Results

In all cases, relative standard deviations did not exceed 10% and R² values were higher than 0.998. The purity of the moth repellent tablets was examined by comparing the response to that of a known standard solution. All tablets were found to be nearly 100% pure. Quantitation was based on extracted ions of m/z 128 naphthalene.

Fig. 1. Results of downward migrations of mothball repellent agents. Analyte concentration vs. the number of the cloth layer in the stack for the moth repellent agents

The concentration of the naphthalene remained nearly constant (at 150µg/g) throughout the stack with the exception of the top layer. This indicates that naphthalene approached equilibrium by saturating or nearly saturating the cloths in the stack. Therefore, naphthalene found in mothball can be transferred onto the clothes.

Fig. 2.Horizontal migration of the moth repellent agents

The concentration distribution decrease exponentially with distance from the position of the mothballs.  However, the concentration of the naphthalene released from mothballs can still be felt at a distance of 60cm.

Fig. 3. Indirect transfer experiments with the moth repellent agents

Naphthalene vapors are heavier than air. Thus,the observed concentration distributions is due the density of the chemicals in relation to that of the air. Concentration of naphthalene on the lower shelf is higher than on the upper shelf. The largest analyte concentration was found on the cotton cloths placed on the middle shelf, containing the mothball. As the shelves act as obstacles hindering vapor transport between the individual compartments defined by the shelves. As a result, the cloths placed on the middle shelf were exposed to moth repellent vapors for the longest time and adsorbed the largest amounts of the analytes.

Fig. 4.  Indirect transfer of the analytes to cloths placed on the middle shelf, with and without airing.

Airing the cloths for one-hour lowered the concentration of the repellent in the cloths. However, the residual concentration of the repellent agent was still high after this time. The results obtained indicate that one-hour airing is insufficient to significantly lower the concentration of the moth repellents.