A Recycling Method for LST® Contaminated During Heavy Liquid Separation in Palynological Processing

An aqueous solution of LST® is one of many heavy liquids used to concentrate palynomorphs. It and aqueous solutions of sodium polytungstate (SPT) are replacing toxic heavy liquids, such as bromoform and zinc bromide, and to a lesser extent zinc chloride, in many palynology laboratories. Both non-toxic heavy liquids can be recycled through filtering and evaporation of water and/or ethanol added to the sample during processing, and commonly are. Both media, and especially LST®, are somewhat reactive with organic matter, and in humic-acid rich samples become contaminated and discoloured. This paper presents the authors' methods for recycling LST® and removing contamination through a combination of filtration through activated charcoal and 0.45 μm nylon membranes. Filtration through Celite® was found to be unnecessary.