Flow-injection detector apparatus

Solvent extraction offers unique advantages among separation techniques. A system based on extraction into a polymer [poly(vinyl chloride)] as solvent was examined here because of possible advantages in speedy simplicity, sample size, solvent handlingy etc.f especially when coupled with flow injection and an amperometric detector. Solutes examined included salicylic acid and 8-hydroxy quinoline. The apparatus typically consisted of 0.8-mm i.d. X 170-cm coiled tubing that could be connected directly to the injection loop of a flow-injection amperometric detector system containing a nickel oxide electrode. 

The electronic tongue system based on flow injection analysis (FIA) with two amperometric detectors was set up. The FLA apparatus consisted of a Jasco (Tokyo, Japan) model 880 PU pump and two EG G Princeton Applied Research (Princeton, NJ, USA) Model 400 thin-layer electrochemical detector connected in series. Each detector was equipped with a working electrode (a dual glassy carbon electrode and a gold... 

An FIA system consists of four basic parts a pump or pumps for regulation of flow, an injection valve to insert sample volumes accurately and reproducibly into the carrier stream, a manifold, and a flow-through detector. A manifold is the term used for the tubing, fittings, mixing coils, and other apparatus used to carry out the desired reactions. The flow-through detector in AAS is the atomizer/detector combination in the spectrometer. 

The flow analyzer involves simple apparatus such as samplers, liquid drivers (peristaltic pumps, piston pumps, solenoid pumps), injection devices (rotary valves, injector-commutators), reactors and flow lines (usually narrow bore tubing), mixing chambers, and flow-through detectors. As a rule, these devices are readily available in most laboratories devoted to chemical analysis. Regarding detection, almost all analytical techniques have been used in flow analysis a small flow cell volume and a short response time that is compatible with system dynamics are important detector parameters. 

A rotating enzyme-immobilized reactor and a flat pH electrode were incorporated into a sealed cell for use under continuous-flow/stopped-flow (SF) operation for the rapid determination of penicillins G and V in tablets and injectables [50]. A co-immobilization in a rotating bioreactor and amperometric detector resulted in a sensitive system for determination of succinylcholine and acetylcholine in pharmaceutical preparations [51]. A tandem system incorporating two rotating bioreactors into a continuous-flow/SF sample/reagentprocessing setup was apphed for the determination of alkaline phosphatase activity in serum samples [52]. By functional combination of the SF and flow-injection analysis (FIA), an automated micro apparatus was constructed resulting in significant reduction of the injection volumes of enzyme and substrate [53]. SF/continuous flow methods were apphed to acquire kinetic information also [54, 55]. 

Conditions apparatus, Hewlett-Packard HP5890 equipped with an HP5972 mass-selective ion detector (quadruple) column, PTE-5 (30 m x 0.25-mm i.d.) with 0.25- am film thickness column temperature, 50 °C (1 min), increased at 20 °C min to 150 °C(5 min) and then at 4 °Cmin to 280 °C (30 min) inlet and detector (GC/MS transfer line) temperature, 250 and 280 °C, respectively gas flow rate, He carrier gas ImLmin" injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70eV scan rate, 1.5 scanss scanned-mass range, m/z 50-550. The retention times of benfluralin, pendimethalin and trifluralin are 15.2, 25.1 and... 

In the bypass position, the carrier solution flows through the bypass loop and across the ISFET. The sample is injected into the sampling valve and is introduced into the carrier solution. The bypass loop has a high hydrodynamic resistance and thus the solution proceeds to the detector. The reference electrode is always immersed only in the carrier solution and is electrically connected with the ISFET through the solutioa The apparatus is regularly calibrated by K, Ca and pH standard solutions. 

Figure 1. Schematic of the apparatus (1) thermal conductivity cell detector, (2) column, (8) flow meter, (4) pressure regulator, (5) drying trap, (6) injection valve, (7) recording device (A) T.C. detector, (B) power supply, (C) recorder, (D) dc micro-voltmeter, (E) FM adaptor, (F) magnetic tape recorder...

Temperature programmed desorption (TPD) of C02 (5 °/min, flow of He, 15 ml/min) was carried out on a conventional flow apparatus. In a typical experiment, 0.29 g of the catalyst were activated as above reported, then the system was cooled to 25°C and approximately 2 10 5 mol of Co2 were injected by means of a gas sampling valve. After degassing in flow of helium for 60 min the amount of the irreversibly adsorbed C02 was determined with an on-line g.l.c. equipped with a thermal conductivity detector,... 

Morrall2 used a HPLC system with two columns. The first column was loaded with the controlled pore glass (CPG) to be modified. The second column was used for separation of the reaction effluents. This column was coupled to a refractive index detector, allowing for quantitative detection of the effluents. The reaction was initiated by injecting an APTS/toluene mixture and stopped by injection of pure toluene. With this so-called stop-flow mechanism reaction times down to 18 seconds could be used. From these analyses it became evident that upon mixing of the aminosilane with the silica, a very rapid physisorption occurs. The initial adsorption of the APTS (from toluene solution on dried CPG) occurred before the 18 second minimum time delay of the stop-flow apparatus. For non-aminated silanes the adsorption proved to be much slower. This study also revealed the pivotal role of surface water in the modification of siliceous surfaces with alkoxysilanes, as discussed in the previous chapter. 

A gas chromatograph is an apparatus consisting of an injection port connected to a column that has a detector at its outlet end. The column is contained in an oven that is electrically heated, either isothermally or at a programmed rate. A stream of inert carrier gas, usually helium, is introduced into the injection port and flows through the column and detector. The injection port is a heated region that is sealed from the outside environment by a silicone rubber septum through which the sample is injected using a hypodermic... 

The necessary apparatus is simple, consisting of a ort column packed with an inactive material containing the polymer di rsed as a thin film on the surface. In some cases the column may also be packed directly with the pdymer in either film, fiber, or powder form. A uniform flow of inert gas is maintained through the column, and a pulse of probe molecules is injected at one end and detected at the other by a suitable detector. A small pulse of noninteracting gas can also be iqected with the probe molecules to aid in detection of the carrier gas front. The usual data recorded are the temperature and pressure drop across the column and the time of the peak maxima. 

Methanol oxidation was carried out in a conventional flow apparatus at atmospheric pressure. The feed mixtures were prepared by injecting the liquid methanol into air flow with a Gilson 302 pump. The catalyst was diluted with inert carborundum (1 3 volume ratio) to avoid adverse thermal effects, and placed in a tubular pyrex reactor with a coaxially centred thermowell with thermocouple. The reactor outlet was kept at 403 K, to prevent condensation of liquid products and formaldehyde polymerization, and it was connected with multicolumn Shimadzu GC-8A gas chromatograph with thermal conductivity detector. The column system used (1.5m of Poropak N+1.5m of Poropak T+0.9m of Poropak R) could separate CO2, formaldehyde, dimethylether, water, methylformate, dimethoxymethane and formic acid. The last product was never detected. 

Two sets of experiments were also carried out by means of a previously described temperature-programmed reaction (TPR) apparatus, equipped with a mass spectrometric (MS) detector [13] and operated isothermally (200°C) in the pulse mode. In the first set some 2 pi pulses of HEP were injected in the flowing carrier gas (ultrapirre helium, > 99.9999 vol%) just before the catalyst bed (50 mg of Y84). The second set of experiments was carried out on another fi esh batch of the same catalyst under exactly the same conditions, but after poisoning the catalyst surface by some pulses of CO2. 

A typical block scheme of gel chromatographic apparatus is shown in Fig. 4.6.4. The mobile phase flows from the solvent container, C, into degassing unit, D, and through filters, F, reaches the pumping system, P, which transports it via the pulse damper, PD, and the sample injecting system, I, into the column, CO. The effluent from the column enters the detector, DE, and flows through the volumeter, V, into the fraction collector, F. 

HPLC measurements were performed on a Waters radial-compression system with a CN column (particle size 5 xm, cartridge 8-mm i.d.). The HPLC apparatus consisted of an ERC-3110 degasser (Erma Optical Works), a Waters U6K injection system, a filter and a precolumn (CN), and a Beckman 160 UV detector with a zinc lamp at a wavelength of 214 nm. The liquid phase was a mixture of 50 vol % acetonitrile and 50 vol % water that contained 0.005 M dibutylamine phosphate. The flow rate was 2.0 mL min" ... 

A schematic block diagram illustrating an entire DP-SCD detection system is shown in Fig. 2. An analytical system consists of a gas chromatogr h equipped with a split/splitless iigector with the option of a Pressurized Liquid Injection System (PLIS), wifli or without low diermal mass gas chromatogr q)hy apparatus, for sample introduction and sulfur speciation (if required) an electrically heated burner with an interface that controls the burner gas flows and temperature and a detector that contains a chemiluminescent reaction cell, ozone generator, optical filter, amplifier, and electronics. Lastly, a vacuum pump is used to keep file reaction cell under low pressure conditions to prevent loss of chemiluminescent species and to reduce collisional quenching. 

Figure 2 Atmospheric pressure g.l.c. apparatus. (A) Carrier gas cylinder , (B) pressure regulator, (C) injection block, (D) column , (E) manometer , (F) katharometer detector, (G) soap-film flow meter. The dotted lines refer to the thermostat...

Countercurrent Chromatography Procedure. The entire column (pair of coiled multilayer columns connected in series) was filled with the stationary phase. The apparatus was then rotated counterclockwise at 600 rpm in planetary motion while the mobile phase was pumped into the inlet of the column at a flow-rate of 2.2 mL/min (head to tail elution mode). Maximum pressure at the outlet of the pump measured 80 psi. After a 1-hour equilibration period, the sample was loaded into the Rheodyne injector loop and injected. Effluent from the outlet of the column was continuously monitored with a Shimadzu UVD-114 detector at 312 nm and fractions collected with a Gilson FC-lOO fraction collector to obtain approximately 8.8 mL of eluant in each tube (during a 4-min interval). Retention of the stationary phase was estimated to be 930 mL (74%) by measuring the volume of stationary phase eluted from the column before the effluent changed to mobile phase (330 mL) and subtracting this volume from the total column capacity of 1260 mL. 

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