Quiz 3 - New Perspectives in Forensic Science

Lecture 5, 6, and 7

What can nutritional deficiency lead to?

Pathophysiological conditions

What is involved in forensic elemental analysis?

Drugs, medicine, environmental quality and impact, potential biomarkers

What are the potential biomarkers of meth users?

Fe, Cu, Cr, and Se
→ Higher levels of Cu have been shown in previous studies

What are common elemental analysis techniques?

AAS, AES, inductively coupled plasma-MS, X-Ray fluorescence spectroscopy

What is atomic spectroscopy?

Quantitative and qualitative technique used to determine types of elements from samples that are decomposed via flame, furnace, or plasma

→ IWhatnvolve the measurement of absorbed or emitted radiation at a particular wavelength rather than recording spectra

What is the difference between AAS and AES?

AAS → Atoms absorb a fraction of light from the source and the rest reaches the detector

AES → The emission that results is from the loss of energy by atoms in a thermally excited state

What is LIBS?

A type of AES called laser-induced breakdown spectroscopy

→ Uses a high-energy pulsed laser as an excitation source

What is AAS used for in forensics?

1. Glass analysis

2. Gunshot residue (Samples dissolved with HNO3)

3. Toxicology (AES is also used)

What is ICP-AES/ICP-OES?

Uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element

How is ICP-AES used in forensics?

For food items with heavy metals, wines, oils and trace metals bound to proteins

What is ICP-MS?

Detects metals and non-metals at low concentrations by ionizing the sample with ICP and then analyzing those ions

Why is LA-ICP-MS good for glass analysis?

Avoids complete destruction of the specimen and the use of hazardous reagents

What can LA-ICP-MS be used for in forensics?

1. Glass analysis

2. Paints (Qualitative and semi-quantitative)

What type of ICP is used for GSR analysis?

ICP-MS for damaged bullets, analyze Sb/Pb ratio, and Pb composition

What is X-Ray fluorescence spectroscopy?

Non-destructive technique that uses an X-ray photon to strike an atom, dislodging an electron from one of its inner shells, in which excess energy is released

→ X-ray fluorescence peak can be correlated to a specific element

What is a K_α X-ray?

Excess energy released when atom fills the vacant K shell with an electron from the L shell, and the electron drops to the lower energy state

What is a K_β X-ray?

Excess energy released when atom fills the vacant K shell with an electron from the M shell, and the electron drops to the lower energy state

What can X-ray fluorescence be used for in forensics?

1. Glass analysis

2. GSR particles

3. Rock and soil analysis

4. Determine purity of element

What is nanotechnology?

The science of designing, producing, and using structures and devices having one or more dimensions of about 100 millionth of a millimeter (100 nanometers) or less

What are the three types of nanotechnology?

Natural, Incidental, and Engineered

Why is nanotechnology used in forensics?

Due to its low detection limits, detection of minute variations, and analysis of physical evidence on the nanoscale

How can nanotechnology be used for explosive evidence?

Can detect specific explosives, and nanoparticulate colloids via SERS 

How can nanotechnology be used for fingerprint detection and visualization?

Can enhance latent fingerprints
→ Photoluminescent CdS semiconductor nanocrystals capped with dioctysulfo-succinate

→ ZnO-SiO₂ nanopowder

What surfaces can SPR be used on?

Semi-porous and non-porous surfaces

What type of evidence can be detected with nanotechnology?

1. Explosives

2. Fingerprints

3. Counterfeits

4. Drugs

5. DNA

6. PMI (Up to 96 hours)

7. Hair, fiber, and document analysis (Nanoscope AFM)

What is the general principle of chromatography?

There is a phase that is held in place (stationary phase), while the other moves past (mobile phase)

What can the stationary phase be made up of?

Solid particles or liquid bonded to the inside of a capillary tube/surface of solid-packed column

What is paper chromatography?

Simplest technique that uses cellulose paper as the separation medium

How do you calculate Rf?

Rf = Distance moved by compound/distance moved by solvent

How can you potentially use paper chromatography to identify compounds?

Calculating the Rf distance

What conditions can influence the Rf value?

pH, solvent used, etc.

What is TLC?

Stationary phase is coated on a plate and sample is spotted on one end, and the mobile phase is a liquid organic solvent; the distance travelled is characteristic to a compound

Why should the origin spots be placed above the solvent level in the chamber in the case of thin layer chromatography?

If the spots are submerged in the solvent, they may be washed off the plate before separation can occur

Why is a UV light used on TLC plates?

To determine how far the compound travelled

What are some applications of TLC in forensics?

1. Drugs

2. Inks

3. Fiber dyes

4. Most commercial explosives

What is gas-liquid chromatography?

Stationary phase is a high-boiling point liquid absorbed into a solid, and mobile phase is a carrier gas (e.g He)

What is gas chromatography (GC)?

Involves the introduction of a gaseous or vaporized sample into a long column where the compounds with the sample are separated

→ Retention time can be used to identify the compound

What is retention time?

Time it takes for a compound to reach a detector

What are the types of GC detectors?

Flame ionization and thermal energy analyzer

What type of plot is generated from a GC?

Plotted as a function of time to produce a chromatogram, in which the peaks are compared to databases to identify the compounds

What does GC require?

Compounds to be thermally stable and volatile

What are some applications of GC?

1. Drug analysis and profiling

2. Body fluid analysis

3. Drug analysis from hair samples (in tandem with MS)

4. Fire/arson (accelerants)

5. Post-blast debris

What is 2D chromatography?

When two different chromatographic columns are connected in sequence and the effluent from the first system is transferred to the second column

What are applications of 2D gas chromatography?

Illicit drugs, fingerprint residue, chemical, biological, nuclear, and radioactive substances, toxicological evidence, odor decomposition, and petroleum analysis for arson investigations and oil spill tracing

Why is 2D gas chromatography useful?

Increases separation and detectability of analytes

What is liquid chromatography?

Components within a mixture are separated in a column based on each component's affinity for the mobile phase

What is HPLC?

Same as LC, but a solvent is forced through a column of small particles

What is ion chromatography?

Based on an attraction between solute ions and the charged sites bound to a stationary phase, and is used to separate charged compounds

What is the stationary phase in IC?

Ion exchange resinW

What does IC detect?

Anions, including nitrate, chlorate and perchlorate, and cations, such as ammonium, potassium and sodium

What is IC suitable for?

Analysis of inorganic pre-and post-blast explosives at the ppm level

What is capillary electrophoresis?

Involves the migration of ions in solution under the influence of an electric field
→ Rate of migration depends on the charge and the size of the molecule

What is the voltage range of CE?

10-30 kV

What is CE used for in forensics?

1. Drug analysis

2. Drug profiling

3. Toxicology (Blood and urine)

4. Hair drug test analysis

5. Explosives

6. GSR

What are the two commonly used methods of CE?

CZE and MECC/MECK

What type of buffer is used in CZE?

Continuous buffer

What is MECK?

Separation principle is based on the differential migration of the ionic micelles and the bulk running buffer under electrophoresis conditions and on the interaction between the analyte and the micelle

What does MECK separate?

Electrically neutral analytes