Q. It appears that the Solujet detergent is leaving a ring on some of the labware that cannot be removed. What is this ring? (sodium silicate?) How do we remove it? The labware has not been completely submerged. We have just added the Solujet soak for some labware that may have stubborn organics. We have been giving the labware a 4 hour soak in 1% Solujet, followed by a warm tap water rinse, then wash with Liquinox, followed by 3x DI rinse.
A. Thanks for the question and the detail you have provided. It sounds like you have a great procedure to remove stubborn organic residue, save one item. With any of the Alconox, Inc. detergents you should not soak parts, especially glass, partially submerged.
Anywhere there is a glass/detergent/air interface there is a risk of etching the glassware. If the glass is completely submerged and there is no air interface, then etching is much less likely to happen. Dissolved oxygen at the meniscus of the interface promotes etching of glassware. It indeed sounds like the glass has been etched. If the glassware is etched, then unfortunately you cannot remove that etch.
Going forward, soaking the glassware completely will avoid etching.