How to calculate the peak areas of every single peak from the mass spectrum?

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Maggie Chen 2019-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/454739-how-to-calculate-the-peak-areas-of-every-single-peak-from-the-mass-spectrum

评论： Maria Basile 2022-1-27

Example.txt

Hi, I am wondering any toolboxs or codes could be used to calculate the peak areas of every single peak from the txt file or fig file. I know how to integrate the peak area in the excel using the txt file, but have to find the tails from the baseline manually. The picture showed how peak area was identified. I also attached a txt file from the mass spectrum. For the output, the centroid mass and peak area of every peak will be needed. Peak Area.jpg

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回答（1 个）

A. Sawas 2019-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/454739-how-to-calculate-the-peak-areas-of-every-single-peak-from-the-mass-spectrum#answer_369290

编辑：A. Sawas 2019-4-5

在 MATLAB Online 中打开

The function findpeaks can find the peak values and locations.

data = importdata('Example.txt');
plot(data);
[pks,loc] = findpeaks(data);
findpeaks(data); %Use findpeaks without output arguments to display the peaks

Then you can find the boundaries around that peaks in order to find the area.

for k = 1:length(loc)
   i = loc(k);
   while i > 1 && data(i-1) <= data(i)
       i = i - 1;
   end
   b_min(k) = i;
   i = loc(k);
   while i < length(data) && data(i+1) <= data(i)
       i = i + 1;
   end
   b_max(k) = i;
end
%b_min: minimum boundary
%b_max: maximum boundary

To find the area under the first peak:

A = trapz(data([b_min(1):b_max(1)]));

You can find the area under all the peaks then the one with maxium area as follows:

for k=1:length(b_min)
    A(k) = trapz(X([b_min(k):b_max(k)]),Y([b_min(k):b_max(k)]));
end
[max_area, i] = max(A); 
max_peak = loc(i);

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Jawaher Seddiq 2020-11-25

I tried this but getting an error can you check please

Maria Basile 2022-1-27

@A. Sawas hi!

I know it's been a while since your comment (sorry for my bad english), but I'm trying to use your code below and it works pretty well until locs indices are non integers, that is my situation. I can't figure out how to fix it, because even if I change "while i>1" with "while i>0" then the indices of data will be a non integer and I'll get an error. I'm new at this type of analysis.. could you help me, please?

for k = 1:length(loc)

i = loc(k);

while i > 1 && data(i-1) <= data(i)

i = i - 1;

end

b_min(k) = i;

i = loc(k);

while i < length(data) && data(i+1) <= data(i)

i = i + 1;

end

b_max(k) = i;

end