Atomic-absorption photometer

Atomic-Absorption Photometer. This instrument operates on the very specific spectral absorption of an atomized sample rather than emission. The equipment is comprised of a stabilized hollow-cathode lamp (one for each element to be analyzed), a flame with sample nebulizer, a monochromator, and a photometer... 

Flame Photometer. See Atomic-Absorption Photometer in this entry. 

If the line source emits radiation on the resonance line only or if the line intensity is so great that any background radiation is rendered negligible, no additional wavelength selection is necessary. This is the case with sodium for which it was possible to construct an atomic absorption photometer without a wavelength selector (B7). 

Before commencing any experimental work with either a flame (emission) photometer or an atomic absorption spectrophotometer, the following guidelines on safety practices should be studied. These recommendations are a summary... 

Although flame emission measurements can be made by using an atomic absorption spectrometer in the emission mode, the following account refers to the use of a simple flame photometer (the Coming Model 410 flame photometer). Before attempting to use the instrument read the instruction manual supplied by the manufacturers. 

At present, calcium and magnesium are estimated almost exclusively by atomic absorption (36). Present instrumentation permits the dilution of the specimen to approximately 1 - 100 for calcium and even higher for magnesium. For many instruments, the two elements are not read out simultaneously such as is practicable for sodium and potassium with the flame photometer. The lower limit of serum volime at present, for the practical assay for calciim and magnesiim in the laboratory of Neonatology, is approximately 10 ul The instruments are very readily automated, and it is not uncommon for results to be available at the rate of 240 per hour in the routine laboratory, where a typical atomic absorption instrument such as a Perkin-Elmer has been attached to an automatic feed system. 

FIA star 5010 Modular, semi- or fully automatic operation. May be operated with process controller microprocessor. Can be set up in various combinations with 5017 sampler and superflow software which is designed to run on IBM PC/XT computer 60-180 samples h Dialysis for in-line sample preparation and in-line solvent extraction.Thermostat to speed up reactions. Spectrophotometer (400-700nm) or photometer can be connected to any flow through detector, e.g. UV/visible, inductively coupled plasma, atomic absorption spectrometer and ion-selective electrodes... 

This is achieved by using an atomic absorption spectrophotometer (or less accurately with a flame photometer). Some details could be instrument specific, so refer to the manufacturer s handbook, application data sheets, and obtain technical support if you lack experience in this area. Some general guidelines will be noted here. 

Potassium at trace concentrations in aqueous samples can be measured by a flame photometer at a wavelength of 766.5 nm. Either a flame photometer or an atomic absorption spectrometer operating in flame emission mode can be used for such analysis. 

Photometric emission measurements are carried out using either atomic absorption spectrophotometers without the light source, or flame photometers. The latter are... 

In contrast to gas chromatographic separations, which require the preparation of volatile derivatives of tin compounds, separations carried out by means of HPLC do not necessarily require preparations of derivatives. HPLC has been used in conjunction with several detection techniques, including photometers, atomic absorption spectrometers and direct current plasma emission spectrometers after hydride generation. Some recent studies have involved fluorimetric detection (Kleibohmer and Cammann, 1989) and hydride generation AAS. The latter has been applied to the quantification of TBT in coastal water. 

Photometric measurements performed in clinical laboratories use advanced chemical and biochemical methods and diverse instrumentation. Most analyses performed in clinical laboratories are based on spectrophotometric methods using photometric systems, such as absorption photometers, atomic absorption spectrophotometers and flame photometers. Typically, the result is expressed as mass concentration of analyte in solution (mg/dl), molar concentration (mmol/1), or catalytic concentration of enzyme activities in solution (U/l) [6],... 

Atomic spectroscopy is a quantitative technique used for the determination of metals in samples. Atomic spectroscopy is characterized by two main techniques atomic absorption spectroscopy and atomic emission spectroscopy. Atomic absorption spectroscopy (AAS) is normally carried out with a flame (FAAS), although other devices can be used. Atomic emission spectroscopy (AES) is typified by the use of a flame photometer (p. 168) or an inductively coupled plasma. The flame photometer is normally used for elements in groups I and II of the Periodic Table only, i.e. alkali and alkali earth metals. 

Chemistry Video Consortium, Praetical Laboratory Chemistry, Edueational Media Film and Video Ltd, Harrow, Essex, UK - Flame photometry, AA and TGA measurements (using a flame photometer, using an atomic absorption spectrometer and thermogravimetric analysis). 

The early workers in this field built their own apparatus, often assembling these from suitable units available from instruments for other purposes. Emission flame photometers have been converted into atomic absorption spectrophotometers by appropriate attachments consisting of specific light sources, choppers, and lenses, a principle also employed by some manufacturers. 

With the use of fuels that produced hotter flames, earlier flame photometers became useful for analyzing elements beyond the alkali and alkaline earth metals. The development of atomic absorption spectrophotometers in the late 1960s provided the analytical chemist with a better tool for many of these applications. Later developments in high-temperature flame photometry narrowed the analytical applications of low-temperature flame photometry even further. The utility of the flame photometer to the clinical chemist, however, was not diminished until the development... 

A widely used photometer used as a high-pressure liquid chromatographic (HPLC) detector uses the intense 254-nm resonance line produced by a mercury arc lamp (see Chapter 6). Others employ a miniature hollow cathode lamp as a very-narrow-wavelength intense source. For example, a zinc hollow cathode lamp gives a line at 214nm that is adequately close to the maximum wavelength of peptide bond absorption (206 nm) so that it can be used to measure peptides and proteins. Details on the hollow cathode lamp are found in the section on Atomic Absorption Spectrophotometry. The hollow cathode lamp also has a long, useful Hfetime if a lower-current, nonpulsed power supply is used. j... 

The most common detectors in How-injection analysis are spectrophotometers, photometers, and fluorometers. Electrochemical systems, refractometers, atomic emission and atomic absorption spectrometers have also been used. 

Photometers At a minimum, an instrument for atomic absorption spectroscopy must be capable of providing a sufficiently narrow bandwidth to isolate the line chosen for a measurement from other lines that may interfere with or diminish the sensitivity of the method. A photometer equipped with a hollow-cathode source and filters is satisfactory for measuring concentrations of the alkali metals, which have only a few widely spaced resonance lines in the visible region. A more versatile photometer is sold with readily interchangeable interference filters and lamps. A separate fdter and lamp are used for each element. Satisfactory results for the determination of 22 metals are claimed. 

Undoubtedly, advances in ISE technology over the past IS years have had their greatest impact in the clinical chemistry laboratory. Indeed, flame photometers and atomic absorption instruments, for years the workhorses of most laboratories, have become obsolete as newer ISE-based instruments and methods now perform the task of determining electrolyte levels in blood and urine samples. Clearly, electrochemical measurement of fluid components is desirable, since in many cases no dilution or pretreatment of the sample is required before the actual measurement. Thus final test results are obtained more rapidly and economically. 

An atomic absorption spectrophotometer has been applied for heavy metal determination in soils. Concentrations of potassium and sodium were determined with a flame photometer. For the determination of soil fluorides, an ion-selective electrode was used. Statistical methods were applied to describe quantitatively the relationships between industrial emissions and other components of the ecosystems. 

Flame Photometry, AA and TGA Measurements (using a flame photometer, using an atomic absorption spectrometer and thermogravimetric analysis). 

Measurements by flame photometry are carried out either using atomic absorption spectrometers with a burner (but without the light source), or flame photometers. The latter are less sophisticate instruments whose price is ten time less that atomic absorption spectrometers. These photometers are designated to make measurements of only five or six elements. They include interchangeable coloured... 

The atomic absorption method for determining the concentration of metallic elements has now gained wide acceptance. Instrumentation is relatively inexpensive and simple to use. Analytical interferences are less prevalent than with most other techniques means of recognizing and combating the interferences that do exist are described. The article discusses the basic principles of atomic absorption and also describes the fundamental design and modern improvements in the major components of instrumentation hollow-cathode lamps, burners, photometers, and monochromators. Atomic absorption is compared with some of its rival techniques, principally flame emission and atomic fluorescence. New methods of sampling and the distinction between sensitivity and detection limit are discussed briefly. Detection limits for 65 elements are tabulated. 

Flame OES can be performed using most modem atomic absorption spectrometers (discussed in Chapter 6). No external lamp is needed since the flame serves as both the atomization source and the excitation source. A schematic diagram of a flame emission spectrometer based on a single-beam atomic absorption spectrometer is shown in Fig. 7.2. For measurement of the alkali metals in clinical samples such as serum or urine, only a low-resolution filter photometer is needed because of the simplicity of the spectra. The filter photometer is discussed in Section 7.1.1.2. Both instmments require a burner assembly, a flame, a wavelength selection device, and a detector. 

Warm up the flame photometer or flame atomic absorption spectrometer in emission mode, following manufacturer s directions. Using an air-acetylene burner, set the flow rates of air acetylene to (a) oxidizing flame, (b) stoichiometric flame, and (c) reducing flame, following manufacturer s directions. 

The majority of commercial atomic absorption spectrometers permit both flame atomic absorption and flame atomic emission measurements to be performed. Thus, flame AES is no longer considered as an independent instrumental technique, except for the determination of sodium and potassium (as well as calcium or lithium) in biological samples by flame photometers. 

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