Total amino acids

Total Amino Acid Analysis by Acid Hydrolysis

The amino acid composition of proteins, protein powders, hydrolysates and biomass, after acid hydrolysis. $150 analysis + $80 hydrolysis = $230 per sample.

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On this page
  1. What you get
  2. What hydrolysis changes
  3. Free and total on the same sample
  4. What to send
  5. Price and turnaround
  6. Key papers
  7. Latest research
  8. Key references
Short answer

We hydrolyze the sample in 6 N HCl at 110 °C for 24 hours, then measure the released amino acids by AQC derivatization and HPLC. You get 16 amino acids in g/100 g and mol%; tryptophan and cysteine are not reported. $230 per sample ($150 analysis + $80 hydrolysis).

What you get

Total amino acid analysis (AA-T) measures the amino acids bound in proteins and peptides as well as the free ones. We hydrolyze the sample in 6 N hydrochloric acid at 110 °C for 24 hours, the standard conditions in the harmonized pharmacopoeial method 1, then derivatize the released amino acids with AQC and separate them by HPLC.

ReportedUnitsNotes
Asx (aspartate + asparagine), Glx (glutamate + glutamine)g/100 g sample, mol%Asparagine and glutamine are converted during hydrolysis 1
Gly, Ala, Val, Leu, Ile, Pro, Phe, Tyr, His, Lys, Argg/100 g sample, mol%Ile and Val can read slightly low after 24 h 1
Ser, Thr, Metg/100 g sample, mol%Partly lost or oxidized during hydrolysis; wider uncertainty 1
Tryptophan, cysteine/cystineNot reportedTryptophan is destroyed; cystine recovery is poor 1

Each report includes the chromatogram, the calibration and the run's QC summary, like every OpenChemWorks report.

What hydrolysis changes

Acid hydrolysis breaks every peptide bond, but it is not gentle. The pharmacopoeial text lists the losses: tryptophan is destroyed, serine and threonine are partly destroyed, methionine can oxidize, cystine recovery is usually poor, and asparagine and glutamine are deamidated to aspartate and glutamate 1. Bonds between valine and isoleucine cleave slowly, so a single 24-hour hydrolysis can under-report them 1.

A single 24-hour hydrolysis therefore gives a good working composition, not an exact one. Hydrolyzing at several time points and modeling the yield and loss of each amino acid gave a mean recovery of 100% (range 94–110%) for a purified protein 2. We offer that time-course approach as a quoted project when you need it.

6 N HCl, 110 °C, 24 h: every peptide bond breaks AlaAsnAspTrpSerGlnGluLeuCysLysRecovered as isConverted: Asn → Asp, Gln → Glu (reported as Asx, Glx)Partly lost: serine, threonineDestroyed or poorly recovered: tryptophan, cystine
What acid hydrolysis does to a short peptide, based on the pharmacopoeial description of protein hydrolysis1. The animation plays once; it stays still if your device asks for reduced motion. Drawn in-house.

Free and total on the same sample

For protein hydrolysates, peptones and yeast extracts, running the free profile (AA-1) and the total profile (AA-T) on the same sample shows how much of each amino acid is already free and how much is still in peptides. Degree of hydrolysis itself is defined as the proportion of cleaved peptide bonds and is usually measured by other methods 4; the free-to-total comparison is the amino-acid-level view of the same question. Our note on free amino acids in hydrolysates explains how to read it.

What to send

SampleAmount
Liquids: protein solutions, media, broth, drinksAt least 200 µL, 400 µL preferred
Solids: protein powders, hydrolysates, peptones, feed, biomassAt least 100 mg (solids preparation, PREP-1, applies)

Salts, detergents, sugars and fats can interfere; tell us what is in the sample when you request a quote. Sodium azide oxidizes cysteine and methionine during hydrolysis, so leave it out where you can 3.

Price and turnaround

AA-T is $150 per sample, plus $80 per sample for acid hydrolysis (PREP-H): $230 per sample in total. Free and total on the same sample (AA-1 + AA-T) is $380. The order minimum is $150. Target turnaround: 5 business days from receipt.

Newer, faster hydrolysis methods are being published, such as a 2-hour high-pressure hydrolysis that matched the 24-hour standard for 15 of 16 amino acids 5. We use the standard conditions so results compare directly with the published literature.

Key papers

Latest research

New papers on this topic, newest first. We check PubMed every month; last checked October 2026.

Key references

  1. Amino Acid Determination (harmonized pharmacopoeial text, B-01, Rev. 1 Corr. 1) — Pharmacopoeial Discussion Group, November 2024.
  2. Correction for amino acid loss during acid hydrolysis of a purified protein — Darragh AJ, Garrick DJ, Moughan PJ, Hendriks WH, Analytical Biochemistry, 1996.
  3. Quantification of cysteine residues following oxidation to cysteic acid in the presence of sodium azide — Manneberg M, Lahm HW, Fountoulakis M, Analytical Biochemistry, 1995.
  4. Methodology for determining degree of hydrolysis of proteins in hydrolysates: a review — Rutherfurd SM, Journal of AOAC International, 2010.
  5. High-pressure hydrolysis: A rapid sample preparation strategy for amino acid analysis of complex biological matrices — Journal of Chromatography A, 2026.

OpenChemWorks Laboratory · Reviewed by the OpenChemWorks laboratory · Updated October 7, 2026

Have samples in mind?

Published prices, a person replies, and every report includes the chromatogram and QC behind the numbers. New customers: 5 samples for $250 total, credited to your first order.

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