Serine is one of the standard amino acids that make up proteins, and it also occurs on its own, unattached, in foods, fermentation samples, and cell culture media. A lab reports serine as part of a wider amino acid profile, not in isolation. One method point matters before anything else on a report: AABA, short for alpha-aminobutyric acid, is the internal standard the lab adds to help quantify the results. AABA is not serine and is not a result for your sample.
Chemistry in plain terms
Standard biochemistry references classify serine as a non-essential amino acid for humans, meaning the body can make it rather than needing to obtain all of it from food. Its side chain carries a hydroxyl group, which makes serine one of the polar amino acids in standard classifications. PubChem lists serine, in its L-form, as a standard proteinogenic amino acid, built into protein chains as well as present free in solution. Both forms of presence, bound and free, are real, and they answer different questions.
Where it occurs
Serine occurs as a building block in proteins across foods, feeds, and biological materials. Free serine also occurs in cell culture and spent media, fermentation and process liquids, protein hydrolysates, and food and supplement products, where a free profile describes the sample as it is.
This page gives no typical level for serine in any material. Levels vary with recipe, organism, process, and sampling point, and no verified figure is available. Measure your sample rather than borrowing a number from a different one.
Free vs total for serine
A free serine result measures the serine already dissolved and unattached in the sample as received, with no hydrolysis step. That is usually the relevant number when the question is about the sample as used or as eaten: what is in the medium now, or what free profile a product presents.
A total serine result is measured after acid hydrolysis, the step in total amino acid analysis that breaks protein chains apart and releases bound amino acids. A total result therefore includes free serine plus serine that was bound inside protein. This page gives no ratio between free and total for any material, because that ratio is a property of the specific sample.
Serine has no special hydrolysis conversion of the kind that affects asparagine and glutamine, whose amide groups are lost during acid hydrolysis and which are therefore reported together with aspartic acid and glutamic acid respectively. The general total-panel caution still applies: a hydrolysed measurement describes the sample after the method has acted on it, not a photograph of its native state.
Method notes: how serine is measured here
At OpenChemWorks, serine is measured as part of a panel using AQC pre-column derivatization, the Waters AccQ-Tag approach, with HPLC-UV detection. The amino acids are chemically tagged, separated on the HPLC column, and quantified against calibrated standards. AABA is added at a known amount as the internal standard, which is why its name appears in method paperwork. To restate the point: AABA is the standard, added by the lab; serine is the analyte, measured from your sample. Different compounds, different roles.
No resolution, recovery, or detection-limit figure is quoted here, because no verified figure from this laboratory's validated method is available.
Which panel includes serine
Serine is included in AA-1, the free amino acid panel: 19 amino acids plus ammonia, measured by AQC HPLC-UV. Cysteine is excluded from AA-1 and needs a separate AA-3 workup. Serine is also part of a total result under AA-T, where the sample is hydrolysed first and serine is reported on that total basis.
Prices are only these: AA-1 costs $150 per sample for liquids, $180 per sample for powders ($150 plus $30 powder preparation), and $150 flat for first-time customers, with $125 per sample at 25 or more samples per month. AA-T, total amino acid analysis, costs $230 per sample. The pilot is $250 for 5 samples, credited in full against a first contract signed within 90 days.
OpenChemWorks, in Davis, California, is validating now and reserving pilot slots. The lab is not GLP, GMP, or ISO/IEC 17025 accredited, and no turnaround is promised here. Email info@openchemworks.com with your sample description and whether your question is about the sample as it is, or its protein as a whole.
Frequently asked questions
Is AABA the same as serine?
No. AABA, alpha-aminobutyric acid, is the internal standard added by the lab for quantification. Serine is a different compound, and it is the analyte measured from your sample.
Do I need free or total serine?
Free answers a question about the sample as received. Total answers a question about protein composition after hydrolysis, and includes the free fraction.
Is serine reported on its own?
At OpenChemWorks it is reported as part of the AA-1 free panel or the AA-T total panel, alongside the other panel analytes.
Can I compare my serine result to a typical value from another product?
Not usefully. This page gives no typical level, because levels depend on the specific material, recipe, and process. Compare like samples measured the same way.
References
- PubChem — L-Serine (CID 5951) — Identity reference for the amino acid named on this page.
- Waters — Derivatization of Amino Acids Using Waters AccQ-Tag Chemistry — Method background for AQC derivatization and HPLC-UV amino acid analysis.
- British Journal of Nutrition (2023) — Asparagine and glutamine lose an amide residue during acid hydrolysis and are measured with aspartate and glutamate respectively.
- OpenChemWorks — Pricing — Published service and pricing copy (2026).
OpenChemWorks Laboratory · Reviewed by the laboratory director, PhD chemist · Published October 29, 2026