Loss on drying test

In loss on drying procedure ,why should the oven be waited till reaching the desired temperature
i mean cant we put the sample in oven before and leave it then start timing when temperature is 105 for example
(oven which i use has automatic timing )

Loss on drying test is to be performed at specific temperature and for specific time duration or untill you get constant weight. Therefore, if you strat this test while temp of the oven rises to the desired temperature, the duration of test would not be exactly the same as described in the test procedure (monograph).

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If the oven set point is 105 C, then during the temperature raising, oven temperature may cross the set point and it should be cooled down to desired set point to get the accuracy of results…After temperature stabilization onlt, LOD bottle to be put into oven…To get accurate result…

Ideally the oven when in operation should not cross the set temperature beyond limit, if it has been properly qualified including temperature mapping studies (under emptyand loaded conditions) to ensure that the heating is uniform across all the trays in the oven and that the temperature is within set limits.
Therefore, please ensure that oven is appropriately qualified and validated before being used for regular analysis of samples.