Purity of Reagents

    In general, there are no analytical methods to determine that a compound is 100% pure.  The analytical technique used to examine purity always has a limit to what it can detect.  For example, if a compound shows one peak after liquid chromatography analysis with a UV detector, one cannot rule out the presence of impurities that are invisible to UV detection (for example water or trace silica gel).  The same applies to say thin layer chromatography with iodine detection to mark the location of hydrophobic compounds on the plate.

    For each GelbChem reagent we provide a specification sheet that gives a statement about purity and the analytical methods used to asses purity.  Since enzyme substrates are used to measure the activity of enzymes in samples, it is important that the amount of enzymatic product be kept to a minimum.  For this reason, we also provide explicit analytical data on the level of enzymatic product contamination.  All GelbChem substrates are sufficiently free of enzymatic product such that the sample-to-blank enzymatic activity ratios are sufficiently high so as to give accurate assessment of enzymatic activities in biological samples, for example using dried blood spots.

    Since compounds are not guaranteed to be 100% pure by weight, it is important that you do not use gravimetric measurement to make accurate concentration stock solutions of biomarkers and their internal standards as well as internal standards for enzymatic activity assays from supplied reagent solids.  The best way to know the absolute moles of compound in the vial is quantitative NMR analysis (qNMR) as explained in the info sheet (qNMR Analysis). The qNMR data is provided in the Specification Sheet with each Biomarker, Biomarker Internal Standard, and Internal Standard for enzymatic activity assays.  For solid enzyme substrates, gravimetric analysis is sufficient since the absolute moles of product formed is based on the use of an Internal Standard that has been quantified by GelbChem using qNMR.


    All enzyme substrates and cocktails  have been tested using a 3 mm punch of a dried blood spot from a healthy human.  Enzymatic activity data is given in the Specification Sheet supplied with each compound.

    Note that GelbChem reagents are for research use only and are not IVDs as defined by the USA FDA.  We make no claims as to the clinical performance of GelbChem reagents.