hey!

[bhargavi]

hai all!
my doubt is dat y does a mass spectrometr detect only cations(esp unipositive ones)y is it dat most of da or rather all time we refer to mol ions wid +ve charge n nt anions?

[Ary]

Mass spectrometers are capable of detecting both positive and negative ions. The choice of detection depends purely on the molecule being investigated.

[kuldeep_mica]

Mass Spectometers can be used in positive mode to scan/quantitate for positive ions and also in negative mode to scan/quantitate the negative ions. Also they take aaccount of the multiple charged ions. e.g. you can scan a protein in MS. Basically it scans for the molecular weight of protein/charges and provides a specific pattern for the target molecular weight multiple charged ions. The molecular weight of protein can then be calculated through deconvoulation. Technique works best for pure samples. Also for mixture of compounds, algorithms have been developed to resolve the complex mixtures of multiply charged ion peaks into a spectrum with a true mass scale and one peak per component.

[bhargavi]

thank u so much for da replies!