Chemical Analysis Terminology

Analyte

the species of interest; produces the analytical signal

Interferant

other things in teh sample that interfere with the analytical singal (increase or decrease)

Sample

a portion of the whole that may or may not contain the analyte

sample = analyte + matrix

Sampling Process

creates a managable, representative homogeneous sample

Lot

total material of interest

Bulk Sample

taken from the lot for analysis

Lab Sample

initially smaller than bulk sample, is what the analyzed sample is drawn from

Aliquot

portion of lab sample that is actually analyzed

Archiving

storing a sample for potential future use

Masking

transforms an interferent into a species that is not detected

RANDOM Heterogeneous Sample

differences of analyte in lot are random and on a small scale

SEGREGATED Heterogeneous Sample

discrete regions of differences of composition in the lot

Random Sample

randomly samples sections of lot become bulk sample

Composite Sample

samples that are proportional to the lot are taken and are made homogeneous into the bulk sample

Qualitative Analysis

what is present / if it’s present

Quantitative Analysis

how much is present?

Semi-Quantitative Analysis

provides an estimate/range of what is present and how much of it

Specific Technique

analytical signal for only one type of analyte

Selective Technique

analytical signal for a few types of analytes

Standard

reagent with an amount of analyte that is known to a high degree of certainty

Primary Standard

use as is; stable; high purity; high formula mass

Secondary Standard

made soluton with known concentration to high degree of certainty (made with 1 std)

External Standard

contains known concentration of analyte, seperate from your sample

Internal Standard

standard is added to the sample; standard may or may not be the analyte

Wet Chemistry

process of relating the actual physical quantity to the quantity indicated on the scale of the instrument

Instrumentation Calibration

determining the response of the instrument to a known amount of analyte

Calibration Curve

graph showing the value of some physical property as a function of analyte concentration

Matrix

all of the components in the sample BUT the analyte

Reagent Blank

a sample with zero analyte present

ideally the matrix

Method Blank

a reagent blank that has been subject to all sample prep procedures

Control

a sample subjected to all sample prep procedures and chamical analysis steps to establish a known ‘positive’ or ‘negative’ result

Accuracy

closeness of a number to its accepted value

Precision

closeness of a series of measurements to each other

Repeatability

can the experiment be repeated using the same reference sample in the same lab by the same operator using the same equipment

Reproducibility

can the experiment be reproduced in two different labs on the same reference sample