EXPERIMENT 2

THE DETERMINATION OF NICOTINE IN TOBACCO: A NON-AQUEOUS ACID-BASE TITRATION

 

Objective:  To quantitatively determine the amount of nicotine present in the tobacco of commercial cigarettes.

Introduction

The theory applied to acid-base titrations can also be applied to non-aqueous acid-base systems.  For example, cigarettes contain several organic bases known as alkaloids  Nicotine is the most well known and abundant of these alkaloids and it has a molecular weight of 162.12 g/mol.  In fact 90% of the alkaloid content in cigarettes is from nicotine or nornicotine.

 

In water the basicity of nicotine is too weak to permit an accurate acid-base titration.  However, in an acidic non-aqueous solvent such as acetic acid, nicotine is readily quantitated by an acid base titration according to the following equation:

 

Experimental

Reagents

Stock (ca. 0.2M) HClO4/HC2H3O2 solution

Dried glacial acetic acid

Ba(OH)2, granular

Ba(OH)2  saturated solution

KHP, (potassium hydrogen phthalate- 204.22g/mol) oven dried for 1-2 hours at 110oC

Crystal violet indicator

Tobacco (6-9 cigarettes minus the paper and filters)

Toluene

Acetone, for drying glassware

 

Equipment

7 – 250 ml Erlenmeyer flask

1 – 100 ml graduated cylinder

2 – 100 ml volumetric flask

1 – 100 ml pipet

1 – 50 ml pipet

1 – 25 ml pipet

1 –20 ml pipet

Whatman No. 2v folded filter paper

Waste bottle located in the laboratory hood

 

Timesaver Hint:  Perform Part B Steps 1 and 2 as your first step in this experiment. By doing this step first, you can perform Part A while the twenty minute process of stirring is underway.

 

Procedure

Part A:  Standardization of  HClO4 in acetic acid

 

1) Obtain 100 ml of the 0.2M stock  HClO4/HC2H3O2 solution and dilute it to to 200 ml with dried glacial acetic acid. The result is an approximately 0.1M HClO4 stock solution.  The question arises: what is the exact concentration?  Is it 0.0987M or perhaps 0.101 M ? The purpose of Part A of the procedure is to standardize this solution or determine the EXACT concentration.

 

2) Into three separate Erlenmeyer flasks (250 mL) weigh 0.2xxx g sample of KHP.  Be sure to record these values in your notebook. To each flask add 50 ml of dried glacial acetic acid.  Carefully heat until the KHP dissolves. Cool the solutions to room temperature.

 

3) Add 4-5 drops of the indicator crystal violet to 1 flask and titrate from the burette filled with the 0.1 M stock solution of HClO4.  A sudden color change (blue-violet to greenish-yellow) will occur to indicate the end of the titration.  Please note that this color change occurs within one drop from the burette. Record in your notebook the exact volume of HClO4  expelled from the burette.  Use this information to calculate the exact molarity of the 0.1 M HClO4 stock solution.

Repeat step 3 for the two remaining flasks.

 

4) Into a clean and DRY 100.ml volumetric flask pipet 25.00 ml of the 0.1 M HClO4 stock solution. Dilute to the mark with dried glacial acetic acid. Using your results from step 3, calculate the molarity of this diluted HClO4 solution.

 

Part B: Determination of Alkaloids in Tobacco as Nicotine

 

1)      Into an Erlenmeyer flask accurately weigh a 6.xxxx g sample of tobacco (6-9

cigarettes without the paper and filter components.)  Record this data in your lab notebook as well as the brand name of the cigarettes.

 

2) To the flasks add approximately 50 ml of the saturated aqueous Ba(OH)2  solution  and 2 g of granular Ba(OH)2. Insure that the tobacco is thoroughly wetted. Into the flask pipet 100.00 ml of toluene, add a stirring bar, stopper the flask, and magnetically stir for 20 minutes.

 

3)      After 20 minutes filter most of the organic layer through a whatman No.2v folded

filter paper and into another clean, DRY Erlenmeyer flask. The aqueous layer should not be poured into the filter.

 

4) Into a clean, DRY Erlenmeyer flask pipet 20.00 ml of the filtered solution. Add 4-5 drops of crystal violet indicator. Using your burette filled with your standardized HClO4 titrate to the characteristic greenish yellow endpoint. Repeat Step 4 two more times for reproducibility

 

 

 

DATA SHEET

THE DETERMINATION OF NICOTINE IN TOBACCO: A NON-AQUEOUS ACID-BASE TITRATION

 

Part A:  Standardization of  HClO4 in acetic acid

(30 points)                                                                              

Weight of KHP (g)                                                                                                    

                                            (1)                                 (2)                                (3)

 

Initial Reading          Final Reading Volume of HClO4                   Conc of

(ml)                              (ml)                              (ml)                                          HClO4 (M)     

 

(1)                                                                                                                                           

 

(2)                                                                                                                                           

 

(3)                                                                                                                                           

 

Average Molarity of HClO4  after 3 runs                                       

Standard Deviation                                                                           

95% Confidence Interval                                                                 

 

Molarity of HClO4 after dilution                                                      

 

 

Part B: Determination of Alkaloids in Tobacco as Nicotine

(40 points)

Weight of tobacco (g)                                                            

 

Initial Reading          Final Reading Volume of HClO4                   Weight %

(g)                                (ml)                              (ml)                                                     

                                                                                                                                               

 

                                                                                                                                               

 

                                                                                                                                               

 

Average Weight Percent                                                      

Standard Dev iation                                                              

95% Confidence Interval                                                     

 

Cleanup (10 points):                                                              

 

Notebook (20 points):                                                                                                                              

Final Grade:                                                  

 

LEAD sheet for Group Leaders:

 

Collect all of the weight percents of nicotine in the tobacco samples throughout the lab.  Determine the 95% confidence interval limits and the average weight percents of all results submitted. 

Can any statistical tests be performed to remove results that appear to deviate from the “norm?”

 

 

Are there any trends in the data.  Does one brand have a higher amount of nicotine over the other brands?  Are the results accurate?  Are the results precise?

Could you perform this test on “the patch”?  How would the experiment have to be altered?