The certified reference material of arsenobetaine (AB) from
(CH3)3 As+CH2COO was supplied by NMIJ as a
standard solution, NMIJ CRM 7901-a. For our internal quality
control, the As concentration in in-house prepared As speciation
standards was determined by ICPMS. For this, As(V), As(III), DMA,
MA, AC, TMAO and AB were standardised against two arsenic
certified standard solutions as well as against As2O3
solution. All stock solutions were kept at 4 C, and further diluted
solutions for the analysis were prepared daily.