Analytical Services : Chemicals
• A reproducible viscometric technique used in determining the molecular size of a species and is often used as a comparative molecular weight. IV is determined by dilute solution viscometry, analyzing the flow time of a polymer solution through a capillary viscometer as related to the flow time of a pure solvent. Chloroform (CHCl3) and hexaflouro-2-propanol (HFIP) are common solvents used for this technique; IV is reported in deciliters per gram (dL/g).
Fourier Transform Infrared Spectroscopy
A technique in which an infrared light source impinges on a sample. Depending on the molecular construction, light of different wavelengths is absorbed to differing degrees. This is often used to develop individual material reference spectra, and like a molecular fingerprint, each material spectra is unique. Poly-Med utilizes reflectance and transmission sample preparation techniques, either as a solution or in thin film formats.
Utraviolet – Visible Light Spectroscopy
An analytical technique that measures the absorption or reflectance in the UV and visible spectral regions. Molecular compounds with π-electrons, or non-bonding electrons, can be measured due to absorption in the UV and visible range and related to concentration using the Beer-Lambert law. One common use for UV/Vis is to determine dye concentrations.
A chromatographic method that separates and detects molecular species based on size. A relative molecular weight (MW) is determined from calibration to known standards. GPC analysis allows for a more detailed description of a species through characterization of polydispersity index (PDI), number average molecular weight (Mn), weight average molecular weight (Mw), size average molecular weight (Mz), and peak molecular weight (Mp). Common solvents used for polymer dissolution are tetrahydrofuran (THF) and dichloromethane (DCM).
For analyzing samples that can be vaporized to the gas phase without decomposing at elevated temperatures. The constituent molecules of the vaporized sample are separated on the column and have different retention times. Separation of molecules by the column allows for the molecular components of the sample to be analyzed qualitatively and quantitatively. Analysis includes sample purity, monomer content, residual solvents, relative amounts of impurities, and/or relative amounts of components in a mixture. Non-volatile samples, such as polymers, can also be analyzed using a headspace unit to collect the volatiles contained within a polymer sample.
High Pressure Liquid Chromatography
A chromatographic method most often used to quantify the presence of a molecule by comparing peak areas to a calibration curve. A solution is injected through a separation column and the analyte is detected by way of a UV detector. Often this is used to study the release kinetics of pharmaceutical compounds from various substrates. Poly-Med’s HPLC also has PDA capabilities, which can be used to study changes in the analyte over time.
Karl Fischer Moisture Content
This analytical technique is used for detecting trace amounts of water in a sample, particularly useful for the analysis of moisture-sensitive materials. The method involves heating a solid sample to vaporize the moisture contained within said sample, and then the vapor is transported to a titration cell via dry, inert gas. Liquid samples can be added directly to the titration cell. An electro-chemical titration named for its inventor, Karl Fischer, determines the amount of water in the sample, which is typically reported in parts per million (ppm).
Nuclear Magnetic Resonance
A method for determining total composition of a sample material by way of measuring the magnetic resonance of hydrogen-1 molecules within the molecules of a substance, which vary based on chemical composition of the molecule. Spectral peaks are associated with different types of bonds, which can be used to calculate the percent presence of known molecules, i.e. determining a polymer contains 94% glycolide and 6% lactide. This is most often performed from a polymer solution using various deuterated solvents.
An in-house method to measure the relative comparative viscosity of highly reactive monomers. This method measures the flow of a liquid through a tube and the comparative viscosity is reported in seconds (s).