A method for determining a demultiplexing matrix for use in deconvoluting ion measurement data, the method comprising: acquiring ion measurement data by injecting ions into a spectrometer at a multiplexed injection rate according to the initial pulse sequence which comprises ON and Off pulses, said data comprising positive-value data points and non-positive- value data points; arranging the ion measurement data into a raw data array comprising a pattern of the positive-value data points and the non-positive-value data points, wherein the pattern matches said pattern of ON pulses and OFF pulses of said initial pulse sequence such that the positive-value data points correspond to respective ON pulses and the non-positive-value data points correspond to respective OFF pulses; constructing a modified pulse sequence by replacing each ON pulse of the initial pulse sequence with a corresponding modified ON pulse, wherein each modified ON pulse has a value proportional to the value of the corresponding positive-value data point, and the modified pulse sequence comprises a pattern of modified ON pulses and OFF pulses that matches the pattern of ON pulses and OFF pulses of the initial pulse sequence; and constructing a demultiplexing matrix based on the modified pulse sequence, the method further comprising: before arranging the ion measurement data, determining whether the pattern of the positive-value data points and non-positive-value data points can be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence and, if it is determined that the pattern of the positive-value data points and non-positive-value data points cannot be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence, then constructing the demultiplexing matrix based on the initial pulse sequence instead of the modified pulse sequence. acquiring ion measurement data by injecting ions into a spectrometer at a multiplexed injection rate according to the initial pulse sequence which comprises ON and Off pulses, said data comprising positive-value data points and non-positive- value data points; arranging the ion measurement data into a raw data array comprising a pattern of the positive-value data points and the non-positive-value data points, wherein the pattern matches said pattern of ON pulses and OFF pulses of said initial pulse sequence such that the positive-value data points correspond to respective ON pulses and the non-positive-value data points correspond to respective OFF pulses; constructing a modified pulse sequence by replacing each ON pulse of the initial pulse sequence with a corresponding modified ON pulse, wherein each modified ON pulse has a value proportional to the value of the corresponding positive-value data point, and the modified pulse sequence comprises a pattern of modified ON pulses and OFF pulses that matches the pattern of ON pulses and OFF pulses of the initial pulse sequence; and constructing a demultiplexing matrix based on the modified pulse sequence, the method further comprising: before arranging the ion measurement data, determining whether the pattern of the positive-value data points and non-positive-value data points can be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence and, if it is determined that the pattern of the positive-value data points and non-positive-value data points cannot be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence, then constructing the demultiplexing matrix based on the initial pulse sequence instead of the modified pulse sequence. before arranging the ion measurement data, determining whether the pattern of the positive-value data points and non-positive-value data points can be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence and, if it is determined that the pattern of the positive-value data points and non-positive-value data points cannot be matched with the pattern of ON pulses and OFF pulses of the initial pulse sequence, then constructing the demultiplexing matrix based on the initial pulse sequence instead of the modified pulse sequence.