Courtesy of Supelco Inc.

Figure 25. The Separation and Specific Detection of Some Herbicides Using the Nitrogen Phosphorus Detector

This is an inherent problem with all NP detectors and as a result the bead needs to replaced fairly regularly if the detector is in continuous use. The specific response of the NPD to nitrogen and phosphorus and its high sensitivity, makes it especially useful for the analysis of many pharmaceuticals and in particular in environmental analyses involving herbicides. Employing appropriate columns traces of herbicides at the 500 pg level can easily be determined.

An example of the separation and identification of a series of herbicides employing the NPD is shown in figure 25. An SPB-5 column was used, 15 m long and 0.53 mm I.D. carrying a 0.5 m film of stationary phase. The column temperature was held at 60^oC for 1 minute and then programmed at 16^o/min. to 290^oC and then held there for 5 minutes. The flow rate was 5 ml/min. and the carrier gas helium. The sample size was 1 ml of ethyl acetate containing 5 ng of each herbicide.