Hi,
Im trying to do my lab work.
I have 1mL of nicotine (possibly 2mL) and I need to make some dilutions to make a calibration curve on UV-VIS 1800.
I have been told to mix the nicotine with HPLC grade water but im not sure how. Due to the quantity of nicotine, i know it will require a serial dilution but im not sure on any of the numbers
any help will be appreciated,
thanks!
EDIT: The cuvettes are 3mL on the UV-VIS and I need roughly (this is adaptable) the following concentration. Also, the concentration needs to cover 20 - 24 mg/ml nicotine as the highest really. (its being compared against e-liquids)
Its impossible! We need more information like the initial concentration of the standard in mg/mL. For 3 mL cuvette you will probably use 5.0 or 10.0 mL glass volumetrics. Thus,
Serial Concentration (mg/mL) = y initial concentration (mg/mL) x [ mL volume/5.0 mL Volumetric]
The initial concentration of the nicotine standard is 98mg/mL I believe? Does that help at all. The problem I am having it with the quantity of nicotine as it is so small and I cant have more.
I have plentiful HLPC grade water though
You would have to use a micropipette, which usually delivers volumes in uL (1/1000 mL). Thus 100 uL is 0.10 mL. As an example;
98 mL/mL x 0.10 mL/5.0 mL = 1.96 mg/mL
You say that the volume of your cuvette is 3mls - is it a semi-micro cuvette with a maximum capacity of 3mls, or is that the minimum volume that you can measure? You should check the height of your light path (can be done with water), so that you know the minimum volume that you can use to measure your samples without risk of interference by the air-liquid interface at the surface of your sample. The construction of the standard curve, to give your maximum standard concentration is easy, if you just want it to be around 24mg/ml: a 1 in 4 dilution of 98mg/ml nicotine would give you 24.5mg/ml - so you could dilute 1.5mls of your stock with 4.5mls HPLC grade water, then make further stepwise dilutions of the resulting 6mls of 24.5mg/ml nicotine. If your cuvettes are semi-micro ones, then you should be able to make each subsequent dilution up to a total volume of 1000ul, mix well, then add 800ul to your cuvette (excluding bubbles) to obtain your absorbance reading. Alternatively, you could alter the dilution to give 'nicer' numbers for your standard curve, eg: 25mg/ml (1.5mls of 98mg/ml nicotine stock, made up to a total of 5.88mls with water) or 20mg/ml (1.5mls of 98mg/ml nicotine stock, made up to a total of 7.35mls with water)for your maximum concentration, with dilutions then possible at
1-5mg/ml steps.
It might also be useful to convert your concentrations to molarity:-
Mwt Nicotine=162.236 g/mol; so 1M=162.236mg/ml;
Therefore, your 98mg/ml divided by 162.236 = 0.6041M
I hope this is of some help.
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