Wet Chemistry for Element Analysis

ICP Chemistry (Mass Spectrometry and Atomic Emission Spectroscopy) & More

Wet Chemistry, also called wet chemical analysis, generally refers to chemistry performed on samples in the liquid phase. Classical wet chemistry is the traditional method of element analysis using laboratory beakers and flasks to manipulate a sample in order to identify a single element. Instrumental wet chemistry utilizes instrumentation to analyze a sample for a full spectrum of elements. Instrumented methods are automated and computerized for streamlined analysis and data storage. Since wet chemical analysis is performed on liquid samples, this type of element analysis can often be performed on samples too small for other instrumental methods.

Both classical and instrumental wet chemistry methods can provide qualitative and quantitative data about elements in the test sample. Laboratory Testing Inc. has the expertise and fully-equipped laboratories to provide both types of analyses. The chemists in LTI’s classical wet chemistry lab can perform traditional techniques including colorimetry, gravimetry and titrimetry. The instrumental laboratory can perform a full array of analyses such as ICP Chemistry (ICP Mass Spectrometry and ICP Atomic Emission Spectroscopy) and carbon, sulfur, oxygen, hydrogen or nitrogen analysis.

The Test Processes

Instrumental Wet Chemistry

ICP Chemistry -  ICP chemistry is offered by LTI using both the ICP-AES (Atomic Emission Spectroscopy) and ICP-MS (Mass Spectrometry Analysis) methods. The test sample must begin as a liquid or be dissolved in a solvent to generate a solution that can be aspirated with high velocity argon to form a mist. The samples are introduced into the spectrometer as a fine aerosol created by a nebulizer in the ICP system. Large droplets are removed and the remaining fine droplets are mixed with heated argon gas that has been charged with radio frequencies in the torch chamber to produce an argon plasma. The hot plasma removes any remaining solvent and causes sample atomization followed by ionization. The resulting absorbance spectrum indicates the elements present in the sample.

LTI performs ICP chemistry with spectrometers that use Charge Coupled Device (CCD) technology, which allows the instruments to measure the whole spectrum necessary for the analysis of all the common metal bases. The instruments are fully computer controlled and monitored to assure reliable processing and reporting of the wet chemical analysis results.

Element analysis by ICP Atomic Emission Spectroscopy produces qualitative data about the composition of samples. LTI’s ICP-AES spectrometers can analyze 52 elements in the periodic table with high resolution and sensitivity. ICP Mass Spectrometry evaluates most elements in the periodic table and provides qualitative and quantitative information about what elements and how much are present in the sample, including trace elements.

Inert Gas Fusion -  Inert gas fusion is used to determine the gas content in ferrous and nonferrous materials. Hydrogen, nitrogen and oxygen are the gases found in materials as a result of the melting processes and subsequent hot and cold working methods. Controlling the gas contents to low levels minimizes their adverse effects on mechanical properties such as strength and ductility. The inert gas method reverses the bonding between the gases and the metals, causing the dissociation of the gases. The dissociated gas is moved along a very elaborate separation chamber by an inert carrier gas. The gas to be analyzed flows into a detection system. An infrared system is used at LTI to detect oxygen, and the thermo-conductivity system is used for hydrogen and nitrogen analysis.

Classical Wet Chemistry

The classical methods of wet chemical analysis include colorimetry, gravimetry and titrimetry. The process of colorimetry relies on changes in color to show qualitative chemical measurements and identify elements. The measurement most commonly used in colorimetry is absorbance/transmittance of light, using the theory that if a solute absorbs light of a particular wavelength, the absorbance is directly proportional to the concentration of substance in solution. Measuring absorbance of light by a sample can lead to information about concentration when a standard with the same absorbance and a known concentration is identified. We can be reasonably sure that the substance with the same absorbance also has the same concentration.

Traditional analyses for quantitative results includes gravimetry based on the measurement of mass and titrimetry (volumetric analysis) using a volume measurement of a liquid. Gravimetric analysis entails the measurement of solids precipitated and weighed from a sample after dissolution. A known amount of sample is weighed, dissolved, manipulated either chemically or physically to precipitate a compound, and the collected solids are weighed. The amount of constituent in the original sample is calculated from the mass of the precipitate and its chemical composition. Titration can be used to determine the concentration of a known reactant. A reagent, called the titrant, of known concentration and volume (standard solution) is used to react with a measured quantity of reactant, making it possible to determine the exact amount that has been consumed when the endpoint is reached. Titrations often use visual indicators, such as a color change in the reactant mixture, to indicate the endpoint of a reaction.

LTI Capabilities

• ICP Chemistry
  • Mass Spectrometry
  • Atomic Emission Spectroscopy
• Inert Gas Fusion Oxygen, Hydrogen & Nitrogen Analysis
• Classical Wet Chemistry