An approach for identification and determination of arsenic species in the extract of kelp
- 503 Downloads
The National Institute of Standards and Technology is developing a kelp powder standard reference material (SRM) in support of dietary supplement measurements. Edible seaweeds such as kelp and laver consumed as diet or dietary supplement contain tens of mg/kg arsenic. The speciation information of arsenic in the seaweed should be provided because the total arsenic alone does not fully address the safety issue of the dietary supplement as the value assignment is originally intended. The inability to avail all arsenic species for value assignment measurements prevented the certification of arsenic species in the candidate SRM; however, approximately 70 % of total arsenic extracted with a 1:1 volume fraction of methanol:water mixture allowed arsenic speciation values to be assigned to a procedure-defined extract, which may be used for method validation in research to improve upon current extraction and measurement practices. Arsenic species in kelp and laver were identified using electrospray ionization ion trap time of flight mass spectrometry (ESI-IT-TOF). Arsenosugars As(328), As(482), and As(392) were found in the kelp candidate SRM while As(328) and As(482) were found in GBW 08521, a certified reference material (CRM) of laver produced by the National Institute of Metrology of China (NIM). A discovery that the digests of kelp and laver contained only dimethylarsinic acid led to the conclusion that the seaweeds did not contain detectible levels of arsenobetaine, arsenocholine or trimethylarsine oxide that could overlap with the peaks of arsenosugars in the separation. The mean ± s of (5.68 ± 0.28) mg/kg and (13.43 ± 0.31) mg/kg found for As(482) and As(392) in kelp, respectively, using instrumental neutron activation analysis (INAA) demonstrated that value assignment measurement of arsenosugars was possible without arsenosugar calibration standards.
KeywordsArsenic species Arsenosugar Microwave Digestion INAA IT-TOF LC-ICP-MS
Certain commercial items are identified in this paper to specify adequately the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the equipment identified is necessarily the best for the purpose.
- 1.USDA National Nutrient Database for Standard Reference, http://ndb.nal.usda.gov/
- 2.Kelp in Herbs and Supplements, New York University Langone Medical Center http://www.med.nyu.edu/content?ChunkIID=21786. Accessed 3/26/2014
- 15.Edmonds JS, Morita M, Shibata Y (1987) J Chem Soc Perkin Trans I, 577Google Scholar
- 24.Le X, Cullen WR, Reimer KJ (1994) Clin Chem 40:617Google Scholar
- 25.Francesconi KA, Tanggaard R, McKenzie CJ, Goessler W (2002) Clin Chem 48:92Google Scholar