Alkylation kit

For improved volatility, better thermal stability or low limit of detection in gas chromatography prerequisite: quantitative, rapid and reproducible formation of only on derivative halogen atoms introduced by derivatisation (e.g. trifluoroacetates) allow specific detection (ECD) with the advantage of high sensitivity elution order and fragmentation patterns in MS can be influenced by a specific derivatisation.
Reagents for silylation - alkylation (methylation) - acylation are available. Which is the proper reagent for methylation?
Test kit for determination of the optimum alkylation.