Introduction Flashcards
Component of the sample that is being determined
Analyte
Is a tool that gives the assurance that a product conforms to standards and specifications through a system of inspection, analysis and action
Quality Control
Six broad areas of application of analytical chemistry
Establish economic value Determining health hazards Diagnosis of diseases Controlling quality Relating properties to composition or structure Conducting research
Based on the number of analyte/s determined
Complete or Ultimate
Partial
Based on the amount of sample used in the analysis
Macro-analysis
Semi-micro analysis
Micro-analysis
Ultra-micro analysis
Establishes the relative amount of one or more species in the sample
Quantitative Analysis
Sample is 1-10mg
Micro-analysis
Amount of all of the constituents is determined
Complete or Ultimate
Sample is more than 0.1g
Macro-analysis
Sample is less than 1mg
Ultra-micro analysis
Based on the measurement of physical and chemical properties
Physico-chemical or Instrumental method
One or more, but not all of the constituents are determined
Partial
Involves measurement of the volume of solution that will react with the analyte
Volumetric or Titrimetic method
Based on the type of analyte determined
Elemental
Molecular
Based on the amount of analyte present
Macro/major
Trace analysis
Based on type of final measurement
Volumetric or Titrimetric method
Gravimetric method
Physico-chemical or Instrumental Method
Special methods of analysis
Sample is more than 10-100mg
Semi-micro analysis
Portions of a material of approximately same size carried thru same analytical procedure
Replicate sample
Indicates closeness of the measurement to its true or accepted value
Accuracy
Involves measurement of the weight of a substance of known identity
Gravimetric method
Analyte is present in low concentration
Trace analysis
Used to correct error due to contaminants
Blank determination
Expressed as degree of error (absolute error or relative error)
Accuracy
Degree of error
Absolute error
Relative error
Reveals the chemical identity of the species in the sample
Qualitative Analysis
Useful when a set of data contains an outlier
Median
Reflected by precision of measurement
Random or indeterminate error
Steps in a typical quantitative analysis
Selecting a method of analysis Sampling Preparing the laboratory sample Defining replicate sample Dissolving the sample Eliminating interferences Treating the sample and measuring the analyte Calculating the amount and evaluating the results
Process of determining the exact concentration of a solution
Standardization
Cause data to be scattered more or less asymmetrically around a mean value
Random or indeterminate error
Species that causes an error by enhancing/attenuating the quantity being measured
Interferences
Caused by imperfections in the measuring devices and instabilities in power supplies
Instrument error
All steps of the analysis are performed in the absence of the sample
Blank determination
Described using standard deviation, variance and coefficient of variation
Precision
Central values
Mean or Average
Median
Types of standardization
Primary standardization
Secondary standardization
Occurs occasionally, are often large and may cause a result to be either too high or too low
Gross error
Analyte is present in high concentration
Macro/major
Effect of systematic errors on analytical results
Constant errors
Proportional errors
An ultra-pure compound in solid form used as standard
Primary standard
Types of systematic error
Instrument error
Method error
Personal error
Refers to the number of moles of solute present in one liter of solution
Molarity
Process whereby a standard solution is made to react with a sample in solution in the presence of an indicator until the endpoint is reached
Titration
Middle value in a set of data that has been arranged in order of size
Median
Arise from non-ideal physical or chemical behavior of analytical systems
Method error
Describes the reproducibility of measurements or the closeness of results that have been obtained in exactly the same way
Precision
Components of titration
Analyte
Standard solution
Indicator
Methods of concentration expression
Molarity Normality Titer Percentage strength Parts per million
Solution that is not necessarily pure, but whose exact concentration is known
Secondary standard
Leads to outliers
Gross error
Refers to the number of equivalents of solute in one liter of solution
Normality
Substance that changes in color when passing from one medium to another or a reagent that changes color at a point when equivalent amounts of reacting substances have already reacted
Indicator
Reagent whose exact concentration is known and that is used in volumetric anlaysis
Standard solution
Two types of endpoint
Practical/experimental endpoint
Theoretical/Stoichiometric endpoint/Equivalence point
Affects accuracy or results
Systematic or determinate error
Properties of primary standard
Chemically-pure Chemically-stable Easily prepared Water-soluble Reacts stoichiometrically with the sample With fairly-high equivalent weight
Substance being analyzed
Analyte
Result from carelessness, inattention or personal limitations of. The analyst
Personal error
Types of standard solution
Primary standard
Secondary standard
Performed simultaneously with actual determination
Blank determination
Types of error in experimental data
Random or indeterminate error
Systematic or determinate error
Gross error
Quantity obtained by dividing the sum of replicate measurements by the number of measurements in the set
Mean or Average
Causes the mean of a set of data to differ from theaccepted value, either all high or all low
Systematic or determinate error
Branch of chemistry that involves separating, identifying and determining the relative amounts of the components in a sample matter
Analytical Chemistry
