Chemi steps in

Analytical Chemistry

is a measurement science consisting of a set of powerful ideas and methods that are useful in all fields of science and medicine.

Quantitative and Quantitative

analysis reveals the identity of the elements and compounds in a sample

Analytes

component of a sample that are to be determined

Gravimetric

Determine the mass of the analyte or some compound chemically related to it

Volumetric

determines the volume of a solution containing sufficient reagent to react completely with the analyte

Electroanalytical

involves the measurement of electrical properties such as voltage, current, resistance

Spectroscopic

based on measurement of the interaction between electromagentic radiation and analyte atoms or molecules or on the production of such radiation by analytes

Miscellaneous Methods

mass to charge ratio

Level of Accuracy Required

What are one of the first questions to be considered in the selection process?

Number of samples to be analyzed

What is the second consideration related to economic factors?

Sampling

involves obtaining a small mass of a material whose composition accurately represents the bulk of the material being sampled

Sampling

frequently the most difficult step in an analysis and the source of greatest error

Material

is heterogenous if its constituent parts can be distinguished visually or with the aid of a microscope

Assay

is the process of determining how much of a given sample if the material indicated by its name

Protein Assay

An example of an assay in which you are looking for a certain protein

No sample processing required

under certain circumstances, no _ is required prior to the measurement step

Preparation of a lab sample

Whats the first step in processing the sample?

solvent evaporation

Liquid samples are subject to ____

kept inside a second sealed container (prevent contamination)

If the analyte is a gas dissolved in a liquid, what to do with analyte?

Replicate 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

Replication

improves the qualitt of the results and provides a measure of their reliability

Interferences or Interferents

Species other than the analyte that affect the final measurement

Interferences or Interferents

is a species that causes an error in an analysis by enhancing or attenuating the quantity being measured

Specific

techniques ir reactions that work for ONLY ONE ANALYTE

Selective

techniques or reactions that apply for only a few analytes

Directly proportional

Whats the relationship of property to concentration?

Calibration

process of determining the proportionality between analyte concentration and a measured quantity

Raw experimental data

computing analyte concentrations are based on ____

estimate of their reliabilitt

Analytical results are incomplete and of no valuewithout ____

Feedback Loop

the cycle of measurement, comparison, and control

Feedback System

the process of continuous measurement and control

Central Value

Analysis of Variation

What are the two ways to justify the extra effort required to analyze replicates?

Central Value

should be more reliable than any of the individual results

Analysis of Variation

allows us to estimate the uncertainty associated with the central result

Mean

widely used measure of central value

Median

middle result when replicate data are arranged in order of size

Outlier

result that differe significantly from other in the set

Median

Outlier can have a significant effect on the mean of the set without affecting the ____

Mean = Median

Whats the ideal relationship between mean and median?

Precision

describes the reproducibility of measurements

Standard Deviation

Variance

Coefficient of Variation

Three terms widely used to describe the precision of a set

Accuracy

closeness of the measurement to its true or accepted value and is expressed by the error

Accuracy

agreement between a result and its true value

Precision

agreement among several results that have been obtained the same way

Error

data is higher than accepted value

Deviation

you can known whether the experimental value is higher or lower than the true value

Any loss or gain of water changes the chemical composition of solid

Why is it a good idea to dry the samples?