The Atomic Absorption Spectrophotometer

AAS is relatively free from elemental interferences because it determines elements using absorption by specific lamps for the metal under test. However, it is prone to background interferences caused by  

Fortunately, methods for background correction are now a part of most modem AAS and the most commonly used background correctors are a deuterium source, the Zeeman effect and the Smith-Hiefte effect. 

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The atomic absorption spectrophotometers are essentially of two types, namely ... 

Firstly, the concentrations of HMs in effluent were determined. At least three samples of 40 mL were acidified with 10 mL of concentrated HNO3 to decompose MOs. These samples were diluted to the sensitivity range of the atomic absorption spectrophotometer (AAS) (Model Philips 9200X-AAS) (diluted 5 times for Cu2+ analysis, and 25 times for Zn2+ analysis) and then analyzed. The average of these measurements yielded the total HM concentration in the effluent, / j (mg/L), for that specific experimental run. To convert (mg metal/L) to (mg metal/kg sludge), the measured metal concentration (as, mg metal/L) at each HRT was divided by the steady state MLSS concentration (as, kg TSS/L). 

Procedure Following the manufacturer s instructions for operating the atomic absorption spectrophotometer, aspirate a suitable portion of the Standard Solution through the flame. In a similar manner, aspirate a suitable portion of the Sample Solution. Any absorbance produced by the Sample Solution should not exceed that produced by the Standard Solution. Mercury Determine as directed under the Cadmium Test (above), except substitute mercury for cadmium, and use the following for the Stock Solution and the Standard Solutions ... 

Urine and fecal samples were collected for 7 consecutive days every 4 weeks. Fecal samples were analyzed for nitrogen, fat, and zinc content. Fecal samples were weighed, lyophilized, digested with nitric acid, diluted to volume with deionized water, and analyzed by the atomic absorption spectrophotometer, model 303 or 306 (Perkin Elmer, Norwalk, Connecticut). Food samples were weighed, wet digested with nitric acid, and diluted to volume with deionized water, then analyzed for zinc level (6). Nitrogen levels of dried samples (food or feces) were determined by Kjeldahl procedure (.]). The fat content of dried samples (food or feces) was ascertained by ether extraction of the lipids ( ). ... 

Atomic Absorption Assay for Arsenic in Urine In this method, the arsine generator is suitably connected to the atomic absorption spectrophotometer. 

Chemical analysis was carried out as following the content of Si was analyzed by the gravitational method and that of Ca was measured by volume method. The atomic absorption spectrophotometer (AAS) is for the analysis of K and Na. 

The methanol extract produced contained small, but varying amounts of free and bound 8-HQ. Because this method introduced a variable background when the extract was vaporized in the graphite furnace of the atomic absorption spectrophotometer, all extracts were spiked with an additional quantity of 8-HQ to ensure a constant matrix the same matrix was used in preparing the AAS standards. All pertinent parameters used in this analysis are summarized in Table II. 

Note The standard atomic conditions for the respective micronutrient elements are to be followed from Instruction Manual of the Atomic Absorption Spectrophotometer. 

The apparatus is set up as shown in Figure 1-3, p. 9, with the cell placed in the beam path of the atomic absorption spectrophotometer. 

Mercury contents were determined by flameless atomic absorption spectrophotometer M.A.S. 50 (Mercury Analyzer System, Bacharach, USA). Ionic mercury was reduced with SnCl2 (5 g/Liter) to metallic mercury which was volatilized by a vector gas (air) and detected at 253.7 nm by the atomic absorption spectrophotometer. 

All samples were dried at 70°C, weighed and mineralized in 200 jxl of suprapure grade nitric acid and perchloric acid mixed as 4 1. Digests were analyzed for their metal content using the atomic absorption spectrophotometer Phillips SP 9 Pye Unicam and Solaar Unicam 939 with a graphite furnace PU-93 090X as described elsewhere (Wilczek and Migula, 1996). 

Probably the most commonly used instruments for cation impurity analysis of silicates are flame atomic absorption spectrophotometers and ion selective electrodes. In most cases, separation of silica is required to reduce interferences. The sample may also have to be diluted to bring the analyte concentration within the linear operating range. For cations, the atomic absorption spectrophotometer is more versatile than ion specific electrodes. If the analyst is concerned with the presence of heavy metals, then accessories such as a hydride system for the elements that form high vapor pressure compounds, e.g., Sb, and a mercury vapor cold trap are useful. If a large number of elements are to be determined, a substantial investment in hollow cathode and electrode discharge lamps must be made. Several gas mixtures will also be required. 

The elemental Hg is subsequently purged and swept out of the sample. Figure 3.40 illustrates what accessories are needed to prepare a sample for direct introduction of elemental mercury vapor into a flow-through atomic absorption cell. This modification to the atomic absorption spectrophotometer is called a cold vapor generator. 

A successful method employs flame photometry, using an atomic absorption spectrophotometer. Basically, the sample is ashed at 800°C, converted to the chloride with HCl and diluted with ionized water to give a test solution. Calibration solutions containing 1.0, 2.5, 5.0 and 10.0 pg/cm of Na are made up from a commercially available Sodium Stock Solution (containing 1 mg/cm Na). A blank of deionized water/HCl is aspirated into an air/acetylene flame set up with the atomic absorption spectrophotometer, followed by the standard solutions and the sample. A portion of the radiation proportional to the concentration of the sodium is absorbed. The absorption is measured and the concentration can be determined. 

Sensitivity in flame atomic absorption is defined as the characteristic concentration of an element required to produce a signal of 1% absorbance (0.0044 absorbance units). Sensitivity values are listed for each element by the atomic absorption spectrophotometer manufacturer and have proved to be a very valuable diagnostic tool to determine if instrumental parameters are optimized and if the instrument is performing up to specification. The sensitivity of the spectrophotometer used in the validation of the flame AAS anal ical technique agreed with the manufacturer specifications (5.6.) the 2 xg/mL cadmium standard gave an absorbance reading of 0.350 abs. units. 

Refer to the instrument instruction manuals and SOPs (5.8., 5.9.) for proper and safe operation of the atomic absorption spectrophotometer, graphite furnace atomizer and associated equipment. 

Set up the atomic absorption spectrophotometer for the air/acetylene flame analysis of cadmium according to the SOP (5.8.) or the manufacturer s operational instructions. For the source lamp, use the cadmium hollow cathode or electrodeless discharge lamp operated at the manufacturer s recommended rating for continuous operation. Allow the lamp to warm up 10 to 20 min or until the energy output stabilizes. Optimize conditions such as lamp position, burner head alignment, fuel and oxidant flow rates, etc. See the SOP or specific instrument manuals for details. Instrumental parameters for the Perkin-Elmer Model 603 used in the validation of this method are given in Attachment 1. 

An alternative method consists of running the gasoline sample through the gas chromatograph to separate the components, which are then introduced, one by one, directly to the atomic absorption burner. The atomic absorption spectrophotometer, which is set up for lead determination, records a peak absorption for each lead compound as it passes from the chromatograph. The method is standardized by using... 

Consult the manufacturer s instructions for the operation of the atomic absorption spectrophotometer. The present test method assumes that good operating procedures are followed. Design differences between spectrophotometers make it impractical to specify the required manipulations in detail here. 

Copolymer was prepared by reacting the foregoing copolymer (0.1 g) with Co(CH3COO)2 4H2O (1 g, 4.02 X 10 mol) in a mixture of acetic acid (5 mL) and water (10 mL) under reflux for 24 h, followed by dialysis to remove metal ion for 3 days yield 0.11 g. The extent of metallation (%Co) was above 97% determined from the atomic absorption spectrophotometer. 

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