Chemical Analysis Terms

Sampling

First step in chemical analysis, procuring a representative, small sample to measure

Analyte

The substance being measured

Quantitative Transfer

A complete transfer

Slurry

A suspension of solid in a liquid

Supernatant

Liquid above packed solid

Sample Preparation

Putting the sample into a state that is suitable for analysis

Standard Solutions

Solutions prepared with a known amount of analyte under investigation

Microbalance

An electronic balance that weighs milligram quantities with readability of 1 microgram

Readability

Smallest increment of mass that can be indicated

Buoyancy

The upward force exerted on an object in a liquid or gaseous fluid

Hygroscopic

Tending to rapidly absorb moisture from air

Absolute uncertainty

An expression of the margin of uncertainty with a measurement (standard deviation), s

Relative uncertainty

Expression of experimental uncertainty relative to the magnitude of measured value. Given with no units.

Percent relative uncertainty

Relative uncertainty expressed as a percent of measured value

Variance

s², indicates how spread out repeated measurements are from mean value.

NIST

National Institute of Standards and Technology, serves as a reference point for calibration

Aliquot

Portions

Species

Any chemical or ion of interest

Interference

Occurs when a species other than analyte increases or decreases the response of the analytical method and makes it appear that there is more or less analyte than is actually present

Masking

Transforming an interfering species into a form that is not detected

Extraction

Process where analyte is dissolved in a solvent that does not dissolve the entire sample and doest not decompose the analyte

Confidence interval

Range of values within which there is a specified probability of finding the population mean

Student’s t test

Statistical tool used to express confidence intervals and to compare mean values from experiments

Grubb’s Test

A statistical test used to decide whether to discard data that appears to be an outlier

Order for a chemical analysis

Formulating question, selecting analytical procedure, sampling, sample preparation, analysis, reporting and interpretation, drawing conclusions

Size of samples

Aliquot, homogeneous lab sample, representative bulk sample, lot