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Introduction: Nowadays, p-dichlorobenzene (paradichlorobenzene, 1,4-dichlorobenzene) is becoming more popular than naphthalene as a moth repellant (insecticide) worldwide. The discrimination between p-dichlorobenzene and naphthalene is usually difficult only by their smells and their appearances. However, specific gravities of their crystals are different; they are 1.152 and 1.5 for naphthalene and p-dichlorobenzene, respectively. Therefore, when the crystals sink in NaCl-saturated water, it is estimated to be p-dichlorobenzene; while when they float in the same solution, it may be naphthalene [1]. Camphor also gives a similar aromatic smell and appearance, but its discrimination is even easier, because its specific gravity is only 0.99;. | 5.7 II.5.7 p-Dichlorobenzene by Kanako Watanabe Introduction Nowadays p-dichlorobenzene paradichlorobenzene 1 4-dichlorobenzene is becoming more popular than naphthalene as a moth repellant insecticide worldwide. The discrimination between p-dichlorobenzene and naphthalene is usually difficult only by their smells and their appearances. However specific gravities of their crystals are different they are 1.152 and 1.5 for naphthalene and p-dichlorobenzene respectively. Therefore when the crystals sink in NaCl-saturated water it is estimated to be p-dichlorobenzene while when they float in the same solution it may be naphthalene 1 . Camphor also gives a similar aromatic smell and appearance but its discrimination is even easier because its specific gravity is only 0.99 it floats in tap water. The weight ofp-dichlorobenzene being sold as a moth repellant is about 4 g the crystal mass of the same compound being used for a toilet mothball ranges from 40 to 200 g. Therefore when a large amount of this compound is ingested it is dangerous for life. Like naphthalene p-dichlorobenzene easily vaporizes from its solid into gas in this chapter a method for headspace GC MS analysis of p-dichlorobenzene is presented utilizing the volatile property. Reagents and their preparation i. Reagents p-Dichlorobenzene and p-dichlorobenzene-d4 product No. 32 933-9 a can be purchased from Aldrich Milwaukee WI USA . Other common chemicals used were of the highest purity commercially available. ii. Preparation p-Dichlorobenzene and p-dichlorobenzene-d4 solutions 2-mg aliquot each is dissolved in 1 mL methanol to prepare stock solutions. A 1-pL volume of each stock solution is injected into GC MS to record each mass spectrum. For spiked tests the above each stock solution is diluted 10-fold with methanol a different volume of the p-dichlorobenzene solution 1-10 pL containing 0.2-2 pg and 10 pL containing 2 pg of p-dichlorobenzene-d4 IS are placed in each glass vial with a Teflon-septum cap .
