Determination and monitoring of polar compounds and acidic herbicides using a modified SAMOS system

A system for the automated monitoring of organic pollutants in surface wate rs (SAMOS) has been developed over the last 5 years to monitor for the pres ence of organic contaminants in surface water. It uses a solid-phase extrac tion (SPE) trace enrichment step followed by on-line elution and separation by HPLC. Detection and provisional identification is obtained with diode a rray detection. For pesticide and herbicide analysis, mainly medium volatil e, neutral compounds such as carbamates, triazines and phenyl ureas have be en reported. Ionic species such as phenoxy acid herbicides are poorly preconcentrated at normal river pH. These ionic/polar compounds frequently show breakthrough from the SPE cartridge prior to complete loading of the sample. Any retaine d polar analytes are also often obscured by the presence of co-extracted hu mic substances in river water samples. The paper presents the required chan ges to the original SAMOS system to allow ionised and polar pollutants to b e successfully analysed. These changes involve allowing the ionic/polar com pounds to break through from the loading onto the primary cartridge (PLRP-S ), allowing all but the last few mi of sample to go to waste. When break th rough of the relevant analytes is achieved, the remaining sample is switche d automatically on-line to a secondary cartridge (again PLRP-S) with acid b eing added just prior to this to neutralise the compounds This secondary ca rtridge effectively preconcentrates the ionic/polar compounds. The two cartridges are desorbed in two subsequent gradient elution LC-DAD r uns. Analysis of several major classes of compounds is achieved, notably me mbers of the triazine, phenyl urea, phenol and acid herbicide groups. The system has been designed and tested in the laboratory and applied at an installation remote from the laboratory on a river site as part of an inta ke protection programme. Details of the method performance, experiences of operation and access of the system via telemetry are discussed.