On-Line Spectrophotometric System Based on Pseudo Liquid Drop and Handheld CCD Spectrometer for Monitoring Formaldehyde Level in Wastewater

• Published in: Instrumentation science & technology 2005-05, Vol.33 (3), p.297-307
• Main Authors: Zhou, Zaide, Zhong, Guanping, Tan, Qing, Li, Yuan, Hou, Xiandeng
• Format: Article
• Language: English
• Subjects: Charge coupled device; Formaldehyde; Liquid drop; On-line monitoring; Spectrophotometry
• ISSN: 1073-9149; 1525-6030
• DOI: 10.1081/CI-200056121

An on-line spectrophotometric system, based on a handheld CCD (charge coupled device) spectrometer and a liquid drop, was constructed for the purpose of monitoring of formaldehyde in wastewater. The liquid drop device was used as a reactor and optical cell for the spectrophotometric measurements to solve the problem of colored species stained onto a traditional quartz optical cell. To overcome the drawback of short optical path of a traditional liquid drop, a simple flow-through type optical cell with open ends was designed and used as a prolonged "liquid drop," i.e., a "pseudo" liquid drop. By using such a pseudo liquid drop, the advantages of a windowless optical cell of a liquid drop are retained, while the optical path is increased to over 7 times of that of a traditional liquid drop. The limits of detection for formaldehyde were found to be 0.05 µg/mL with the liquid drop, and 0.01 µg/mL with the pseudo liquid drop. The method was applied to the determination of formaldehyde in wastewater with satisfactory analytical results.