Cuvettes types

The lifetime of TPCs is much longer than pyrolytically coated or normal graphite tubes. Figure 60 shows peak shapes for vanadium and platinum using totally pyrographite cuvettes, pyrolytically coated cuvettes, and electrographite cuvettes. The TPC peak is narrower and appears earlier than the peaks of the other cuvette types. 

Determine an appropriate cuvette type for the sample. Use a 1-nun pathlengtb quartz cuvette for strongly absorbing samples or when only a small volume of the sample is available. Otherwise, use a lO-mm pathlength rectangular quartz cuvette. ... 

Place the quartz cuvette containing the sample solution into the sample compartment and ensure that the light beam is not clipping the meniscus of the solution (increase the volume of liquid in the cuvette if necessary or perhaps raise the height of the cuvette or the walls or base of the cuvette (in which case lower the cuvette or use a different cuvette type). You may be able to remove the cuvette holder assembly to view down the light beam path. Alternatively use a mirror. 

Other cuvette types may be appropriate in certain circumstances. See main text for details. 

A cuvette-type sample cell is often used. The cell is often surrounded by a liquid maintained at a constant temperature. The refractive index of this liquid is matched to that of the suspending medium. 

In some systems, known as continuous-flow analy2ers, the reaction develops as the sample —reagent mixture flows through a conduit held at constant temperature. In such systems, the reaction cuvettes are replaced by optical reading stations called flow cells. In most analy2ers, whether of discrete- or continuous-flow type, deterrnination of electrolyte tests, eg, sodium and potassium levels, is done by a separate unit using the technique of ion-selective electrodes (ISE) rather than optical detection. 

We have extended the seed-mediated technique for the synthesis of bimetallic nanoparticles, having core-shell type structure appending photoreduction of metal ions. It has been proved that the deposition of a less noble metal (M) as shell on a preformed nobler nanoparticle core (M ) seems to be very effective by UV activation. Using this seed-mediated method we were able to synthesize Aucore Agsheii particles. First for the preparation of gold seeds (S), TX-lOO (10 M) and HAuC (5.0 x 10 %) were taken in a quartz cuvette so that the final concentration of Au(III) ion remained 5.0 x 10 M. Then the... 

What material is the sample tube made of Just like a cuvette in a UV-visible spectrometer has to be optically transparent, the EPR sample tube must be transparent for the magnetic component of microwaves. High-quality quartz is the preferred construction material low-quality quartz and especially any type of glass will not... 

Quantitative Photolysis. Photolysis experiments were performed by exposing samples to a 450 Watt medium pressure mercury lamp. A shutter was placed between the samples and the lamp so that the exposure time could be accurately controlled. Unless otherwise stated, the samples were placed 4 inches from the lens. Filters (254 nm, 280 nm and 366 nm) when used, were placed immediately in front of the shutter. Sample holders were available for 1" x 1" quartz plates, NaCl windows and quartz UV cuvettes, and samples of each type were utilized. 

Conventional flame techniques present problems when dealing with either small or solid samples and in order to overcome these problems the electrothermal atomization technique was developed. Electrothermal, or flameless, atomizers are electrically heated devices which produce an atomic vapour (Figure 2.36). One type of cuvette consists of a graphite tube which has a small injection port drilled in the top surface. The tube is held between electrodes, which supply the current for heating and are also water-cooled to return the tube rapidly to an ambient temperature after atomization. 

Sample chambers for spectrometers come in two varieties—those holding only one cuvette at a time (single-beam) and those holding two cuvettes, one for a reference, usually solvent, and one for sample (double-beam). In a double-beam instrument, the sample spectrum is continuously corrected by subtraction of the reference spectrum. In the past, single-beam instruments were usually less expensive but more cumbersome to use because reference and sample cuvettes required constant exchange. However, modern singlebeam instruments with computer control and analysis can be programmed to correct automatically for the reference spectrum, which may be stored in a memory file. The use of both types of instruments is outlined in the applications section. 

The experimental setup employed 785 nm excitation with a 90° collection geometry. Each spectrum was obtained with excitation power 300 mW and integration time equivalent to 2.5 min. Because filtered serum is nearly transparent at 785 nm, excitation of Raman scattering is effectively along the entire laser path, creating a line source in the cuvette. Thus, the authors surmise that better collection efficiency could be obtained with optics designed specifically for this type of source, as opposed to the standard spherical lens they employed. 

Fig. 3.120. Scheme of the devices (three types - a, b and c) for formation and study of asymmetric films a 1 - microscrews 2 - tube with organic liquid 3 - tube with air and vapour of the liquids 4 - films holder 5 - tube with aqueous solution b 1 - glass cuvette 2 - liquid substrate (water phase) 3 - glass plate with an orifice 4 -capillary (orifice) where the film forms 5 - porous material 6 - microvalve for regulating the liquid level c I -capillary tube 2 - glass tube with the surfactant solution 3 - a drop of organic liquid or bubble 4 - optical glass 5 - microscope eye-piece. 

Bulk photolyses were carried out using a 1000-W, high pressure, Xe lamp (Model 6117, Oriel Corp., Stamford, Conn. 06902) and a UV-VIS grating monochromator. For purposes of comparison and evaluation of power, 8.5 mW of power at 425 nm is produced at the sample surface within the cuvette cell. The procedure for determining this is found elsewhere 3 ). Samples were loaded in a type 52-H 2mm light path quartz cell purchased from Precision Cells, Inc., Hicksville, NY. The amount of zeolite used was 0.3 grams. Solutions of 1.5 M isopropanol dissolved in acetonitrile were used for the bulk photolyses. 

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