Comparison between an ultraviolet spectrophotometric procedure and the 2,4-xylenol method for the determination of nitrate in groundwaters of low salinity

An ultraviolet spectrophotometric procedure for the determination of nitrate in groundwaters of low salinity has been investigated and compared with the recommended 2,4-xylenol method. The ultraviolet procedure is not subject to interference from the major cations present in typical groundwaters and interference from high levels of nitrite is overcome by the addition of sulphamic acid. Good agreement is demonstrated between nitrate values obtained by both methods on a number of groundwater samples.The ultraviolet procedure offers a rapid and sensitive means of determining nitrate in such waters, which are generally low in content of organic matter, particularly where the volume of sample is limited, e.g., studies on pore water samples.