Onsite testing for arsenic: field test kits.

The performance of existing field test kits for arsenic has generally been unsatisfactory. Reports of false-negative and false-positive results exceeding 30% are not unusual, although more recent techniques appear to be more reliable. However, studies using these recent techniques had only to meet the local water standard of 50 microg/L. If the new WHO guideline (10 microg/L) is adopted as a decision-making criterion, the sensitivity of most arsenic testing kits is not sufficient, particularly in the hands of nontrained operators. New developments with sophisticated electrochemical sensors may deliver the needed sensitivity but suffer from matrix effects, even with trained operators. A failing of all available commercial methods is that they do not determine organoarsenicals, despite the fact that, in some cases, organic species may be the predominant ones present.