University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Plant -> lichen

Citations 3

"Comparison Of Plumbane And Tetraethyllead For The Determination Of Lead By Inductively Coupled Plasma Atomic-emission Spectrometry"
Anal. Chim. Acta 1995 Volume 309, Issue 1-3 Pages 369-378
M. C. Valdés-Hevia y Temprano, M. R. Fernández de la Campa and A. Sanz-Medel*

Abstract: Sediments and lichen (200 mg) were microwave digested in 1.5 mL concentrated HNO3, 0.5 mL 80% HClO4 and 0.5 mL concentrated HF (details given). After cooling, the excess HF was reacted with 3.5 mL 6% H3BO3, the mixture re-digested and the contents made to 100 mL with water. Citrus leaves and lyophilized vegetables (0.5 g) were digested in 5 mL 65% HNO3 and 2 mL H2O2 and the contents made to 25 mL with water. The solutions were mixed to contain 0.3% or 0.7% K2Cr2O7 for PbH4 (I) or tetraethyllead (II) analysis and merged at 1 ml/min with carrier streams (1 ml/min) of 360 mM or 600 mM lactic acid for I and II, respectively, and 5% NaBH4 in 0.1% NaOH for I or 1% sodium tetraethylboron in 1% NaOH for II. The mixed solutions were aspirated at 2.4-3 ml/min into a detuned grid-nebulizer for ICP-AES and Pb determined at 0.7 kW and 20.353 nm. Calibration graphs were linear up to 0.5 mg/ml of I and 1.5 mg/ml of Pb for II with detection limits of 2 ng/ml and 1 ng/ml of Pb, respectively. At 50 ng/ml of Pb the RSD (n = 10) were 1.3% for I and 1.2% for II. The selectivity of the two methods in the presence of chloride, nitrate and a range of cations was confirmed. The analysis of Pb via II was preferred as only Ni and Sb interfered.
Lead Sample preparation Spectrophotometry Interferences Volatile generation Optimization Volatile generation

"Sensitive Method For Determination Of Lead By Potassium Dichromate-lactic Acid Hydride Generation Inductively Coupled Plasma Atomic-emission Spectrometry"
J. Anal. At. Spectrom. 1993 Volume 8, Issue 6 Pages 821-825
M. C. Valdés-Hevia y Temprano, M. R. Fernández de la Campa and Alfredo Sanz-Medel

Abstract: For the continuous-flow determination of Pb as PbH4 by hydride-generation ICP-AES, generation with use of 0.3% K2Cr2O7/3% lactic acid and 5% NaBH4 in 0.1% NaOH as reagents was chosen and optimization of the detection limit was studied. With use of a r.f. forward power of 700 W and detection at 220.353 nm, a detection limit of 2 ng/ml of Pb was obtained with an RSD of 1.3% at 50 ng/ml. The cited method was applied to the determination of Pb in soft-drinks, sediment and lichen reference materials. Soft drinks, containing 11-66 ng/ml, were injected directly and Pb was determined with the aid of a standard-additions procedure.
Lead Spectrophotometry Reference material Optimization Standard additions calibration Volatile generation

"The Use Of Surfactants To Obtain Cadmium Atoms At Room Temperature And Its Application For The Cold Vapor AAS Determination Of The Metal"
Anal. Proc. 1995 Volume 32, Issue 2 Pages 49-52
A. Sanz-Medel, M. C. Valdés-Hevia y Temprano, N. Bordel García and M. R. Fernández de la Campa

Abstract: So far, mercury is the only metal that has been proved to be able to form a monoatomic vapor at room temperature. This property has been widely used in analytical techniques, particularly in atomic spectroscopy, where cold vapor atomic absorption spectrometry (CV-AAS) has become the most common method for the determination of low levels of Hg.In this communication we will show evidence that cadmium appears also to be able to form cold atomic vapor in appropriate conditions. Experimental results show that by reduction of Cd2+ with sodium tetrahydroborate in vesicles of didodecyldimethylammonium bromide (DDAB), some volatile cadmium species (probably hydrides) can be produced that transport the metal to the atomic absorption measurement cell, where atomic cadmium vapor has been proved to be present in measurable concentrations.Based on these facts, a new determination of traces of cadmium by cold vapor atomic absorption spectrometry is proposed. Such CV-AAS determination of the metal is very sensitive in normal conditions (detection limit of 0.08 ng ml-1) and the sensitivity can be improved further by working at lower temperatures for generation of the volatile species.
Cadmium Spectrophotometry Volatile generation Volatile generation