Chapter 7: Introduction to Ana Chem Flashcards
is the science of obtaining, processing, and communicating information about the composition and structure of matter
Analytical Chemistry
Application of Analytical chemistry
applied throughout industry, medicine, and all the sciences
reveals the identity of the elements and compounds in a sample.
Qualitative analysis
indicates the amount of each substance in a sample.
Quantitative analysis
Qualitative or quantitative : Test for protein
Qualitative
Qualitative or quantitative : Iodine test for starch, color of the solution indicates the presence of starch
Qualitative
Qualitative or quantitative : Iodine test for starch, measuring the light that passes through a sample.
Quantitative
a chemical substance that is the subject of a chemical analysis
Analyte
The results of a typical quantitative analysis are computed from two measurements:
- Mass or the volume of the sample to be analyzed.
- the measurement of some quantity that is proportional to the amount of analyte.
Quantitative analytical methods (classification)
- Gravimetric Methods
- Volumetric methods
- Eletroanalytical methods
- Spectroscopic methods
determine the mass of the analyte or some
compound chemically related to it.
Gravimetric methods
Gravimetric methods is based on the principle of?
- Precipitation or volatilization methods
steps in Gravimetric method
a. Weighing the sample to be analyze
b. Dissolving this sample in water
c. Adding suitable chemical to form a precipitate.
d. Filtering to collect the precipitate
e. Repeated drying and weighing (until a constant mass of precipitate is obtained)
determine the volume of a solution containing sufficient reagent to react completely with the analyte.
Volumetric methods
measurement of the volume of a solution of known concentration
Titrant
involve the measurement of such
electrical properties as voltage, current, resistance, and quantity of electrical charge
Eletroanalytical methods
Electrical properties used to measure
- voltage
- current
- resistance
- quantity of electrical charge
are based on measurement of the interaction between electromagnetic radiation and analyte atoms or molecules
Spectroscopic methods
Electro magnetic spectrum from lowest to highest
- Radio
- Microwave
- Infrared
- Visible
- Ultraviolet
- X-ray
- Gamma Ray
10^3
Radiowave
10^-2
Microwave
10^-5
Infrared
10^-6
Visible
10^-8
Ultraviolet
10^-10
X-Ray
10^-12
Gamma Ray
General Steps in Quantiative analysis
- Select Method
- Acquire sample
- Process sample
Picking a method steps
- Consider in the selection process is the level of accuracy required.
- Second consideration to economic factors is the number of samples to be analyze
- The complexity of the sample and the number of components in the sample.
Acquiring the sample steps
Sampling, obtaining a small mass of materal whose composition represents tha bulk
involves obtaining a small mass of a material
Sampling
if its constituent parts can be distinguished visually or with the aid of a microscope
A material is heterogeneous
is the process of determining how much of a given sample is the material indicated by its name.
Assay
Processing the sample
- Preparation of a laboratory sample.
- Defining replicate samples
- Preparing solutions
Steps of preparing a laboratory sample: Solid
- Ground to decrease particle size, mixed to ensure homogeneity, and stored for various lengths of time before analysis
- To Dry the samples before starting analysis (due to loss or gain of water changes in solid)
are subject to solvent evaporation.
Liquid Samples
are 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 or replicate sample
Replicate samples analytical procedure are …..
carried at the same time and in the same way
improves the quality of the results and provides a measure of their reliability.
Replication
are performed on the results to establish their reliability
Statistical tests
Steps in preparing solutions
- Solvent should dissolve the entire samle
- The sample may require heating with aqueous solutions.
- It may be necessary to ignight the sample in or oxygen or perfrom high-temp fusion.
Species other than the analyte that affect the final measurement
Interferences or interferents
Techniques or reactions that work for only one analyte are said to be
Specific
Techniques or reactions that apply for only a few analytes are
selective
is all of the components in the sample containing an analyte
Matrix or sample matrix
General steps in quantitative analysis
- Select method
- Acquire sample
- Process sample
