A peptide solution can read as almost blank on an assay while the vial in front of you looks entirely normal. The powder went in. The buffer went in. The liquid is clear. Most of the material simply never reached the measurement, because it's sitting on the inside wall of the container. Everything discussed here concerns research-grade material handled in a laboratory setting. These compounds are for research use only and are not intended for human or animal consumption of any kind.
Adsorption to the vessel is one of the most common invisible sources of error in low-concentration peptide work, and it earns attention because it isn't a quality problem with the peptide. It's a surface problem with the container. Below we cover what drives the loss, why borosilicate glass and polypropylene fail on different peptides, how large the loss gets in published measurements, and where bovine serum albumin — the classic carrier-protein fix — genuinely helps.
Why Peptides Disappear From Solution: The Sample You Never Measured
A container wall is not a neutral boundary. It's a competing surface with enormous area relative to the volume it holds, and a dilute peptide is constantly choosing between staying solvated and binding to it.
A Wall Is a Competing Surface
Peptides are chemically well suited to sticking. Many research-grade sequences are amphipathic, carrying charged residues on one face and nonpolar residues on the other, which gives them a plausible binding mode on almost any material. A hydrophilic surface engages the charged face; a greasy surface engages the nonpolar one. That contest between water and the wall also governs whether a peptide dissolves cleanly, which is why getting a peptide into solution in the first place and keeping it there are two views of one problem.
The Loss Is Silent
What makes this failure mode dangerous is that nothing looks wrong. The solution stays clear, and the label still says the nominal concentration. Instead the error surfaces indirectly — a curve sitting lower than expected, a signal that never appears at the bottom of a dilution series, poor agreement between vessels that should have held identical material. Those symptoms get blamed on the compound or the assay when the culprit is the tube.
Glass and Plastic Grab Peptides in Two Different Ways
Here's the point that undermines most rules of thumb. Glass and plastic differ less in how much they bind than in which peptides they bind, and the two mechanisms are chemically distinct.
Borosilicate Glass and Residual Silanol Groups
Glass surfaces carry residual silanol groups, and published handling guidance notes that basic amino acids can form electrostatic interactions with residual silanol groups on glass vials. The consequence is straightforward. Cationic peptides — anything rich in lysine, arginine or histidine — are the vulnerable class on glass. The wall is mildly negative, the peptide is positive, and the two find each other.
Polypropylene and Hydrophobic Contact
Plastic fails the opposite population. Nonpolar amino acids, per that same guidance, interact with the hydrophobic surface of polypropylene vials. Greasy sequences bind plastic for the same reason they linger on a reversed-phase column, which makes peptide hydrophobicity and how RP-HPLC reads it a useful predictor of storage behaviour. A late-eluting peptide is telling you about its affinity for nonpolar surfaces generally, not just about the column.
Neither Material Is Universally Safer
It's tempting to conclude that plastic simply wins. One comparison found a single unstable peptide in polypropylene vials against 13 and 14 in non-deactivated and deactivated glass respectively. But that result is population-dependent, and other work pushes the opposite way: in intact-peptide mass spectrometry, deactivated glass showed little or no recovery for hydrophobic peptides. Silanization, the standard fix for the glass problem, does nothing for a sequence whose issue was never electrostatic. Match the container to the sequence, not to a general rule.
How Much Peptide Actually Disappears
The magnitude here is the part that surprises people. This is not a rounding error.
The Headline Numbers
Analytical HPLC work on three cationic peptides — mastoparan X, melittin and magainin 2 — found that at 1 micromolar in 220 microlitre volumes, only 10 to 20 percent of peptide was recovered from borosilicate glass vials. Polypropylene tubes did comparably badly on that cationic set, and quartz cuvettes, widely assumed inert, returned 50 percent or less for all three.