273 Questions
Which of the following is a preliminary/presumptive test used in forensic toxicology?
Immunoassay
Which method is considered the 'gold standard' in drug confirmation?
Mass Spectrometry
What can cause drug degradation?
Exposure to heat or light
What is the purpose of liquid-liquid extraction in forensic toxicology?
To separate drug compounds from a sample
What is the main principle behind immunoassay in forensic toxicology?
Detection of drug compounds using antibodies
What type of spectroscopy is commonly used in forensic toxicology for drug analysis?
Infrared Spectrophotometry
Discuss the process of processing an unknown sample in forensic toxicology, from intake into the lab through the final confirmatory analysis.
The process of processing an unknown sample in forensic toxicology involves several steps. First, the sample is received and logged in the laboratory, ensuring proper chain of custody. Then, the sample is prepared for analysis, which may include extraction, purification, and derivatization. Next, preliminary tests are conducted to determine the presence of drugs or other substances. These tests can include color tests, immunoassays, or thin layer chromatography. If the preliminary tests indicate the presence of drugs, confirmatory analysis is performed using more specific and sensitive techniques such as gas chromatography/mass spectrometry (GC/MS) or high performance liquid chromatography/mass spectrometry (HPLC/MS). The final confirmatory analysis provides a definitive identification and quantification of the drugs present in the sample.
What can cause drug degradation? Why is this important?
Drug degradation can be caused by various factors such as exposure to light, heat, moisture, or chemical reactions. It is important to understand drug degradation because it can affect the stability, potency, and effectiveness of drugs. In forensic toxicology, drug degradation can also impact the accuracy and reliability of analytical results. Therefore, it is crucial to consider and control potential degradation factors during sample storage, handling, and analysis.
What are preliminary/presumptive tests in toxicology? Provide different examples and explain how they work in detail.
Preliminary/presumptive tests in toxicology are initial tests used to detect the presence of drugs or other substances in a sample. These tests provide a preliminary indication of the presence of specific classes of drugs but do not provide definitive identification or quantification. Examples of preliminary tests include color tests, immunoassays, and thin layer chromatography. Color tests involve the use of reagents that react with specific drugs to produce characteristic color changes. Immunoassays utilize antibodies that bind to specific drugs, leading to the formation of a detectable signal. Thin layer chromatography separates the components of a sample based on their different affinities to a stationary phase and a mobile phase, allowing for visual identification of specific drugs.
Explain the principles and working mechanisms of liquid-liquid extraction in forensic toxicology.
Liquid-liquid extraction is a sample preparation technique used in forensic toxicology to extract drugs or other compounds from a liquid sample into an organic solvent. It is based on the principle of partitioning, where the analyte of interest partitions between two immiscible liquid phases. The process involves adding the sample to an organic solvent and mixing them to allow for partitioning. After separation, the organic phase containing the analytes is collected for further analysis. The choice of organic solvent and extraction conditions, such as pH and temperature, can influence the efficiency and selectivity of the extraction process.
Describe the process and working principle of solid phase extraction (SPE) in forensic toxicology.
Solid phase extraction (SPE) is a sample preparation technique used in forensic toxicology to extract drugs or other compounds from a liquid sample. It involves the use of a solid sorbent, such as a solid-phase cartridge or disk, to selectively retain the analytes of interest while allowing interfering substances to pass through. The process begins by conditioning the solid phase with a solvent to remove impurities. The sample is then applied to the solid phase, and the analytes are retained while the unwanted substances are washed away. Finally, the analytes are eluted from the solid phase using a solvent, and the eluate is collected for analysis. SPE is based on the principles of adsorption and desorption, where analytes are selectively adsorbed onto the solid phase based on their chemical properties.
Explain the principles and working mechanism of gas chromatography (GC) and mass spectrometry (MS) in forensic toxicology. Why is GC/MS considered the 'gold standard' in drug confirmation?
Gas chromatography (GC) is a chromatographic technique used to separate and analyze volatile compounds in a sample. It involves the sample being vaporized and injected into a column packed with a stationary phase. The compounds in the sample then undergo partitioning between the stationary phase and a carrier gas, resulting in their separation based on their different affinities. Mass spectrometry (MS) is a technique used to identify and quantify compounds based on their mass-to-charge ratio. It involves the ionization of the separated compounds and the detection of their mass spectra. GC/MS is considered the 'gold standard' in drug confirmation because it combines the separation power of GC with the identification capability of MS. The GC separates the drugs in the sample based on their affinity to the stationary phase, and the MS provides specific identification of the separated compounds based on their mass spectra.
Which of the following factors can catalyze drug degradation reactions?
All of the above
Which type of drug is particularly susceptible to hydrolysis?
Drugs with an ester bond
What is the temperature dependence of reaction rates revealed through?
Arrhenius' equation
Which factor should be considered when making measurements during the examination of drug samples?
The accuracy and precision of the measuring device
What is the recommended storage temperature for biological specimens prior to testing?
Refrigerated
What is one of the biggest concerns in a forensic laboratory regarding sample analysis?
Sample contamination
Which of the following factors can affect the stability of a drug?
All of the above
What can be added to pharmaceutical preparations to prevent degradation of drugs?
All of the above
Which type of sample container composition should be considered to prevent interference with drug detection?
Teflon stoppers/caps
Which of the following is NOT a factor that should be recorded when acquiring seized drug samples for testing?
WeighWolume/Amount
What is the purpose of assessing all associated specimen documents when samples are submitted to a forensic laboratory for testing?
To verify the authenticity and integrity of the samples
What is the responsibility of the forensic laboratory in relation to the storage of submitted samples?
To store the samples in a secure manner
According to the text, what is the purpose of stability testing in the context of drug substances or drug products?
To establish a retest period or shelf life for the drug
According to the text, what are three factors that can influence the stability of a drug?
Temperature, humidity, and light
According to the text, what are three forms of drug contamination that can occur in a laboratory environment?
Contamination with impurities, degradation products, and adulterants
Which of the following is a disadvantage of color tests for drug identification?
Color tests are not specific to a single drug
Which of the following is an advantage of color tests for drug identification?
Color tests are quick
What is the name of the color test used to screen for opiate drugs?
Scott test
What color change would you expect with Ehrlich's reagent in the presence of LSD?
Purple
Why are color tests considered to be preliminary tests and not confirmatory drug identification tests?
Color tests are not specific to a single drug
Which of the following is NOT a type of trichome or hair that can be microscopically observed on the cannabis plant?
Stem hairs
Which cellular structures of cannabis are specific to the flowering and fruiting tops of the plants?
Glandular hairs
Which cellular features of cannabis do not contain cannabis oil?
Cystolithic hairs
What is the purpose of the Duquenois-Levine color test in analyzing suspected cannabis samples?
To identify the presence of THC
What are the three types of hairs or trichomes that can be microscopically observed on the cannabis plant?
Cystolithic hairs, glandular hairs, stem hairs
What are the two chemical substances involved in microcrystal tests?
Substance tested and test reagent
Which type of microcrystal test involves a color change or precipitate formation due to some change in the reagent caused by the test substance?
Indirect tests
What is the purpose of microcrystal tests in forensic drug identification?
To identify the presence of compounds that contain basic nitrogen and readily precipitate from aqueous solution
What is the most common type of reagent used in microcrystal tests?
Double chlorides
What is the range of quantities needed for the identification of alkaloids using microcrystal tests?
1 µg to 100 µg
What can cause supersaturation in microcrystal tests?
Evaporation of the solvent
What is the advantage of using microcrystal tests for preliminary drug identification in forensic cases?
Directness, simplicity, sensitivity, and rapidity of the technique
Which of the following is an advantage of microcrystal tests in forensic drug identification?
They are highly specific and sensitive
What is the main difference between direct and indirect microcrystal testing?
Direct testing involves the use of a reagent, while indirect testing does not
Which of the following is a disadvantage of microcrystal tests?
They are time-consuming
Which of the following crystalloptic parameters can be used to identify or distinguish drug microcrystals?
All of the above
What is the purpose of polarized light microscopy in microcrystal testing?
To identify specific compounds based on crystallographic features
What can cause distortions in the crystal habit or form of microcrystals?
All of the above
Which of the following is NOT a requirement for microcrystal testing?
A reagent specific to the drug being tested
What is one disadvantage of microcrystal tests in forensic drug identification?
They require a great deal of expertise and experience in microscopy
Which of the following is true about the extraction of a drug or metabolite from interfering compounds?
It is achieved by extracting the analyte from an aqueous solution into an organic solvent.
According to the Bronsted-Lowry Theory of Acids and Bases, which of the following is true?
A basic substance can only behave as a base in the presence of an acid.
How are the relative strengths of acids and bases measured?
By the tendency to give up and accept protons.
Which of the following is true about the strength of an acid in different solvents?
The strength of an acid can vary in different solvents.
Which of the following is an example of a weak acid?
Acetic acid
According to the Bronsted-Lowry theory, which of the following statements is true?
An acid is a proton donor and a base is a proton acceptor.
What is the Henderson-Hasselbalch equation for acids?
pH = pKa + log([HA]/[A-])
What is the Henderson-Hasselbalch equation for bases?
pOH = pKb + log([BOH]/[B+])
When extracting an acidic drug with a pKa of 3, what should the pH be to extract the unionized form of the drug, primarily?
pH > 3
Which of the following drugs is an example of an acidic drug?
Aspirin
Which of the following is true about the strength of an acid?
The strength of an acid depends on both its ability to give up a proton and the ability of the solvent to accept it.
Which of the following is true about the ionization process of acids and bases in aqueous solution?
Weak bases completely ionize in aqueous solution.
Which of the following is true about the relationship between the acidity of an acid and the basicity of the base?
The acidity of an acid depends on the basicity of the base that accepts the proton.
Which of the following is true about protolytic reactions?
Protolytic reactions involve the transfer of a proton from an acid to a base.
Which of the following is true about the ionization constant, Ka?
Ka is a measure of the strength of a weak acid or base.
Which of the following is an advantage of liquid-liquid extraction in forensic toxicology?
Requires smaller volumes of solvent
What is one disadvantage of liquid-liquid extraction in forensic toxicology?
Requires larger volumes of solvents
Which of the following is true about amphoteric compounds?
They can be extracted using acid or base extraction procedures
What is the optimal pH for extracting morphine in its unionized form?
pH 8
What is one advantage of liquid-liquid extraction in forensic toxicology?
Relatively simple to conduct
What is one disadvantage of liquid-liquid extraction in forensic toxicology?
Time consuming and cumbersome
What is one advantage of solid phase extraction in forensic toxicology?
Capable of being optimized for different classes of drugs
What is one disadvantage of solid phase extraction in forensic toxicology?
Less selective than other extraction methods
Which of the following factors affects the partition coefficient (K) in liquid-liquid extraction?
The nature of the drug and the organic solvent
What determines the degree to which a drug partitions between an aqueous and an organic medium?
The hydrophilic and lipophilic nature of the compound
Which type of compound is more likely to partition into the aqueous phase in liquid-liquid extraction?
Polar compounds
What is the purpose of making a drug as non-polar as possible during an extraction from a biological matrix?
To enhance its partitioning into the organic phase
What is the equation to calculate the partition coefficient (K) in liquid-liquid extraction?
K = C1 / C2
What is the main purpose of liquid-liquid extraction in forensic toxicology?
To remove a drug from a biological matrix
What does the degree of ionization of a compound depend on?
The pH of the environment
What are the advantages of liquid-liquid extraction?
Low volumes of solvent, vast amount of literature references, relatively simple to conduct, low cost, capable of being optimized for different classes of drugs
What are the disadvantages of liquid-liquid extraction?
Immiscible solvents are required, time consuming and cumbersome in some instances, glassware clean up required, larger volumes of solvents needed for traditional methods, less selective than other extraction methods
What is the optimal pH for extracting morphine?
Around a pH of 8
What are amphoteric compounds?
Compounds that exhibit both acid and base properties
How are amphoteric compounds best extracted?
By carefully adjusting the pH to get the drug into an unionized form
Which of the following is the purpose of sample pretreatment in solid phase extraction?
To ensure the samples will flow easily through the sorbent bed
What are the two phases involved in solid phase extraction?
Liquid phase and stationary sorbent phase
What is the purpose of pH adjustments in solid phase extraction?
To isolate the drug(s) of interest
What is the role of the solid phase cartridges in solid phase extraction?
To contain the sorbent bed
What was the initial extraction media used in early solid phase extractions?
C1S sorbents
Which of the following solvents is particularly effective for conditioning the sorbent in solid phase extraction?
Methanol
What is the purpose of passing a buffer through the extraction cartridge in solid phase extraction?
To adjust the pH environment
Which of the following is NOT a step in the solid phase extraction procedure?
Eluting the analyte of interest
What is the goal of washing the extraction cartridge with a suitable solvent in solid phase extraction?
To remove endogenous compounds
What is the optimal solvent strength for eluting the analyte of interest in solid phase extraction?
A solvent with moderate polarity
Which step in the Solid Phase Extraction (SPE) process ensures that acidic drugs become organic solvent soluble?
Step 7: Elute Acidic Drugs
What is the purpose of drying the sorbent bed in the Solid Phase Extraction (SPE) process?
To ensure that all water is removed from the sorbent bed
What is the purpose of adding 4 ml of 2% ammoniated ethyl acetate (pH = 12) to the sorbent bed in the Solid Phase Extraction (SPE) process?
To ensure that the basic drugs become unionized
What is the purpose of adding 4 ml of 1:1 acetone/chloroform to the sorbent bed in the Solid Phase Extraction (SPE) process?
To attract acidic drugs to the hydrophobic portion of the stationary phase
Which step in the Solid Phase Extraction (SPE) process ensures that basic drugs become positively charged and will be retained by the cation exchange portion of the stationary phase?
Step 3: Dry the Sorbent Bed
What is the purpose of drying the sorbent bed in the Solid Phase Extraction (SPE) process?
The purpose of drying the sorbent bed in the SPE process is to remove all water from the sorbent bed, as water can interfere with the contact the organic solvent will have with the sorbent during the elution steps.
What is the purpose of adding 4 ml of 2% ammoniated ethyl acetate (pH = 12) to the sorbent bed in the Solid Phase Extraction (SPE) process?
The purpose of adding 4 ml of 2% ammoniated ethyl acetate (pH = 12) to the sorbent bed in the SPE process is to raise the pH and ensure that the basic drugs become unionized, allowing them to be removed by the organic solvent.
What is the optimal pH for extracting morphine?
The optimal pH for extracting morphine is not mentioned in the text.
Which of the following is an advantage of solid phase microextractions (SPME) compared to liquid-liquid extractions (LLE)?
SPME requires less solvent
Which of the following is a disadvantage of microextraction by packed sorbent (MEPS)?
MEPS requires more solvents than LLE
What is the purpose of liquid phase microextractions (LPME) in drug extraction?
To extract drugs using solvents
What effect could protein binding have on drug extraction and what steps can be taken to overcome this?
Protein binding can decrease drug extraction efficiency; protein precipitation can be performed to remove proteins from the sample
Why is it important to dry a solid phase cartridge prior to eluting drugs of interest with organic solvent?
To prevent loss of volatile compounds of interest
Which of the following is NOT a factor that affects the reproducibility of a drug's Rf value in TLC?
Mobile Phase
Which of the following is a property of cellulose as a stationary phase in TLC?
High polarity
Which of the following is NOT a locating agent used in TLC?
Ethanol
What is the definition of Rf value in TLC?
Relative front value
Which of the following statements about Thin Layer Chromatography (TLC) is correct?
TLC is a technique that uses a mobile phase moving across a thin layer of stationary phase
What is the primary use of Thin Layer Chromatography (TLC)?
To separate and identify drugs in body fluids and tissues
What are some reasons for the popularity of Thin Layer Chromatography (TLC)?
It is a simple, reliable, and cost-effective technique
What is the purpose of the Rf value in TLC?
To measure the distance the substance travels from the origin
What is the advantage of using a reversed-phase system in TLC?
It allows for the separation of high molecular weight substances
What are the advantages of TLC compared to gas chromatography and high performance liquid chromatography?
Ability to run several samples simultaneously
What are the advantages of Thin Layer Chromatography (TLC)?
TLC is a quick and cost-effective method for drug analysis. It requires small sample volumes and can separate a wide range of compounds. TLC also allows for visual detection of separated compounds.
Describe the properties of the following stationary phases used in TLC: Cellulose, Silica gel, Ion exchange resins.
- Cellulose: Cellulose is a polar stationary phase that interacts mainly via hydrogen bonding. It is suitable for separating polar compounds.
- Silica gel: Silica gel is also a polar stationary phase, but it interacts via both hydrogen bonding and dipole-dipole interactions. It is commonly used for separating a wide range of compounds.
- Ion exchange resins: Ion exchange resins are charged stationary phases that interact with analytes based on their charge. They are used for separating charged compounds.
Name three locating agents used in TLC and their properties.
- Iodine: Iodine is a universal locating agent that forms colored complexes with a wide range of compounds.
- Ultraviolet (UV) light: UV light is used to visualize compounds that absorb UV light, such as aromatic compounds or compounds containing double bonds.
- Ninhydrin: Ninhydrin reacts with primary and secondary amines, producing a purple color, making it useful for locating amino acids and amines.
Which type of antibodies are produced through the immunization process?
Both polyclonal and monoclonal antibodies
What are haptens?
Molecular structures too small to elicit an immune response
Which of the following is NOT a commonly used carrier protein in antibody production?
Mouse
Which type of antibodies have greater affinity for an antigen due to their multisite linkage?
Polyclonal antibodies
What is the basis for immunoassay testing?
The attachment between antigens and antibodies
Which type of antibodies can attach to several epitopes on an antigen?
Polyclonal antibodies
What is the purpose of a label in an immunoassay?
To create a measurable response
Which type of immunoassay involves competition between labeled antigens and the sample's antigens for antibodies?
Competitive immunoassay
What is the difference between a heterogeneous and homogenous immunoassay?
Heterogeneous immunoassays require wash steps, while homogenous immunoassays do not
Which immunoassay technique is used more routinely in forensic toxicology laboratories?
Competitive immunoassay
Which type of immunoassay does not require a substrate for detection?
RIA
What is the purpose of a stop reagent in ELISA?
To stop the reaction from continuing
What is the main advantage of EMIT compared to RIA and ELISA?
It is a homogenous assay
What is the purpose of the wash step in ELISA?
To remove unbound antigens
Which immunoassay technique was developed first?
RIA
Which of the following labels is commonly used in Enzyme-Linked Immunosorbent Assay (ELISA) for antigen detection?
Enzyme
What is the purpose of a substrate in Enzyme-Linked Immunosorbent Assay (ELISA)?
To produce an optically detectable change
What type of immunoassay is Enzyme-Linked Immunosorbent Assay (ELISA)?
Heterogeneous
Which body fluids can be analyzed using immunoassay techniques in forensic toxicology?
All of the above
What is the most commonly used immunoassay technique in forensic toxicology laboratories?
Enzyme-Linked Immunosorbent Assay (ELISA)
Which of the following is a common strength of immunoassay techniques?
Sensitive and good precision
Why is urine usually the matrix of choice for immunoassay?
It has fewer interfering compounds and decomposition products
What two parameters may be used to determine drug 'cutoff' levels?
Limit of detection and linear range
Which immunoassay technique is more suitable for matrices other than urine?
RIA
Which immunoassay technique uses a label which increases sensitivity?
EMIT
Which of the following labels is used in Fluorescence Polarization Immunoassay (FPIA)?
Fluorophore
Which of the following immunoassay techniques involves a precipitation process?
KIMS
What is the label used in Cloned Enzyme Donor Immunoassay (CEDIA)?
Enzyme
Which of the following immunoassay techniques is based on the recombination of two inactive protein fragments?
CEDIA
What is the relationship between the concentration of drug and the instrumental response in Fluorescence Polarization Immunoassay (FPIA)?
Inversely proportional
According to Lambert's Law, what happens to the intensity of radiation transmitted through a homogeneously absorbing system as the path length increases?
It decreases exponentially
According to Beer's Law, what happens to the transmitted intensity of radiation through a homogeneously absorbing system as the sample concentration increases?
It decreases exponentially
What is the purpose of creating a calibration curve in drug analysis using Beer's Law?
To determine the concentration of a drug sample
In the equation for a line, y = mx + b, what does the slope (m) represent in the context of drug analysis using Beer's Law?
The product of path length and molar absorptivity
What is the role of chromophores in energy absorption?
They modify the absorption spectrum
Which type of lamps are commonly used as a source of visible and near infrared radiation in spectrophotometry?
Tungsten lamps
What is the range of usable visible light in spectrophotometry?
350-2000 nm
What type of spectrophotometer configuration compensates for fluctuations in the output of the light source?
Double beam spectrophotometer
Which region of the infrared spectrum provides useful information about pesticides and drugs?
Mid infrared
What type of absorption occurs at frequencies that are multiples of the fundamental band frequency?
Overtone absorption
What is the relationship between the spring constant of a bond and its wavenumber or vibrational frequency?
Stronger bonds have a higher spring constant and higher wavenumber
Which of the following is an advantage of FTIR compared to dispersive spectrophotometers?
All frequencies detected simultaneously
What is the most common phase used when analyzing drugs with FTIR?
Solid phase
What is the purpose of Attenuated Total Reflection (ATR) in FTIR analysis?
To provide a non-destructive avenue for analyzing small samples
Which of the following is NOT a major component of an IR spectrophotometer?
Sample holder
What is the purpose of a monochromator or interferometer in an IR spectrophotometer?
To produce a traditional IR spectrum
What type of detector is used in a Fourier Transform Infrared (FTIR) spectrophotometer?
Quantum detector
Which of the following is NOT a component of instruments used for measuring UV or visible absorbance?
Signal processor
In an aqueous solution, what effect does making the solution more alkaline have on the absorbance spectrum of phenolic compounds?
Absorption shift to a longer wavelength
What is the absorption maximum wavelength of barbiturates at pH 9.2?
240 nm
What is the basis of the resultant spectrum in Raman spectroscopy?
Changes in energy or frequency between incident light and scattered light
What is a disadvantage of using Raman spectroscopy for analyzing fluorescent substances?
Fluorescence interference
What is the advantage of using Surface Enhanced Raman Spectroscopy (SERS)?
Sample can be directly analyzed through packaging, water, and glass
What is the benefit of using microscopic methods in Raman spectroscopy?
Provides a three-dimensional look at the sample
Why is Raman spectroscopy a preferred technique versus traditional color tests for seized drugs?
High discriminating power
Which technique can be used for onsite preliminary drug identification of unknown seized drugs?
ATR-FTIR
What can ATR-FTIR instruments be combined with for enhanced spatial resolution?
Microscope
What are ATR-FTIR instruments being used for in response to increasing fentanyl overdoses?
Testing street drugs for the presence of fentanyl and other drugs
What type of light source is generally used in Raman Spectroscopy?
Monochromatic laser
What is the change in energy state called when incident photons lose energy to molecular bond vibrations in Raman Spectroscopy?
Stokes scattering
Which type of pump is commonly used in chromatography to ensure constant flow rate?
Dual-piston pump
What is the purpose of a fixed loop in a manual injection system?
To hold excess sample
What are the main differences between gas chromatography (GC) and high-performance liquid chromatography (HPLC)?
Different types of mobile phases
What is the primary material used to make HPLC columns?
Stainless steel
What is the purpose of the stationary phase in HPLC columns?
To separate sample components
What are the main differences between HPLC columns and GC capillary columns?
Different column diameters
What are HPLC columns packed with?
Small porous particles
What determines the retention time of solutes in HPLC?
The polarity of the mobile phase
What is the main purpose of adsorption HPLC?
To separate non-polar materials
What are HPLC columns packed with in the case of packed gels?
Silica
Which of the following is the most commonly used detector for HPLC?
Ultraviolet - Variable Wavelength or Diode array
What is the difference between HPLC and UHPLC?
UHPLC uses columns that are less than 2 um inner diameter
What is the purpose of adding an ion pair agent to an HPLC mobile phase?
To improve the selectivity of the separation
What is the difference between adsorption phase and partition phase chromatography?
Adsorption phase chromatography uses a solid stationary phase, while partition phase chromatography uses a liquid stationary phase
What are theoretical plates in chromatography?
Theoretical calculations used to predict the separation efficiency of a chromatographic column
Which of the following is an advantage of fluorescence detectors in chromatography?
Improved sensitivity over UV detectors
What is the main disadvantage of electrochemical detectors in chromatography?
Electrodes require high maintenance
Which type of compounds can be detected by fluorescence detectors in chromatography?
Only compounds with a chromophore can be detected
What is the main advantage of electrochemical detectors in chromatography?
Sensitive to pg/ml levels
Which of the following is a disadvantage of fluorescence detectors in chromatography?
Eluent may absorb at the optimum detection wavelength
Which of the following is true about the operation of an electron multiplier in a mass spectrometer?
The electron multiplier creates a cascade effect of electrons being generated.
What is the unit of measurement for mass-to-charge ratio (m/z) in a mass spectrum?
Atomic mass units (amu)
What is the purpose of Total Ion Current (TIC) in mass spectrometry?
To measure the total number of ions in the mass spectrum.
What is the purpose of Single Ion Monitoring (SIM) in mass spectrometry?
To measure the intensity of a specific ion in the mass spectrum.
What is the molecular ion in a mass spectrum?
The ion with the highest mass-to-charge ratio.
What is the base peak in a mass spectrum?
The ion with the highest relative abundance.
Where does ionization take place when using Electrospray Ionization (ESI)?
In the ion trap.
Why would a laboratory choose to use a LCMSMS versus a GCMS?
LCMSMS provides higher sensitivity.
What is the main difference in the operation of a quadrupole mass spectrometer compared with an ion trap?
Quadrupole mass spectrometers use a series of dynodes.
What is the purpose of the electron multiplier in a mass spectrometer?
To release electrons to increase the signal.
Which term describes a pattern where the variance of measured residuals is homogenous or uniform across the calibration curve?
Homoscedasticity
What type of model is appropriate when the residual plot reveals a U-shape?
Quadratic least square regression model
When is a weighted regression model needed?
When the variance of measured residuals is heterogenous
What does a funnel-shaped residual plot indicate?
Heteroscedasticity
What is the purpose of a weighted regression model?
To establish an appropriate relationship between instrumental response and concentration
What can be done to determine the concentration of an analyte using a nonlinear model?
Mathematical transformation process of both variables
What is the main difference between a linear model and a nonlinear model?
The type of regression used
What is the purpose of a quadratic least square regression model?
To capture nonlinearity in the data
What is the role of weighting in regression models?
To account for heteroscedasticity in the data
What should a laboratory assess in determining the most appropriate model to use?
The shape of the residual plot
Which of the following best describes measurement uncertainty?
A statistical description of how certain the laboratory is about their reported results
What is the purpose of determining uncertainty when validating a method?
To identify potential sources of error
How is uncertainty initially determined when validating a method?
Through the use of a budget or spreadsheet
What is the expanded uncertainty?
The uncertainty calculated during method validation
When should the expanded uncertainty be recalculated?
Following the method's validation and routine analyses
Why is it necessary to recalculate the expanded uncertainty?
To account for any changes in the method
What is the purpose of using a coverage factor and confidence level when reporting the expanded uncertainty?
To provide a measure of the laboratory's confidence in the reported results
What is the advantage of recalculation using data gathered from routine analyses?
To improve the accuracy of the measurements
What is the primary purpose of determining uncertainty in laboratory measurements?
To determine the accuracy of the measurements
What is the role of standard deviations in determining uncertainty?
To calculate the expanded uncertainty
Which parties may need access to validation information?
Designated laboratory personnel
What measures should be taken during validation to ensure a quality process?
All of the above
When should the uncertainty of measurement be determined?
During validation
What should be done if changes need to be made to the method?
Both B and C
What should be done when deviations occur during continuous monitoring of a validated method?
They should be documented and approved
What is the general approach to forensic analysis for a seized drug sample?
The general approach to forensic analysis for a seized drug sample involves sample preparation, identification, quantification, and interpretation of the results.
What is the general approach to forensic analysis for a biological specimen?
The general approach to forensic analysis for a biological specimen involves sample collection, preservation, analysis, and interpretation of the results.
What are the main steps in the forensic analysis of a seized drug sample?
The main steps in the forensic analysis of a seized drug sample include sample extraction, separation, identification, quantification, and data interpretation.
What are two techniques that can be used for confirmatory forensic drug analysis?
Infrared Spectroscopy (IR) and Mass Spectrometry (MS)
What is the purpose of the TLC technique in drug identification?
To separate and retain different components of the sample based on their distribution between the mobile and stationary phase
What is the advantage of using mass spectrometry for structural identification?
Mass spectrometry is considered the gold standard for structural identification and provides the most accepted technique for confirmation.
Which of the following techniques is primarily used to distinguish isomers such as dextromethorphan and levomethorphan?
Microcrystal Tests
What is the purpose of the mobile phase in Thin Layer Chromatography (TLC)?
To produce colored spots on the plate
Which technique is considered the gold standard for structural identification and confirmation of drugs?
Thin Layer Chromatography (TLC)
What is the purpose of Infrared Spectroscopy (IR) in forensic drug analysis?
To separate and retain components of the sample
What is the purpose of the stationary phase in Thin Layer Chromatography (TLC)?
To form crystals characteristic of the drug
Which of the following is a common method used to prepare a sample for LCMSMS analysis?
Precipitating proteins by diluting the sample in acetonitrile
In a forensic chemistry lab, how is a sample typically prepared for analysis using gas chromatography and/or mass spectrometry?
Dissolving the sample in a solvent like methanol
What is added to a sample prior to extraction or analysis in order to ensure accurate quantitation?
An internal standard
What information is reported when cocaine and its major metabolites are found in a sample?
The associated measurement uncertainty
What is the purpose of reconstituting the extract with the appropriate diluent in LCMSMS preparation?
To ensure accurate quantitation of the extract
What is the purpose of LCMSMS preparation?
The purpose of LCMSMS preparation is to dilute a small portion of the sample in a solvent, precipitate proteins, and reconstitute the extract for analysis using liquid chromatography coupled with mass spectrometry.
What is the role of an internal standard in forensic chemistry analysis?
The role of an internal standard in forensic chemistry analysis is to ensure accurate quantitation of cocaine and its major metabolites by providing a reference measurement.
What is the purpose of evaporating and reconstituting the subsequent supernatant in LCMSMS preparation?
The purpose of evaporating and reconstituting the subsequent supernatant in LCMSMS preparation is to prepare the extract for analysis using liquid chromatography.
Which of the following is NOT a requirement for maintaining the appropriate storage and security conditions in a forensic laboratory?
Recording storage temperatures at least once a day
What is a required part of a forensic scientist's courtroom testimony?
All of the above
Why is documentation important in forensic cases?
All of the above
What is gas chromatography and what is its purpose?
Gas chromatography is a technique used to separate and analyze volatile compounds in a mixture. Its purpose is to identify and quantify the components of a sample.
What are the steps involved in thin layer chromatography?
The steps involved in thin layer chromatography include sample application, development, visualization, and calculation of Rf values.
What are the advantages and disadvantages of liquid-liquid extraction?
The advantages of liquid-liquid extraction include high selectivity and the ability to handle complex samples. However, it can be time-consuming and requires the use of large volumes of solvents.
Which of the following is the primary goal of forensic toxicology?
To determine the role of toxic agents in causing death
What is the most commonly used specimen for drug analysis in forensic toxicology?
Blood
What do blood drug concentrations represent?
The drugs currently affecting the body
Why is blood preferred over urine for analyzing the behavioral effects of drugs?
Blood provides more accurate results
What is the ultimate goal of a forensic toxicologist?
To provide answers during investigations
Which body fluids are commonly analyzed in forensic toxicology?
Urine and blood
What can the presence and amount of drugs in a person's body fluids help determine?
The behavioral effects of drugs
What types of cases do forensic toxicology typically involve?
All of the above
Which of the following questions may a forensic toxicologist be asked to answer during an investigation?
All of the above
What is the significance of drug and/or metabolite levels in a person's body fluids?
All of the above
Test your knowledge on forensic toxicology drug analysis, drug degradation, preliminary/presumptive tests, and examination processes. Learn how to process unknown samples, identify causes of drug degradation, understand the importance of preliminary tests, and gain detailed insights into examination processes.
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