Chapter 8: Introduction to Analytical Chemistry Flashcards
- science of obtaining, processing, and communicating information about the composition and structure of matter
- art and science of determining what matter is and how much of it exists
- measurement science consisting of a set of powerful ideas and methods that are useful in all fields of science and engineering
Analytical Chemistry
Two information required in an analysis
- Qualitative
- Quantitative
what makes analytical chemistry a vital tool in medical, industrial, government, and academic laboratories throughout the world?
interdisciplinary nature
reveals the identity of the elements and compounds in a sample
qualitative analysis
indicates the amount of each substance in a sample
quantitative analysis
chemical test used for detecting the presence of at least two peptide bonds in a molecule
Biuret test
how do metal ions produce color
become excieted and emit light of a specific wavelength
test for detecting the presence of starch
iodine test
Qualitative or Quantitative:
- Determining the concentration of a compound in solution
Quantitative
Qualitative or Quantitative:
- Identifying the cationic groups in a compound
Qualitative
Qualitative or Quantitative:
- Identifying the anionic groups in a compound
Qualitative
Qualitative or Quantitative:
- Identifying the functional group in a molecule
Qualitative
Qualitative or Quantitative:
- Determining the elemental composition of a molecule
Qualitative
chemical substance that is the subject of a chemical analysis
analyte
Two measurements in quantitative analysis
- mass or volume
- measurement of some quantity that is proportional to amount of analyte
- determine the mass of the analyte or some compound chemically related to its
- based on the principle of precipitation or volatilization methods
Gravimetric methods
- determine the volume of a solution containing sufficient reagent to react completely with the analyte
- involves the measurement of the volume of a solution of known concentration, referred to as the titrant, required to react completely with a particular substance, or analyte, in the solution being analyzed
Volumetric methods
substance (as a reagent solution of precisely known concentration) that is added in titration.
titrant
involve the measurement of such electrical properties as voltage, current, resistance, and quantity of electrical charge
Electroanalytical methods
based on the measurement of the interaction between electromagnetic radiation and analyte atoms or molecules or on the production of such radiation by analytes
Spectroscopic methods
Steps in picking a method for analytical chemistry
- level of accuracy
- economic factors
- complexity of the sample
involves obtaining a small mass of a material whose composition accurately represents the bulk of the material being sampled
sampling
sampling is frequently the most __ __ in an analysis and the source of __ __
- difficult step
- greatest error
constituent parts of a material can be distinguished visually or with the aid of a microscope
heterogenous
process of determining how much of a given sample is the material indicated by its name
assay
under __ circumstances, no sample processing is required prior to the measurement step
certain
under __ circumstances, we must process the sample in any of a variety of different ways
most
Preparing Laboratory Sample (solid)
- ground and mixed to ensure homogeneity
- dried
- moisture content may be determined
Preparing Laboratory Sample (liquid)
- liquid samples are subject to solvent evaporation
Preparing Laboratory Sample (gas)
- Gas sample dissolved in liquid
- Must be kept inside a second container to prevent contamination of atmospheric gases
portions of a material of approximately the same size that are carried through an analytical procedure at the same time and in the same way
replicates
Replication improves and provides what?
- quality of results
- measure of reliability
Preparing Solutions
- solvent should dissolve entire sample, rapidly and completely
- sample may require heating
species other than the analyte that affect the final measurement
- interferences or
- interferents
what do interference do
enhance or attenuate the quantity being measured
techniques or reactions that work for only one analyte
specific
techniques or reactions that apply for only a few analytes
selective
all of the components in the sample containing an analyte
- matrix or
- sample matrix
Ideally, the measurement of the property X is directly proportional to the concentration (CA)
Calibration and Measurement
CA formula
CA = kX
computing analyte concentrations are based on the raw experimental data collected in the measurement step, the chracteristics of the measurement instruments, and the stoichiometry of the analytical reaction
calculating results
analytical results are incomplete without an estimate of their __
reliability
used to determine if the standard deviation of a set of data is small or large when compared to the mean
Relative standard deviation (RSD)
Relative standard deviation (RSD) may also be referred to as.. ?
Coefficient of Variation (CV)
relative standard deviation can tell you how __ the average of your results is
precise
