Sampling Methods: Sample Types

Sampling materials are classified into three main types: solid, liquid, and gas. Solid samples include sediments from water bodies, rocks, metals, and biological tissues. Liquid samples encompass water, blood, urine, and solvents. Gaseous samples are collected from atmospheric air, exhaust vents, and industrial smokestacks for analysis.

Two standard methods extract sediments from water bodies: grab sampling and piston coring. Grab sampling uses a device lowered to the riverbed that closes around sediment to extract a discrete sample with minimal disturbance. Piston coring retrieves a continuous sediment column, allowing analysis of changes over time within sediment layers.

Homogeneous liquids like water and blood are collected using precise volumes via pipette or syringe. For heterogeneous liquids such as industrial effluents, an automated sampler collects representative samples at regular intervals. This programmed device ensures comprehensive analysis of the effluent's composition by collecting samples over predetermined time periods.

Gaseous samples from atmospheric air, exhaust vents, and industrial smokestacks are collected using solid sorbents like activated carbon, which selectively adsorb target compounds from the gas stream. The adsorbed compounds are then extracted through desorption techniques such as heating or solvent extraction and analyzed using suitable analytical methods.

Industrial effluents are heterogeneous liquids containing various chemicals and pollutants with spatial and temporal variability. An automated sampler collects representative samples at regular intervals, providing comprehensive analysis of the effluent's composition. This systematic approach ensures accurate characterization of pollutants that may vary throughout the sampling period.

Grab sampling collects a discrete sediment sample from a specific location at the bottom of a water body, but samples may not represent the entire area due to spatial variability. Piston coring retrieves a continuous sediment column, enabling analysis of temporal changes within sediment layers and providing a more comprehensive historical record.

Solid sorbents such as activated carbon selectively adsorb target compounds from gas streams during sampling. The adsorbed compounds are extracted through desorption methods including heating and solvent extraction. The extracted compounds can then be analyzed using characterization techniques like spectroscopy or chromatography to identify and quantify target analytes.