US EPA

1360517 

Technical Report 

A rapid and highly sensitive singel-sweep polarographic method of analysis for arsenic ( III ) in drinking water 

Whitnack, GC; Brophy, RG 

1969 

HAPAB/70/01495 

Chim 

1 

123-7 

HAPAB A simple, rapid and very sensitive method of analysis for srsenic in dirnking water is presented which uses linear sweep cathode-ray polarotrace. Resublimed arsenious acid was dissolved in sodium hydroxide and neutralized with dilute sulfuric acid to serve as a standard solution of arsenic ( III ). A 2-ml sample of untreated, unfiltered well water was palced in a 5-ml polarographic cell containing a pool of mercury as the anode. Three dorps of concentrated sulfuric acid were added to the cell solution which was then flushed for 5 min with notrogen. The voltage range form -0.70 to -1.20 V was then scanned with the 2-sec sweep of the polarograph. The current voltage cirve was recorded after six to eight sweeps of the instrument showing the peak for arsenic ( III ) to be at about -0.97 v. A moseley Model 2-D X-Y recorder was used to record the polarogrrams. After the unknown polarogram had been recorded, a microaliquot of 0.000011 g/ml arsenic ( III ) standard solution was added to the cell solution which was then flushed with nitrogen. The wave height and peak for arsenic were again measired. A ratio of the two wave-lenghts gave the concentration of arsenic ( III ) in the sample. Thsi technique determined arsenic concentrations a low as 5 ppb with a relative error of 5 to 10% of the actual concentration. The method is useful in the analysis of drinking water containing arsenic in low quantities, 50 ppb or less. The results obtained by this new tichnique gave more reliabel results on drinking water than the Gutzeit method currently used by water chemists in such analysis. The altter method gives questionable results with water containing 40 ppb arsenic or less and is more time consuming. Analysis 70/09/00, 426 1969