Forensic Analysis Demonstration Via Hawaii Five-O

Article excerpt

Byline: Brian R. Shmaefsky

Figure 1. Scientific vocabulary introduced during demonstration.

analyte-a substance detected, identified, or measured in the laboratory.

limitations-identification of all known limitations of an analytical procedure and its use.

sample-the subject of an analytical procedure. The sample in this case consists of a potential target analyte found in a mixture.

selectivity-the extent to which an analytical measurement is not altered by certain non-analytes in the mixture.

standard-a substance of known identity and purity used as a comparison for testing the analyte.

validation-an accepted process by which an analytical procedure is evaluated to determine its accuracy and fitness for its intended use.

Forensics, in its most universal sense, is defined as the use of science or technology in the investigation and establishment of facts or evidence for determining identity or relatedness. Most forensic reasoning is used for arguing legal matters. However, forensic studies are also used in agronomy, biology, chemistry, geology, and physics to identify the properties of materials or compare two different materials.

The interdisciplinary nature of a forensics-based demonstration encourages science majors to move beyond their own narrow fields of study. The demonstration described in this column emphasizes the interconnectedness of biology, chemistry, and geology. Forensics-based demonstrations such as this can also be used to introduce the protocols governing the application of discipline-specific information to other fields of study. Introducing fundamental science terminology can also be a teaching objective. The terms introduced during this demonstration are listed in Figure 1.

Linking the demonstration to a real-world scenario makes the science relevant and, therefore, more valuable to students. This demonstration asks students to determine the purported origins of three soils collected from three different regions on a Hawaiian island. Students are guided step-by-step through a forensic analysis procedure using two data sets for determining each sample's origin.

Materials

Figure 2. Soil map of Hawaii for projection to class. (University of Texas Libraries)

The following materials are needed to produce the artificial soils and test reagents for carrying out this demonstration:

Test reagents:

Bottle of universal pH indicator with dropper

Bottle of 3% hydrogen peroxide with dropper

Bottle of vinegar or dilute acetic acid with dropper

Bottle of pH 3 water or buffered solution (pH standard)

Bottle of pH 7 water or buffered solution (pH standard)

Bottle of pH 10 water or buffered solution (pH standard)

Small vial of powdered calcium carbonate

Small package of baker's yeast

Artificial soils:

Soil A-(Central mountain region of Hawaii) Homogenous mixture composed of 50 mL playground sand and 15 mL granulated.

Soil B-(Northeast coast region of Hawaii) Homogenous mixture composed of 50 mL playground sand and 5 mL yeast.

Soil C-(Far eastern coast region of Hawaii) Homogenous mixture composed of 50 mL playground sand, 10 mL powdered calcium carbonate, and 5 mL yeast.

Figure 3. Range of pH for universal indicator solution.

Demonstration materials:

6 petri plates

3 scoopulas or spoons

Computer with internet access linked to an LCD projector

Figure 2

Figure 3

Procedure

Start the procedure by describing to the class an engaging or humorous scenario in which three soil samples were collected from the island of Hawaii. Make the scenario relevant to a particular topic being covered in the lecture, such as the nature of matter, measures of metabolism. The job of the class is to perform three forensic tests to determine the probable locations of the soils based on an old soil map of Hawaii. …