Guides
The questions that decide whether a result is worth anything, answered without reference to who performed the analysis. Written for the question, not for the brand.
| Opens with | A standalone answer containing a number |
| Contains | At least one comparison table |
| Cites | Compendial chapters and guidelines by designation |
| Closes with | The question as it is actually asked |
Purity is not content: why a 99 percent peptide is 78 percent peptide
HPLC purity and net peptide content answer different questions. A peptide at 99 percent purity typically contains 70 to 85 percent peptide by mass. Where the rest of the mass goes, and how each figure is measured.
02USP 61 is not a sterility test
USP <61> counts organisms in non-sterile products and reports colony forming units. USP <71> asks whether any viable organism is present in a sterile product, over fourteen days. The two are routinely confused, and the confusion matters most for injectables.
03How the 5 EU/kg/hour endotoxin limit is calculated
The parenteral endotoxin limit is 5 EU per kilogram of body weight per hour, and 0.2 EU/kg for intrathecal administration. How the limit converts into a per-vial figure, and why a result without spike recovery cannot be relied on.
04How to read a certificate of analysis, and what it cannot tell you
A field-by-field guide to reading an analytical certificate: which figures carry information, which phrases are empty, and why verification proves the document rather than the vial in your hand.
05Why an XRF heavy metal screen is not a compliance result
Energy-dispersive X-ray fluorescence detects at parts per million. ICP-MS detects at parts per billion and below. When permitted limits sit at parts per billion, a not-detected XRF result is compatible with a failing sample.
06How to prepare and ship a peptide sample without ruining the result
Sample handling decides how much a result is worth. Why raw powder ships in sealed glass, why microbiological work needs unopened units, and how much material each determination actually consumes.
Updated 2026-09-01