Extraction of Parquat from Blood by Clinoptilolite

Paraquat is a bipyridyl herbicide and organic divalent cation which due to its high polarity and water solubility cannot be readily extracted by common organic solvents from body fluids. Dithionite color test for qualitative and quantitative determination of paraquat in urine has been proposed and used for many years. Although some methods were proposed for solvent extraction of paraquat from blood, they are less practical in clinical laboratories and lack high extraction recovery. Clinoptilolite is a highly porous natural zeolite with cation-exchange property and high surface area. In the present work, extraction of paraquat from human blood by clinoptilolite was investigated and compared with Amberlite CG-50 I, a well-known weak cation-exchanger. Blood paraquat was adsorbed by adsorbents (clinoptilolite or Amberlite) and extracted from them by saturated sodium chloride solution. Extracted paraquat was spectrophotometrically measured by means of sodium dithionite reagent at 394.5 nm. Recovery, limit of detection, considering signal-to-noise (S/N) ratio of 3, and limit of quantification, regarding S/N of 10, of paraquat extraction by clinoptilolite and Amberlite CG-50 were 81.7% ± 3.4%, 0.58 μg, and 1.93 μg and 83.6% ± 3.2%, 0.49 μg, and 1.63 μg, respectively. Repeatabilities (within-laboratory error) of paraquat extraction by clinoptilolite and Amberlite CG-50 I were 7.1% and 6.3%, respectively.