A chemical analysis is meaningless unless you begin with a meaningful sample.

is the process of collecting a representative sample for analysis.

The process of selecting a portion of the material, in some manner, to represent or provide information about a larger body of material.

Generally require some degree of sample preparation to remove substances that interfere with the analysis of the desired analyte

Bulk sample also called a _____ _____is taken from the lot for analysis or archiving (storing for future reference).

Types of Sampling: Sample is collected randomly from the target population. Increments are taken in such a way that any portion of the bulk has the same probability of being sampled out. Bias is reduced to a minimum if not eliminated

Available information about the target population is used to help select samples Sample are taken according to a sampling plan to screen out materials with certain characteristics and/or select materials with other relevant characteristics. More biased, but fewer samples are required Used when the number of independent variables influencing the results of an analysis are to be limited

Types of Sampling The target population is sampled at regular intervals in space or time (Systematic sample) Increments are taken at predetermined intervals as defined by the sampling plan Intermediate bias with respect to random and selective sampling.

Sample Preparation Target populations are conveniently subdivided into distinct units , in each of which random sampling is done. Advantage: the composition of each stratum is often more homogeneous than that of the entire target population, leading to lower sampling variance (uncertainty).

One lot of lotion in the finished goods section (1000 bottles)

Polymer film manufactured by a chemical company

Patient suspected of chronic poisoning

Soil in your hacienda

SAMPLING OPERATIONS A single sample taken from the target bulk.

SAMPLING OPERATIONS Several grab samples combined to form a single sample

SAMPLING OPERATIONS Sampling done within the population without physically removing the sample

Canned sardines coming out through a conveyor belt

Analysis of lunar soil in lunar environment

Soil in your hacienda

______is a notorious ion exchanger that alters the concentrations of trace ions in solution.

Therefore,plastic (especially ______) collection bottles are frequently employed.