Should I Use XRPD or SAXS for My Pharmaceutical Sample at DANNALAB?

Updated

Choose XRPD when your question is about the solid state — polymorphism, crystallinity, identity, or salt form of an API or formulation. Choose SAXS when your question is about structure in solution or in dispersion — proteins, peptides, antibodies, liposomes, LNPs, nanoemulsions, or nanoparticles. If your sample is a lipid carrier or a peptide system where both solid-state form and solution structure matter, DANNALAB offers combined SAXS/WAXS characterization. Both techniques are run under cGMP with regulatory-ready documentation.

The deciding question: solid state or solution structure?

DANNALAB's service pages split along one practical line: whether the property you need to demonstrate lives in the crystal lattice or in the arrangement of molecules in a liquid or dispersed phase.

Your question Technique Typical sample types
Which polymorph is present? How crystalline is the material? Is this the correct API form? XRPD Small-molecule APIs, solid formulations, peptide API solids
What is the higher-order structure, aggregation state, or particle inner structure? SAXS Proteins, antibodies, peptides in solution, LNPs, liposomes, nanoemulsions, nanoparticles
Lipid phase behavior plus solid-state form in one package Combined SAXS/WAXS Lipid carriers, peptide–lipid systems

When XRPD is the right choice

XRPD is DANNALAB's small-molecule workhorse. The site lists it for polymorphism, crystallinity, and identity of APIs and formulations, and positions it inside release packages with QA-approved CoA and 24–48 hour turnaround available.

Use XRPD if you are:

  • Releasing batches or running QC. XRPD fits release packages where the solid form must be confirmed against specification.
  • Developing or validating a method. DANNALAB describes ICH-compliant validation with LOD/LOQ determination in the 0.17–0.5% wt range and rapid feasibility assessment.
  • Supporting identification and quantification. Both are listed XRPD applications for small-molecule drugs.
  • Handling EU import testing. Pharmaceuticals imported into the EU require GMP testing in an EU laboratory under Directive 2001/83/EC; XRPD release testing is one of the services DANNALAB maps to that requirement.
  • Working on peptide solids. For peptides, XRPD covers amorphicity, crystallinity, polymorph and salt-form characterization, and CMC structural comparability.

A practical example: you have a generic solid oral product and need to show the API is present in the same polymorph as the reference, plus confirm crystallinity has not changed after stability storage. That is an XRPD question end to end.

When SAXS is the right choice

SAXS answers questions XRPD cannot: how molecules are arranged in native solution or inside a dispersed particle. DANNALAB lists SAXS for:

  • Biopharmaceuticals and biosimilars — higher-order structure in native solution, comparability studies, aggregation and oligomerisation detection, and stability or forced-degradation studies.
  • Drug delivery systems — LNP, liposome, and nanoemulsion structure; mRNA-LNP assembly characterization; lipid phase and polymorph analysis. cGMP documentation is available for selected methods.
  • Nanoparticles — size distribution and inner structure.
  • Peptides in solution — aggregation, higher-order structure, oligomerisation and stability monitoring, and lipid-carrier characterization when combined with WAXS.

A practical example: you are developing an mRNA-LNP and need evidence that the lipid carrier's internal structure is consistent between batches, or that it survives a stress condition. That is a SAXS question.

When you need both

Two application areas on DANNALAB's site explicitly combine the techniques:

  • Peptide CMC. Solution-state work uses SAXS (with WAXS for lipid carriers), while solid-state work uses XRPD for amorphicity, crystallinity, and polymorph/salt form. A full peptide CMC comparability package can draw on both.
  • Lipid-based carriers. SAXS gives the mesophase structure; WAXS resolves the sharper-length-scale lipid phase and polymorph information.

If your program spans drug substance solid form and a formulated carrier, plan the combined approach up front rather than sequencing two separate studies.

A third case: patents and specifications

DANNALAB also offers technical analysis of XRPD and SAXS data against patent claims and specifications. The technique follows the claim: if a patent asserts a polymorph, the analysis is XRPD-based; if it asserts solution structure or particle characteristics, it is SAXS-based. Decide the technique from the claim language, not the other way around.

What applies regardless of technique

DANNALAB states cGMP accreditation since 2014, alignment with USP <941> and Ph.Eur <2.9.33>, 21 CFR Part 11 compliance, traceable data, QA-approved CoA, and 24–48 hour turnaround available. These are the documentation and timeline conditions to confirm for your specific method when you request a technical quote or price list — the site does not publish pricing, so scope and cost come through that request rather than from a public rate card.

Quick decision rule

  • Solid, crystalline, or polymorph question → XRPD.
  • Solution, dispersion, particle, or aggregation question → SAXS.
  • Peptide or lipid system where both matter → combined SAXS/WAXS plus XRPD.
  • Patent or specification comparison → match the technique to what the claim describes.