 Spectral interpretation is like a puzzle, similar to a crossword, a jigsaw or sudoku where to the uninitiated, it can be difficult to know where to start. However it can just take a small amount of knowledge to understand the problem so future puzzles, no matter how complicated, can be solved.

In that theme, here is a little interpretation quiz to follow on from the mass spectra interpretation poster. How many can you get right the first time and how many after understanding the theory?
Charge States

Some ionisation techniques, such as ESI, are capable of transferring more than one charge to the analyte. This is when it is very important to remember that the mass spectrum displays not the mass of the analyte but the mass divided by the charge. The nominal mass difference between isotopes is 1 and so this mass difference will be observed as mass difference divided by charge.

Therefore an analyte with two charges will have distances between the isotopes of 1 / 2 = 0.5 m/z units. If we look at the spectrum and calculate the distances between the isotopes, we can deduce the charge state. What is the charge state in each of following 3 examples?

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#### 3. What is the charge state in this example? During the ionisation process, may different ions are present and can be transferred to the analyte to create an ion. Adding a proton can be the most commonly observed ion in any given spectra but if salts and buffers are used in the mobile phase or sample diluent then species such as [M+NH4]+, [M+Na]+ and [M+K]+ can also be observed in positive mode Can you assign the correct adduct to each of the following peaks?

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#### 6. Assign the correct adduct to peak 3 Isotope Pattern

An element is defined by the number or protons in the nucleus and when there are different numbers of neutrons, these are called the isotopes. Carbon can have either 6 or 7 neutrons and it will be seen in a mass spectrum as 12C and 13C with their heights equivalent to their relative abundance, 100% 12C and 1.1% 13C. Many elements exist as A+1, such as carbon, hydrogen and nitrogen, but others can be A+2, such as Chlorine, Sulphur and Bromine whilst transition metals will have very distinctive isotope patterns If an analyte contains more than one element with multiple isotopes, then the abundances are cumulative: Using the table below, identify which element the following spectra indicate. T