A highly sensitive gradient microbore ion chromatographic method was developed with electrolytically generated hydroxide eluents for the determination of low microg/L levels of chloroacetate, bromoacetate, trifluoroacetate, dichloroacetate, chlorodifluoroacetate, dibromoacetate, trichloroacetate, bromodichloroacetate and dibromochloroacetate disinfectant by-products formed as a result of chlorination of drinking waters. The possibility of using a packed bed Dionex Atlas suppressor with a hydroxide gradient at microbore flow rates was investigated in order to reduce baseline noise levels. The Atlas suppressor displayed a very significant reduction in noise levels compared to the standard alternative ASRS Ultra suppressor, reducing noise by a factor of 15-20 in some cases, allowing trace haloacetic acids (HAs) to be seen with the direct injection of 100 microL of treated water, with prior chloride and sulfate removal. To lower detection limits even further, a solid phase extraction was employed to preconcentrate HAs, resulting in detection limits of between 0.09 and 21.5 microg/L. The method was applied to the determination of HAs in environmental samples and standard addition curves for three drinking water samples were carried out for both direct injection and preconcentration methods. R2 values in both cases were > or =0.98. Combined content for US Environmental Protection Agency regulated HAs in the three drinking water samples from Dublin City University; New Ross, Co. Wexford and Drogheda, Co. Louth were 46.5, 58.3 and 12.6 microg/L, respectively.