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An approach for identification and determination of arsenic species in the extract of kelp



Lee L. Yu, Rolf L. Zeisler, Rabia Oflaz, Wei Chao, Junting Tong, Haixia Bao, Jun Wang


The National Institute of Standards and Technology is developing a kelp 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 in the candidate SRM alone does not address the safety issue of the dietary supplement as the value assignment is originally intended. The inability to avail all arsenic species for value assign 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 was 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. That 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 assign measurement of arsenosugars was possible without arsenosugar calibration standards.
Analytical and Bioanalytical Chemistry


arsenic specie, arsenosugar, extraction, microwave, digestion, INAA, IT-TOF, LC-ICP-MS.


Yu, L. , Zeisler, R. , Oflaz, R. , Chao, W. , Tong, J. , Bao, H. and Wang, J. (2015), An approach for identification and determination of arsenic species in the extract of kelp, Analytical and Bioanalytical Chemistry, [online], (Accessed June 13, 2024)


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Created March 3, 2015, Updated November 10, 2018