It has been a pleasure working for this esteemed company for the last [duration since you joined]. I have always labelled myself as a professional and I am always keen to stay on top of my tasks. I am perfectly comfortable facing new challenges and ready to step in to handle new duties at any moment.
As you aware, my list of duties has been recently augmented to include: [list here new duties]. I view this increase in duties as an act of trust in my capacities and believe in my potential. This decision only increases my self confidence and is a driving force to my never ending quest for delivering best results. This is a challenge to my abilities that I cheerfully accept.
Having said so, I would like to kindly ask for my salary to be adjusted to correspond with the increased number of tasks and duties assigned to me. Such an adjustment would resemble the utmost acknowledgment to my efforts and never ending dedication.