AA instrument

Comparisons between AAS instruments and the Jerome show statistically equivalent results. The Jerome gives accurate results for samples with a mercury content of less than 1 ppb and requires less work space, set up time, chemical reagents and sample size. 

The AAS instrumental parameters are adjusted to optimum following the manufacturer s recommendations. A detailed list of instrumental parameters for the total analytical system is given in Table I. 

Conventional AA instruments (Figure 1) use a flame atomization system for liquid sample vaporization. An air-acetylene flame (2300°C) is used for most elements. A higher temperature nitrous oxide-acetylene flame (2900°C) is used for more refractory oxide forming elements. Electrothermal atomization techniques such as a graphite furnace can be used for the direct analysis of solid samples. 

Conventional AA instruments will analyze liquid samples only. Dilute acid and xylene solutions are common. The volume of solution needed is dependent on the number of elements to be determined. 

AA offers excellent sensitivity for most elements with limited -interferences. For some elements sensitivity can be extended into the sub-ppb range using flameless methods. The AA instruments are easy to operate with "cookbook methods" available for most elements. 

Determination of lead in water by atomic absorption spectrometry (AAS) The AAS instrument has be to calibrated using reference solutions made up by dissolving known amounts (balance) of a certified reference material (CRM) or a pure substance such as Pb(N03)2 in a de-... 

Neutron activation analysis (NAA) with a rapid radiochemical separation has been the method generally used in recent years, but requires substantial investment, has high operating cost and limited availability. Modem flameless atomic absorption (AAS) instruments provide sensitivity approaching that of NAA and offer a viable alternative for the detection of firearms discharge residue. 

A second problem with nitrous oxide was its property of cooling dramatically when allowed to expand very rapidly on going from high pressure to low pressure. This resulted frequently in ice formation on the cylinder head, and poor gas flow stability. To avoid the consequential loss in precision, cylinder heads were often warmed, or a ballast tank at an intermediate pressure could be used as a stabilizer.9 Most modern AAS instruments employ quite high oxidant pressures and flow rates in the interests of safety, in spite of the greater cost, and this problem is less common than it used to be. 

At the present time, the majority of elemental determinations conducted by FES are performed using instruments designed primarily for AAS. The only modification required is the incorporation of an amplifier capable of measuring the unmodulated emission signals from the flame, a standard feature on almost all AAS instruments. 

Copper. Copper is the most easily detected element by AAS. Although copper has been determined as the dithizone complex or ethyl-xanthate (6,13), air-acetylene AAS analysis by P CAM 173 or S-186 (12) is superior. Copper lamps are used to test AAS instrumentation because the Cu HC1 sensitivity is nearly independent of lamp current, and a large linear range is observed for the analytical curve. 

The interest in assessing the presence of A1 in wines is often motivated by its ability to produce bad taste and clouding effects. In an attempt to improve the sensitivity of ET-AAS instrumentation with end-capped transverse heated graphite tubes (ECTHGTs) for A1 determination in Port wine, Almedia et al. [63] investigated the performance of several chemical modifiers. Compared with other commonly used and recommended chemical compounds, K2Cr207 turned out to be better in terms of sensitivity and reduction of blank levels. The concentrations of Al in real samples were relatively high in comparison with other metals and varied from 273 to 803 pg 1 1. 

Other authors have reported the use of a simultaneous multielement (SM) AAS instrument to identify the content of Pb and other metals in wines. In a 2000 review the principal characteristics and applications of the technique were discussed and the authors made reference to the determination of Cd and Pb in beverages and other matrices [76], Freschi et al. [77] determined Pb and Cd in 10 white and red table wines. The characteristic mass was approximately 0.6 pg for Cd and 33 pg for Pb and the LoD was found to be 0.03 and 0.8 pg l-1 for Cd and Pb, respectively. The comparative results of diluted and digested wines and recovery values indicated that the simple dilution of samples was sufficient to determine those elements in Brazilian wines. Fernandes and coworkers [78]... 

All the solid phases were identified and characterized for crystallinity by X-ray powder diffraction (Philips PW 1730/10 diffractometer, Cu Kq radiation equipped with a PW 1030/70 vertical goniometer and connected to a P.C. computer for quantitative analyses). Crystallinities for Nu-10 and cristobalite were computed by comparing the intensity of the most characteristic diffraction peaks of each sample to that of the corresponding pure 100% crystalline phases used as standards. In some cases calibration curves derived from Nu-10/cristobalite mechanical mixtures were used. Si, Al, and alkali contents were determined either on precursors or calcined samples (900 C, air flow, 4h) by atomic absorption, using a Perkin-Elmer 380 AA instrument after digestion and dissolution of the samples in H,S04/HF solutions and further elimination of HF by gentle heating at 60 C for 12 n. 

Even in relatively large programs, few laboratories will justify the initial expense and calibration effort required for development of the emission spectrographic method. As reported by Scott etal. [3], sample preparation will generally not differ significantly from that required for AAS. Instrumental neutron activation analysis (INAA) is only attractive where a reactor is already available, and multielement analysis by this technique requires the use of high resolution Ge(Li) crystals and multiple irradiations for elements with differing activation product half-lives. The key elements, cadmium, nickel and lead still require analysis by AAS because of limitations of the INAA method [4]. 

Almost any standard AAS instrument can be used for basic work in applied geochemistry, but there are a number of features which can improve the scope and speed of analysis. 

The petroleum sample must be prepared for analysis prior to its presentation to the AAS instrument The choice of sample preparation method is... 

Atomic absorption sample preparation procedures applied to archaeological samples can be streamlined. Important factors include sample preparation, sample size, sample decomposition, standards, instrumentation, and practical and conceptual applications of atomic absorption analysis. On a comparative basis the sample preparation procedure reported was convenient and rapid the AAS instrumentation proved to be flexible, sensitive, rapid, and inexpensive in the analysis of archaeological materials. 

Sodium, potassium, and strontium were determined by flame emission. Most AAS instruments are capable of this mode of operation. Ideally, the sample to be analyzed for sodium would be heavily spiked with calcium and potassium that for potassium, with sodium and calcium. This was not done in the current study however, potassium was added before the determination of sodium, calcium, and strontium. 

There are good reasons for acceptance of AA instrumentation. Archaeologists universally have found that funding is a major consideration in element analysis research. However, the purchase cost of necessary AA equipment, including support equipment, is minimal (approximately 8,000- 12,000). In addition the cost of analysis per... 

The availability of AA instrumentation compared with many other forms of instrumentation is again a significant consideration. AA spectrophotometers are found on almost every campus and usually in various departments on the other hand, few universities possess nuclear reactors. 

Set-up and optimise the AAS instrument for determinations of zinc. Calibrate the instrument with the zinc working standard solutions and measure the concentration of zinc in all the blank, check and sample solutions, as for manganese. 

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