Editing Guide to technical writing (section)

===Split infinitives===
A ''split infinitive'' is when you insert a word between "to" and its verb. For example:
:'''Normal phrase''':  The spectrum analyser was used to study the device closely.
:'''Split infinitive''': The spectrum analyser was used to closely study the device.

Here, "study" is the verb and it has been split from the "to" in the second example. Split infinitives used to be thought of as bad grammar, but now in modern times many people accept them.  However, some PhD examiners may be annoyed by them. Therefore the general advice is to minimize their use in formal and technical writing, where possible. However, feel free to use them occasionally when it makes the sentence clearer or flow better.