Name: icp-ms signal interference sources and fixes
Uploaded: 2024-04-04T10:51:35.000Z
Duration: 1 min 20 s
Channel: JoVE

Malgré les avantages offerts par l’ICP-MS, l’analyse élémentaire précise est affectée par les interférences spectroscopiques et non spectroscopiques.
L’interférence spectroscopique est causée par des ions ayant les mêmes valeurs m/z que les ions analytes. Les espèces interférentes comprennent les espèces isobares, les ions polyatomiques et les ions oxydes réfractaires.
L’interférence isobare provient des isobares de l’analyte, qui sont des nucléides différents qui ont le même numéro de masse, ce qui signifie que les valeurs m/z sont identiques.
L’interférence ionique polyatomique résulte de la combinaison d’espèces plasmatiques avec des espèces matricielles ou atmosphériques pour former des espèces polyatomiques qui se fragmentent ensuite en ions moléculaires de la même valeur m/z qu’un analyte.
Une interférence critique se produit en raison de la formation d’espèces d’oxydes et d’hydroxydes réfractaires à partir des espèces analytes et matricielles. 
L’interférence non spectroscopique comprend l’effet de matrice, qui est associé à une forte concentration d’espèces matricielles et provoque généralement une réduction du signal de l’analyte.
Les effets matriciels peuvent être largement compensés par l’utilisation d’un étalon interne approprié.

spectrométrie plasma-masse à couplage inductif (icp-ms) : interférences

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS): Interferences

La spectrométrie de masse plasma à couplage inductif (ICP-MS) est une technique hautement sélective et sensible pour une analyse élémentaire précise. Bien que l’analyse des spectres de masse ICP-MS soit relativement simple, elle est affectée par des interférences spectroscopiques et non spectroscopiques. Des interférences spectroscopiques surviennent lorsque le plasma contient des espèces ioniques avec une valeur m/z identique à celle de l'ion analyte. Les interférences spectroscopiques peuvent être classées en interférences isobares, polyatomiques et oxydes réfractaires.

Une interférence isobare se produit lorsque le plasma à couplage inductif contient des espèces d'analytes isobares. Ces espèces sont des nucléides différents ayant le même nombre de masse et ont donc les mêmes valeurs m/z que l'analyte, en supposant la même charge. Par exemple, 40Ar+ et 58Fe+ chevauchent généralement les pics de 40Ca+ et 58Ni+, respectivement. Les instruments de masse quadripolaires, ayant une résolution inférieure à 1 u, sont considérablement affectés par les interférences isobares. Cependant, il peut être minimisé en utilisant des instruments à plus haute résolution.

Une autre interférence spectroscopique est observée lorsque divers composants du plasma interagissent avec des composants matriciels ou atmosphériques pour former des espèces polyatomiques, qui peuvent subir une fragmentation supplémentaire pour former des ions moléculaires ayant la même valeur m/z que l'ion analyte. 40ArH+, 16O2+ et 40ArO+ sont des interférents potentiels. Une correction à blanc ou l’utilisation d’un isotope d’analyte différent supprime ces interférences.

Une autre interférence critique se produit lorsque plusieurs composants d'analyte et de matrice forment des oxydes et des hydroxydes dont les pics chevauchent les ions de l'analyte. La formation d'oxydes et d'hydroxydes dépend de divers facteurs expérimentaux, tels que le débit de l'injecteur, la taille de l'orifice de l'échantillon, l'espacement des écumeurs de l'échantillonneur, etc. Ces interférences sont plus difficiles à éliminer que les interférences ioniques isobares et polyatomiques.

Les interférences non spectroscopiques incluent principalement l'effet matrice. Elle est associée à une concentration élevée d’espèces matricielles – généralement de 500 à 1 000 mg/mL – provoquant une réduction du signal de l’analyte. Des conditions expérimentales spécifiques améliorent le signal de l'analyte. Les interférences matricielles peuvent être éliminées en incorporant un étalon interne avec une masse et un potentiel d'ionisation proches de l'analyte.

Spectrométrie plasma-masse à couplage inductif (ICP-MS) : interférences

Malgré les avantages offerts par l’ICP-MS, l’analyse élémentaire précise est affectée par les interférences spectroscopiques et non spectroscopiques.
...

inductively-coupled-plasma-mass-spectrometry-icp-ms-interferences

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Analytical Chemistry

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Principles of Mass Spectrometry

Principes de la spectrométrie de masse

KEY TERMS AND CONCEPTS

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icp-ms signal interference sources and fixes

Inductively coupled plasma-mass spectrometry (ICP-MS) is a sensitive method for elemental analysis, but its spectra can be affected by interferences. These interferences can make the mass signal less accurate, even when the instrument is working well.

Spectroscopic interferences happen when ions in the plasma have the same mass-to-charge ratio, or m/z, as the analyte ion. This group includes isobaric interferences, polyatomic ion interferences, and refractory oxide ion interferences. Isobaric interference occurs when different nuclides share the same mass number and therefore the same m/z value if the charge is the same. For example, 40 Ar+ can overlap with 40 Ca+, and 58 Fe+ can overlap with 58 Ni+.

Quadrupole-based mass instruments, which have a resolution of less than 1 u, are strongly affected by isobaric interference. Using a higher-resolution instrument can help reduce this problem. Polyatomic interferences can appear when plasma species react with matrix or atmospheric components to form molecular ions. Examples include 40 ArH+, 16 O2+, and 40 ArO+.

These polyatomic interferences can be reduced with a blank correction or by choosing a different analyte isotope. Another important spectroscopic problem is the formation of oxides and hydroxides. These peaks can overlap with analyte ions. Their formation depends on experimental conditions such as injector flow rate, sample orifice size, and sampler-skimmer spacing. These interferences are often harder to remove than isobaric and polyatomic interferences.

Non-spectroscopic interferences mainly involve the matrix effect. A matrix is the other material in the sample, and a high matrix concentration of about 500 to 1000 mg/mL can reduce the analyte signal. Certain experimental conditions can improve the analyte signal. Matrix interference can also be reduced by using an internal standard with a mass and ionization potential close to the analyte.

ICP-MS Signal Interference Sources and Fixes

icp-ms-signal-interference-sources-and-fixes

mass spectrometry: overview

Mass Spectrometry and Molecular Identity

Mass spectrometry helps identify a compound by measuring its molecular mass and molecular formula. It does this by turning the analyte molecule into ions and then comparing ion abundance with mass-to-charge ratio. One common ionization method is electron ionization, or EI. In EI, high-energy electron beams strike analyte molecules in the gas phase. The beam removes an electron and leaves a molecular ion behind. A molecular ion is a radical cation, so it has a positive charge and an unpaired...

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mass-spectrometry-molecular-fragmentation-overview

Mass Spectrometry Fragmentation Patterns

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Reading Peaks in a Mass Spectrum

A mass spectrum shows the charged fragments in an analyte as peaks plotted by mass-to-charge ratio, or m/z. The x-axis gives the mass of each charged fragment divided by the number of charges it carries. The y-axis shows the relative abundance of each charged species based on the signal intensity recorded at the detector. The tallest peak is called the base peak. It is assigned an abundance of 100%, and the other peaks are scaled against it. The peak from the molecular ion is called the parent...

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Mass analyzers separate ions by their mass-to-charge ratio, or m/z, in a mass spectrometer. After a sample is vaporized in the ionization chamber, it is hit with a high-energy electron beam. This creates a radical cation and also produces neutral molecules, radicals, and cations. Negatively charged accelerator plates then push the cations into the mass analyzer, where they are sent on to the detector. Several mass analyzer designs are commonly used. These include magnetic sector,...

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Quadrupole, TOF, and Ion Trap Analyzers

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inductively-coupled-plasmamass-spectrometry-icpms-overview

ICP-MS Sample Ionization and Detection

ICP-MS uses an inductively coupled plasma torch to turn samples into ions for mass analysis. Solid samples are first dissolved and volatilized before they enter the hot argon plasma. Solution samples are nebulized, which means they are converted into a fine spray, and then passed through the same plasma. Inside the plasma, the analytes break apart. Their atoms become positively charged ions, along with some molecular species. These positive ions are sent to the mass spectrometer, where they...

inductively coupled plasma-mass spectrometry (icp-ms): interferences

Inductively coupled plasma-mass spectrometry (ICP-MS) is a sensitive method for elemental analysis, but its spectra can be affected by interferences. These interferences can make the mass signal less accurate, even when the instrument is working well. Spectroscopic interferences happen when ions in the plasma have the same mass-to-charge ratio, or m/z, as the analyte ion. This group includes isobaric interferences, polyatomic ion interferences, and refractory oxide ion interferences. Isobaric...

key terms and concepts

Learn how ICP-MS signals can be affected by isobaric, polyatomic, oxide, and matrix interferences, and how blank correction and internal standards help.

ICP-MS Signal Interference Sources and Fixes | JoVE K12

analytical chemistry

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ICP-MS Signal Interference Sources and Fixes

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