Chemical Technician Reviewer

• Helps in separating immiscible liquids like oil and water into two samples

  Separatory funnel
• Mixtures of liquids and solids are usually separated prior analysis by

  • filtering
  • decanting
  • centrifuging
• Pre-treatment of solid samples prior analysis

  • Leaching and extraction of soluble components
  • Filtering of mixtures of solids, liquids and gases to leave particulate (solid) matter
  • Grinding
• Decomposition and dissolution of solids during sample preparation

  • Acid treatment using oxidation
  • Fusion technique
  • Dissolution using ultrasound&appropriate solvent
  • Simple dissolution
• Reliability of the results


  Decreases with a decrease in the level or concentration of the analyte
• Properties of nitric acid making it the preferred acid for digesting samples for the analysis of metals


  • Acts as a strong acid
  • Acts as an oxidizing agent
  • Does not form insoluble compounds with metals/nonmetals
• Primary sample preparation method for organics

  • Sonication
  • Acid-digestion
  • Extraction
• Possible sources of contamination during sample preparation

  • Reagents (tracers)
  • Glassware/equipment
  • Cross-contamination between high- and low-activity samples
• Containers that should not be used for dry ashing

  • Glass and plastic
• The size of the sample taken for analysis depends on

  • the concentration of the analyte
  • equipment to be used
  • specific tests
• Equipment commonly used to homogenize the contents of an open beaker

  • Magnetic stirrer
  • V-blenders
  • Ball and rod mills
  • tube rotator
• The maximum holding time for acid preserved samples that will be subjected to determination of metals

  • 3 months
• Laboratory sample


  A fraction of the sample actually used in the final laboratory analysis
• Matrix effect


  A change in the analytical signal caused by anything in the sample other than analyte
• Matrix


  Medium containing analyte
• The total error of an analytical result is the sum of

  • sampling
  • sample preparation
  • analytical errors
• The holding time for samples for metal determination preserved using nitric acid, 4 mL of dilute 3:1


  • 28 days
• When samples cannot be dried because they decompose at the temperatures necessary to drive off the water, the samples can be analyzed as


  • wet basis
  • dry basis
  • received basis
• Soxhlet extraction


  Organic components in solid samples are extracted from the matrix by continuously washing the solid with a volatile solvent in a specialized piece of glassware
• Nonaqueous


  In liquid-liquid extraction, if a drop of water dissolves in the top layer, the top layer is nonaqueous
• Sampling


  Process by which a sample population is reduced in size to an amount of homogeneous material that can be conveniently handled in the lab in which the composition is representative of the population
• Error in sampling and the sample preparation portion of an analytical procedure

  Considerably higher than that in the methodology
• Homogenization during sample preparation can be achieved using

  • mechanical devices (mixers, blenders, etc.)
  • enzymatic methods
  • chemical methods
• Glass container is not suitable for

  • inorganic trace analyses
  • oil and grease determination
  • microbiological analyses
• To increase/decrease analyte concentration, pre-concentration is needed for almost all trace analysis, _______ is used for the analysis of highly contaminated samples so the concentration falls within the calibration range

  • dilution
• Chemical derivatization


  Used to increase or decrease volatility for GC and HPLC analysis
• Acid digestion via hot-plate digestion or microwave-assisted is one way of sample preparation in the analysis of


  • Total metal
  • Bioactive compounds
  • Alcohols
  • Sugars
• Nitric Acid


  Used in GFAA (Graphite Furnace Atomic Absorption) as it does not interfere with Cl-
• Partitioning of analytes between water phase and organic phase

  • Liquid-liquid extraction
  • Soli phase extraction
  • Ultrasonic extraction
  • Pressured Fluid Extraction (PFE)
• The amounts of all constituents in the samples were determined

  • Complete (or ultimate) analysis
  • Partial analysis
  • Elemental analysis
• Macro analysis


  Implies that the constituent determined was present in high concentration
• Gravimetric analysis


  Quantitative chemicall analysis of weighing a sample, usually of a separated and dried precipitate
• ACS grade


  A chemical grade of highest purity and meets or exceeds purity standards set by American Chemical Society
• Reversible reactions


  Bidirectional harpoons or double arrows (⇆) should be used to indicate
• A few ways in which solution composition can be described are as follows

  • Molarity
  • Normality
  • Molality
• Solvent


  The substance which does the dissolving and must be
• In the preparation of 1 liter of 1.0 N acid from 35% Hydrochloric Acid, what weight of the impure acid should be taken, assuming standardization in the recommended manner?

  g=(1 eq.wt. HCl/li x 1 liter x 1mole/1 eq. wt. HCl x 36.45 g HCl/mole)

  a. 101.29

  b. 113.29

  c. 111.29

  d. 124.89
• A few ways in which solution composition can be described are as follows

  • Molarity

  Normality

  Molality

  All of the above
• Solvent


  The substance which does the dissolving and must be greater than 50% of the solution
• Used to measure volumes approximately, typically with errors of several percent except for one

  • Beakers

  pipettes

  reagent bottles

  graduated cylinders