Quality Control
Candor Chemicals is proud to be your vendor of choice for quality chemicals, and part of that pride comes from knowing that our customers are receiving products that they can trust. Our quality control philosophy has two core tenets:
- Products should be sufficiently pure such that they can be immediately introduced into laboratory applications upon receipt.
- Product identity should be sufficiently established such that customers can trust that they are receiving the product they ordered.
We believe in transparency regarding the nature of reagents and products we use, manufacture and supply to customers. This page will thus detail the nature of the processes we use for the purpose of Quality Assurance and Quality Control.
Reagents
- Reagent Selection and Testing
A. Reagents purchased for use in our manufacturing processes are, in all possible cases, sourced from reputable vendors based or operating physical locations within the United States of America who have an established track record of quality chemical production (Fisher Scientific, Sigma-Aldrich, VWR, etc.) and who provide informative certificates of analysis which can be readily compared to third party analyses in the event of a discrepancy.
B. Reagents which must be purchased from territories other than the USA are sampled and provided to a third-party lab for analytical confirmation of the stated product purity, identity, and other specifications. Only upon receipt and examination of these results do we determine that a reagent is or is not sufficient for use in our manufacturing processes.
Analytical Processes
Compound Identification Methods –
- Nuclear Magnetic Resonance (NMR) Spectroscopy
A. NMR is a spectroscopic technique from which we obtain structural information about molecules. Molecules for study are placed in the presence of an intense magnetic field and irradiated with radio-frequency photons to stimulate transitions in their nuclear spin states, the measured resonant frequencies of which (expressed as chemical shifts relative to a probe) are strongly influenced by their local chemical environment.
B. The resultant spectra are highly characteristic of the molecules which produced them, and any change or difference in chemical structure from that which is expected, even between constitutional or stereoisomers, can be readily identified. NMR is thus perhaps the most simultaneously efficient and authoritative method available to organic synthetic chemistry to demonstrate compound identity.
Purity Analysis Methods –
- Liquid Chromatography (LC)
A. LC is an analytical technique whereby molecules in solution are separated by introduction to a column packed with adsorptive material (stationary phase) via a solvent (mobile phase). Molecules pass through and ultimately leave the column at different times depending on their specific properties (polarity, size, structure, etc.) and the nature of the stationary and mobile phases, and are detected upon exiting the column by some means, typically a combination of UV/Vis spectrophotometry and mass spectrometry.
B. LC allows for the quantification of molecules which can be detected by these means. Typically reported is the ratio of the detected amount of the desired molecule over the amount of all molecules detected during the analysis, which is expressed as a percentage and referred to as “chromatographic purity”. Larger values of chromatographic purity – up to 100% – are indicative of a nominally purer compound.
- Mass Spectrometry (MS)
A. MS is an analytical technique by which the mass-to-charge ratio (m/z) of molecules may be measured. Molecules for analysis are ionized and introduced (typically by electrospray ionization in the case where the MS is coupled to LC) to a component known as the mass analyzer, which separates molecules based on their molecular mass and columbic charge. These molecules are detected upon exiting the mass analyzer and the number of each molecular species is counted, resulting in what is known as a mass spectrum.
B. The information contained in the mass spectrums permits us to identify what the components of a given sample are, identify contaminants, and quantify the presence of those contaminants. MS is rarely run by itself, and instead is most commonly coupled to LC or ICP (below), as in LC-MS and ICP-MS, as a complementary technique.
- Inductively Coupled Plasma-Optical Emission Spectroscopy/Mass Spectrometry (ICP-OES/ICP-MS)
A. ICP-OES and ICP-MS are techniques which are commonly used to detect and quantify the presence of heavy metals in compounds. Samples are dissolved, typically in a strong, oxidizing acid, and introduced via nebulizer to a source of an ionized rarefied gas (typically argon).
B. The extreme temperature of the plasma ionizes metals present in the sample, and these excited ions release electromagnetic radiation in the form of photons that can be (in the case of ICP-OES) detected and measured. As the frequencies of radiation released upon relaxation to the ground state are characteristic of each element, this can be used to both identify and quantify the presence of heavy metal contaminants in a sample.
C. In ICP-MS, ions generated by the plasma are instead guided to a mass analyzer after reaching the plasma source and are quantified by the principles of mass spectrometry as above.
Reagents which do not meet our standards are either returned and resourced from a different vendor, or subjected to further purification until they are of satisfactory quality. Products for sale are guaranteed to meet our stated specifications per the individual product pages; any discrepancies should be reported alongside supporting analytical results to [email protected] for consideration.
