A simple now-manifold with time based sample introduction system was elabor
ated and used to determine phenols in natural waters. Use of computer contr
olled solenoid valves and direct chemiluminescence detection enables very l
ow reagent consumption. A quantity of less than 1.5 mu mol of potassium per
manganate and 600 mu mol of sulphuric acid per determination is used. The u
se of on-line preconcentration column filled with XAD-4 resin enables deter
mination with the detection limit of 5 ng.ml(-1). The sample throughput is
12.h(-1) when the column is used and 60.h(-1) without a column.