Analysis and Screening of Volatile Organic Compounds in Solvent-Based Coatings by Thermal Desorption-Gas Chromatography-Mass Spectrometry

To inspect the liberation of volatile organic compounds (VOCs) of solvent-based coating into air of our residence, a climate chamber of 1 m³ with its chamber temperature of (23±2) ℃ and relative humidity of (50±5) % and rate of air ventilation of once an hour was used to simulate actual enviromental condition. And about 10 g of coating sample was applied onto the surface of a piece of toughened glass (30 cm×30 cm), which was placed into the climate chamber. An aged Tenax TA absorption tube was used to collect air sample from the climate chamber by connecting one of its terminal which was nearer to the absorbent to the chamber and the other terminal to the sampler. The sampler was adjusted to work at air flow-rate of 0.20 L·min^-1 and a sample of 2 h flowing was collected for analysis. The absorption tube, by which VOCs in air were absorbed, was placed into the instrumental system of thermal desorption-GC-MS. The analytes on the absorbent were thermodesorbed and separated by passing through the HP-VOC chromatographic column under the mode of constant pressure and programed temperature elevation between 35 ℃ to 250 ℃, and then determined by MS under the modes of EI and whole scanning. As shown by the results, among the 65 VOCs, CH₂Cl₂, CCl₄ and glycol gave only weak signals, and linearity of their standard curves were not so good, while linearity of standard curves of the remaider 62 VOCs were quite good and were found same between 0.01, 0.20 μg, with their limits of detection (3S/N) in the range of 0.018-0.25 μg·kg^-1. Recoveries of the 62 VOCs were tested by standard addition method, giving results in the range of 85.0% to 116%. 8 solvent-based coatings obtained in the market were screened and analyzed by the present method, and 4 categories of VOCs, i.e., the aromatic series, alcohols, alkanes, ethers and esters, were inspected with high frequencies; and as shown by the contents of VOCs determined, among the VOCs liberated, the aromatic series, esters and ethers constituted the great majority. Amounts of VOCs liberated from the 2 h-samples of the 8 coatings were as follows: 2.51, 2.29, 1.54, 1.47, 1.64, 13.01, 3.37, 17.14 mg·kg^-1.