Bond Elut PBA is a unique silica based SPE adsorbent containing phenylboronic acid functional groups, which can retain analytes through reversible covalent bonds. This very strong covalent retention mechanism produces high selectivity and purification efficiency. Borate groups have strong affinity for compounds containing cis diol structures, such as catechins, nucleic acids, some proteins, carbohydrates, and PEG compounds. Amino acids, alpha hydroxy amides, and ketone compounds can also be preserved.