Identification and determination of arsenic compounds by chromatographic and mass spectrometric methods

Typescript (photocopy).Arsenate, arsenite, methylarsonic acid and dimethylarsinic acid are arsenic compounds commonly found in the environment. An efficient method combining high performance liquid chromatography with a Hitachi-Zeeman graphite furnace atomic absorption spectrophotometer was developed for the separation and quantitative determination of these four arsenic compounds. The compounds were separated by ion-pair chromatography (C-18 reverse phase column, 75% H(,2)O/25% CH(,3)OH saturated with tetraheptylammonium nitrate as the mobile phase, pure methanol for the elution of arsenate). The samples to be injected for chromatography may contain 30 to 300 ng As of each compound. The separation scheme developed for the four arsenic compounds were used to speciate these compounds in drinking waters. The mass spectral behavior or the organylarsonic acids, RAsO(,3)H(,2) (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,9)H(,19), and C(,6)H(,5)), the diorganylarsinic acids, R(,2)AsOOH (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,4)H(,9), C(,5)H(,11), C(,8)H(,17), c-C(,6)H(,11), C(,6)H(,5), and C(,6)H(,5)CH(,2)CH(,2)), the organyldiiodoarsines, RAsI(,2) (R = CH(,3), C(,2)H(,5), C(,3)H(,7), C(,4)H(,9), C(,5)H(,11), C(,7)H(,15), C(,9)H(,19), C(,15)H(,31), C(,17)H(,35), C(,19)H(,39), C(,6)H(,5), and C(,6)H(,5)CH(,2)CH(,2)), and the diorganyliodoarsines, R(,2)AsI (R = CH(,3), C(,8)H(,17), C(,9)H(,19), C(,11)H(,23), C(,13)H(,27), C(,14)H(,29), C(,15)H(,31), C(,17)H(,35), C(,19)H(,39), c-C(,6)H(,11), and C(,6)H(,5)CH(,2)CH(,2)) were investigated to explore the usefulness of mass spectrometry as a tool for the identification of organic arsenic compounds. The organylarsenic acids were thermally dehydrated and decomposed at the probe temperatures required to obtain satisfactory spectra. The complicated spectra of the decomposition products are not very useful for analytical purposes. The reactions of organylarsenic acids with aqueous hydriodic acid produced organyliodoarsines which are more volatile than their parent acids. The mass spectra of the iodoarsines contain predominant molecular ion peaks, which can be used for the identification of long- and short-chain compounds