Question

How do I prepare the four standards?

Materials

Methanol

200. ppm w/v nicotine stock in methanol

250. ppm w/v quinoline stock in methanol

Standard Preparation

Prepare four standards using methanol as the dilution solvent. These standards should be prepared directly in GC vials assuming additivity of all solutions (use micropipets). The final volume of each should be 1.00 mL. The nicotine concentration should vary as follows: 10.0, 20.0, 30.0, 40.0, and 50.0 ppm w/v. The quinoline concentration should be 25.0 ppm w/v for each standard. Create a table that clearly shows what volume of each stock and methanol needs to be added to create these standards.

Answer 1

Ans. # Quinoline Standard:

Given, stock [Quinoline] = 250.0 ppm w/v

            Required standard [Quinoline] = 25.0 ppm, w/v

            Final volume of standard to be made upto = 1.0 mL = 1000.0 uL

Now,

            Using C1V1 (stock soln) = C2V2 (standard solution)

            Or, 250.0 ppm x V1 =25.0 ppm x 1000.0 uL

            Or, V1 = (25.0 ppm x 1000.0 uL) / 250.0 uL

            Hence, V1 = 100.0 uL

Hence, required volume of the stock solution = 100.0 uL

# Required volume of Methanol solvent = Final volume of std. soln. – Vol. of stock soln

                                                = 1000.0 uL – 100.0 uL

                                                = 900.0 uL

# Nicotine Standard: Nicotine standards are prepared similarly. The result is tabulated below-