Measurement of paraquat in human samples would be challenging for many hospitals. The sodium dithionate test can rapidly screen plasma for paraquat.
Reagent: sodium dithionite (Na2S2O4) as an alkaline aqueous solution (1% in 0.1 N NaOH).
Sample: plasma
Specimen handling: deproteination with sulfosalicylic acid, with analysis performed on the supernatant.
Reaction with dithionite creates a free radical.
Color generated: blue
Absorption maximum: 603 nm
A negative control provides baseline.
A positive control allows a semiquantitative estimate of concentration, especially if positive controls of different concentrations are used to create a concentration curve.
Koo et al compared the patient sample collected at 10-12 hours after ingestion against a control with a concentration of paraquat of 2.0 mg/L (a concentration associated with mortality). A specimen generating a darker color was associated with 100% mortality.
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