T5 PM Emerging Pollutants
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 321-323

(SEY-1117-824405) Uptake and quantification of low part-per-billion concentrations of perchlorate (ClO₄^-) in lettuce using IC-ESI-MS.

Seyfferth, A.¹, Parker, D.¹, ¹ University of California, Riverside, CA, USA

ABSTRACT- Perchlorate (ClO₄^-) has caused widespread pollution in the United States, and many questions regarding potential human exposure from food crops remain unanswered. To date, there have been no controlled studies of plant uptake at environmentally relevant (low ppb) concentrations coupled with the accurate quantification of the resulting low levels of perchlorate in plants. The primary aims of this research are to develop an analytical method to quantify low levels of perchlorate in plants and to understand the factors controlling perchlorate uptake by several cultivars of winter lettuce. A sample clean-up method was developed to measure low ppb levels of perchlorate (ClO₄^-) in several varieties of lettuce using Ion Chromatography-Electrospray Ionization-Mass Spectrometry (IC-ESI-MS). Butterleaf lettuce was hydroponically grown, containing no perchlorate, and was spiked with 3.5 ppb perchlorate during the clean up procedure. Recoveries were between 91.4 – 94.3%. Similarly, hydroponically grown Romaine lettuce containing no perchlorate was spiked with 15.7 ppb perchlorate and recoveries were between 96.8 – 100%. This method was applied to 5 types of store-bought lettuce as part of a market survey. This method was also applied to Butterleaf, Redleaf, and Romaine lettuce grown hydroponically at concentrations of 1, 5 or 10 ppb perchlorate for 60 days. It has been suggested that perchlorate is likely taken up with the transpiration stream and thus should accumulate to a greater extent in large outer leaves as compared to smaller inner leaves. Factors such as these as well as variation amongst cultivars on perchlorate uptake will be addressed.

Key words: Perchlorate, IC-ESI-MS, part-per-billion