This page provides some background information on a suite of instruments, nearly all of which use spectroscopy for chemical analysis. This will be useful in deciding which instrument is likely to be most suited for a particular application. Clicking on the links will take you to additional information.
Spectroscopy - Brief Introduction
Spectroscopy involves the study of the interaction of radiation with matter. Ultimately, It is via these interactions that the bond lengths and bond angles of molecules are determined. Every different atom and molecule has a unique spectroscopic fingerprint and spectroscopy is akin to a forensic exercise in that it involves decoding these fingerprints.
Once the specific wavelengths of interaction have been determined for a particular atom or molecule, spectroscopy can then be used to quantify how much of these species are present in a sample. For this reasons, spectroscopy has become an essential tool in chemical analysis. The information here will be useful and important for those who may have little or no background in spectroscopy.
What factors determine the quality of a water sample, and how are the compounds in a water sample measured ? pH measurements and colorimetry are discussed here.
This instrument uses light emitting diodes and low cost solid state detectors to measure the concentrations of a compound in solution. The instrument is very sensitive, and various techniques can be implemented, including colorimetry and fluorometry. In addition, the turbidity (or cloudiness) of a water sample containing dissolved solids can also be measured with a Chameleon.
A versatile optical detection system for use with the FIA, CL and LIA-ODS instruments described next.
Flow Injection Analysis (FIA)
In applications requiring remote sampling, flow injection analysis is a useful method for introducing samples on a continuous basis. Here, a chemical reaction in a flow manifold produces a species that can be detected by the absorption, or emission of light. You can find out how to set up and use an FIA system here.
Light emission resulting from chemical energy released in a chemical reaction is called "chemiluminescence". This page explains various instrument configurations for measuring CL and shows how it can be used for the ultra-sensitive determination of metal ions in solution.
Lock-In Amplifier-Based Optical Detection System (LIA-ODS)
Phase-sensitive detection is a means for successfully extracting extremely weak signals in the presence of noise. This is useful in the development of instrumentation for measuring very low light levels, for example when studying the fluorescence from extremely dilute solutions. This instrument can use either low cost solid-state detectors or for higher performance, a more expensive photomultiplier tube (PMT).
Fluorescence Lifetime Measurement
When excited by light, many molecules fluoresce. When the fluorescence is excited by very short duration light pulses, the emission timescale can be extremely short, perhaps lasting only a few tens of nanoseconds. The instrumentation described here uses a light emitting diode or LED to generate nanosecond duration optical pulses and a digital pulse counting system to measure a sample's fluorescence decay curve. On-board circuitry makes possible the detection of much slower events - ranging through the microsecond and millisecond time domains.