A SIMPLE AND VALIDATED LC METHOD FOR THE SIMULTANEOUS ANALYSIS OF GLUCOSAMINE AND CHONDROITIN SULFATE EQUIVALENT IN DIETARY PRODUCTS

Abstract

A simple and reliable reversed-phase liquid chromatographic (RP-LC) method was developed and validated to determine simultaneously a glucosamine and chondroitin sulfate equivalent in dietary products. The procedure is based upon the reaction of o-phthaldialdehyde with glucosamine and galactosamine coming from the galactosaminoglycan hydrolysis. The hydrolysis reaction was carried out with hydrochloric acid (7.5 N) at 80°C for 8 hr, whereas, the pre-column derivatization reaction was carried out in alkaline media for 1 min at ambient temperature. The chromatographic separations were performed on a Phenomenex Synergi 4 μ fusion-RP 80 A (250 mm × 3.0 mm i.d.) using a mobile phase consisting of a mixture of sodium acetate buffer (pH 5.9; 0.05 M) and methanol (85:15, v/v). UV-DAD detection at λ = 340 nm was used. Linear responses were observed and the limit of quantitation for both aminosaccharides was about 60 pmol. The intra-day precision (RSD) was ≤1.8% and there was no significant difference between intra- and inter-day data. Recovery studies showed good results (99.3–101.0%) with RSD ranging from 1.1 to 2.1%.

Keywords:

• chondroitin sulphate equivalent
• galactosaminoglycans dietary supplements
• glucosamine
• method validation
• o-phthaldialdehyde OPA
• reversed-phase liquid chromatography RP-LC

ACKNOWLEDGMENTS

We are grateful to Dr. Federica Ranalli for her valuable technical assistance. This work was supported by a grant from MIUR (“cofinanziamento PRIN” 2004, Rome Italy).

Notes

^a According to y = a x + b, where x is the analyte concentration and y is the ratio of amino sugar peak-area to IS peak-area.

^b Standard solution in HCl 7.5 N.

^c GlcN and CS spiked in placebo solution and subjected to hydrolysis procedure. [GalN] = ([CS] × CF)/100, where CF = conversion factor (26.70).

^a Analyte to IS area ratio.

^b Confidence percentage (α = 0.05).

^a  mg in about 120 mg of placebo.

^a Mean of five determinations expressed as a percentage of the claimed content.

^b Other ingredients: magnesium stearate, aerosil® 200 VV Pharma.

^c Other ingredients: methylsulfonylmethane, magnesium stearate.