Methods to Distinguish and Identify Your Contribution
The fact that you are so familiar with what you did means that your own contribution is obvious to you — but it may not be obvious to your reader.
One way to make sure that your own contribution is clear and easy to identify is by marking it with words — perhaps by adding phrases like In this study, the samples were collected using a suction tube or In our experiments the samples were collected using a suction tube, and by identifying the procedure used by other researchers with careful references at the appropriate place in the sentence (In Brown (1999) the samples were collected using a suction tube).
There are five possible uses that you may need. Note the different tenses.
Glasman, H. (2010). Science research writing for non-native speakers of English (pp. 50). Imperial College Press, London.