AWWA WQTC60710

There are numerous cases where groundwaters have been found to be high in nitrate and attributed to either septic influence or agricultural practices. In many cases the nitrate data alone have been insufficient to differentiate between these causes for contamination. Corrective measures in response to high nitrates vary depending upon the cause. With the advent of ultrasensitive methods for trace analysis for pharmaceuticals and personal care products (PPCPs) as demonstrated by the USGS (Kolpin et al, 2002), other analytical results could be used to shed light on such situations. The Kolpin methods detect numerous compounds at the 1-50 part per trillion level. However, they rely on LC-MS, expensive instrumentation that is not found in most environmental labs. In contrast, HPLC systems are widely available in many commercial and utility labs. Therefore, the lab developed a sensitive HPLC/UV method for the analysis of 3 representative surrogate human tracers, caffeine, cotinine, and acetaminophen. This HPLC method was targeted to achieve a reporting limit of 30 ppt (with a 10 ppt detection limit), sensitive enough to be useful in natural systems impacted by human activities. A 1000 milliliter (mL) sample aliquot is passed through a methanol and water conditioned Waters Oasis-HLB polymeric cartridge. After a sorbent wash step, the compounds are eluted from the cartridge with a small quantity of methanol followed by acidified methanol, and concentrated further by evaporation of some of the solvent. A 10 mM Formate buffer is used to bring the extract to volume. The extract is then analyzed by HPLC at two wavelengths (254 and 280 nm) with conditions optimized to separate the compounds in a 15 minute run time. This run time is short enough to allow analysis of large numbers of samples to establish patterns of groundwater occurrence. The method was validated using a variety of standard protocols to assess precision and accuracy (analysis of LFB, LFM, MRL checks). As confirmation of accuracy, selected samples are also analyzed for caffeine by a separate GCMSSPE method that has a reporting limit of 5 ppt (MDL of 1 ppt). Includes 4 references, table, figures.