:(a) Describe the steps in QuEChERS and explain their purpose.

(b) Why is an internal standard used in QuEChERS?

(c) What is displayed in the total ion chromatogram in Figure 28-22?

(d) What is displayed in the extracted ion chromatogram in Figure 28-22? What is the difference between an extracted ion chromatogram and a selected ion chromatogram? Which would have greater signal-to-noise ratio?

(e) What mass spectrometric method could be used to obtain even greater signal-to-noise ratio from the same QuEChERS extract?

QuEChERS is a solid-phase extraction method for assessing or identifying pesticide residues in food.

(a)

QuEChERS is a solid-phase extraction method for assessing or identifying pesticide residues in food. The name is abbreviated as "Quick, Easy, Cheap, Effective, Rugged, and Safe."

- In this process, the sample can be taken as a homology solution, centrifuged with the reagent, and agitated for 1 minute.

- Pesticide residue in food samples is identified using this method.

(b)

- An internal standard solution is one that has documented results and will not alter the QuEChERS technique. We will use it in conjunction with the analyte solution to record the readings. Whose value is the analyte solution's reference value, i.e. we wanted to get results.

- The internal standard is used in QuFChFRS because the internal standard experiences the same losses as the analyte.

(c)

The current from all ions over a given mass is shown as a function of time in this chromatogram.

Rebuilt total ion chromatogram is defined as a total ion chromatogram that has been reconstructed by adding or summing the intensities of all observed values of \(m/z\)

The reconstructed total ion chromatogram shows all of the ions that appear in the column. By looking at the chromatogram in figure 28-22, we can see that the complete signal from all ions was seen and recorded as a chromatogram at any given time.

(d)

We may state that an extracted ion chromatogram displays a value of \({\rm{m}}/{\rm{z}}312\) that is obtained from the complete spectrum, while a chosen ion chromatogram shows a value of \({\rm{m}}/{\rm{z}}312\)that is recorded continuously and has a greater signal-to-noise ratio.

The following is an explanation of the difference between an extracted ion chromatogram and a chosen ion chromatogram.

Ion chromatogram after extraction:

This chromatogram depicts detector current as a function of time for one or more values of \({\rm{m}}/{\rm{z}}\)

The depicted intensities are taken from the entire mass spectrum obtained at each interval period.

- This is for analyte interest only.

- Which means there isn't a good signal-to-noise ratio.

Ion chromatogram using a few selected ions:

This chromatogram, similar to an extracted ion chromatogram, can display detector current for a single or small number of \({\rm{m}}/{\rm{z}}\)values.

The signal for all \({\rm{m}}/{\rm{z}}\)values at each time interval is not measured by the selected ion chromatogram.

It may be used to gather data for specified or desired \({\rm{m}}/{\rm{z}}\) values over a period of time.

This is for analyte interest only.

- Because the most time is provided to detect signal at the designated mass, this chromatogram has a better signal-to-noise ratio.

(e)

- Because the longest time is given to detect signal at the targeted mass, the selective ion chromatogram is employed to acquire a higher signal-to-noise ratio.