First of all thanks for the encouraging acronyms referred by you relate to detectors for Gas Chromatography.
FID- Flame ionization detector, NPD-Nitrogen Phosphorus - Flame photometric query raised by you is mainly a method development issue. You will be fortunate if you come across a standard operating procedure based on a validated method using a technique with the right choice of technique combined with a suitable column and detector. In absence of any such method you can develop your own in-house method depending on availability of resources. However, for proficiency level testing in different laboratories there has to be the same method of analysis using identical set of conditions
In British English, some words from French, Latin or Greek end with a consonant followed by an unstressed -re (pronounced ( non-rhotic accent ) /ə(ɹ)/ or ( rhotic accent ) /ɚ/ ). In American English, most of these words have the ending -er .   The difference is most common for words ending -bre or -tre : British spellings calibre , centre , fibre , goitre , litre , lustre , manoeuvre , meagre , metre , mitre , nitre , ochre , reconnoitre , sabre , saltpetre , sepulchre , sombre , spectre , theatre (see exceptions) and titre all have -er in American spelling.
Second, I feel the specific comment about such approach here should be cited:
Judgments of Similarity Are Psychological: The Importance of Importance.
Zuriff, G E. 1,2 [Editorial] American Psychologist. 61(6):641, September 2006.
It emphasized that the conclusion about the data of the Gender Similarity Hypothesis can differ with different methodological tools and is therefore highly circumstancial.