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About Recipe Maker (ver 1.0)


I) The Use of Recipe Maker II) A Note on Density and Volume III) A note on mixtures (ie dNTPs) IV) Conversions NOT attempted by program V) Calculations I) The Use of Recipe Maker
Scientific investigators and technicians need to be adept at calculating the amounts of stock materials needed to give the desired concentrations in the final reagent. Because a small error in calculation can result in an experiment's failure, or worse: unreproducible data, verification of such calculations is often sought. Recipe Maker was intended to fill the role of the guy at the next bench when he/she is too busy to check your calculations.
II) A Note On Density and Volume          To Top of Document
When a pure substance is measured by mass, Recipe Maker calculates its volume based on its density. If the user does not enter a value for density the program will assume a density of 1.0 g/ml. This is the density of water and will be too small for most crystalline substances. If the user does not enter a value for density, the calculated volume of solvent may be incorrect. There may also be a small change of combined volume upon solution. If the amount of pure substance is relatively small, the error will be insignificant. However, if a relatively large amount of pure substance is used in a solution, the value given by Recipe Maker for the volume of solvent should be used only as a rough guide. The author recommends the use of a volumetric cylinder to measure the final volume as the last of the solvent is added. The addition of acids and/or bases to adjust the solution's pH will also demand the use of volumetric cylinder to adjust the final volume.
NOTE: If the user enters a value for density but not for its units, g/ml is assumed.

III) A Note On Mixtures (ie: dNTPs)                    To Top of
At this time, Recipe Maker has no elegant way of treating mixtures. Except when the individual components all have the same concentration (ie: 10mM dNTPs), it might be best to designate mixtures in terms of X (as in 10X MOPS buffer).

IV) Conversions NOT attempted by Recipe-Maker:          To Top of Document
percentageactivity (U/vol, U/mass)
molarityactivity (U/vol, U/mass)
mass/volumeactivity (U/vol, U/mass)
activity (U/vol, U/mass)percentage
activity (U/vol, U/mass)molarity
activity (U/vol, U/mass)mass/vol
All of these conversions can be made (given the appropriate information). The author chose to leave these uncommon but critical calculations to the experimenter. The above conversions involving percentage are not attempted because the choice of meaning (g/100ml, parts/100) is ambiguous and should be left to the experimenter.
V) Calculations          To Top of Document
x(%)y(%)vol*(x/y) literssee below
x(%)y(g/l)vol*(x*10)/y liters1%=1g/100ml
x(%)purevol*(x*10) grams1%=1g/100ml
x(M)y(M)vol*(x/y) liters
x(M)y(g/l);z(MW)vol*(x*z)/y liters
x(M)pure;z(MW)vol*(x*z) grams
x(g/l)y(M)vol*x/(z*y) liters
x(g/l)y(g/l)vol*(x/y) liters
x(g/l)purevol*x grams
x(U/l)y(U/g)vol*(x/y) grams
x(U/l)y(U/l)vol*(x/y) liters
g/l = grams per liter.
M = moles per liter.
MW = molecular weight in grams/mole.
pure = a pure substance.
U/l = units per liter.
vol = desired volume in liters.

Note that the meaning of % has been inferred from the context. Thus if x% is desired and the stock is a pure substance or a solution with concentration expressed in g/l, Recipe Maker infers the user wants x grams/100 ml.

The calculations are based on stoichiometric multiplication: Determine what you want, then multiply it by one until it is expressed in terms of what you have. For example, if I want 500 ml of a 4 M solution of NaCl and I have a pure crystalline salt: Therefore I want: 0.5 liters * 4 moles/liter = 2 moles. Since I know that: 1 mole of NaCl = 58.44 grams, I can multiply 2 moles by 1: 2 moles * (58.44 grams/1 mole) to get 116.88 grams. The trick is to express 1 so that when you multiply, the units cancel each other:
For example, the factor 10 in entries 2 and 3 above derive from the conversion:
1% = 1g/100ml = (1g/100ml) * (10/10) * (1000 ml/1liter) = 10g/liter
Therefore: (10g/liter)/1% = 10g/%liter = 1

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