221-chapter-2~3

221-chapter-2~3 - Tools of the Trade Laboratory Notebook...

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Tools of the Trade Laboratory Notebook Objectives of a Good Lab Notebook (a) State what was done (b) State what was observed (c) Be easily understandable to someone else
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Laboratory Notebook Bad Laboratory Practice ( A Recent Legal Case) Medichem Pharmaceuticals v. Rolabo Pharmaceuticals Tools of the Trade Two Patents describe a method for making the antihistamine drug Loratidine ( Claritin) - US sales of $2.7 billion - the two patents are essentially identical - Medichem sued to invalidate Rolabo patent and claimed priority - Medichem had to prove it used the method to make loratidine before Rolabo did A co-inventor’s lab notebook was a primary piece of evidence to support Medichem’s claim - documented analysis of a sample claimed to be made using the patented method - NMR spectral data confirmed the production of loratidine The evidence was not enough to support Medichem's claim of reduction to practice - NMR data do not show the process by which loratidine was made - lab books were not witnessed Rolabo Pharmaceuticals won the case (and the rights to make Loratidine) because of problems with a Lab Notebook!! Nature Reviews Drug Discovery (2006) 5, 180
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Weight Measurements 1.) Analytical Balance (principal of operation): (i) sample on balance pushes the pan down with a force equal to m x g M is mass of object g is acceleration of gravity (ii) balance pan with equal and opposing mass Mechanical – standard masses Electronic – opposing electromagnetic force (iii) tare –mass of empty vessel (pan) Tools of the Trade Double-pan balance (a) balance beam suspended on a sharp knife edge (b) Standard weights are added to the second pan to balance sample weight (c) Weight of sample is equal to the total weight of standards m1 m2 l1 l2 m m
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Single-pan balance (a) balance beam suspended on a sharp knife edge (b) Sample pan is balanced by counterweights on right (c) Knob adjusted to remove weights from a bar above the pan (d) Pan is moved back to its original position and the removed weights equals the mass of the sample. Tools of the Trade Weight Measurements
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Tools of the Trade Weight Measurements Electronic balance (a) Uses electromagnetic force to return the pan to original position (b) Electric current required to generate the force is proportional to sample mass Determines amount of deflection of pan due to mass of sample Increase in current causes magnetic field that raises pan
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Tools of the Trade Weight Measurements 2.) Methods of Weighing: (i) Basic operational rules Chemicals should never be placed directly on the weighing pan - corrode and damage the pan may affect accuracy - not able to recover all of the sample Balance should be in arrested position when load/unload pan Half-arrested position when dialing weights - dull knife edge and decrease balance sensitivity accuracy (ii) Weight by difference: Useful for samples that change weight upon exposure to the atmosphere - hygroscopic samples (readily absorb water from the air)
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221-chapter-2~3 - Tools of the Trade Laboratory Notebook...

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