Locking PLGEL (PLG) provides increased protection and ease of handling when working with standard organic extraction mixtures. The use of PLG can result in the recovery of 20 to 30% more nucleic acid than with traditional methods. After organic extraction, it is often difficult to recover nucleic acid in the aqueous, upper phase that is free from the denatured protein present at the aqueous and organic phase interface. PLG present during Phenol, Phenol: Chloroform, and Chloroform: Isoamyl Alcohol extractions migrate under centrifugal force to form a seal between the organic and aqueous phases. The organic phase and the interface material are effectively trapped below the PLG. The barrier is sufficiently durable that the aqueous upper phase, containing the nucleic acid, can then be recovered quantitatively by simply decanting or pipetting to a fresh tube. PLG is inert, heat-stable, and does not interfere with standard nucleic acid restriction and modification enzymes. In fact, many of the reactions can be carried out in the presence of PLG at the appropriate temperature and then terminated by extraction with Phenol or Phenol: Chloroform. PLG can be present during the heat inactivation of enzymes (65°C for 10 minutes) prior to the organic extraction. The ability of PLG to separate the phases is based on the density differences of the aqueous and organic media. The organic layer must have a higher density than the PLG and aqueous phase, and the PLG must have a higher density than the aqueous phase. High salt and protein concentrations in the aqueous phase may affect both aqueous and organic phase densities. Different organic phase formulations also vary in density. When choosing a type of PLG, the composition of all components must be taken into consideration. For optimum phase separation, the compositions of the aqueous phase, organic phase, and PLG must be compatible. As a result, PLG is offered in two different density formulations: Light and Heavy.