Please put large blocks of code into a code block as I have done for your post above (edit your post to see how I did this).
Although your code looks like it would work, I think you are overcomplicating things a little. Remember that you can include quotes inside a string by using the alternative type of quote:
_numberOfObjective = _this select 0
_myString = format ["'%1' objStatus 'DONE'", _numberOfObjective]
_capture = createTrigger ["EmptyDetector", _start]
_capture setTriggerArea [100,100, 0, false]
_capture setTriggerTimeout [60, 180, 120, false]
_capture setTriggerActivation ["WEST SEIZED", "PRESENT", false]
_capture setTriggerStatements ["this", _myString, ""]