Isotope dilution mass spectrometry , lead isotopes

Ultraviolet spectroscopy has been applied to the determination of lead and lead speciation studies [407]. Scaule and Patterson [408] used isotope dilution-mass spectrometry to determine the lead profile in the open North Pacific Ocean. 

Wu and Boyle [837] have developed a method using magnesium hydroxide coprecipitation and isotopic dilution mass spectrometry to determine lead, copper, and cadmium in 1 ml seawater samples, with detection limits of 1,40, and 5 pM, respectively. 

Murozumi M (1981) Isotope dilution mass spectrometry of copper, cadmium, thallium, and lead in marine environments. Presented at The American Chemical Society Congress, Hawaii... 

Barnes, I.L, Murphy, T.J., Michiels, E. (1982). Certification of lead concentration in standard reference materials by isotope dilution mass spectrometry, J. Assoc. Off. Anal. Chem. 65, 953-956. 

Trincherini, P.R. and Facchetti, S. (1983). Isotope Dilution Mass Spectrometry applied to lead determination. Analytical Techniques for Heavy Metals in Biological Fluids, ed. by Facchetti, Elsevier Amsterdam. 

Isotope dilution mass spectrometry (cf. (Heumann, 1992 Yu et al., 2002)) has two main requirements. The first is that the element being analyzed must have more than one isotope. The second is to have a well-characterized and pure tracer solution that has a significantly different isotopic composition from the element under analysis. In practice, a known amount of the tracer is added to the sample, which is then treated by any necessary chemical separations before being inserted into the mass spectrometer. The tracer must be isotopically equilibrated with the sample by forcing them into a common valence state, as discussed in Section 4.7. For elements with multiple valence states (such as uranium or plutonium) this is a crucial requirement. Failure to achieve isotopic equilibration will lead to erroneous results. Sample quantitation by isotope dilution can be determined by use of the following general equation ... 

Rosman KJR, Kempt NK. 1991. Determination of copper, zinc, cadmium and lead in marine sediments SD-M-2/TM and BCSS-1 and dogfish muscle DORM-1 by isotope dilution mass spectrometry. Geostandards Newsletter 15(1) 117-119. 

Isotope dilution mass spectrometry is an accurate and sensitive technique for determining toxic trace elements in food matrices. Lead, cadmium, and thallium have been analyzed rapidly down to very low levels by ICP-MS. The latter technique is particularly useful for simultaneous measurement of a wide range of elements. Because the toxicity of an element can be highly dependent on its chemical form, ICP-MS is also useful in the speciation of toxic minerals in foodstuffs by combination with HPLC or SEC. 

Methods also employed for determination of inorganic lead include isotope dilution mass spectrometry, flame atomic fluorescence spectrometry, and molecular absorption spectrometry, but these methods are not used for routine applications. Methods for the determination of organolead speciation are high-performance liquid chromatography with a separation of the species and flame AAS or UV detection. 

Other methodologies fall into the category of definitive or alternative reference methodologies. The definitive method for lead, against which other methods are qualified for reference use, and the one employed for standard sample lead certification by the National Institute of Science and Technology (NIST), is isotope-dilution mass spectrometry (IDMS). Among its cardinal virtues, in addition to accuracy and precision, are sensitivity and applicability to many lead-containing environmental matrices. 

Isotope Dilution Mass Spectrometry (IDMS). Lead concentrations are only approximated with any analytical technique, since there is no method that can measure the true concentration of any element in any matrix. The most accurate concentration measurements are made with definitive methods, including isotope dilution mass spectrometry (IDMS) using TIMS. Isotope dilution TIMS is considered the definitive method because it is a yield-independent method of analysis, extremely sensitive, and precise (Webster 1960). The analysis is capable of distinguishing lead from false... 

Everson J, Patterson CC (1980) Ultra-clean isotope dilution/mass spectrometry analyses for lead in human blood plasma indicate that most reported values are artificially high. Clin Chem 26 1603-1607. 

J. R. Dean, L. Ebdon, R. C. Massey, Isotope ratio and isotope dilution analysis of lead in wine by inductively coupled plasma-mass spectrometry, Food Addit. Contam., 7 (1990), 109-116. 

Of the various analytical techniques, methods using mass spectrometry with isotope dilution play a special role. Initially they were used for determination of inorganic analytes, but later, in the last decades of twentieth century, they were also used for the analysis of organic species. These methods require the use of isotope-labeled compounds, but lead to very good precision and accuracy, as required in definitive procedures [14]. 

Paschal, D. C., Caldwell, K. L., andTing, B. G. (1995). Determination of lead in whole blood usit inductively coupled argon plasma mass spectrometry with isotope dilution. /.y4mj/. At. Spectrom. 10(5), 367. 

The following analytical techniques seem to be adequate for the concentrations under consideration copper and nickel by Freon extraction and FAA cold vapour atomic absorption spectrometry, cobalt by Chelex extraction and differential pulse polarography, mercury by cold vapour atomic absorption absorptiometry, lead by isotope dilution plus clean room manipulation and mass spectrometry. These techniques may be used to detect changes in the above elements for storage tests Cu at 8 nmol/kg, Ni at 5 nmol/kg, Co at 0.5 nmol/kg, Hg at 0.1 nmol/kg, and Pb at 0.7 nmol/kg. 

Mykytiuk et al. [184] have described a stable isotope dilution sparksource mass spectrometric method for the determination of cadmium, zinc, copper, nickel, lead, uranium, and iron in seawater, and have compared results with those obtained by graphite furnace atomic absorption spectrometry and inductively coupled plasma emission spectrometry. These workers found that to achieve the required sensitivity it was necessary to preconcentrate elements in the seawater using Chelex 100 [121] followed by evaporation of the desorbed metal concentrate onto a graphite or silver electrode for isotope dilution mass spectrometry. 

Spark source (SSMS) and thermal emission (TEMS) mass spectrometry are used to determine ppb to ppm quantities of elements in energy sources such as coal, fuel oil, and gasoline. Toxic metals—cadmium, mercury, lead, and zinc— may be determined by SSMS with an estimated precision of 5%, and metals which ionize thermally may be determined by TEMS with an estimated precision of 1% using the isotope dilution technique. An environmental study of the trace element balance from a coal-fired steam plant was done by SSMS using isotope dilution to determine the toxic metals and a general scan technique for 15 other elements using chemically determined iron as an internal standard. In addition, isotope dilution procedures for the analysis of lead in gasoline and uranium in coal and fly ash by TEMS are presented. 

Isotope Dilution By Thermal Emission Mass Spectrometry. A three-stage thermal emission mass spectrometer (TEMS) was used for quantitatively measuring lead and uranium in coal and fly ash and lead in gasoline (Figure 3). The basic design of the instrument is modeled on that developed by White and Collins, 1954 ( 6) and modified at ORNL. The addition of an electrostatic third stage increased the abundance sensitivity to 108 as described by Smith et al. (7). 

Spark source mass spectrometry (SSMS) is also a multielement technique. Conventionally the data obtained are semiquantitative, and the results have an uncertainty of 50% or less. If the stable isotope dilution technique is performed, the SSMS can be 3%. This latter technique was used for lead, cadmium, and zinc as noted in the results tabulations. NAA and SSMS complement each other quite well, and those elements for which one technique has poor sensitivity can usually be measured by the other. 

In the last decade or two, the advent of new instrumentation directed at elemental analysis has provided fertile new ground for expanded use of isotope dilution. Glow discharge mass spectrometry is in many ways the modem replacement for spark source and has similar impediments to ready application of isotope dilution. A recent report of Barshick et al. describes assaying lead in oil residues using the technique [21]. The obstacles spark source and glow discharge mass spectrometry both present to ready use of isotope dilution make it unlikely that widespread application of the technique will occur in conjunction with them. 

---