Oil (kerosene) Spill: Detection/Monitoring of Row Water

We need a online monitoring system that can find less than  5ppb (part per bilion) / 5micrograms of kerosene in one liter of row water.  We need this monitoring system because near our source/water spring was a spill of kerosene. Now we want to do online monitoring  of the quality of row water. Do you know any supplier/machine that can reach less than 5ppb precision?