A method of testing the purity or stability to degradation of a sample of lamotrigine or a pharmaceutical dosage form comprising lamotrigine comprises assaying the said sample for the presence of a compound selected from 3-amino-6–1,2,4-triazine-5–one and N-5-amino-6–1,2,4-triazine-3-yl-2,3-dichlorobenzamide. Wireless local area network frequency band usage is modified based on the performance impact estimation and the state of the wireless cellular and wireless local area network connections. The system controller of the single-lens reflex camera extracts a part of the area in the captured image captured by the image pickup device, and records the image of the area in a memory card. In this way, the oxidation life under the contamination of water content is improved.