What kind of chemical used in a chromatography run could be denoted with the letters D.H.?

Question

A fellow translator is having trouble translating (into Russian) the mysterious D.H. abbreviation in the following passage:

Slight variations of the ratio of the mobile phase constituents or adjustments of the mobile phase flow-rate can be made occasionally, in order to provide a suitable elution times for Methyl p-hydroxybenzoate and D.H., and to meet the requirements of the system suitability tests.

If by some chance it's a widely known compound, or at least there are several chemicals that could be abbreviated thus, I'd be grateful for answers. A crapshoot, I know, but I became curious.

It could be some rare chemical; in that case it would be futile to try figuring it out.

Answer 1

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

1. Protein Liquid Chromatography; Kastner, M., Ed.; Journal of chromatography library; Elsevier: Amsterdam; New York, 2000; Vol. 61. ISBN 978-0-444-50210-0.
2. 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.

Answer 2

Since the context is about chromatography and elution times it seems probably that D.H. actually stands for an abbreviation of DHBA. Dihydroxybenzoic acids are family of phenolic acids (as it can be seen here) similar to methyl 4-hydroxybenzoate.

Another possibility is that D.H. stands also for Dorset-Henley liquid which is a synthetic medium for the culture of tubercoline but this seems improbable.