Cause of Death

Cause of Death

Toxicology is the science that deals with poisons and their effect on the body. In this activity you will investigate four possible causes of death, lead or mercury poisoning, aspirin overdose, and diabetes. On the bases of toxicological evidence a forensics scientist may be able to decide whether the death is due to natural causes, an accident, suicide, or homicide.

Mercury Poisoning: Mercury in the body causes damage to the proximal renal tubules in the kidneys and cause the excretion of large amount of the amino acid glycine in the urine.

Lead Poisoning: Lead in the body causes damage to the proximal renal tubules in he kidneys and cause the excretion of large amount of the amino acid methionine in the urine.

Aspirin Overdose: Aspirin, acetysalicylic acid, can cause poisoning and result in death, especially in children. Aspirin is hydrolyzed in the body to produce salicylic acid and acetic acid.

Diabetes: It is uncommon but possible for sudden death to occur due to diabetes. This is caused when the body is unable to control the amount of sugar, glucose, in the blood. When blood sugar reaches a high level, toxic substances are produced, causing sickness and sometimes death. At the same time, large amounts of sugar are excreted in the urine. This presence of sugar is an indicator of diabetes.

Purpose: In this lab you will test sample solutions for the presence of glycine, methionine, salicyic acid and sugar. You will also test an unknown sample.

Procedure:

Part I Testing for Lead and Mercury using Paper Chromatography

Touch the paper only at the edges to avoid contamination

1. On a piece of chromatography paper draw a pencil line 2 cm from and parallel to the bottom of the paper. (don’t use a pen)

2 cm

2. Along the line place a small “x” 3.0 cm from each side and two additional “x”s evenly spaced between the outer two. Label each “x”, Gly, Meth, Unk, Mix

3. Apply small spots of the glycine, methionine, unknown, and mixture of glycine and methionine using a capillary tube. Let each drop dry before applying a second spot.. Dry with a hair dryer. Keep the spots smaller that .75 cm.

4. After the spots are dry, roll the paper into a cylinder with the spots to the outside. Staple the sides together without overlap. The lowest staple should be even with the pencil line at the bottom of the paper.

5. Add 15 mL of the solvent solution to the chromatography chamber so that the depth is BELOW the pencil line at the bottom of the paper when the chromotography paper stands upright on the bottom of the chamber. Do Not Move the Chamber. Cover with plastic wrap. Leave it in the chamber until the solvent reaches within an inch of the top of the paper. (About 20 minutes)

6. Go to Part II and return in 20 minutes

7. Remove the paper from the chamber and pencil mark the point at which the solvent reached. Initial your chromatography paper and take it to the drying area. A lab assistant will dry and develop your print.

8. Go to Part III. Return and pick up your developed print after completing Part III

9. Calculate the R_f value for each spot that appears on your chromatogram by measuring the distance the spot traveled divided by the distance the solvent traveled.

R_f= .85/3.8

= .22

Part II Testing for sugar

10. Place 10 drops of your sample in a small test tube. To this add 20 drops of Benedict’s solution. Heat the test tube in a boiling water bath for 5 minutes.

11. Repeat the procedure with your unknown sample.

12. Record your observations.

Part III Testing for Aspirin

13. Place 10 drops of the aspirin solution in a small test tube . To this add 50 drops of FeCl₃ test solution.

14. Repeat with your unknown and record your results.

Name ____________________________________

Data Table

Part I

1. Sketch your chromotogram.

2. Calculate the R_f values for each spot.

Substance	Distance Traveled	R_f
Glycine
Methionine
unknown
mixture
Solvent		xxxxxxxxxx

3. Describe the results from the sugar test.

__________________________________________________________________________________________________________________________________________

4. Describe the results from the aspirin test.

__________________________________________________________________________________________________________________________________________

5. Unknown sample labeled __#_____ is _____________________.

6. Describe the evidence you used to draw your conclusion.

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Teacher Notes

Solution Preparation:

Glycine -- Add 1.0 grams of glycine to enough water to make 100 mL of solution

Methionine -- Add 1.0 grams of methionine to enough water to make 100 ml of solution

Aspirin -- Mix 60 mL water to 30 mL of ethanol and add 1.0 g of salicylic acid

or dissolve 10 aspirins in a mixture of 60 mL water and 30 mL ethanol. Filter solution

Glucose-- dissolve 10 grams of glucose in 100 mL of water

Benedict’s solution --

FeCl₂ solution -- Dissolve 2 grams of FeCl₂ · 4 H₂O in enough distilled water to make 100mL

Ninhydrin -- Add 0.5 g of ninhydrin in 100 mL of actone

Developing solution -- Add 125 mL of n-butaonl and 125 mL of distilled water and 60 mL of

glacial acetic acid. Shake thorouglhy in a separatory funel and use only the TOP LAYER

Set-up a drying station to collect the chromograms. An adult or student aid should dry the paper, add the ninhydrin, and dry the finished chromogram. The ninhydrin will stain you hands - wear gloves