What kind of chemical used in a chromatography run could be denoted with the letters D.H.?
Recently I had to read up on HPLC-MS technique and I encountered D.H./DH several times as an acronym for dehydrogenase, also, like in the quoted section, in the context of parabens analysis with HPLC.

For example, DH is explicitly defined as an acronym for dehydrogenase in Kastner's Protein liquid chromatography [1, p. 5] or in the paper by Zimmerling et al. [2].

Other examples for the exact dehydrogenase composition include acronyms such as ADH (alcohol dehydrogenase), FDH (formate dehydrogenase), $\small\text{D}$-LDH ($\small\text{D}$-lactate dehydrogenase), 11βDH (11β-hydroxysteroid dehydrogenase) and many more.

References


Protein Liquid Chromatography; Kastner, M., Ed.; Journal of chromatography library; Elsevier: Amsterdam; New York, 2000; Vol. 61. ISBN 978-0-444-50210-0.
Zimmerling, J.; Tischler, D.; Großmann, C.; Schlömann, M.; Oelschlägel, M. Characterization of Aldehyde Dehydrogenases Applying an Enzyme Assay with In Situ Formation of Phenylacetaldehydes. Appl Biochem Biotechnol 2017, 182 (3), 1095–1107. DOI: 10.1007/s12010-016-2384-1.