Removal of arsenic in the form of anions from solid matrices by supercritical CO₂ extraction with ion-pairing

A new method for the removal of the arsenic in the form of anions such as arsenite and arsenate, from solid samples by supercritical CO₂ extraction coupled with ion pairing was investigated. Tetrabutylammonium bromide (Bu₄NBr) was used as the ion-pairing reagent. As a result of the insolubility of Bu₄NBr in supercritical CO₂, the extraction of the anions by supercritical CO₂ with the in situ ion-pairing is not effective. The arsenic in the form of anions in the solid samples can be effectively removed by supercritical CO₂ extraction with pre-ion-pairing. For the case of the pre-ion-pairing, the extraction efficiency was strongly dependent on the dosage of Bu₄NBr.