343
ions formed, which are formed within about 10 ms of the aerosol entering the
plasma, are positioned at about 7 mm in the plasma (Ammann 2007).
Plasma/introductory part in vacuum The positively charged ions generated in
the plasma are extracted into a vacuum system using metal cones. These cones are
special metal plates with central openings (<1 mm) allowing high vacuum to be
maintained between the input system and the mass spectrometer.
Ion focusing system The ions created in the plasma that pass through the holes of
the cones are focused with the help of electrostatic lenses and thus pass into the
system which is under high vacuum (where the mass spectrometer is located).
Extraction lenses are a secondary essential part that allows ions to be separated from
photons and residual neutral atoms (Ammann 2007; Linge and Jarvis 2009).
Ion separation and measurement system In inductively coupled plasma mass
spectrometry, three types of mass spectrometers are used: quadrupole, magnetic
sector, and TOF (time-of-flight). The most commonly used mass spectrometer is the
quadrupole, which uses a combination of DC (direct current) and AC (alternating
current) electrostatic fields to separate ions based on their mass/charge ratio (m/z).
Since almost only single ions are generated in plasma, the mass/charge ratio is identical to the mass of the ion, creating a very simple mass spectrum for interpretation.
The DC/AC electrostatic field ratio is fixed but the spectrometer voltages can be
varied. For a given voltage tuning, only one isotope is stable, and the quadrupole
quickly scans in the 2–260 amu mass range, missing any mass of interest to the
electronic multiplier (EM). An electronic multiplier is a device that detects any ions
that are leaked through the quadrupole. The detector calculates each signal for one
isotope, thus creating a mass spectrum. The mass spectrum is a simple and accurate
qualitative representation of the analyzed sample. The size of each peak is directly
proportional to the concentration of one element in the sample. The quantitative
result is created by comparing the signal of interest with the signals obtained for the
calibration standards for the respective elements (Ammann 2007).
Comparative analysis for AES-ICP and MS-ICP The use of these two spectrometric methods has shown that both techniques are characterized by certain strengths
and weaknesses. The sensitivity of AES-ICP systems is much lower than MS-ICP
when it comes to total dissolved solid (TDS). Particular care should be taken when
using mass spectrometry, where TDS is required to range within 0.1–0.4%.
Therefore, in atomic emission spectrometry, the total dissolved salts in the sample
can range up to 20%. This suggests that certain samples require a large dilution or
an initial small sample, which can sometimes affect the accuracy of the results. Both
techniques are multielement, with a dynamic determination area for AES-ICP of
106 and for MS-ICP of 108 (Linge 2009). Both techniques are suitable for
semiquantitative and isotopic analysis. Mass spectrometry shows a larger distribution of the multielement determination range (82 elements) as opposed to atomic
emission spectrometry with inductively coupled plasma (73 elements). Mass spec11 Chemical Composition and Nutritional Properties of Functional Food
ions formed, which are formed within about 10 ms of the aerosol entering the
plasma, are positioned at about 7 mm in the plasma (Ammann 2007).
Plasma/introductory part in vacuum The positively charged ions generated in
the plasma are extracted into a vacuum system using metal cones. These cones are
special metal plates with central openings (<1 mm) allowing high vacuum to be
maintained between the input system and the mass spectrometer.
Ion focusing system The ions created in the plasma that pass through the holes of
the cones are focused with the help of electrostatic lenses and thus pass into the
system which is under high vacuum (where the mass spectrometer is located).
Extraction lenses are a secondary essential part that allows ions to be separated from
photons and residual neutral atoms (Ammann 2007; Linge and Jarvis 2009).
Ion separation and measurement system In inductively coupled plasma mass
spectrometry, three types of mass spectrometers are used: quadrupole, magnetic
sector, and TOF (time-of-flight). The most commonly used mass spectrometer is the
quadrupole, which uses a combination of DC (direct current) and AC (alternating
current) electrostatic fields to separate ions based on their mass/charge ratio (m/z).
Since almost only single ions are generated in plasma, the mass/charge ratio is identical to the mass of the ion, creating a very simple mass spectrum for interpretation.
The DC/AC electrostatic field ratio is fixed but the spectrometer voltages can be
varied. For a given voltage tuning, only one isotope is stable, and the quadrupole
quickly scans in the 2–260 amu mass range, missing any mass of interest to the
electronic multiplier (EM). An electronic multiplier is a device that detects any ions
that are leaked through the quadrupole. The detector calculates each signal for one
isotope, thus creating a mass spectrum. The mass spectrum is a simple and accurate
qualitative representation of the analyzed sample. The size of each peak is directly
proportional to the concentration of one element in the sample. The quantitative
result is created by comparing the signal of interest with the signals obtained for the
calibration standards for the respective elements (Ammann 2007).
Comparative analysis for AES-ICP and MS-ICP The use of these two spectrometric methods has shown that both techniques are characterized by certain strengths
and weaknesses. The sensitivity of AES-ICP systems is much lower than MS-ICP
when it comes to total dissolved solid (TDS). Particular care should be taken when
using mass spectrometry, where TDS is required to range within 0.1–0.4%.
Therefore, in atomic emission spectrometry, the total dissolved salts in the sample
can range up to 20%. This suggests that certain samples require a large dilution or
an initial small sample, which can sometimes affect the accuracy of the results. Both
techniques are multielement, with a dynamic determination area for AES-ICP of
106 and for MS-ICP of 108 (Linge 2009). Both techniques are suitable for
semiquantitative and isotopic analysis. Mass spectrometry shows a larger distribution of the multielement determination range (82 elements) as opposed to atomic
emission spectrometry with inductively coupled plasma (73 elements). Mass spec11 Chemical Composition and Nutritional Properties of Functional Food