Report Ld 50 of Cockroaches

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Pharmacology Report 1: Determination of an insecticide in cockroaches

Pesticides are toxic and go through many different testings and procedures before they are put on the shelf in various industries. One general method that is used to asses toxicity of pesticides before released for sale is the LD50 (Lethal Dose 50) method. This method is conducted by calculating the most accurate dose of toxin that will kill animals 50% of the time. Before determining an accurate LD50 of a chemical however, a range finding analysis of the chemical will be performed in order to calculate the most accurate LD50. Undergoing this procedure includes using a wide-spread range of concentrations which are mostly preformed at log dose intervals.
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Table 1.2 shows one of the greatest errors possibly in this experiment. The average weight lies at a range of 0.106g which speaking on the insect level is quite a significant number here. The method of weighing out the cockroaches was extremely inaccurate and in order to achieve an accurate LD50 an accurate weight is required as stated earlier. Also not all cockroaches were exactly 2cm in length as suggested by the method hence some cockroaches had a higher resistance to propoxur due to greater weight and size which meant consistency was not at all achieved.

Another reason why results may have varied from group to group could be due to miscalculations and human error while performing dilutions. Dilutions is a very important part of the experiment and if there was an error in one simple dilution then it could have carried on from tube to tube having detrimental effects on the concentrations of the solution being created.

Also application of the solution to the cockroaches was not an easy task, the cockroaches were able to move around and escape from containment prosing an extremely large problem because if the cockroach were to escape and become lost, the entire average weight would have to be changed. Preventing this setback happened to cause another dilemma, to slow down the cockroaches and comatose them freezing was applied. However if the

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