Flameless atomizers

For the deterrnination of trace amounts of bismuth, atomic absorption spectrometry is probably the most sensitive method. A procedure involving the generation of bismuthine by the use of sodium borohydride followed by flameless atomic absorption spectrometry has been described (6). The sensitivity of this method is given as 10 pg/0.0044M, where M is an absorbance unit the precision is 6.7% for 25 pg of bismuth. The low neutron cross section of bismuth virtually rules out any deterrnination of bismuth based on neutron absorption or neutron activation. 

Jeschke, W.D. Stelter, W. (1976). Measurement of longitudinal ion profiles in single roots of Hordeum and Atriplex by use of flameless atomic absorption spectroscopy. Planta, 128,107-12. 

Chool, M. K., Todd, J. K., and Boyd, N. D. "Effect of Carbon Cup Aging on Plasma Zinc Determination by Flameless Atomic Absorption Spectrometry". Clin. Chem. (1975), 21, 632-634. 

Findlay, W. J., Zdrojewskl, A., and Qulckert, N. "Temperature Measurements of a Graphite Furnace Used In Flameless Atomic Absorption". Spectrosc. Lett. (1974), 7, 63-72. 

Hwang, J. Y., Mokeler, C. J., and Ulluccl, P. A. "Maximization of Sensitivities In Tantalum Ribbon Flameless Atomic... 

Flameless Atomic Absorption Determination of Lead In Blood . Anal. Chem. (1973), 795-798. 

Kurz, D., Roach, J., and Eyrlng, E. J. "Determination of Zinc by Flameless Atomic Absorption Spectrophotometry . 

Lundgren, G., Lundmark, L., and Johansson, G. "Temperature Controlled Heating of the Graphite Tube Atomizer in Flameless Atomic Absorption Spectrometry . Anal. Chem. (1974), 46, 1028-1031. 

Machata, G. and Binder, R. "The Determination of Lead, Thallium, Zinc and Cadmium Traces in Biological Material with Flameless Atomic Absorption". Z. Rechtsmed. (1973),... 

Maessen, F. J. M. J., and Posma, F. D. "Fundamental Aspects of Flameless Atomic Absorption Using the Mini-Massmann Carbon Rod Atomizer". Anal. Chem. (1974), 46, 1439-1444. 

Rosen, J. F. and Trinidad, E. E. "The Mlcrodetermlnatlon of Blood Lead In Children by Flameless Atomic Absorption ... 

Schramel, P. "Determination of Eight Metals In the International Biological Standard by Flameless Atomic Absorption Spectrometry". Anal. Chlm. Acta (1973), 67 69-77. 

Yeh, Y-Y., and Zee, P. Mlcromethod for Determining Total Iron-Binding Capacity by Flameless Atomic Absorption Spectrophotometry". Clin. Chem. (1974), 20, 360-364. 

Day 2 for lead, cadmium, copper, cobalt, and nickel by Chelex extraction and differential pulse polarography, as well as manganese by Chelex and flameless atomic absorptiometry. 

Day 4 for cadmium, copper, iron, lead, and zinc by Freon extraction and flameless atomic absorptiometry. 

Mercury was determined after suitable digestion by the cold vapour atomic absorption method [40]. Lead was determined after digestion by a stable isotope dilution technique [41-43]. Copper, lead, cadmium, nickel, and cobalt were determined by differential pulse polarography following concentration by Chelex 100 ion-exchange resin [44,45], and also by the Freon TF extraction technique [46]. Manganese was determined by flameless atomic absorption spectrometry (FAA). 

Cranston and Murray [35,36] took samples in polyethylene bottles that had been pre-cleaned at 20 °C for four days with 1% distilled hydrochloric acid. Total chromium Cr(VI) + Cr(III) + Crp (Crp particulate chromium) was coprecipitated with iron (II) hydroxide, and reduced chromium Cr(III) + Crp was co-precipitated with iron (III) hydroxide. These co-precipitation steps were completed within minutes of the sample collection to minimise storage problems. The iron hydroxide precipitates were filtered through 0.4 pm Nu-cleopore filters and stored in polyethylene vials for later analysis in the laboratory. Particulate chromium was also obtained by filtering unaltered samples through 0.4 pm filters. In the laboratory the iron hydroxide co-precipitates were dissolved in 6 N distilled hydrochloric acid and analysed by flameless atomic absorption. The limit of detection of this method is about 0.1 to 0.2 nM. Precision is about 5%. 

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). 

The chemiluminescence technique has been used to determine trivalent chromium in seawater. Chang et al. [187] showed Luminol techniques for determination of chromium (III) were hampered by a salt interference, mainly due to magnesium ions. Elimination of this interference is achieved by seawater dilution and utilising bromide ion chemiluminescence signal enhancement (Fig. 5.7). The chemiluminescence results were comparable with those obtained by a graphite furnace flameless atomic absorption analysis for the total chromium present in samples. The detection limit is 3.3 x 10 9 mol/1 (0.2 ppb) for seawater with a salinity of 35%, with 0.5 M bromide enhancement. 

A hanging mercury drop electrodeposition technique has been used [297] for a carbon filament flameless atomic absorption spectrometric method for the determination of copper in seawater. In this method, copper is transferred to the mercury drop in a simple three-electrode cell (including a counterelectrode) by electrolysis for 30 min at -0.35 V versus the SCE. After electrolysis, the drop is rinsed and transferred directly to a prepositioned water-cooled carbon-filament atomiser, and the mercury is volatilised by heating the filament to 425 °C. Copper is then atomised and determined by atomic absorption. The detection limit is 0.2 pg copper per litre simulated seawater. 

Neve et al. [547] digested the sample with nitric acid. After digestion the sample is reacted selectively with an aromatic o-diamine, and the reaction product is detected by flameless atomic absorption spectrometry after the addition of nickel (III) ions. The detection limit is 20mg/l, and both selenium (IV) and total selenium can be determined. There was no significant interference in a saline environment with three times the salinity of seawater. 

Ammonium pyrrolidine dithiocarbamate (APDC) chelate coprecipitation coupled with flameless atomic absorption provides a simple and precise method for the determination of nanomol kg 1 levels of copper, nickel, and cadmium in seawater. With practice, the method is not overly time-consuming. It is reasonable to expect to complete sample concentration in less than 20 min, digestion in about 4 h, and sample preparation in another hour. Atomic absorption time should average about 5 min per element. Excellent results have been obtained on the distribution of nickel and cadmium in the ocean by this technique. 

Tikhomirova et al. [685] developed a procedure for simultaneous concentration of mercury, lead, and cadmium from seawater by coprecipitation with copper sulfide. The isolation yield is 99% for mercury and lead, and 89% for cadmium. Mercury is determined by flameless atomic absorption spectrophotometry, and lead and cadmium by flame atomic absorption spectrophotometry. 

In the analysis of seawater, isotope dilution mass spectrometry offers a more accurate and precise determination than is potentially available with other conventional techniques such as flameless AAS or ASV. Instead of using external standards measured in separate experiments, an internal standard, which is an isotopically enriched form of the same element, is added to the sample. Hence, only a ratio of the spike to the common element need be measured. The quantitative recovery necessary for the flameless atomic absorption and ASV techniques is not critical to the isotope dilution approach. This factor can become quite variable in the extraction of trace metals from the salt-laden matrix of seawater. Yield may be isotopically determined by the same experiment or by the addition of a second isotopic spike after the extraction has been completed. 

Yamamoto et al. [33] have studied the differential determination of heavy metals according to their oxidation states by flameless atomic absorption spectrometry combined with solvent extraction with ammonium pyrrolidinedithio-carbamate or sodium diethyldithio-carbamate. 

Le Bihan and Courtot-Coupez [202] used the copper complex and flameless atomic absorption spectroscopy to determine anionic detergents. Crisp [200]... 

Millward and Bihan [59] studied the effect of humic material on the determination of mercury by flameless atomic absorption spectrometry. In both fresh and seawater, association between inorganic and organic entities takes place within 90 min at pH values of 7 or above, and the organically bound mercury was not detected by an analytical method designed for inorganic mercury. The amount of detectable mercury was related to the amount of humic material added to the solutions. However, total mercury could be measured after exposure to ultraviolet radiation under strongly acid conditions. 

Two forms of flameless atomizer are in use, i.e. the graphite tube or L Vov furnace and the carbon rod or filament. Of these the first has proved to be the most generally effective and popular. It is widely used in a variety of modifications. In both cases, the temperature is raised rapidly to about 2500 K by the passage of a heavy current for a period of 1-2 minutes. Tube furnaces, which are usually 5 or 10 cm x 3 mm, may be flushed through with argon before vaporizing the sample so as to prevent the formation of... 

A 35- to 40-fold incorporation (relative to other fractions) of labelled mercury into a nonhistone fraction of rat kidney nuclei has been reported [44]. By using flameless atomic absorption, a 12 to 15-fold enrichment of mercury was found in the euchromatin fraction of mouse liver nuclei [45, 46]. Mercury was not detected in the inactive heterochromatin. 

Flameless atomic absorption spectrometric techniques offer a high sensitivity (5xl0 ug Se) but are not simple nor free from interference, due to the high volatility of selenium. This technique is suitable specially for direct analysis of samples and its additional advantage lies in possibilities of chemical treatment of samples in the graphite cell in order to diminish chemical interferences. 

Earlier work on the determination of total mercury in river sediments also include that of Iskander et al. [41], Iskander applied flameless atomic absorption to a sulphuric acid nitric acid digest of the sample following reduction with potassium permanganate, potassium persulphate and stannous chloride. A detection limit of one part in 109 is claimed for this somewhat laborious method. 

A method [62] has been described for the determination of down to 2.5pg kg-1 alkylmercury compounds and inorganic mercury in river sediments. This method uses steam distillation to separate methylmercury in the distillate and inorganic mercury in the residue. The methylmercury is then determined by flameless atomic absorption spectrophotometry and the inorganic mercury by the same technique after wet digestion with nitric acid and potassium permanganate [63]. The well known adsorptive properties of clays for alkylmercury compounds does not cause a problem in the above method. The presence of humic acid in the sediment did not depress the recovery of alkylmercury compounds by more than 20%. In the presence of metallic sulphides in the sediment sample the recovery of alkylmercury compounds decreased when more than lmg of sulphur was present in the distillate. The addition of 4M hydrochloric acid, instead of 2M hydrochloric acid before distillation completely, eliminated this effect giving a recovery of 90-100%. 

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