SAMPLING AND DETERMINATION OF FORMALDEHYDE USING SOLID-PHASE MICROEXTRACTION WITH ON-FIBER DERIVATIZATION

Gaseous formaldehyde is sampled by derivatization with o-(2,3,4,5,6-pe ntafluorobenzyl)hydroxylamine hydrochloride (PFBHA) adsorbed onto poly (dimethylsiloxane)/divinylbenzene solid-phase microextraction fibers. The product of the reaction is an oxime which is thermally very stabl e and insensitive to light. The oxime can be analyzed by gas chromatog raphy with name ionization detection and other detectors. Loading PFBH A on the fiber is by room-temperature headspace extraction from aqueou s solutions of PFBHA. The process of loading and desorption of unreact ed PFBHA, and oxime formed, is both highly reproducible and reversible , with more than 200 loading, sampling, and analysis steps possible wi th one fiber. The standard formaldehyde gas concentrations studied ran ged from 15 to 3200 ppbv with sampling times from 10 s to 12 min. Quan tification can be achieved via interpolation from calibration curves o f area counts as a function of formaldehyde concentration for a fixed sampling time. Sampling for 10 s yields a method detection limit of 40 ppbv and at 300 s the method detection limit is 4.6 ppbv. This is equ al to or better than all other conventional grab sampling methods for gaseous formaldehyde employing sampling trains or passive sampling tec hniques, Alternatively, gaseous formaldehyde can be quantified with an empirically established apparent rst-order rate constant (0.0030 ng/( ppbv s) at 25 degrees C) fdr the reaction between sorbed PFBHA and gas eous formaldehyde, This first-order rate constant allows for quantitat ive analyses without a calibration curve, only requiring detector cali bration with the oxime. This new method was used for the headspace sam pling of air known to contain formaldehyde, as well as other carbonyl compounds, and from various matrixes such as cosmetics and building pr oducts.