Determination of formaldehyde in Brazilian alcohol fuels by flow-injection solid phase spectrophotometry

In this work, a solid phase spectrophotometric method in association with flow injection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C18 material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C18 support and the spectrophotometric detection was performed simultaneously at 412 nm. The retained complex was quickly eluted from C18 material with the eluent stream consisting of a 50% (v/v) ethanol solution. The results showed that the proposed method is simple, rapid and the analytical response is linear in the concentration range of 0.050–1.5 mg L−1. The limit of detection was estimated as 30 μg L−1 and the R.S.D. 2.2% using a sample volume of 625 μL. The system presented an analytical throughput of 20 determinations per hour. The method was successfully applied in the determination of formaldehyde in ethanol fuel.