Organic Analysis

Laboratory AnalysisForensic ScienceElements and CompoundsA. Matter - anything that has mass & takes up spaceB. Element - cannot be broken down into simpler substances by chemical meansC. Periodic table - chart of elements arranged in a systematic fashionD. Atom - smallest particle of an element that can exist and still retain its identity as that elementMixtures & CompoundsMixture Two or more substances that are mixed together, but not chemically combined. Examples of mixtures ...Air mixture of gasesBowl of cereal mixture of cereal and milkSoda pop mixture of soda syrup, water, and CO2 gasFog water suspended in airKool-Aid mixture of water, sugar, and flavor crystalsExamples of compounds ...Salt Sodium and chlorine combined chemicallyWater Hydrogen and oxygen combined chemically Carbon Dioxide Carbon and oxygen combined chemicallyCompounds Two or more elements that are chemically combined.

SolutionsSolutions are mixtures in which one substance is dissolved in another.Solutions have two parts: solute and solventThe solute is the substance that is dissolved.The solvent is the substance that does the dissolvingIdentify the solute and solvent in each solution ...SolutionSoluteSolventLemonadeSoda popOcean waterSolubility - A measure of how much of a given substance will dissolve in a liquid. A substance that does not dissolve in water is called insoluble. A substance that does dissolve in water is called soluble.The periodic table is a listing of all elements by increasing atomic number.

The vertical columns are called groups. There are 18 groups

The horizontal rows are called periods. There are 7 periods.6The periodic table can be separated into metals, nonmetals, and metalloids.

Metals are shiny, malleable, ductile, and good conductors of heat and electricity.

Nonmetals are not shiny, malleable, ductile, or good conductors of heat and electricity.

Physical statesSubstances change from one state to anotherPhase - a uniform piece of matter, different phases are separated by definite visible boundariesThere are four phases of matter: solid, liquid, gas, and plasma.

Phase Changes Physical ChangesEvaporation =

Condensation =

Melting =

Freezing =

Sublimation =Liquid -> Gas

Gas -> Liquid

Solid -> Liquid

Liquid -> Solid

Solid -> Gas Solidsparticles vibrate but cant move aroundfixed shape fixed volumeincompressible

Liquidsparticles can move around but are still close togethervariable shapefixed volumeVirtually incompressible

Gasesparticles can separate and move throughout containervariable shapevariable volumeEasily compressedVapor - gaseous state of a substance that is a liquid or solid at room temperature

Plasmaparticles collide with enough energy to break into charged particles (+/-)gas-like, variableshape & volumestars, fluorescentlight bulbs, TV tubes

Four States of Matter

Selecting an Analytical TechniqueNeed to know whether substance is organic or inorganicA. Organic - substance composed of carbon and hydrogenB. Inorganic - CO2 and all substances that lack carbonNeed to consider the need for qualitative and quantitative determinationOrganic AnalysisSpectrophotometryChromatographyGas Chromatography (GC)High Performance Liquid Chromatography (HPLC)Thin Layer Chromatography (TLC)ElectrophoresisSpectrophotometryAn analytical method for identifying a substance by its selective absorption of different wavelengths of lightMost applicable to organic analysisOptimum utilization requires that a material be in relatively pure state

ChromatographyOrganic mixtures are separated into their components by their attraction to a stationary phase while being propelled by a moving phase.Useful technique for purifying substances1st observed in 1803 by William Henry (Henrys Law)One phase is always made to move continuously in one direction over a stationary or fixed phaseIts like a race between chemical compounds.At the beginning, all substances are mixed together.As the race progresses, those that have preference for the moving phase will move faster and pull ahead of others.At the end, all the substances are separated.

Gas Chromatography (GC)separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phaseused widely because of its ability to resolve a highly complex mixture into its components within a time period usually measured in minutesis very sensitivesample must be vaporized and passed through heated tube

High-Performance Liquid Chromatography (HPLC)Different types of stationary phases (usually non- aqueous) with a liquid moving phasecan perform process at room temperatureused for organic explosives and drugs that are heat sensitiveThin-Layer Chromatography (TLC)incorporates solid stationary phase & liquid moving phase because most compounds are colorless, uses UV light to reveal those that fluorescecannot by itself provide absolute identification; has to be used in conjunction with other procedures to prove absolute identitypowerful tool for solving analytical problemsrapid and sensitiveminimal cost and space requirements

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Electrophoresisrelated to TLC in that it separates materials according to their migration rates on solid phaseuses electrical current instead of moving liquid phasecharacterization of proteins, enzymes, and DNA

Gas ChromatographyUsed to determine the chemical composition of unknown substances, such as the different compounds in gasoline shown by each separate peak in the graph below.

Paper ChromatographyCan be used to separate the components of inks, dyes, plant compounds (chlorophyll), make-up, and many other substances

Liquid ChromatographyUsed to identify unknown plant pigments & other compounds.

Thin-Layer ChromatographyUses thin plastic or glass trays to identify the composition of pigments, chemicals, and other unknown substances.Examples of ChromatographyPaper Chromatography LabObtain the supplies youll need.1 large beaker (or plastic cup)1 small beaker (or plastic cup) filled with water4 pieces of filter paper4 black markers for testing4 small pieces of masking tapePencil (to attach to the top of the filter paper)Permanent markerTimerWrite the pen number on a piece of masking tape with a permanent marker and place it at the top of the strip. Choose one of the testing markers and draw a thick line near the bottom of the filter paper - about inch from the bottom. Pour a small amount of water into the large cup and then hang the paper strip in the cup. Make sure the ink line does not touch the water only the bottom of the filter paper.Allow the water to move up the paper for 5 minutes and then remove the strip from the water. Hang it on the side of the table to dry. Follow these directions to test the other pens. PencilFilter PaperInkMarkTape Label with marker

Questions:What colors did your group observe in each of the black ink samples?

Do the colors occur in the same order on all the samples? Explain.

Did some ink samples not work? Why? Complete the chart on your worksheet and then answer the questions.Work with your group to identify the pens used for each of the Mystery Marks. 1st Test each of the Mystery Mark strips using the procedure from yesterday.2nd Compare your strips to the strips hanging in the classroom.3rd Write the number of the pen that you think matches each of the mystery marks in the space on your worksheet.4th Have your answers checked by the teacher. Keep trying until you are able to identify all 6 pens!

Pen A matches # _____Pen D matches # _____Pen B matches # _____Pen E matches # _____

Pen C matches # _____Pen F matches # _____

Chromatography ChallengeInorganic AnalysisCarbon does not appear among earths most abundant elements.Inorganics are also encountered as physical evidenceMetals in tools, coins, weapons, scrapingsPigments in paints and dyesExplosive formulationsPoisonsFor ID & comparison of physical evidence

The Emission Spectrum of ElementsElements selectively absorb and emit lightWhen the light passes through a prism, it is separated into its component colors or frequencies (emission spectrum).Types of emission spectrumsContinuous spectrumshows a continuous band of colors all blending into one anotherEx sunlight or light from incandescent bulb passes through a prism

Types of Emission Spectrum cont.Line spectrum 1. shows a series of lines separated by black areas 2. Each line represents a definite wavelength or frequency3. Ex light from a sodium lamp or mercury arc lamp

Emission Spectrographinstrument used to obtain and record the line spectra of elementsRequires: a means for vaporizing and exciting the atoms of elements so that they emit light a means for separating light into its component frequencies a means for recording the resultant spectrumUses in Forensics: Rapid comparison of the elemental composition of two or more specimens

Inductively Coupled Plasma (ICP) Emission SpectrometryIdentifies and measures elements through light emitted by excited atomsUses hot plasma torch instead of electrical arc to excite atomsHas been applied in the area of identification and characterization of mutilated bullets and glass fragments

Atomic Absorption SpectrophotometerWhen an atom is vaporized, it will absorb many of the same frequencies of light that it emits in an excited state.In this technique, the specimen is heated to a temperature that is hot enough to vaporize its atoms while leaving a substantial number of atoms in an unexcited state.Provides a determination of an elements concentrationUseful in detecting trace amounts of elementsDrawbacks:only one element at a time each time the proper lamp has to be selected to match the particular element under investigation

Origin of Emission & Absorption SpectraSubatomic particlesProton positive electrical charge; in nucleusNeutron neutral particle; in nucleusElectron negative charge; outside the nucleus# of protons = # of electrons in a neutral atom

Electrons and EnergyElectrons move around the nucleus and are confined to specific electron orbitals or energy levels.Atoms are most stable when all of the electrons are in the lowest possible energy orbitals.When the atom absorbs energy (heat or light), its electrons are pushed into higher energy orbitals. (excited state)Only a definite amount of energy can be absorbed when moving an electron from one level to another.

Elements are selective in the frequency of light they absorb.Energy levels determine the selectivity.If atoms are exposed to intense heat, energy is generated to push electrons into higher unoccupied energy levels.Normally, an electron does not remain in this excited state for long, but falls back to its original energy level. As it falls, it releases energy in the form of light.Because each element has its own characteristic set of energy levels, each will emit a unique set of frequency values providing a picture of the energy levels that surround the nucleus of each element.Neutron Activation AnalysisAtoms of the same element have the same number of protons. They do not always have the same # of neutrons.Atomic mass - the # of protons + # of neutronsIsotopes - atoms with the same # of protons but different # of neutronsMost elements have two or more isotopes, and most are stable.Isotopes that are unstable and decompose are considered radioactive.

RadioactivityAtoms having the same number of protons but differing solely in the number of neutrons are called isotopes.Most elements have two or more isotopes and most are stable.Isotopes that are unstable and decompose are considered to be radioactive.Radioactivity is the emission of radiation that accompanies the spontaneous disintegration of unstable nuclei.

RadioactivityTypesAlpha particles () composed of a helium nucleus; positive chargeBeta particles () electrons; negative chargeGamma rays () high energy form of electromagnetic radiation emitted by a radioactive element

Neutron Activation AnalysisThe technique of bombarding specimens with neutrons and measuring the resulting gamma-ray radioactivityAdvantage provides a non-destructive method for identifying and quantitating trace elementsIt has been employed for characterizing the trace elements present in metals, drugs, paint, soil, gunpowder residues, and hair.

X-Ray DiffractionTechnique for identifying crystalline materialsAs x-rays penetrate the crystal, a portion of the beam is reflected by each of the atomic planes. They interact with one another to form a series of light and dark bands known as a diffraction patternEvery compound is known to produce its own unique diffraction pattern, thus giving analysts a means for fingerprinting compoundsDrawback not very sensitive and often fails to detect the presence of substances comprising less than 5% of a mixture

The MicroscopeAn optical instrument that uses a lens or combination of lenses to magnify and resolve the fine details of an object

ImagesVirtual imageCan only be seen by looking through a lens and cannot be viewed directlyReal imageCan be viewed directlyTypes of MicroscopesMagnifying glassMagnification of 5-10 timesSingle lensCompound Light MicroscopeComparison MicroscopeStereoscopic MicroscopePolarizing MicroscopeMicrospectrophotometerScanning Electron Microscope (SEM)

Compound Light MicroscopeMagnification up to 1500 timesMultiple lensesObjective lens lower lens of a microscope that is positioned directly over the specimenEyepiece lenslens of a microscope into which the viewer looks, same as ocular lens

Mechanical systembase support on which instrument restsarm C-shaped/handle/supportstage horizontal plate upon which specimens are placed for studybody tube hollow tube on which objective and eyepiece are mounted at opposite endscoarse adjustment focuses lensesfine focus focuses but on smaller magnitude

Optical systemIlluminatortransmitted illumination light that passes up from condenser and through specimenvertical or reflected illumination illumination of a specimen from aboveCondenser collects light rays from illuminator and concentrates them onto specimenObjective lens lens closest to specimenmost microscopes are parfocal when an image is focused with one objective in position, the other objective can be rotated into place and then the field will remain in focusEyepiece or ocular lensmonocular one eyepiecebinocular two eyepieces

Optical system (cont.)Magnifying power: power of objective lens x power of eyepiece lensNumerical apertureThe ability of an objective lens to resolve details into separate images instead of one blurred image is directly proportional to the numerical aperture.Ex. A lens with a NA of 1.30 can separate details that are twice as close as compared to lens with NA of 0.65. Field of viewthe area of the specimen that can be seen after it is magnifiedas magnifying power increases, field of view decreasesDepth of focusthe thickness of a specimen entirely in focus under a microscopedecreases as magnifying power increases

Comparison MicroscopeTwo compound microscopes combined into one unitUses a bridge incorporating a series of mirrors and lenses to join themVery useful in forensic science when side-by-side comparisons are necessaryVertical or reflected illuminationUsed when comparing bullets, cartridges, other opaque objectsTransmitted illuminationCompare hairs or fibers

Stereoscopic MicroscopePower of 10x to 125xCan present a 3-D image of objectFormation of right side up imageVery frequently used in crime labWide field of view and great depth of focusUsed often for examination of paint, soil, gunpowder residues, marijuana, etc.

Polarizing MicroscopeWhen a beam of light passes through certain types of substances, it emerges vibrating in only one plane.Plane-polarized light: Light confined to a single plane of vibrationPolarizing Microscope (cont.)Polarizer: Device that permits passage of light waves vibrating in only one planeSecond polarizing crystal analyzerCan modify stereo or compound microscopes so they can detect polarized lightApplication study materials that polarize light ex. Birefringent substancesMicrospectrophotometerAn instrument that links microscope to a spectrophotometerSpectrophotometer - an instrument used to measure and record the absorption spectrum of a chemical substanceAllows better comparison of substances

Scanning Electron Microscope (SEM)Image is produced by aiming a beam of electrons onto the specimen and studying electron emissions on a closed TV circuit or computerHigh magnificationHigh resolution

Scanning Electron Microscope (SEM) (cont.)High depth of focusUsed as tool for determining whether or not a suspect has recently fired a gunX-ray analyzer