Analysis of disinfection by products in drinking water by solid phase extraction
The objectives of this research were to develop a broad spectrum method for the extraction, concentration, and analysis of drinking water disinfection by products using solid phase extraction (SPE), and to determine if this method had lower detection limits and less variability than the proposed liquid-liquid extraction method, EPA Method 551. The disinfection by products investigated were halogenated nitriles, ketones, and aldehydes. The SPE method extracted and concentrated samples using the C-18 Empore Extraction Disks, and desorbed the analytes with methyl-tert-butyl ether (MTBE) as a solvent. The results showed that with the SPE method the recoveries were low (0-50%) for most compounds, and the limit of detection (LOD) values were in the range of 0.2 to 50 ug/L, which were much higher than those for EPA Method 551. The variability was also higher than for EPA Method 551. The SPE method also appeared to be concentration dependent; the recoveries decreased as analyte concentration increased. Highly saline conditions (250 g/L NaCl) resulted in low recoveries and concentration dependencies for some compounds. Even though the SPE method was easier and faster, the lower method detection limit (MDL) values and lower variability made Method 551 more preferable. Further analysis of the SPE method using a new cyclohexyl disk was also recommended.