Plasma mass spectrum

An intense peak at m/e = 689, eonsistent with [Co(15b-H)2 ], was observed in the positive ion plasma desorption mass spectrum. 

Detailed examination of another madder preparation proved that the sample can be premordanted with alum. [ 19] After hydrolysis performed with hydrochloric acid and extraction with M-amyl alcohol, only four colourants are found alizarin, purpurin, and probably lucidin and ruberythric acid. Additionally, signals at m/z 525 and 539 are observed in the mass spectrum. Analysis of the preparation by inductively coupled plasma mass spectrometry (ICP MS) shows that aluminium and calcium are the main inorganic components of the sample. This is why it was suggested that the signal at m/z 539 can be attributed to the complex of aluminium with alizarin, and the second one, observed at m/z 525, to an aluminium-calcium cluster. 

The MC-ICP-MS consists of four main parts 1) a sample introduction system that inlets the sample into the instrument as either a liquid (most common), gas, or solid (e.g., laser ablation), 2) an inductively coupled Ar plasma in which the sample is evaporated, vaporized, atomized, and ionized, 3) an ion transfer mechanism (the mass spectrometer interface) that separates the atmospheric pressure of the plasma from the vacuum of the analyzer, and 4) a mass analyzer that deals with the ion kinetic energy spread and produces a mass spectrum with flat topped peaks suitable for isotope ratio measurements. 

In 1C, the election-detection mode is the one based on conductivity measurements of solutions in which the ionic load of the eluent is low, either due to the use of eluents of low specific conductivity, or due to the chemical suppression of the eluent conductivity achieved by proper devices (see further). Nevertheless, there are applications in which this kind of detection is not applicable, e.g., for species with low specific conductivity or for species (metals) that can precipitate during the classical detection with suppression. Among the techniques that can be used as an alternative to conductometric detection, spectrophotometry, amperometry, and spectroscopy (atomic absorption, AA, atomic emission, AE) or spectrometry (inductively coupled plasma-mass spectrometry, ICP-MS, and MS) are those most widely used. Hence, the wide number of techniques available, together with the improvement of stationary phase technology, makes it possible to widen the spectrum of substances analyzable by 1C and to achieve extremely low detection limits. 

In Figure 6.1, two parts of the mass spectrum of the glass sample NIST SRM 613 measured by rf GDMS are illustrated.4 In the mass spectrum of the glass sample, the orientation for a qualitative analysis focuses on the ions from matrix, major and minor elements (Si+, Al+, Na+, Rb+, Sr+ or Pb+) and the plasma gas species, such as 40Ar16O+, 40Ar2+ or 40Ar12C+. The plasma gas ions... 

An alternative to quantitative analysis by ICP-MS is semiquantitative analysis, which is generally considered as a rapid multielement survey tool with accuracies in the range 30-50%. Semiquantitative analysis is based on the use of a predefined response table for all the elements and a computer program that can interpret the mass spectrum and correct spectral Interferences. This approach has been successfully applied to different types of samples. The software developed to perform semiquantitative analysis has evolved in parallel with the instrumentation and, today, accuracy values better than 10% have been reported by several authors, even competing with typical ones obtained by quantitative analysis. The development of a semiquantitative procedure for multielemental analysis with ICP-MS requires the evaluation of the molar response curve in the ICP-MS system (variation of sensitivity as a function of the mass of the measured isotope) [17]. Additionally, in the development of a reliable semiquantitative method, some mathematical approaches should be employed in order to estimate the ionisation conditions in the plasma, its use to correct for ionisation degrees and the correction of mass-dependent matrix interferences. 

Figure 2 1 -28 Partial elemental profile of coffee beans by inductively coupled plasma-mass spectrometry. Both beans have similar Pb content, but the Cuban beans have a much higher Hg content than the Hawaiian beans. A blank has not been subtracted from either spectrum, so the small amount of Hg in the upper spectrum could be in the blank. [Courtesy G. S. Ostrom and M. D. Seltzer, Michelson Laboratory. China lake. CA ]... 

Figure 22-1 Mass spectrum showing natural isotopes of Pb observed as an impurity in brass. [From Y. Su, Y. Duan, and Z. Jin, Development and Evaluation of a Glow Discharge Microwave-Induced Plasma Tandem Source lor Time-ot-Fllght Mass Spectrometry," Anal. Chem. 3000, 72,5600.]...

Kim, C. S., Kim, C. K., Lee, J. I., and Lee, K. J., Rapid determination of Pu isotopes and atom ratios in small amounts of environmental samples by an on-line sample pretreatment system and isotope dilution high resolution inductively coupled plasma mass spectrometry, J. Anal. At. Spectrum., 15, 247-255, 2000. 

Kanazawa et al. [124] determined omeprazole and its metabolites in human plasma by liquid chromatography-three-dimensional quadrupole mass spectrometry with a sonic spray ionization interface. The analytical column was YMC-Pack Pro Cig (5 cm x 2 mm) using acetonitrile-50 mM ammonium acetate (pH 7.25) (1 4) at a flow-rate of 0.2 ml/min. The drift voltage was 30 V. The sampling aperture was heated at 110 °C and shield temperature was 230 °C. In the mass spectrum, the molecular ions of omeprazole, hydroxyomeprazole, and omeprazole sulfone were clearly observed as base peaks. The method is sufficiently sensitive and accurate for pharmacokinetic studies of omeprazole. 

Figure 21 Ultrahigh mass resolving power inductively coupled plasma (ICP) mass spectrum that demonstrates separation of 40Ca+ from 40Ar+ obtained with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a 3-tesla superconducting magnet.

Figure 22 Inductively coupled plasma (ICP) mass spectrum demonstrating better than 5-jxg/L limits of detectability.

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