Determination of arsenic in seagrass using inductively coupled plasma mass spectrometry q

A study has been conducted for the determination of arsenic in seagrass using inductively coupled plasma mass Ž . spectrometry ICP-MS with emphasis on sample digestion procedures and interference reduction. Open-vessel digestion with four different media, HClO rH SO rHNO H SO rHNO , HNO rH O , and HNO , was tested 4 2 4 3, 2 4 3 3 2 2 3 and compared. The HNO rH O mixture was found to be the most suitable medium for sample digestion. Different 3 2 2 inorganic and organic arsenic compounds gave similar ICP-MS responses, indicating that complete conversion from organic form to inorganic form in the sample digestion is not required. Although the HClO rH SO rHNO mixture 4 2 4 3 is frequently used in plant sample digestion for other analytical techniques, it is not recommended for the ICP-MS technique. The formation of the polyatomic interference ion, ArCl, hampers the determination of arsenic even when the interference equation is employed. The interference of ArCl can be accurately corrected only at Ž . minimum chlorine concentration -500 ppm . The concentrations of HNO in the final solutions have a significant 3 Ž . effect on the arsenic signal. This type of interference cannot be corrected by internal standards Sc, Y, and In because the signal suppression due to the use of HNO is dependent on the mass number. The ratios of AsrSc, 3 AsrY and AsrIn vary with the concentrations of HNO . Standard addition has been found to be an excellent 3 method for reducing this type of matrix effect. The analytical procedure proposed in this paper has been validated by Ž . analyzing standard reference material 1572 citrus leaves , and successfully used for the determination of arsenic in seagrass collected from Florida Bay. Q 2000 Elsevier Science B.V. All rights reserved.