Potential Bias in Arsenic Species Results for Tissues by EPA Method 1632
Oral Presentation
Prepared by A. Carter, I. Joslin, M. Briscoe
Brooks Rand Labs, 3958 6th Ave NW, Seattle, Washington, 98107, United States
Contact Information: [email protected]; 206-632-6206
ABSTRACT
There are two sample preparation procedures for tissue samples that are described in EPA Method 1632A for the determination of arsenic species, including dimethylarsinic acid (DMAs): a sodium hydroxide (NaOH) digestion and a hydrochloric acid (HCl) digestion. As there was not a certified reference material (CRM) previously available that was certified for DMAs in tissue samples, for quality control (QC) purposes, sample batches were prepared with a blank spike (lab fortified blank) to ensure no analyte loss or conversion during the sample preparation procedure. Recently, more tissue (e.g., fish, rice, etc.) CRMs have been certified for arsenic species. The availability of these new CRMs has resulted in a finding that the NaOH tissue digestion procedure described in EPA Method 1632A is not appropriate for the analysis of DMAs for two reasons: it consistently results in a low bias for plant-based tissues (such as rice) and it consistently produces a significantly high bias for many marine tissues that contain arsenobetaine (AsB). A comparison of the two methods will be presented showing results from blank spikes, matrix spikes, CRMs, and various tissue samples. Additionally, data for the tissue samples analyzed using EPA Method 1632A will be compared to results from a method that couples anion chromatography to ICP-MS.
Oral Presentation
Prepared by A. Carter, I. Joslin, M. Briscoe
Brooks Rand Labs, 3958 6th Ave NW, Seattle, Washington, 98107, United States
Contact Information: [email protected]; 206-632-6206
ABSTRACT
There are two sample preparation procedures for tissue samples that are described in EPA Method 1632A for the determination of arsenic species, including dimethylarsinic acid (DMAs): a sodium hydroxide (NaOH) digestion and a hydrochloric acid (HCl) digestion. As there was not a certified reference material (CRM) previously available that was certified for DMAs in tissue samples, for quality control (QC) purposes, sample batches were prepared with a blank spike (lab fortified blank) to ensure no analyte loss or conversion during the sample preparation procedure. Recently, more tissue (e.g., fish, rice, etc.) CRMs have been certified for arsenic species. The availability of these new CRMs has resulted in a finding that the NaOH tissue digestion procedure described in EPA Method 1632A is not appropriate for the analysis of DMAs for two reasons: it consistently results in a low bias for plant-based tissues (such as rice) and it consistently produces a significantly high bias for many marine tissues that contain arsenobetaine (AsB). A comparison of the two methods will be presented showing results from blank spikes, matrix spikes, CRMs, and various tissue samples. Additionally, data for the tissue samples analyzed using EPA Method 1632A will be compared to results from a method that couples anion chromatography to ICP-MS.
