Boiling temperature of salt water at low pressure
According to this 1927 paper, "THE VAPOR PRESSURE OF THE SATURATED AQUEOUS SOLUTIONS OF CERTAIN SALTS" at 25 °C, 6 mol per kg salt solution gives a pressure of 18.5 mmHg instead of 24.5 mmHg for pure water.
So yes there should be a measurable difference (unless salt destroys the diaphragm pump). 

Edit: This recent paper "Water vapour pressure above saturated salt solutions at low temperatures", gives the same results