1. define the problem
must know what information is needed, by whom, for what purpose, and what type of sample is to be analyzed
2. select a method
identify the sample type, size of sample, its cost, etc.
3. obtain a representative sample
get the sample type and its sampling statistics
4. prepare the sample for analysis
any preparations such as chemical separation and/or concentration for the sample
5. prepare any necessary chemical separations
such as distillation, precipitation, extraction etc.
6. perform the measurement
calibrate, validate, and replicate
7. calculate the results and report
using statistical analysis, the results are interpreted and evaluated carefully
contamination, loss, decomposition, matrix change
certain precautions should be taken in handling and storing samples to prevent or minimize
the container, atmosphere, heat, temperature, or light
prevent contamination or alteration of the sample by
method of standard additions
calibration technique wherein if there is any interference or spike in the sample, a known amount of substance helps compensate it
internal standard calibration
adding a known quantity of a substance that behaves the same way as the analyte, but is not the analyte or present in the sample naturally.
two validations of a method
random and systematic
random
measurement has some imprecision associated with it, which results in random distribution of results, for example, a Gaussian distribution
systematic
one that biases a result consistently in one direction (analytical balance is skewed high or low)
analyze
a sample is analyzed for all its constituents and the substance measured are the analytes
determination
process of measuring the analyte