ALS Environmental uses advanced and specialized instruments for its analytical testing capabilities. Below are examples of some the instruments we use and examples of its application in the laboratory.
Gas Chromatography (GC)
Gas-liquid chromatography (GLC), or simply gas chromatography (GC), is a type of chromatography in which the mobile phase is a carrier gas,. It is usually an inert gas, such as helium or an unreactive gas like nitrogen. The, of which the stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside glass or metal tubing, called a column. The instrument used to perform gas chromatographic separations is called a gas chromatograph (also: aerograph, gas separator).
Gas Chromatography is different from other forms of chromatography (HPLC, TLC, etc.) because the solutions travel through the column in a gas state. The interactions of these gaseous analytes with the walls of the column (coated by different stationary phases) causes different compounds to elute at different times called retention time. The comparison of these retention times is the analytical power to GC. This makes it very similar to HPLC.
Gas Chromatography-Mass Spectrometry (GC/MS)
Gas chromatography-mass spectrometry (GC/MS) is a method that combines the features of gas-liquid chromatography and mass spectrometry to identify different substances within a test sample. Applications of GC/MS include drug detection, fire investigation, environmental analysis, explosives investigation, and identification of unknown samples. GC/MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, it can identify trace elements in materials that were previously thought to have disintegrated beyond identification.
The GC/MS has been widely heralded as a "gold standard" for substance identification because it is used to perform a specific test. A specific test positively identifies the actual presence of a particular substance in a given sample. A non-specific test, however, merely indicates that a substance falls into a category of substances. Although a non-specific test could statistically suggest the identity of the substance, this could lead to false positive identification.
This GC/MS/MS instrument is the same as the gas chromatography-mass spectrometry (GC/MS), except a second phase of mass fragmentation is added. This second quadrupole gives rises to the often used name, Tandem MS. It’s also known as a MS/MS. The GC/MS/MS is very sensitive and effective instrument for the analyses of organic compounds, including many major classes of pesticides.
Liquid Chromatography-Mass Spectrometry (LC/MS)
Liquid chromatography-mass spectrometry (LC/MS) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography (aka HPLC) with the mass analysis capabilities of mass spectrometry. LC/MS is a powerful technique used for many applications which has very high sensitivity and specificity. This technique is used to analyze compounds that are too large, too polar, or too thermally labile for the GC technique. Generally, its application is oriented towards the specific detection and potential identification of chemicals in the presence of other chemicals (in a complex mixture).
Liquid Chromatography-Mass Spectrometry (LC/MS/MS)
This LC/MS/MS instrument is the same as the LC/MS, but has the advantage of a tandem MS-MS.
Inductively Coupled Plasma-Mass Spectroscopy (ICP/MS)
ICP-MS, short for inductively coupled plasma mass spectrometry, is a type of mass spectrometry which is very sensitive and capable of determining of a range of metals and several non-metals at concentrations below one part in 1012. The ICP/MS allows detection of trace metals to parts-per-trillion. The instrument is based on coupling together an inductively coupled plasma as a method of producing ions (ionization) with a mass spectrometer as a method of separating and detecting the ions. ICP-MS is also capable of monitoring isotopic speciation for the ions of choice.
Freeze-drying of samples may be used as a tool for environmental analysis. Freeze-drying of sediment and tissue samples can be performed prior to extraction and analysis for Polynuclear Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs), Pesticides, Dioxins, and Metals. The use of freeze-drying eliminates or reduces the undesirable effects of water. The most significant benefits are lower detection limits and more quantitative determinations. In addition to lower detection limits and better recoveries, freeze-drying of samples allows for complete homogenization of the sample matrices. Thus, improved precision is realized. This is particularly significant when analyzing heterogeneous samples (e.g. high organic sediments, whole-body tissues, etc.).
Solvent extraction and partitioning, also known as liquid-liquid extraction is a method to separate compounds based on their relative solubilities in two different immiscible liquids (known as the partition coefficient), usually water and an organic solvent. It is an extraction of a substance from one liquid phase into another liquid phase. Liquid-liquid extraction is a basic technique in chemical laboratories, where it can be performed manually using a separatory funnel or with an automated system. This type of process is commonly performed after a chemical reaction as part of the work-up.
A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. However, a Soxhlet extractor is not limited to the extraction of lipids. Typically, a Soxhlet extraction is only required where the desired compound has only a limited solubility in a solvent, and the impurity is insoluble in that solvent.
Gel Permeation Chromatography (GPC)
Gel permeation chromatography (GPC) is a separation technique based on hydrodynamic volume (size in solution). Molecules are separated from one another based on differences in molecular size. In environmental analysis, this technique is generally used as a clean-up method to remove large molecules which interfere with target analytes from the extract prior to analysis on the instrument. This technique is also used for polymer molecular weight determination. GPC is performed in organic mobile phases and is used mostly for synthetic polymers. GFC (gel filtration chromatography) is defined as sized-based separation performed in an aqueous mobile phase and is typically applied for protein analysis or for water-soluble polymers. A broader term that encompasses both of these separation methods is size exclusion chromatography (SEC).