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.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 8 |
| Published : | 11/15/2004 |
