Determination of Residual Formaldehyde in Urea–Formaldehyde Fertilizer and Formaldehyde Release from Urea–Formaldehyde Fertilizer During Decomposition

In view of the fact that a large amount of formaldehyde was involved in the production of urea–formaldehyde fertilizer, and the residual and decomposed formaldehyde has never been paid attention to. In this paper, the determination method of free formaldehyde content in urea–formaldehyde fertilizer was studied. A simple and accurate method for the determination of formaldehyde in urea–formaldehyde fertilizer was established based on the screening of traditional iodometry titration and acetylacetone colorimetry. The recovery rate of titration method and colorimetric method were 73.9–94.5% and 96.5–103.9%, which indicated that colorimetric method was more accurate. The optimized test conditions are as follows: fertilizer/water extraction ratio 1/20, developer acetylacetone 6 mL, the condition of reacting at 60 °C for 30 min. The linear range of formaldehyde content in urea–formaldehyde fertilizer determined by optimized method is 0.21–3.26 g/mL.