Lead, spectrometric analytical methods

Hiimers TA, Hughes R, Outridge PM, Davis W, Simon K, Woolard DR (1998) Interlaboratory comparison of mass spectrometric methods for lead isotopes and traee elements in NIST SRM 1400 bone ash. J Analyt Atomic Spectros 13, 963-970... 

In the most sensitive eiectroanaiytical methods, exclusively treated within this context, the analyte ion is electrodeposited on an electrode from an electrically conducting sample solution. Current and potential of subsequent redissolution are due to the concentration and the kind of ion to be determined. For thallium, the reversible redox couple TI /TI° at about -0.5 V versus saturated calomel electrode is used (Bellavance and Miller, 1975). Infinite tolerance towards alkali, alkaline earths and halogenides are great merits for the analysis of biological materials. Because of the preconcentration step included, thallium determination is more sensitive than atomic spectrometric methods. For thallium, the multielement capabilities of the method can hardly be used, because lead and frequently cadmium have to be masked with excess of complexants, leaving just Tl in the potential... 

The ease of incorporating funchonal groups to modify the pSi surface for mass spectrometric application has allowed for the development of a convenient and simple method for enriching the concentration of analytes. This technique, termed DIOS solid-liquid extraction (SLE), uses the property of differential adsorption selectively to capture analytes from a solution containing contaminants that impede MS analysis. Hydrophobically modified DIOS surfaces could be readily used selectively to remove interferences prior to analysis. DIOS S LE simply involves the deposition of a droplet containing analytes onto the chemically modified DIOS surface then, after approximately 3 s, the sample is aspirated with the same pipette. This short-term deposition allows for any molecule with a propensity to be adsorbed onto the surface to attach itself, while any potential hydrophilic contaminants such as salts and buffers will remain in solution, leaving the surface free from such contaminants. The van der Waals interaction between the analyte and surface leads to a selective extraction of the small molecules, while the hydrophilic contaminants such as salts are removed with the droplet. The DIOS analysis of peptides and small molecules from complex matrices is greatly enhanced by differential adsorption [47]. 

---