Long term stability of benzo[a]pyrene in stored atmospheric particulate matter samples

An experiment was conducted to check the stability of benzo[a]pyrene in the atmospheric particulate matter samples collected on quartz glass fiber filters. Subgroups of each lot of samples were subjected to the following different storage conditions to be analyzed at yearly intervals: (i) 20°C under air, (ii) 20°C in argon gas, (iii) −20°C under air, and (iv) −20°C under argon gas. The concentrations of benzo[a]pyrene in the sample filters were measured after 0.5, 1, 2, 4 and 12 years storage. After 12 years, benzo[a]pyrene in the samples stored at 20°C decreased to about half of the initial value. In the samples stored in −20°C, on the other hand, the benzo[a]pyrene content was reduced by 12% indicating a temperature-dependent stability. Since the rate of decrease of benzo[a]pyrene after six months was nearly zero in the −20°C storage condition, and at least 85% was preserved, the samples can be used for the future analysis.