dipyrone solution). The calculated sample throughput was 60 h−1. The column was stable for at least 8 h of continuous use (500 injections) at 25°C. Pharmaceutical formulations were analyzed and the results from an official procedure measurement were compared with those from the proposed FIA method in order to validate the latter method.

Parametric Study of Acoustic Excitation-Based Glycerol-Water Microsphere Fabrication in Single Nozzle Jetting

Microspheres or droplets are increasingly finding various biomedical applications as drug microspheres and multicellular spheroids. Single nozzle-based continuous jetting with the help of acoustic excitation and/or carrier stream is a basic process for monodisperse microsphere fabrication. Precise control of microsphere size and size distribution in single nozzle jetting is still of great manufacturing interest. The objective of this study is to numerically model a glycerol-water microsphere fabrication process during acoustic excitation-based single nozzle continuous jetting. Using a volume of fluid method, this study has investigated the effects of material properties and fabrication conditions such as the acoustic excitation frequency and amplitude and the carrier stream velocity on the size of microspheres fabricated. (1) The microsphere diameter decreases as the glycerol volume percentage increases. (2) The excitation frequency and pressure have a pronounced effect on the microsphere size. The microsphere diameter decreases as the excitation frequency increases, and the microsphere diameter increases with the excitation pressure amplitude. (3) The microsphere size decreases as the carrier stream velocity increases.

Heat Exchange Characteristics in Heat Supply and Heat Removal Parts of a Nonisothermal Circuit, Including Temperature and Velocity Fields in a HLMC Flow, for Controlled Impurity Content

Results of the experimental studies of the heat exchange to the lead heat-transfer agent in the annular clearance in the circulation contour with the controlled and operated processes of mass exchange and mass transfer of the oxygen content are presented. And results of experimental research of lead-bismuth heat-carrier stream velocity structure at a varied content of oxygen content are presented.

Combined Characteristics of MHD Resistance and Heat Exchange in a HLMC Flow in a Transverse Magnetic Field

Results of experimental research of lead-bismuth heat-carrier stream velocity structure in the cross-section magnetic field at a varied content of oxygen admixture and characteristics of oxide electroinsulating covers are presented. Experimental studies were carried out for the following operation parameters: the lead-bismuth eutectics temperature T = 400–420 °C; thermodynamic activity of oxygen in the coolant a = 10−4–100; the eutectics flow rate through the experimental part Q = 1.8–3.0 m3/h, the coolant velocity in the experimental part w = 1.0–1.7 m/s; the magnetic induction value B = 0–0.85 T; the Reynolds number Re = (1,6–2,7)·105; the Peclet number Pe = 320–4600, and the Hartmann number Ha = 0–365.

Simulation and Characterization of Microreactors for Aerosol Generation

This paper shows the application of T-shaped micromixers for the generation of nanoscale aerosols by the mixing of a hot gas-vapor-mixture with a cold gas. The fast mixing within a T-shaped micromixer leads to a quasi-instantaneous and high saturation of the vapor and therefore to homogeneous nucleation. After nucleation, the particles grow to their final size until the vapor is saturated. Different mixer geometries, mixing ratios, and gas temperatures have been investigated by numerical simulation to yield optimum mixing results over a wide range of operational parameters. The main selection parameters are the mixing time, the mixing quality, and the flow regimes in the mixer. Six different microreactor geometries were designed and fabricated in silicon and covered with a Pyrex glass lid for optical observation. Special attention was paid to thermal insulation and particle deposition at the channel walls. This concerns not only the entire mixing chip, but also the design of the fluidic mount with only few bends and corners. First experimental results for particle deposition (prefabricated NaCl nanoparticles in a nitrogen carrier stream,) and aerosol generation (Vitamin E droplets in nitrogen) are presented. High temperature gradients up to 1 Mio. K/s lead to a rapid condensation and forming of nanosized particles with a mean diameter of 20 to 50 nm and a narrow size distribution.

Flow-Injection Spectrophotometric Determination of Phenolic Drugs and Carbamate Pesticides by Coupling with Diazotized 2,4,6-Trimethylaniline

A flow-injection (FI) spectrophotometric system is proposed for the determination of phenols and carbamates. In the FI manifolds, the solutions of phenols or carbamates (the latter after hydrolysis with NaOH) were injected into a diazonium ion carrier stream at pH 9.5 (buffered with tetrahydroborate), which was formed by mixing 2,4,6-trimethylaniline (TMA) with nitrate in a sodium dodecyl sulfate aqueous micellar medium. Absorbance was measured at 550 nm. The system combines the advantages derived from the use of TMA for the coupling of phenols in basic micellar media, because of the inhibition of the self-coupling reaction of the reagent, with the precision and speed of the FI procedures. Other diazotized reagents produced excessive blank signals. The procedures were successfully applied to the determination of phenolic drugs (epinephrine, acetaminophen, and guaiacol) in pharmaceuticals and carbamates (bendiocarb, benfuracarb, carbaryl, carbofuran, methiocarb, promecarb, and propoxur) in pesticide products and water samples.

FLow-injection analysis: a new approach to quantitative measurements in clinical chemistry.

Flow-injection analysis, founded on an approach that is entirely different from continuous-flow analysis, involves use of three principles: sample "injection," controlled dispersion of sample (rather than a dispersion retarded with gas bubbles), and reproducible timing. The conditions governing the dispersion of the sample in the flowing carrier stream are considered, and we illustrate how the dispersion can be manipulated to suit particular analytical requirements. Instrumentation and practical aspects of flow-injection analyses are discussed, especially with regard to clinical chemistry applications, and the technique is compared with the more conventional gas-segmented-flow analysis system. We conclude that, because of its speed, economy, and simplicity, flow-injection analysis will eventually replace the gas-segmented approach for many clinical chemistry analyses.

Flame stabilization by plasma jets

The possibility of increasing flame reaction rates, stability and hence the throughput of chemical energy achievable by the addition of a small proportion of electrical power is stuided. The power is added to a subsidiary stream of different gases by a magnetically rotated plasma jet. Rates of rotation of the order 10 5 rev/min contribute to uniform heating and mixing with the very much larger main stream flow (up to blow-out) of methane + air mixtures. The products are sampled by a traversing micro-probe and analysed. Quite small additions of electrical power (e. g. 10% of the chemical energy flux—equivalent to an increase of approx. 116 °C in final temperature) produce large increases in throughput— almost 700 % with N 2 plus argon as the carrier gas. This compares with about 50 % predicted for a perfectly stirred system on the basis of measured global kinetics. Even the effect of argon alone, as the carrier gas, cannot be accounted for by such predictions. Radicals known to be important in flame propagation, such as OH, H and O were deliberately produced by including H 2 O, O 2 and CH 4 in the carrier stream . These were an improvement over argon alone but none appreciably exceeded N 2 in effectiveness. The conclusion is that a limited amount of electrical power used to stabilize a large throughput of flame reactants is most effective if employed to generate energetic and long-lived molecular fragments by imparting it in high concentration to a species of large dissociation energy which is capable of producing, subsequently, radicals important in flame propagation. The practical implications may be important, e. g. for stabilizing large throughputs in jet propulsion.