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

Nonostante i vantaggi offerti dall'ICP-MS, l'analisi elementare accurata è influenzata dalle interferenze spettroscopiche e non spettroscopiche.
L'interferenza spettroscopica è causata da ioni con gli stessi valori m/z degli ioni analita. Le specie interferenti includono le specie isobariche, gli ioni poliatomici e gli ioni ossidi refrattari.
L'interferenza isobarica deriva dalle isobare dell'analita, che sono nuclidi diversi che hanno lo stesso numero di massa, il che significa che i valori m/z sono gli stessi.
L'interferenza ionica poliatomica deriva dalla combinazione di specie di plasma con specie di matrice o atmosferiche per formare specie poliatomiche che si frammentano ulteriormente in ioni molecolari dello stesso valore m/z di un analita.
Un'interferenza critica si verifica a causa della formazione di specie di ossidi e idrossido refrattari dalle specie dell'analita e della matrice. 
L'interferenza non spettroscopica include l'effetto matrice, che è associato a un'alta concentrazione di specie di matrice e generalmente causa la riduzione del segnale dell'analita.
Gli effetti della matrice possono essere ampiamente compensati utilizzando uno standard interno appropriato.

spettrometria al plasma-massa accoppiato induttivamente (icp-ms): interferenze

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

La spettrometria plasma-massa accoppiata induttivamente (ICP-MS) è una tecnica altamente selettiva e sensibile per un'analisi elementare accurata. Sebbene l’analisi degli spettri di massa ICP-MS sia relativamente semplice, è influenzata da interferenze spettroscopiche e non spettroscopiche. Le interferenze spettroscopiche si verificano quando il plasma contiene specie ioniche con un valore m/z uguale allo ione dell'analita. L'interferenza spettroscopica può essere classificata come interferenza di ioni isobarici, poliatomici e di ioni ossido refrattari.

L'interferenza isobarica si verifica quando il plasma accoppiato induttivamente contiene specie isobariche di analiti. Queste specie sono nuclidi diversi con lo stesso numero di massa e quindi hanno gli stessi valori m/z dell'analita, assumendo la stessa carica. Ad esempio, 40Ar+ e 58Fe+ generalmente si sovrappongono rispettivamente ai picchi di 40Ca+ e 58Ni+. Gli strumenti di massa basati su quadrupolo, aventi una risoluzione inferiore a 1 u, sono sostanzialmente affetti da interferenza isobarica. Tuttavia, può essere minimizzato utilizzando strumenti a risoluzione più elevata.

Un'altra interferenza spettroscopica si osserva quando vari componenti del plasma interagiscono con la matrice o i componenti atmosferici per formare specie poliatomiche, che possono subire un'ulteriore frammentazione per formare ioni molecolari aventi lo stesso valore m/z dello ione analita. 40ArH+, 16O2+ e 40ArO+ sono alcuni potenziali interferenti. Una correzione in bianco o l'utilizzo di un isotopo dell'analita diverso elimina tali interferenze.

Un'altra interferenza critica si verifica quando diversi componenti dell'analita e della matrice formano ossidi e idrossidi i cui picchi si sovrappongono agli ioni dell'analita. La formazione di ossidi e idrossidi dipende da vari fattori sperimentali, come la portata dell'iniettore, la dimensione dell'orifizio del campione, la spaziatura degli skimmer del campionatore, ecc. Queste interferenze sono più difficili da eliminare rispetto alle interferenze degli ioni isobarici e poliatomici.

Le interferenze non spettroscopiche includono principalmente l'effetto matrice. È associato a un'elevata concentrazione di specie della matrice, generalmente da 500 a 1.000 mg/ml, che causa una riduzione del segnale dell'analita. Condizioni sperimentali specifiche migliorano il segnale dell'analita. Le interferenze della matrice possono essere eliminate incorporando uno standard interno con massa e potenziale di ionizzazione vicini all'analita.

Spettrometria al plasma-massa accoppiato induttivamente (ICP-MS): Interferenze

Nonostante i vantaggi offerti dall'ICP-MS, l'analisi elementare accurata è influenzata dalle interferenze spettroscopiche e non spettroscopiche.
...

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

Education

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JoVE Core

Analytical Chemistry

Chimica Analitica

Unit 1

Unità 1

Principles of Mass Spectrometry

Principi della spettrometria di massa

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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 Fragmentation Patterns

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How Mass Spectrometers Sort Ions

A mass spectrometer sorts charged ions by their mass-to-charge ratio and records their relative abundance. It turns vaporized analyte molecules into ions, separates them, and then measures the signal from each type of ion. The process begins in the ionization chamber. The analyte is in the gas phase inside a vacuum, and it is struck by high-energy electrons. The electrons have about 70 eV of energy, which is enough to remove an electron from the analyte and form a molecular ion. After...

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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: overview

Mass Analyzers and Ion Separation

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,...

mass analyzers: common types

Quadrupole, TOF, and Ion Trap Analyzers

Quadrupole, time-of-flight, and ion trap mass analyzers each separate ions in a different way. They are common tools in mass spectrometry and help sort ions by their mass-to-charge ratio, or m/z. A quadrupole mass analyzer uses four cylindrical metal rods arranged in a diamond shape. The rods carry a direct current, or DC, voltage and a radio-frequency AC voltage. Ion motion depends on the field strength, so only ions with a certain m/z resonate and reach the detector at that setting. This...

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Mass Accuracy in HRMS Analysis

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gas chromatography&ndash;mass spectrometry (gc&ndash;ms)

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inductively coupled plasma&#8211;mass spectrometry (icp&#8211;ms): overview

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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