Atomic spectroscopy is an instrumental technique used for quantitative analysis of cations. This technique gives atomic (not molecular) concentrations and is commonly used for metals/transition elements. Some non-metals such as arsenic and boron may also be analyzed.
Within the WERC laboratory an Agilent 4200 MP-AES is used for atomic spectroscopy analysis. This instrument uses a microwave energy source to generate a nitrogen plasma. Within the high energy plasma elements emit unique wavelengths of light, with the intensity being proportional to concentration. The Agilent 4200 is capable of quantifying 71 elements, with quantitation limits typically in the single digit ppm range or below. Special sample introduction techniques utilizing sodium borohydride can reduce detection limits one to two orders of magnitude for some elements such as Selenium and Arsenic.
Chromatographic methods are used to separate complex mixtures and quantify one or more of the individual components. Ion chromatography with conductivity detection may be used to quantify a variety of ionic compounds in aqueous samples.
Dionex Aquion instrumentation, equipped with a conductivity detectors, gives the WERC lab High Performance Ion Chromatography (HPIC) capability. Common analyses include the anions fluoride, chloride, nitrate, bromide, nitrite, orthophosphate, and sulfate.
Within the WERC laboratory two separate gas chromatography instruments are available. An Agilent 6890N and 5973 MSD gives the lab mass spectrometry capability for analysis of volatiles and semi-volatiles, and a Shimadzu GC2014 gives the lab flame ionization detection and thermal conductivity detection capabilities for volatiles, semi-volatiles, and gas samples.
Gas chromatography techniques are applicable to gas samples, and samples containing volatile and/or semi-volatile organic compounds dissolved in an organic solvent such as hexane or methylene chloride.
Gas chromatography with flame ionization and thermal conductivity are strictly quantitative techniques, i.e. no qualitative capability. The selection between thermal conductivity and flame ionization is compound dependent. Hydrocarbons such as methane will ionize and conduct within a flame, making them good candidates for flame ionization detection. Analytes that will not ionize within a flame such as nitrogen, oxygen, and carbon dioxide, are limited to thermal conductivity detection.
The Agilent GC/MS is used primarily for analysis of volatile and semi-volatile organics, such as the gasoline, diesel, and residual range organics found in crude oil. The MSD detector is unique in that it generates a mass spectrum for each individual compound within a chromatogram. This mass spectrum gives GC/MS its qualitative analysis capability.
Organic carbon and inorganic carbon in aqueous samples may be measured with the OI Analytical 1030C. Direct analysis of the samples yields total carbon results, while dissolved carbon requires filtration prior to analysis.
Carbon values for a sample are quantified by measuring carbon dioxide with a non-dispersive infrared detector. Analysis for inorganic carbon includes the addition of hydrochloric acid followed by purging of the resulting carbon dioxide. Organic carbon is converted to carbon dioxide using a platinum based catalyst.
In addition to the instrumental analysis capabilities, the WERC laboratory is also equipped with CAMO Unscrambler experimental design, data analysis, and multivariate data modeling software. This software is excellent for designed experiments and analysis such as factorial designs and analysis of variance. Data that lacks the structure of a designed experiment, such as environmental data, may also be analyzed and modeled with the Unscrambler. The multivariate capabilities of the Unscrambler offer an excellent means of identifying hidden structure in complex data sets.
