Atomic absorption spectrometers

Atomic Absorption Spectroscopy. Mercury, separated from a measured sample, may be passed as vapor iato a closed system between an ultraviolet lamp and a photocell detector or iato the light path of an atomic absorption spectrometer. Ground-state atoms ia the vapor attenuate the light decreasiag the current output of the photocell ia an amount proportional to the concentration of the mercury. The light absorption can be measured at 253.7 nm and compared to estabUshed caUbrated standards (21). A mercury concentration of 0.1 ppb can be measured by atomic absorption. 

In this work, atmospheric particles (PM 10 and PM 2.5) were collected by a dichotomos air sampler. Several leaching procedures were investigated for decomposition of heavy metals. The digests were pre-concentrated with sodium diethyldithiocarbamate. The determinations were canted out on a Vartan Model AA-220 atomic absorption spectrometer. The instrarment was equipped with a GTA-110 graphite furnace system. Table 1 shows the concentrations of heavy metals associated with PM 10 and PM 2.5 particles. Table 1. Concentrations of heavy metals in PM 10 and PM 2.5 atmospheric particles (ng/m )... 

Magnesium may conveniently be determined by atomic absorption spectroscopy (Section 21.21) if a smaller amount (ca 4 mg) is used for the separation. Collect the magnesium effluent in a 1 L graduated flask, dilute to the mark with de-ionised water and aspirate the solution into the flame of an atomic absorption spectrometer. Calibrate the instrument using standard magnesium solutions covering the range 2 to 8 ppm. 

At present, however, the usual flame emission method is obtained by simply operating a flame atomic absorption spectrometer in the emission mode (see Fig. 21.3). 

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. 

Atomic absorption spectrometers with dual monochromators are commercially available from Jarrell-Ash Division of Fisher Scientific Co.9 and from Instrumentation Laboratories Inc. 

Dabeka, R. W. and McKenzie, A. D. (1991). Graphite furnace atomic absorption spectromet-ric determination of selenium in foods after sequential wet digestion with nitric acid, dry ashing and coprecipitation with palladium. Can. J. Appl. Spectrosc. 36,123-126. 

In the stripping voltammetry, in general it is anodic SV which, owing to its extreme sensitivity and selectivity together with its cheapness, has gained so much analytical importance that for instance the Kemforschungsanlage Jiilich (F.R.G.) recently (1983) replaced their atomic absorption spectrometer with an SV system for the simultaneous determination of Cu, Cd, Pb, etc. 

Silver acetylide is a more powerful detonator than the copper derivative, but both will initiate explosive acetylene-containing gas mixtures [1]. It decomposes violently when heated to 120-140°C [2], Formation of a deposit of this explosive material was observed when silver-containing solutions were aspirated into an acetylene-fuelled atomic absorption spectrometer. Precautions to prevent formation are discussed [3], The effect of ageing for 16 months on the explosive properties of silver and copper acetylides has been studied. Both retain their hazardous properties for many months, and the former is the more effective in initiating acetylene explosions [4],... 

XRD analyses were performed on oriented samples prepared by spreading of the sample suspension on a glass slide, followed by drying at room temperature. The XRD patterns were obtained with a PW 1130/00/60 Philips diffractometer using CuKa radiation (/, = 1,5405 A). Chemical analysis was carried out on a Perkin Elmer 3100 atomic absorption spectrometer after dissolution of the sample with several acids (HF, HCIO4, HC1) for 24h, and HN03 in a second time. 

Gill and Fitzgerald [481] determined picomolar quantities of mercury in seawater using stannous chloride reduction and two-stage amalgamation with gas-phase detection. The gas flow system used two gold-coated bead columns (the collection and the analytical columns) to transfer mercury into the gas cell of an atomic absorption spectrometer. By careful control and estimation of the blank, a detection limit of 0.21 pM was achieved using 21 of seawater. The accuracy and precision of this method were checked by comparison with aqueous laboratory and National Bureau of Standards (NBS) reference materials spiked into acidified natural water samples at picomolar levels. Further studies showed that at least 88% of mercury in open ocean and coastal seawater consisted of labile species which could be reduced by stannous chloride under acidic conditions. 

The sensitivity achieved should enable seawater samples to be analysed for molybdenum, because the concentration of molybdenum in seawater is usually 2.1 -18.8 pg/1. The selected temperature of 1700-1850 °C during the charring stage permits separation of the seawater matrix from the analyte prior to atomisation with the Perkin-Elmer Model 603 atomic absorption spectrometer equipped with a heated graphite atomiser (HGA-2100). 

Andreae [564] coprecipitated tellurium (V) and tellurium (VI) from seawater and other natural waters with magnesium hydroxide. After dissolution of the precipitate with hydrochloric acid, the tellurium (IV) was reduced to tellurium hydride in 3 M hydrochloric acid. The hydride was trapped inside the graphite tube of a graphite furnace atomic absorption spectrometer, heated to 300 °C, and tellurium (IV) determined. Tellurium (VI) was reduced to tellurium (IV) by boiling with hydrochloric acid and total tellurium determined. Tellurium (VI) was then calculated. The limit of detection was 0.5 pmol per litre and precision 10-20%. 

Huang and Shih [616] used a graphite furnace atomic absorption spectrometer with a stabilised platform furnace involving atomisation from a graphite surface pretreated with vanadium to determine down to 24 ppt of zinc in seawater. 

Figure 5.17. Dual-column ion exchange preconcentration valve. Sa, Sb samples A and B Ca, Cb ion exchange columns A and B Ea, Eb eluant (2 M nitric acid) for columns A and B Wa, Wb waste lines for samples and eluants A and B W waste lines AAS atomic absorption spectrometer. The dimensions of the base plate of the valve are 70 x 45 x 10 mm. See text for details of operation. Source [661]...

The primary requirement for all equipment (whether it be a volumetric flask, an oven used for drying samples or an atomic absorption spectrometer used for determining trace metal concentrations) is that it must be fit for its intended... 

The heart of a traditional atomic absorption spectrometer is the burner, of which the most usual type is called a laminar flow burner. The stability of the flame is the most important factor in AAS. Typical working temperatures are 2200 2400°C for an air-acetylene flame, up to 2600-2800°C for acetylene-nitrous oxide. The fraction of species of a particular element that exist in the excited state can be calculated at these temperatures using the Boltzmann equation ... 

The design of a conventional atomic absorption spectrometer is relatively simple (Fig. 3.1), consisting of a lamp, a beam chopper, a burner, a grating monochromator, and a photomultiplier detector. The design of each of these is briefly considered. The figure shows both single and double beam operation, as explained below. 

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... 

Table 1.3 Available flame and graphite furnace atomic absorption spectrometers... 

The system used by these workers consisted of a Microtek 220 gas chromatograph and a Perkin-Elmer 403 atomic absorption spectrophotometer. These instruments were connected by means of a stainless steel tubing (2mm o.d.) connected from the column outlet of the gas chromatograph to the silica furnace of the atomic absorption spectrometer. The silica furnace was set at 1000°C. The gas chromatographic column was packed with 3% OV-1 supported on Chromosorb W. The column was temperature programmed at 15°C h to 150°C. 

Figure 2.8 Detection of alkylmercury compounds using flameless atomic absorption detector. Conditions column, Corasil I, 50 cm x 2.1 mm i.d. eluent, n-hexane flow rate, 0.5 ml min-1 detection, flameless atomic absorption spectrometer. Peaks 1, benzene, 2, ethylmercury chloride, and 3, methylmer-cury chloride.

The values of solutions were adjusted with 0.1 mol/L NH OH or HNOj and measured with Metrohm Herisau E510 pH meter. A magnetic stirrer model Arex was used for stirring the adsorption batches. The concentration of solution before and after adsorption was measured by using Atomic Absorption Spectrometer (AAS) Analytika Jena. All the measurements were made under optimization of the below mentioned parameters. 

Analytikjena Atomic Absorption Spectrometer equipped with an aluminum hollow cathode lamp was used to measure aluminum concentrations. The wavelength and spectral bandpass were set at 309.3 and 1.2 run, respectively. Gas/Oxidant ratio was 0.553. A digital pH meter model Metrohm was used for pH measurements. 

Metal ions such Cu, Cd, and Pb can be preconcentrated from water samples using liquid membranes containing 40% w/w of di-2-ethylhexylphosphoric acid in kerosene diluent in a PTFE support. The liquid membrane can be coupled on-line to an atomic absorption spectrometer and has been shown to be stable for at least 200 h with extraction efficiencies over 80%, and enrichment factors of 15 can be obtained. A liquid membrane has also been used for sample cleanup and enrichment of lead in urine samples prior to determination by atomic absorption spectrometry [100]. The experimental setup for metal enrichment is shown in Fig. 13.4. Lead was enriched 200 times from urine [80] and several metals were enriched 200 times from natural waters [88]. Using hollow fiber... 

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