Development of Isotope Dilution Cold Vapor Inductively Coupled Plasma Mass Spectrometry and Its Application to the Certification of Mercury in NIST Standard Reference Materials

2001 ◽  
Vol 73 (10) ◽  
pp. 2190-2199 ◽  
Author(s):  
S. J. Christopher ◽  
S. E. Long ◽  
M. S. Rearick ◽  
J. D. Fassett
Keyword(s):  
Mass Spectrometry ◽  
Reference Materials ◽  
Isotope Dilution ◽  
Inductively Coupled Plasma ◽  
Standard Reference Materials ◽  
Cold Vapor ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

Determination of Ultratrace Levels of Lead in Infant Formula by Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

1993 ◽  
Vol 76 (6) ◽  
pp. 1378-1384 ◽  
Author(s):  
Joseph J Thompson
Keyword(s):  
Mass Spectrometry ◽  
Infant Formula ◽  
Reference Materials ◽  
Isotope Dilution ◽  
Inductively Coupled Plasma ◽  
Standard Reference Materials ◽  
Inductively Coupled ◽  
Relative Standard ◽  
Plasma Mass Spectrometry

Abstract A simple method was developed for the accurate and precise determination of low- and sub-ppb (ng/g) concentrations of lead in infant formula by isotope dilution inductively coupled plasma mass spectrometry using ultrasonic nebulization. After addition of a known amount of 207Pb, samples were microwave digested and the ratio 207Pb/208Pb was measured in the digests. Agreement with certified values for lead in milk powder standard reference materials was good, and isotope dilution analysis using 206Pb yielded identical results for the standard reference materials. Lead concentrations determined for several infant nutritional products were verified by an independent method. Typically, relative standard deviations of <4% were obtained with this method for lead concentrations above 2 ppb. The recovery of 2 ng of lead from an aqueous standard carried through the microwave digestion was 104 ± 4%. Infant formula (containing 0.6 ppb lead) to which 0.4 ng of natural-abundance lead had been added, to simulate a formula containing 0.9 ppb lead, was analyzed by isotope dilution, and the result was 96 ± 18% of the theoretical value. Thus, differences of 0.3 ppb lead could be clearly distinguished, and the detection limit was estimated to be 0.1 ng lead per gram of infant formula. The keys to accuracy for this method are minimizing contamination and accurately determining the concentration of lead in the isotopically enriched standard.

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