Anal. Chem. 1989, 6 1 , 2116-2118
2116
(22) Standard Methods for the Examination of Water and Wastewaters, 16th ed.; American Public Health Association: Washington DC, 1985; pp 290-292. (23) Nagy, G.; Feher, 2. S.; Toth, K.;Pungor, E. Anal. Chim. Acta 1977, 9 1 , 87. (24) Nagy, G.; Feher, 2 . S.;Toth, K.; Pungor, E. Anal. Chim. Acta 1977, 91, 97. (25) Toth, K.; Nagy, G.; Feher, 2.; Horvai, G.; Pungor, E. Anal, Chim, Acta 1980, 114. 45.
(26) Van Staden, J. F. Anal. Chim. Acta 1986, 779, 407. (27) Nagy, G.; Pungor, E.; Toth, K.; Havas, J.; Feher, Z. (EGYT, Budapest, Hungary). U.S. Patent 4,120,657, 1978. (28) Hara, H.; Waizaka, Y.; Okazaki. S. Anal. Chem. 1986, 58, 1502.
RECEIVED for review December 14, 1988. Accepted June 10, 1989.
CORRESPONDENCE Exchange of Comments on Identification and Quantitation of Arsenic Species in a Dogfish Muscle Reference Material for Trace Elements Sir: Marine organisms generally accumulate substantial amounts of arsenic, and information on the arsenic complex is quite important to evaluate the toxicological implications as well as to elucidate the cycling of the element in the marine environment. The ubiquitous nature of arsenobetaine in marine animals has been well documented (1, 2 ) , but there is only limited information on the presence/absence of other arsenic species in the samples. Among the arsenic species, arsenocholine has attracted attention (3,4 ) . Arsenocholine is expected to be a precursor of arsenobetaine (3, 4 ) . Furthermore, it was speculated to be a constituent of lipid-soluble arsenic ( 5 ) ,though the major lipid-soluble arsenic in a macroalga is recently identified as a diacylated derivative of arsenic-containing ribofuranoside (6). We have developed a combination of high-performance liquid chromatography (HPLC) with inductively coupled argon plasma atomic emission spectrometry (ICP-AES) for the chemical speciation of arsenic (7,8) and analyzed arsenic species of various marine animals, including fish, crustaceans, and molluscs (9). We could not detect arsenocholine in any of them, but found a strong basic species identified as tetramethylarsonium ion in some of the samples (9). Recently, Beauchemin et al. identified and quantified arsenic species in a dogfish muscle reference material, DORM-1, and reported the presence of trace amounts of arsenocholine (10). The detection of arsenocholine reported before their paper had been limited in shrimp samples (3, 11, 12). Therefore, we examined the reference material together with another one, DOLT-1, by using an HPLC/inductively coupled plasma mass spectrometry (ICP-MS) optimized for the speciation of arsenic (13). EXPERIMENTAL SECTION Sample. The reference materials DORM-1 (dogfish muscle) and DOLT-1 (dogfish liver) (14) were obtained from the National Research Council of Canada. Reagents. Fifteen water-soluble arsenic compounds reported so far from the marine samples were used as the authentic standards (Table I). They were prepared as reported previously (9, 13). All the chemicals and solvents were the commercial products of reagent grade or special grade for LC but were selected carefully to keep the contaminated arsenic and chloride levels as low as possible. 1-Butanesulfonate sodium salt was used after being recrystallized twice from ethanol (95%). Instrumentation. An ICP-MS, PMSlOO (Yokogawa Electric Co. Ltd., Japan), was used as the arsenic-specific detector for HPLC. Quantitation of arsenic in the sample was done by an ICP-AES (JY-38; Seiko Electric Co. Ltd., Japan) after wet digestion by nitric acid. The operating conditions of the ICP-MS, the chromatographic conditions, and the construction of the
Table I. Structures of Arsenic Standards
(I) AsOt-, (11) AsO:-, (111) CH3As03*-,(IV) (CH3)2As02-, (V) (CHJ~ASO, (VI) (CH~)~AS+, (VII) (CH~)~AS+CH~CH~OH, (VIII) (CH~)~AS+CH~COO-, (IX) (CH~)~AS(O)CH&H~OH
b'
R2 I
OH OH R2
X XI XI1 XI11 XIV XV
(CHJZAs(0)- -OH (CH~)~AS(O)-OH (CH,),As(O)- -OH (CH,),As(O)- -NH3+ (CH,)ZAs(O)- -OH (CH3)3As+- -OH
-OH -0P(O)
