Question 1: Chromatography is a technique used to separate mixtures into their individual components based on differences in their movement through a stationary phase under the influence of a mobile phase. It is widely used in forensic science to analyse substances such as drugs, toxins, and inks.

Answer: Chromatography separates mixture components based on their differing affinities for stationary and mobile phases, allowing analysis of complex samples.

Question 1: Define the term 'retention factor' (Rf) in chromatography.

Answer: The retention factor (Rf) is the ratio of the distance travelled by a substance to the distance travelled by the solvent front in chromatography.

Question 2: Explain why different substances in a mixture travel different distances during chromatography.

Answer: Different substances travel different distances because they have varying affinities for the stationary and mobile phases, affecting their speed of movement.

Question 1: A substance travels 3.5 cm in a chromatography experiment, while the solvent front moves 10 cm. Calculate the Rf value of the substance.

Answer: Rf = 0.35

Question 2: If a pure drug sample shows an Rf value of 0.45 in a specific solvent, but a sample from a crime scene shows an Rf of 0.60, what could this indicate about the sample?

Answer: It suggests that the sample from the crime scene may be contaminated, mixed with other substances, or has a different composition.

Question 1: Describe the key safety precautions that should be taken when performing chromatography in a forensic laboratory setting.

Answer: Wear protective gloves and goggles, handle chemicals in a well-ventilated area, and dispose of solvents and samples according to safety protocols.

Question 2: Identify the variables that must be controlled to ensure reliable chromatography results in forensic analysis.

Answer: Variables include the type and volume of solvent, temperature, stationary phase consistency, and sample application method.

Question 1: A forensic scientist analysed two ink samples from different pens found at a crime scene. Sample A has an Rf value of 0.43, and Sample B has an Rf value of 0.44 in the same solvent. What can be inferred about these samples?

Answer: The similar Rf values suggest that the inks are likely from the same or very similar sources, indicating a possible link to the same pen or ink batch.

Question 2: If a sample's Rf value deviates significantly from the expected value, what potential issues could this indicate?

Answer: Potential issues include contamination, improper sample preparation, differences in solvent composition, or experimental error.

Question 1: Describe how chromatography is used in the pharmaceutical industry to ensure drug purity.

Answer: Chromatography is used to separate and identify components in drug formulations, ensuring they meet purity standards and are free from contaminants.

Question 2: Explain the importance of chromatography in monitoring environmental pollutants.

Answer: Chromatography allows detection and quantification of pollutants in air, water, and soil, helping to assess environmental safety and enforce regulations.