ANACHEM

• Analytical Chemistry


  Concerned with the chemical characterization of matter, both qualitative and quantitative
• Analytical Chemistry


  Used to identify the substances which may be present in a material and to determine the exact amounts of the identified substance
• Impact of Analytical Chemistry


  • Agricultural
  • Clinical
  • Environmental
  • Forensic
  • Manufacturing
  • Metallurgical
  • Pharmaceutical
• The Analytical Process

  Define the Problem, Select a Method, Obtain a Representative Sample, Prepare the Sample for Analysis, Perform any Necessary Chemical Separations, Perform the measurement, Calculate the Results and Report
• Accuracy


  How close you get to the true value
• Precision


  How close the repetitive measured values are to one another
• Kinds of Error


  • Determinate Error (Systematic Error)
  • Indeterminate Error (Random Error)
• Determinate Error (Systematic Error)


  Nonrandom and occur when something is intrinsically wrong in the measure
• Types of Determinate Error


  • Instrumental Error
  • Operative Error
  • Errors of the Method
• Indeterminate Error (Random Error)

  Random and cannot be avoided
• Sources of Indeterminate Error


  • Accidental/Random
  • Due to intrinsic nature of things
• Absolute Error


  The difference between the true value and the measured value, with regard to the sign, reported in the same units as the measurement
• Relative Error


  The absolute or mean error expressed as a percentage of the true value
• Standard Deviation


  A measure of the amount of variation of a random variable expected about its mean
• Relative Standard Deviation


  The standard deviation expressed as a fraction of the mean, usually given as a percentage (% rsd), which is the coefficient of variation
• Propagation of Errors


  The errors in the individual numbers will propagate throughout a series of calculations, in either a relative or an absolute fashion, depending on whether the operation is a multiplication/division or an addition/subtraction
• Propagation of Errors: Addition and Subtraction


  Absolute uncertainties are additive, the most probable error is represented by the square root of the sum of the absolute variances
• Propagation of Errors: Multiplication and Division


  Relative uncertainties are additive, the most probable error is represented by the square root of the sum of the relative variances
• Experimental Error

  All measured data are subjected to errors.
• Statistical Analysis

  necessary to understand the significance of the data that are collected and thus sets limits on each step of analysis.
• Stoichiometry


  Deals with the ratios in which chemicals react
• Atomic Weight


  Mass of an atom per mole, the average mass of the different isotopes in relation to its relative abundance
• Molecular Weight


  Mass of a molecule, summation of all atomic masses present in a molecule
• Moles


  The basic unit for equating things
• 1 mole of different elements has different masses depending on their molecular weight
• Stoichiometric coefficients in a chemical equation


  Can be interpreted as the number of moles of each substance

  
• Concentration


  Quantitative study of a solution requires knowing its concentration, that is, the amount of solute present in a given amount of solution
• Molarity


  A one-molar solution is defined as one that contains one mole of substance in each liter of a solution. Molarity (M) = moles of solute / volume of solution in litre
• Molality


  A one-molal solution contains one mole per 1000g of solvent. Molality (m) = moles of solute / kg of solvent
• Density


  The weight per unit volume at the specified temperature, usually g/mL or g/cm3 at 20C. One milliliter is the volume occupied by 1 cm3
• Dilutions - Preparing the right concentrations


  To prepare a dilute solution from a concentrated stock solution, use: C1V1 = C2V2
• Percent Weight (% w/w)

  Calculations for solid samples are based on weight. The most common way of expressing the results of macro determinations is to give the weight of analyte as a percent of sample (weight/weight basis). % (wt/wt) = [wt solute (g) / wt sample (g)] x 102 (%/g solute/g sample)

  
• Parts per thousand (ppt)


  [wt solute (g) / wt sample (g)] x 10^3
• Parts per million (ppm)


  [wt solute (g) / wt sample (g)] x 10^6
• Parts per billion (ppb)


  [wt solute (g) / wt sample (g)] x 10^9
• Milligram percent (mg%)


  Defined as milligrams of analyte per 100g of sample
• Percent on weight/volume basis (% w/v)

  Equal to grams of analyte per 100 mL of sample
• Parts per million

  (wt/vol) = [wt solute (g) / vol sample (mL)] x 10^6
• Parts per billion (wt/vol)

  (wt/vol) = [wt solute (g) / vol sample (mL)] x 10^9
• Parts per trillion (wt/vol)


  [wt solute (g) / vol sample (mL)] x 10^12