TABLE 1.

Troubleshooting table.

Step	Problem	Possible reason	Solution
7	No peaks (oligosaccharides) are observed in SAX- or RPIP-HPLC and UV detection	Enzyme is inactive	Check for enzyme activity on a GAG standard
		Insufficient enzymatic treatment	Extend the digestion time
	Baseline chromatogram in SAX- or RPIP-HPLC and UV detection is noisy and contains spurious peaks	Solvent inadequately degassed	Use an on-line vacuum degasser to the HPLC system
		Purity of reagents has been compromised	Reprepare fresh reagents and HPLC solvents
		GAG sample was impure	Repurify GAG sample and treat again with lyase
12	Overlapping of oligosaccharides species in RPIP-HPLC-ESI-MS	pH values of HPLC solvents are different than 7.0	Carefully check for pH of HPLC solvents. Reprepare fresh HPLC solvents
		Sample contains salt	Either repeat purification and depolymerization of GAG sample or desalt oligosaccharides
	Elution time periods change or become unstable from run to run in RPIP-HPLC-ESI-MS	The column has not been well conditioned from run to run	Reequilibrate the C18 column(s) in solvent C for 20 min at a flow rate of 0.5 ml min−1 (for the Discovery C18 column) or 0.3 ml min−1 (for the Gemini C18 column)
	No peaks are evident by mass spectrometry	Solvent flow is inadequate	Make sure the solvent is flowing from the needle
			Make sure that the divert valve setting is correct
		High voltages and spay chamber currents are off	Make sure the electrospray high voltages are switched on
		Drying gas flow is insufficient	Check the drying gas flow and temperature
		Pressure is too low	Make sure the fore and high-vacuum pressure are within normal ranges