On-line trace level determination of polar organic microcontaminants in water using various pre-column-analytical column liquid chromatographic techniques with ultraviolet absorbance and mass spectrometric detection

A range of organic micropollutants with different polarities, such as neutral pesticides, phenolic compounds and acidic herbicides, was determined down to sub-ug per litre levels. A combination of solid-phase extraction (SPE) and liquid chromatography with diode-array UV-particle beam mass spectrometry was used to separate and analyse micropollutants. A dual pre-column set-up was examined along with the effect of pH and oven temperature. More than 100 compounds representing different classes were analysed. The optimized procedure was used to distinguish bentazone and several dichlorobenzoic acids from samples and detected phenol down to 0.1 mg per litre. The pre-column set-up prevented interference caused by the matrix constituent. Highly polar compounds which showed breakthrough on the first pre-column were trapped on the second column. Most of the humic substances were retained on the pre-columns. Further study suggested the evaluation of highly hydrophobic sorbents such as Lichrolute EN and Isolute ENV.