Atomic absorption spectrometry/gas

The techniques used for the investigation of organotin compounds in seawater are atomic absorption spectrometry, gas chromatography, or gas chromatography using AAS as detector. 

Bern [210] has reviewed methods developed up to 1981 for the determination of selenium in soil. These methods include neutron activation analysis, atomic absorption spectrometry, gas chromatography and spectrophotomet-ric methods. Square-wave cathodic stripping voltammetry has been used to determine selenium in soils [212],... 

Simplex optimization has been used with success in many areas of analytical chemistry, e.g. atomic-absorption spectrometry, gas chromatography, colorimetric methods of analysis, plasma spectrometry, and the use of centrifugal analysers in clinical chemistry. When an instrument is interfaced with a computer, the results of simplex optimization can be used to initiate automatic improvements in the instrument variables. 

The element specificity of atomic absorption spectrometry has also been used in conjunction with gas chromatography to separate and determine organo-metallic compounds of similar chemical composition, e.g. alkyl leads in petroleum here lead is determined by AAS for each compound as it passes from the gas chromatograph.75... 

In modern times, most analyses are performed on an analytical instrument for, e.g., gas chromatography (GC), high-performance liquid chromatography (HPLC), ultra-violet/visible (UV) or infrared (IR) spectrophotometry, atomic absorption spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), mass spectrometry. Each of these instruments has a limitation on the amount of an analyte that they can detect. This limitation can be expressed as the IDL, which may be defined as the smallest amount of an analyte that can be reliably detected or differentiated from the background on an instrument. 

MDHS 14 General method for the gravimetric determination of respirable and total dust MDHS 15 Carbon disulphide MDHS 16 Mercury vapour in air Laboratory method using hopcalite adsorbent tubes, and acid dissolution with cold vapour atomic absorption spectrometric analysis MDHS 17 Benzene in air Laboratory method using charcoal adsorbent tubes, solvent desorption and gas chromatography MDHS 18 Tetra alkyl lead compounds in air Continuous on-site monitoring method using PAC Check atomic absorption spectrometry... 

Chakraborti D, DeJonghe WRA, Mol WE, et al. 1984. Determination of ionic alkyllead compounds in water by gas chromatography/atomic absorption spectrometry. Anal Chem 56 2692-2697. 

Sturgeon et al. [59] have described a hydride generation atomic absorption spectrometry method for the determination of antimony in seawater. The method uses formation of stibene using sodium borohydride. Stibine gas was trapped on the surface of a pyrolytic graphite coated tube at 250 °C and antimony determined by atomic absorption spectrometry. An absolute detection limit of 0.2 ng was obtained and a concentration detection limit of 0.04 pg/1 obtained for 5 ml sample volumes. 

Other methods reported for the determination of beryllium include UV-visible spectrophotometry [80,81,83], gas chromatography (GC) [82], flame atomic absorption spectrometry (AAS) [84-88] and graphite furnace (GF) AAS [89-96]. The ligand acetylacetone (acac) reacts with beryllium to form a beryllium-acac complex, and has been extensively used as an extracting reagent of beryllium. Indeed, the solvent extraction of beryllium as the acety-lacetonate complex in the presence of EDTA has been used as a pretreatment method prior to atomic absorption spectrometry [85-87]. Less than 1 p,g of beryllium can be separated from milligram levels of iron, aluminium, chromium, zinc, copper, manganese, silver, selenium, and uranium by this method. See also Sect. 5.74.9. 

Soo [96] determined picogram amounts of bismuth in seawater by flameless atomic absorption spectrometry with hydride generation. The bismuth is reduced in solution by sodium borohydride to bismuthine, stripped with helium gas, and collected in situ in a modified carbon rod atomiser. The collected bismuth is subsequently atomised by increasing the atomiser temperature and detected by an atomic absorption spectrophotometer. The absolute detection limit is 3pg of bismuth. The precision of the method is 2.2% for 150 pg and 6.7% for 25 pg of bismuth. Concentrations of bismuth found in the Pacific Ocean ranged from < 0.003-0.085 (dissolved) and 0.13-0.2 ng/1 (total). 

Fitzgerald et al. [477] have described a method based on cold-trap preconcentration prior to gas-phase atomic absorption spectrometry for the determination of mercury down to 2 ng/1 in seawater. 

Campbell and Ottaway [672] have described a simple and rapid method for the determination of cadmium and zinc in seawater, using atomic absorption spectrometry with carbon furnace atomisation. Samples, diluted 1 + 1 with deionised water, are injected into the carbon furnace and atomised in an HGA-72 furnace atomiser under gas-stop conditions. A low atomisation temperature... 

Atomic absorption spectrometry used either by direct aspiration (to determine total mercury) or as an element-specific detector for gas chromatography (to determine organically bound mercury) are now discussed. 

Techniques for analysis of different mercury species in biological samples and abiotic materials include atomic absorption, cold vapor atomic fluorescence spectrometry, gas-liquid chromatography with electron capture detection, and inductively coupled plasma mass spectrometry (Lansens etal. 1991 Schintu etal. 1992 Porcella etal. 1995). Methylmercury concentrations in marine biological tissues are detected at concentrations as low as 10 pg Hg/kg tissue using graphite furnace sample preparation techniques and atomic absorption spectrometry (Schintu et al. 1992). 

Spectrophotometric methods Gas chromatography Atomic absorption spectrometry Miscellaneous... 

It is seen by examination of Table 1.11(b) that a wide variety of techniques have been employed including spectrophotometry (four determinants), combustion and wet digestion methods and inductively coupled plasma atomic emission spectrometry (three determinants each), atomic absorption spectrometry, potentiometric methods, molecular absorption spectrometry and gas chromatography (two determinants each), and flow-injection analysis and neutron activation analysis (one determinant each). Between them these techniques are capable of determining boron, halogens, total and particulate carbon, nitrogen, phosphorus, sulphur, silicon, selenium, arsenic antimony and bismuth in soils. 

Atomic absorption spectrometry (organomercury and tin compounds) and gas chromatography (organoarsenic, lead, mercury and tin compounds) are the two most popular techniques (Table 1.11(c)) while supercritical fluid chromatography is making some inroads (organotin compounds). 

Again, as in the case of soil analysis, atomic absorption spectrometry and gas chromatography are the methods of choice (Table 1.12(c)). 

The application of a combination of gas chromatography and atomic absorption spectrometry to the determination of tetraalkyllead compounds has been studied by Chau et al. [f 7] and by Segar [20], In these methods the gas chromatography flame combination showed a detection limit of about O.lpg Pb. Chau et al. [f 7, 18] have applied the silica furnace in the atomic absorption unit and have shown that the sensitivity limit for the detection of lead can be enhanced by three orders of magnitude. They applied the method to the determination of tetramethyllead in sediment systems. 

The most important features of liquid membranes are that they olfer highly selective extraction, efficient enrichment of analytes from the matrix in only one step, and the possibility of automated interfacing to different analytical instruments such as liquid chromatography, gas chromatography, capillary zone electrophoresis, UV spectrophotometry, atomic absorption spectrometry, and mass spectrometry [82]. 

Other frequently used methods for determining fluoride include ion and gas chromatography [150,204,205] and aluminium monofluoride (AIF) molecular absorption spectrometry [206,207]. Less frequently employed methods include enzymatic [208], catalytic [209], polarographic [210] and voltammetric methods [211], helium microwave-induced [212] or inductively coupled plasma atomic emission spectrometry [213], electrothermal atomic absorption spectrometry [214], inductively coupled plasma-mass spectrometry [215], radioactivation [216], proton-induced gamma emission [217], near-infrared spectroscopy [218] and neutron activation analysis [219]. 

Hydride generation for analytical use was introduced at the end of the 1960s using arsine formation (Marshal Reaction) in flame atomic absorption spectrometry (FAAS). A simple experimental setup for a hydride generator is shown in Figure 5.18. Today, hydride generation,91,92 which is the most widely utilized gas phase sample introduction system in ICP-MS, has been developed into... 

C. Schickling and J. A. C. Broekaert, Determination of mercury species in gas condensates by online coupled high-performance liquid chromatography and cold-vapor atomic absorption spectrometry, Appl. Organo-met. Chem., 9(1), 1995, 29-36. 

Carbon Monoxide. Methods for determining carbon monoxide include detection by conversion to mercury vapor, gas filter correlation spectrometry, TDLAS, and grab sampling followed by gas chromatograph (GC) analysis. The quantitative liberation of mercury vapor from mercury oxide by CO has been used to measure CO (73). The mercury vapor concentration is then measured by flameless atomic absorption spectrometry. A detection limit of 0.1 ppbv was reported for a 30-s response time. Accuracy was reported to be 3% at tropospheric mixing ratios. A commercial instrument providing similar performance is available. 

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