forensic chem 1

forensic chemistry

the application to analyze materials found at a crime scene, and figure out how they connect to the person who committed the crime.

60 % of Forensics Lab work is drugs

85-90% of all Criminal Cases involve drugs

Alcohol

the most popular psychoactive substance over the millennia.

Drug Classes

Opioids, Stimulants, Controlled Prescription Drugs, Marijuana, Psychoactive Substances

Psychoactive drugs

Any substance that directly alters normal functioning of the central nervous system. These drugs are described by their chemical, trade, and street names.

Physical Effects of Stimulants

• Energized muscles

• Increase in heart rate and blood pressure

• Insomnia

• Decrease in appetite

Mental/Emotional Effects of Stimulants

• Increased confidence

• Gives you a rush

• Anxiety, aggressiveness, paranoia, and psychosis

Physical Effects of Depressants

• Slows heart rate

• Relaxes and decreases inhibitions

• Dulls senses, sedates

• Sexual dysfunction

All Arounders: (psychedelics)

substances that can distort perceptions and induce illusions, delusions, or

hallucinations.

Illusions

a mistaken perception of an external stimulus (i.e. rope misinterpreted as a snake)

Delusions

a mistaken idea that is not swayed by person or other powerful evidence (someone thinking that they can fly)

Hallucinations

a sensory experience that does not come from external stimuli (seeing something that does not exist)

Physical Effects of Anabolic Steroid and Sports Drugs

• Increased muscle mass

• Acne

• Shrunken testes; masculinized women

Mental/Emotional Effects of Anabolic Steroid and Sports Drugs

• Confidence

• Rhoid Rage (outbursts of anger; temper tantrums)

Five common ways that drugs enter the body

1. Inhaling

2. Injecting

3. Mucous Membrane Absorption

4. Oral Ingestion

5. Contact Absorption

Inhaling

Acts more quickly than any other method of use (7-10 seconds before the drug reaches the brain and begins to cause changes).

Injecting

Intravenous, intramuscular, and subcutaneous (15-30 seconds intravenously, 3-5 minutes in a muscle or under the skin)

Mucous Membrane Absorption

Snorted in the nose, under the tongue, or between the cheeks and the gums (3-5 minutes)

Oral Ingestion

Absorbed in stomach (20-30 minutes)

Contact Absorption

Applied to the skin through saturated adhesive patches (1 to 2 days)

Physical addiction

causes withdrawl symptoms

Psychological addiction

Dopamine release; satisfies an emotional need

Psychological dependence

The conditioned use of a drug caused by underlying emotional needs.

Physical dependence

Physiological need for a drug that has been brought about by its regular use

Controlled Substances Act

serve to illustrate a legal drug-classification system created to prevent and control drug abuse.

Flexible

as the US attorney general has the authority to add, delete, or reschedule a drug as more information becomes available

This federal law establishes five schedules of classification for controlled dangerous substances on the basis of a drug’s

• potential for abuse

• potential for physical and psychological dependence

• medical value

Opiates/Narcotics

• Reduce sensation – sleep like state

• morphine, heroin, codeine, fentanyl

• Both physically and psychologically addictive

Stimulants

• Stimulates, speeds up, the central nervous system (CNS)

• high energy, euphoria

• amphetamines, cocaine, nicotine

• Psychologically addictive

Hallucinogens

• Alters perceptions, “gen”erates illusions

• LSD (acid), PCP(angel dust), MDMA (Ecstasy), Mescaline (peyote cactus), Marijuana (THC), hallucinagenic mushrooms (psilocybin)

• Most neither physical nor psychological dependence

Depressants

• Depress CNS, drowsiness, slowed response

• Barbiturates(Phenobarbital), Ethanol

• Valium (diazepam), Xanax (alprazolam)

• Physically and psychologically addictive

Schedule I

• No approved medical use

• Substances in this schedule have no currently accepted medical use in the United States, a lack of accepted safety for use under medical supervision, and a high potential for abuse.

Schedule II

• Medical use, severely addictive

• Substances in this schedule have a high potential for abuse which may lead to severe psychological or physical dependence.

Schedule III

Substances in this schedule have a potential for abuse less than substances in Schedules I or II and abuse may lead to moderate or low physical dependence or high psychological dependence.

Schedule IV

Substances in this schedule have a low potential for abuse relative to substances in Schedule III.

Schedule V

Substances in this schedule have a low potential for abuse relative to substances listed in Schedule IV and consist primarily of preparations containing limited quantities of certain narcotics.

Opioids

• Fentanyl (and other synthetic opioids) of highest concern

• Nearly 70% of overdose deaths

• Highly available

Analytical Methods of Drug Detection

Presumptive vs confirmatory tests

Presumptive Methods

• Determine presence or absence of drugs

• Used in forensic and clinical settings

• Low detection limits

• Simple to perform

Confirmatory Methods

• Determination of specific analytes

• GC/MS “gold standard”

• Confirmation vs identification

• Not necessarily finding all compounds present

Classical Qualitative

identification by color, indicators, boiling points, odors

Classical Quantitative

mass or volume (e.g. gravimetric, volumetric)

Instrumental Qualitative

chromatography, electrophoresis and identification by measuring physical property (e.g. spectroscopy, electrode potential)

Instrumental Quantitative

measuring property and determining relationship to concentration (e.g. spectrophotometry, mass spectrometry)

Radiation emission

Emission spectroscopy - fluorescence, phosphorescence, luminescence

Radiation absorption

Absorption spectroscopy -spectrophotometry, photometry, nuclear magnetic resonance, electron spin resonance

How reproducible?

Precision

How close to true value?

Accuracy/Bias

How small a difference can be measured?

Sensitivity

What range of amounts?

Dynamic Range

How much interference?

Selectivity

How many samples?

Efficience (time, money cost)

Precision

the reproducibility of a series of measurements.

Accuracy

How close a measured value is to the known or accepted value.

How to choose an analytical method?

How good is measurement?

Systematic Error

has a definite value and an assignable cause.

three common sources of systematic error

1. Instrument error

2. Personal error

3. Method error

Random Error

Uncertainty in a measurement arising from an unknown and uncontrollable source. (Also commonly referred to as Noise.)

Dynamic Range

At detection limit we can say confidently analyte is present but cannot perform reliable quantitation

Selectivity

No analytical method is completely free from interference by concomitants. Best method is more sensitive to analyte than interfering species (interferent).

Analyte

the substance being identified or quantified.

Sample

the mixture containing the analyte. Also known as the matrix.

Qualitative analysis

identification of the analyte

Quantitative analysis

measurement of the amount or concentration of the analyte in the sample.

Signal

the output of the instrument (usually a voltage or a readout).

Blank Signal

the measured signal for a sample containing no analyte (the sample should be similar to a sample containing the analyte)

standard

(a.k.a. control) is a sample with known conc. of analyte which is otherwise similar to composition of unknown samples.

blank

one type of a standard without the analyte.

calibration curve

a plot of signal vs concentration for a set of standards.

dynamic range

linear part of the plot

Linear regression

method of least squares) is used to find the best straight line through experimental data points

Limit of detection LOD

the conc. at which one is 95% confident the analyte is present in the sample.

signal

output measured as difference between sample and blank (averages)

limit of quantitation LOQ

the smallest conc. at which a reasonable precision can be obtained

Spectroscopy

The study of the interactions of electromagnetic radiation (radiant energy) and matter (molecules, atoms, or ions)

Spectrometry

Quantitative measurement of the intensity of one or more wavelengths of radiant energy

Spectrophotometry

The use of electromagnetic radiation to measure chemical concentrations (used for absorption measurements)

electromagnetic radiation

Also known as radiant heat or radiant energy

- One of the ways by which energy travels through space

Visible Light

VIBGYOR

Violet, Indigo, Blue, Green, Yellow, Orange, Red

400 – 750 nm

Wavelength (λ)

Distance for a wave to go through a complete cycle

(distance between two consecutive peaks or troughs in a wave)

Frequency (ν)

The number of waves (cycles) passing a given point in space per second

Cycle

Crest-to-crest or trough-to-trough

Speed (c)

All waves travel at the speed of light in vacuum (3.00 x 10^8 m/s)

Plane Polarized Light

Light wave propagating along only one axis (confined to one plane)

Monochromatic Light

Light of only one wavelength

Polychromatic Light

Consists of more than one wavelength (white light)

Visible light

The small portion of electromagnetic radiation to which the human eye responds

Inverse relationship between wavelength and frequency

c = λ ν

h

Planck’s constant (6.626 x 10^-34 J-s)

ν

frequency of the radiation

λ

wavelength of the radiation

E

proportional to ν and inversely proportional to λ

interactions with matter

- Takes place in many ways

- Takes place over a wide range of radiant energies

- Is not visible to the human eye

- Light is absorbed or emitted

- Follows well-ordered rules

- Can be measured with suitable instruments

Solids

Atoms or molecules are arranged in a highly ordered array (crystals)

or

arranged randomly (amorphous)

Liquids

Atoms or molecules are not as closely packed as in solids

Gases

Atoms or molecules are widely separated from each other

Many types of motion are involved

- Rotation

- Vibration

- Translation (move from place to place)

Atoms or Ions

Move between energy levels or in space but cannot rotate or vibrate

Light striking a sample of matter may be

- Absorbed by the sample

- Transmitted through the sample

- Reflected off the surface of the sample

- Scattered by the sample

Samples can also emit light after

absorption (luminescence)