Paraquat poisoning.

Abstract

This paper deals with the development of methods for the detection and determination of the weed‐killer, paraquat, in body fluids (urine, blood, gastric aspirate, dialysates) and tissues. These have been obtained from 6 cases of paraquat poisoning (2 of which were fatal) admitted to hospital and from several other negative cases. A specific colour reaction is described for the detection and determination of paraquat. Thus when sodium hydrogen carbonate followed by sodium dithionite is added to the test solution, a blue colour is produced. The detection limit is about 1 microgram/ml. Following admission to hospital shortly after the ingestion of paraquat, the reaction can be applied directly to diluted urine and diluted (filtered) gastric aspirate. Paraquat can be detected in small quantities in urine for quite a long period after ingestion. It is necessary, however, to use a column of a cation exchange resin to achieve concentration and also to remove any interfering substances. Under these conditions, it is preferable to assess the absorbance of the blue colour on a recording spectrophotometer. The concentration of paraquat in the blood serum is extremely low and only detectable shortly after ingestion. It has been extremely difficult to detect any traces of paraquat in dialysates (haemo‐ and peritoneal). Depending on the interval of time between ingestion and death, paraquat may be detected in some tissues e. g. liver and kidney. Using the cation exchange resin technique, paraquat in quantities of 50 to 100 micrograms added to 100 ml of urine can be recovered with an accuracy of 86 to 91 %.