Metrological Traceability
Definition
An unbroken chain of comparisons linking a result back to a recognised reference, each step with its own stated uncertainty. It is what allows two laboratories using different instruments to be talking about the same milligram.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Measurand
The quantity actually being determined, stated precisely enough to be unambiguous. Peptide content, net peptide content and chromatographic purity are three different measurands on one vial, and they return three different numbers.
Limit of Detection (LOD)
The smallest amount a method can reliably distinguish from background, without being able to say how much is present. A result below it is reported as not detected rather than as zero.
Limit of Quantitation (LOQ)
The smallest amount a method can measure with acceptable accuracy and precision. It is higher than the limit of detection, and a figure reported below it carries more uncertainty than the digits suggest.
Reporting Limit
The lowest value a laboratory will put on a certificate, set at or above the limit of quantitation. Anything smaller is reported against that limit rather than as a number nobody can defend.
Chromatogram
The detector trace a chromatographic run produces: signal against time, with each component appearing as a peak. The purity figure on a certificate is arithmetic performed on the areas of those peaks.
Retention Time
How long a component takes to travel through the column and reach the detector. It is characteristic of a compound under fixed conditions, which is why identity is often confirmed by a sample and a reference standard eluting at the same time.
Co-elution
Two components leaving the column together and arriving as one peak. It is the main way a purity figure can be honestly measured and still be too high, and it is why an orthogonal method is worth running.
Peak Integration
Deciding where a peak starts and stops so its area can be calculated. Where the baseline is drawn changes the number, which is why integration parameters belong in the method rather than in the analyst's judgement on the day.