Matrix modifiers electrothermal

Electrothermal atomic absorption spectrophotometry with Zeeman background correction was used by Zhang et al. [141] for the determination of cadmium in seawater. Citric acid was used as an organic matrix modifier and was found to be more effective than EDTA or ascorbic acid. The organic matrix modifier reduced the interferences from salts and other trace metals and gave a linear calibration curve for cadmium at concentrations < 1.6 pg/1. The method has a limit of detection of 0.019 pg/1 of cadmium and recoveries of 95-105% at the 0.2 pg of cadmium level. 

Figure 21-10 Reduction of interference by using a matrix modifier, (a) Graphite furnace temperature profile for analysis of Mn in seawater, (b) Absorbance profile when 10 xL of 0.5 M reagent-grade NaCl is subjected to the temperature profile in panel a. Absorbance is monitored at the Mn wavelength of 279.5 nm with a bandwidth of 0.5 nm. (c) Reduced absorbance from 10 nl of 0.5 M NaCl plus 10 of 50 wt% NH4NO3 matrix modifier. [From M. N. Quigley and F. Vernon, "Matrix Modification Experiment lor Electrothermal Atomic Absorption Spectrophotometry." J. Chem. Ed. 1996, 73. 980.]...

Electrothermal vaporization has also been used for seawater sample introduction into an ICP-MS. Trace metals were complexed and then vaporized as dithiocarbamate complexes in one study [322]. Addition of a matrix modifier [Pd(N03)2-Mg(N03) ] enhanced analyte sensitivity. Addition of a matrix modifier to act as a physical carrier in ETV-ICP-MS has become common. Seawater was used as a matrix modifier for ETV-ICP-MS in one report [323]. 

Electrothermal AAS (ETAAS), although being sensitive, cannot be applied in a continuous (on-line) mode and is not generally used in speciation analysis since the necessary manipulations caused by the off-line character of the method may increase the risks of errors considerably. Whenever applied, the precautions for the measurement are the same as for inorganic analysis the choice of the matrix modifier, the temperature programme, etc., should follow the same rules as for the determination of the element content. 

Most commerical electrothermal atomizers based on the L vov furnace as simplified by Massman (3) and undergo vigorous changes in tube temperature. The analyte atoms volatilized from the tube wall come into a eooler gas, so that molecular species that are not detected are formed. This leads to what is termed matrix interferences. For example, equal concentrations of Pb + in a matrix of deionized water versus one of high chloride content would yield different absorbances. One way to remove this chloride matrix interference is to use a matrix modifier. The addition of an ammonium salt to the chloride-containing matrix would cause volatilization of NH4CI with removal of chloride from the sample matrix. 

AAS is the most widely used analytical technique for the determination of lead in biological materials [57,58], The majority of AAS methods employ the electrothermal atomic absorption spectrometry (ETAAS) technique, using either Zeeman background correction or deuterium background correction for the determination of lead in biological fluids [55,59-65], Urine is less often employed as an indicator of exposure however, similar problems associated with AAS determination of lead exist for blood as well as urine (1) incomplete atomization (2) volatile lead salts (3) spectral interferences (4) buildup of carbonaceous residue reducing sensitivity and precision. These analytical problems are eliminated by optimal sample preparation, e,g., dilution, addition of matrix modifiers, deproteinization, and background correction and calibration by matrix-matched standards [66],... 

D.O. Matthews and M.C. McGahan. Cysteine—an effective matrix modifier for determination of gold in biological samples by electrothermal atomic absorption spectrophotometry. Spectro-chimica Acta Part B Atomic Spectroscopy 42 909-913, 1987. 

Electrothermal atomizers for AES share many of the advantages associated with their use for AAS. The argon inert gas that prevents oxidation of the graphite tube ensures that minimal quenching occurs, although a number of other interferences may occur. By and large, the interferences are very similar to those experienced in traditional electrothermal AAS, such as carbide formation (for some analytes), scatter by particulate matter, and losses during thermal pretreatment. A more comprehensive overview of interferences may be found in the sections on AAS. The use of matrix modifiers to assist in the separation of the analyte from the matrix is still often necessary. 

Cadmium in blood, urine, hair, saliva, and human milk is predominantly analyzed with graphite furnace atomic absorption spectrometry (GF-AAS), also known as electrothermal AAS (ET-AAS). Samples are usually prepared by digestion with nitric acid [16-20]. Solubilizers (Triton X-100) or matrix modifiers (e.g., diammonium hydrogen phosphate, Pd-components) are added [17,21-23]. 

Barium is present at very low concentrations in most environmental samples. Thus, in spite of the availability of a detection limit of only a few ng ml 1 by flame AES, the element is rarely determined by flame methods AAS with electrothermal atomization or ICP-AES is more commonly used. A notable exception is in the determination of the element in barium-rich geological deposits.8 Another exception is in the analysis of formation waters from offshore oil wells.9 However, in this matrix, inter-element interferences are encountered from alkali and alkali-earth elements. These could be effectively eliminated by the addition of 5 g 1 1 magnesium and 3 g 1 1 sodium as a modifier.9... 

M. H. Canuto, H. G. Luna Siebald, G. Magela de Lima, J. B. Borda Silva, Antimony and chromium determination in Brazilian sugar cane spirit, cachaca, by electrothermal atomic absorption spectrometry using matrix matching calibration and ruthenium as permanent modifier, J. Anal. Atom Spectrom., 18 (2003), 1404-1406. 

Electrothermal vaporization. With ETV/ICP-MS, a small amount of solid sample ( lmg) is introduced into a graphite furnace and subjected to a multi-step temperature program for atomization. Additionally, a modifier can be used for thermal stabilization of the analytes or to improve the matrix mineralization. The vapours produced during the vaporization step are transferred into the plasma by argon carrier gas. 

Byrne,]. P, Chakrabarti, C. L., Gregoire, D. C., Lamoureux, M., and Ly,T. (1992). Mechanisms of chloride interferences in atomic absorption spectrometry using a graphite furnace atomizer investigated by electrothermal vaporization inductively coupled plasma mass spectrometry. Part 1. Effect of magnesium chloride matrix and ascorbic acid chemical modifier on manganese.J. A [Pg.199]

---