Apparatus for determining if an aqueous mobile phase solution is properly being delivered by a mass spectrometry liquid sample delivery device, said apparatus comprising: an ion source device ; a tandem mass spectrometer ; and a processor ; wherein the processor is configured to: instruct the ion source device, before a sample is introduced into the liquid sample delivery device , to receive aqueous mobile phase solution from the liquid sample delivery device and ionize compounds of the aqueous mobile phase solution, producing an ion beam of aqueous mobile phase solution compounds; instruct the tandem mass spectrometer, before the sample is introduced into the liquid sample delivery device or between sample introductions into the liquid sample delivery device, to receive the ion beam of aqueous mobile phase solution compounds from the ion source device, to perform a first neutral loss scan of the ion beam with a first neutral loss value set to a molecular weight of a first known solvent, producing a first intensity, to perform a second neutral loss scan of the ion beam with a second neutral loss value set to a molecular weight of a second known solvent, producing a second intensity, and calculate a ratio of the first intensity to the second intensity, and determine if the aqueous mobile phase solution is properly being delivered by the liquid sample delivery device based on the ratio. an ion source device ; a tandem mass spectrometer ; and a processor ; wherein the processor is configured to: instruct the ion source device, before a sample is introduced into the liquid sample delivery device , to receive aqueous mobile phase solution from the liquid sample delivery device and ionize compounds of the aqueous mobile phase solution, producing an ion beam of aqueous mobile phase solution compounds; instruct the tandem mass spectrometer, before the sample is introduced into the liquid sample delivery device or between sample introductions into the liquid sample delivery device, to receive the ion beam of aqueous mobile phase solution compounds from the ion source device, to perform a first neutral loss scan of the ion beam with a first neutral loss value set to a molecular weight of a first known solvent, producing a first intensity, to perform a second neutral loss scan of the ion beam with a second neutral loss value set to a molecular weight of a second known solvent, producing a second intensity, and calculate a ratio of the first intensity to the second intensity, and determine if the aqueous mobile phase solution is properly being delivered by the liquid sample delivery device based on the ratio. instruct the ion source device, before a sample is introduced into the liquid sample delivery device , to receive aqueous mobile phase solution from the liquid sample delivery device and ionize compounds of the aqueous mobile phase solution, producing an ion beam of aqueous mobile phase solution compounds; instruct the tandem mass spectrometer, before the sample is introduced into the liquid sample delivery device or between sample introductions into the liquid sample delivery device, to receive the ion beam of aqueous mobile phase solution compounds from the ion source device, to perform a first neutral loss scan of the ion beam with a first neutral loss value set to a molecular weight of a first known solvent, producing a first intensity, to perform a second neutral loss scan of the ion beam with a second neutral loss value set to a molecular weight of a second known solvent, producing a second intensity, and calculate a ratio of the first intensity to the second intensity, and determine if the aqueous mobile phase solution is properly being delivered by the liquid sample delivery device based on the ratio. <EOS>