The methods we run.
Five techniques, each written up at length: what it separates or images, how to read what it produces, the instrument behind it, and — the part usually left out — what it cannot tell you however good the sample is.
These are the methods run in this laboratory, and the ones a ZEIKKA certificate can cite. Each page says what the method measures, how its output is read, and — the part usually left out — what it cannot establish.
They exist because a certificate is worth what its method is worth. If you are holding one of ours, this is where you find out what the figure on it can support — and if you are deciding what to have measured, it is where you find out which method answers your question.
Gas chromatography with flame ionisation detection
Volatile components are carried by an inert gas through a heated capillary column and separated by boiling point and by affinity for the column coating, then burned in a hydrogen flame whose ion current is proportional to the carbon passing through it.
- Reports
- Residual solvents · Volatile impurities · Assay of a volatile substance
- Cannot establish
- Anything not volatile is invisible, and most of what a certificate is about usually is not. Gas chromatography says nothing about the purity, identity or molecular weight of an active that will not travel as a gas; it is on a certificate for what the liquid methods cannot reach.
Liquid chromatography tandem mass spectrometry
Chromatographic separation followed by tandem mass analysis, confirming the observed molecular weight against the theoretical value for the declared sequence.
- Reports
- Identification (MS) · Confirmation of identity
- Cannot establish
- Mass is not structure. Two different molecules with the same formula have the same mass, and the intact mass alone cannot separate them. Distinguishing them needs the fragment pattern, and even then not always.
Reversed-phase HPLC with UV detection
Separation on a C18 stationary phase with gradient elution, quantified by UV absorbance against a certified reference standard.
- Reports
- Purity · Identity · Net quantity
- Cannot establish
- A purity figure by UV area is an area percentage at one wavelength. It is not a mass percentage, and converting between them requires response factors the method does not provide.
Scanning electron microscopy
A focused electron beam is scanned across the specimen and the secondary and backscattered electrons it releases are collected point by point, building an image of surface topography and compositional contrast at magnifications an optical microscope cannot reach.
- Reports
- Appearance and particle morphology · Coating and film integrity · Foreign particle characterisation
- Cannot establish
- An image is evidence about the fields imaged and about nothing else. An instrument that looks at a few square microns at a time can be pointed at the most convincing part of the stub, and the resulting micrograph will be entirely true and completely unrepresentative. A morphology statement is worth what its sampling is worth, so a certificate citing one should say how many fields were examined and how they were chosen.
Supercritical fluid chromatography with UV detection
Separation on a chiral stationary phase with supercritical carbon dioxide and an alcohol co-solvent as the mobile phase, resolving enantiomers and quantifying their ratio by UV absorbance.
- Reports
- Enantiomeric excess · Diastereomer and isomer separation · Purity of low-polarity compounds
- Cannot establish
- Enantiomeric excess is not chemical purity, and the two are routinely confused. A sample can be 100% ee and still be half solvent, half degradant or the wrong compound entirely: ee describes the ratio between two mirror images and says nothing about anything else in the vial. A certificate carrying ee% and no purity figure has reported one thing, not two.
Which method answers which question
They are not alternatives, and a certificate carrying more than one is not carrying the same measurement twice. Each answers a question the others cannot: how much of what is here, is this the compound it is declared to be, what volatile material is left in it, which of two mirror images is present. That is why purity, identity, residual solvent and enantiomeric excess are separate lines rather than one, and why a method is quoted beside every figure.
Measured by none of them
- Water content
- Counter-ion and salt form
- Endotoxin, sterility and bioburden
- Biological activity or potency
A certificate reports the lines its analysis covers. A line the data does not cover is one the certificate cannot fill in.
Not sure which method answers your question?
Tell us what the material is and what you need established about it. We will say which of these reaches it — and if none of them does, we will say that rather than run the nearest one and report a figure that answers a different question.