Heavy Metals

 Individual metal concentration in oil or in water is determined by ICP-MS. After proper dilution (for oil phase, 10 or 20mg oil to 1ml ultra-pure HNO3), samples are placed in small teflon tubes and subjected to acid digestion while heated at >100ºC under pressure for at least 24 hours and later washed with 1% dilute HNO3. Metal concentration is then determined by ICP-MS (Fission, Model PQII-Plus). Although more than 60 elements can be determined for every sample in one scan, As, Ba, Cd, Cr, Pb, and Zn will be our major concerns. Any metal with an exceptionally high concentration also needs special attention.