Formaldehyde Quantification Using HPLC. Derivatization of formaldehyde was performed with a saturated solution of purified DNPH in acetonitrile. The derivitization procedure featured a reaction of 5 mL of the aqueous solution from the reactor, 5 mL of pH 4 buffer (NaH2PO4 + H3PO4), and 1 mL of saturated solution of DNPH at 40 °C for 1 h. The hydrazone thus formed was equilibrated to room temperature for 30 min and then analyzed on the HPLC-UV/vis at 360 nm. The analysis was performed on a Perkin-Elmer reverse phase HPLC unit with a Supelcosil LC-18 column using acetonitrile and 0.5% acetic acid solution.