The National Institute of Standards and Technology has developed a new series of organic As reference materials, SRMs 3030, 3031, 3033 and 3034, for monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine, respectively. These SRMs will be used for the calibration of measurements of these species in various matrices. Conversion of the organic As species to inorganic As V was required to prevent bias in the ICP-OES measurements. Different acid/solvent combinations were studied to provide the optimum conversion conditions during microwave digestion. TMAO was used as a model system. Hydrochloric acid was the best acid to use at a minimum of 3 mL. The average As mass fractions for the organic speciation standards were successfully determined with an expanded uncertainty ≤ 2.4 % using ICP-OES. These results were in control and compared favorably to INAA measurements.
arsenic speciation, reference materials, organic, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), arsenobetaine (AB), arsenocholine (AC)