3-53: Residual calcium in neutralized hydrolysates can destroy HPLC columns

 HPLC (high pressure liquid chromatography) columns containing weak anion exchange resins in the lead form (eg. BioRad Aminex HPX-87P) are frequently used to quantify the carbohydrates (sugars) that are found in lignocellulosic hydrolysates (sugarcane bagasse, sorghum, etc.). These columns are expensive and are easily damaged by both extreme pH (5>x>9) and ash. The newer NREL (National Renewable Energy Laboratory) procedure specifies the use of calcium carbonate (CaCO₃) rather than barium hydroxide (Ba(OH)₂) to neutralize the hydrolysate prior to analysis via HPLC. Since this change was made, we noted a column-mortality rate exceeding that observed when using Ba(OH)₂. The columns were irrevocably damaged, and could not be regenerated. The cause of this was observed to be excessive Ca²⁺ remaining in the hydrolysate after neutralization. The phenomenon is described here, along with a quick colorimetric assay which can be performed to determine if the samples are likely to cause column damage. It was found to be simpler and less expensive, overall, to return to the use of Ba(OH)₂.