A capable laboratory arrives, and the short-peptide problem becomes visible
Nordanalyt begins contributing ion-pair, SEC and ICP-MS work. Its first records show that a large part of the index had been measuring the wrong thing.
Nordanalyt Laboratories began accepting index submissions in 2024-Q3. It is the slowest and most expensive contributor and it brought three capabilities that existed nowhere else in the dataset: ion-pair chromatography, size-exclusion chromatography, and ICP-MS. Each one immediately invalidated a category of existing records.
Short peptides on C18
Compounds below about 520 Da have almost no hydrophobic surface and are barely retained on a C18 column. Vilon elutes at 3.94 min on RG-2, carnosine at 3.72, epitalon at 4.62 — all within a couple of minutes of the column dead time, where nothing is separated from anything.
Nordanalyt's ion-pair results on the same lots produced genuinely resolved chromatograms, and in several cases resolved impurities that the C18 method had integrated into the main peak. Epitalon is the clearest case: its β-aspartyl isomer is mass-identical and elutes 0.10 min from the parent, which on a compound retained for under five minutes is not a separation at any gradient length.
The index responded by marking C18-only submissions in the short bioregulator class as method-inappropriate. Twelve of nineteen vilon reports fall into that category, which is why the compound's headline median carries a method caveat rather than a low-n caveat.
| Laboratory | Records | Share of quarter | Median purity |
|---|---|---|---|
| Janoshik | 256 | 49.0% | 99.00 |
| PeptideMeter | 82 | 15.7% | 98.94 |
| Medutest | 67 | 12.8% | 99.12 |
| VendorInvestigate | 40 | 7.7% | 98.55 |
| Nordanalyt | 45 | 8.6% | 98.52 |
| Kestrel | 32 | 6.1% | 99.44 |
Metal complexes
ICP-MS gave the index its first copper numbers on GHK-Cu, and they showed the scale of the problem: a lot with essentially no copper and a fully complexed lot produce indistinguishable reverse-phase chromatograms, because the acidic mobile phase strips the metal on-column in both cases. Every GHK-Cu record without a metal determination was reclassified as PARTIAL, and most of them are.
Conjugates and recombinants
Size-exclusion chromatography made the PEG-MGF and IGF-1 records interpretable for the first time. The finding on PEG-MGF was that a single purity figure for a polydisperse conjugate is not a comparable quantity at all, and that eleven records in the index reported one above 98 %. Those are now recorded as method errors. For IGF-1 LR3 and DES, SEC showed measurable aggregate content in lots whose reverse-phase purity was unremarkable — which is exactly what the reverse-phase method is blind to.