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2-(4-Hydroxyphenylazo)benzoic acid

matrix substance for MALDI-MS, ≥99.5%

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2-(4′-Hydroxybenzeneazo)benzoic acid, 4′-Hydroxyazobenzene-2-carboxylic acid, HABA, HBABA
Linear Formula:
CAS Number:
Molecular Weight:
EC Number:
MDL number:
PubChem Substance ID:


matrix substance for MALDI-MS

Quality Level


≥99.5% (HPLC)

analyte functional class(es)


analyte chemical class(es)

glycans, peptides, proteins


MALDI-MS: suitable


204-208 °C (lit.)
204-208 °C


ethanol: 20 mg/mL, clear

cation traces

Ca: ≤10 mg/kg
Cd: ≤5 mg/kg
Co: ≤5 mg/kg
Cr: ≤5 mg/kg
Cu: ≤5 mg/kg
Fe: ≤50 mg/kg
K: ≤50 mg/kg
Mg: ≤5 mg/kg
Mn: ≤5 mg/kg
Na: ≤100 mg/kg
Ni: ≤5 mg/kg
Pb: ≤5 mg/kg
Zn: ≤5 mg/kg


≥2000 at 337 nm (mol. absorption)

SMILES string




InChI key


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General description

2-(4-Hydroxyphenylazo)benzoic acid) (HABA), can be used for desorption of proteins, peptides and glycoproteins, thereby making it very advantageous for matrix-assisted laser desorption ionization mass spectrometry.

related product

Product No.

Storage Class Code

11 - Combustible Solids



Flash Point(C)

Not applicable

Personal Protective Equipment

dust mask type N95 (US), Eyeshields, Gloves

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Matrix-assisted laser desorption ionization mass spectrometry with 2-(4-hydroxyphenylazo) benzoic acid matrix.
Juhasz, Peter, Catherine E. Costello, and Klaus Biemann.
Journal of the American Society For Mass Spectrometry, 4 (5), 399-409 (1993)
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The chicken genome encodes several biotin-binding proteins, including avidin and avidin-related protein 4 (AVR4). In addition to D-biotin, avidin binds an azo dye compound, 4-hydroxyazobenzene-2-carboxylic acid (HABA), but the HABA-binding properties of AVR4 are not yet known. Differential scanning calorimetry

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