Development, optimization, and use of an APCI source with temperature-controlled vaporization of solid and liquid samples

Abstract

A trend is observed in mass spectrometry, in which solid samples without prior dissolution and chromatographic separation are brought directly into the ion source and are ionized, e.g., by corona discharge (Atmospheric Solids Analysis Probe) or plasma (Direct Analysis in Real Time). The Direct Inlet Probe-atmospheric-pressure chemical ionization (APCI) ion source presented here, which was coupled to a high-resolution quadrupole time-of-flight-mass spectrometer, differs from most of the other ion sources in having temperature-programmed heating of the sample. The resulting possibility to reduce ion suppression and ion-molecule reactions in the ion source was shown by the separation of two fatty acid methyl esters as a result of their boiling point difference. Using caffeine as sample, certain source parameters such as the auxiliary gas flow, the drying gas flow, and the position of the probe tip in the ion source were optimized. The ability to perform quantitative analyses was shown by the linear concentration response (R(2) = 0.9984) observed when analyzing different caffeine concentrations. An extract of a Chinese medicinal herb was used to examine the reproducibility (relative standard deviations of the most abundant m/z signals were ≤8.1 %). It was also possible to distinguish milled samples of Radix Angelicae sinensis and Radix Angelicae gigas from each other and to identify the coumarins they contain without sample preparation. Supplying synthetic air instead of nitrogen to the ion source makes APCI in the negative mode possible as well; this was proven by the analysis of n-nonyl-β-D-maltoside.

Quantitative Analysis of Bisphenol A in Recycled Paper with a Novel Direct Inlet Probe-Atmospheric Pressure Photoionization–IonTrap-MS

“…Since the first publications in 2004 and 2005 by Takáts et al [8] and Cody et al [9], numbers of different ambient ion sources have been introduced [10,11]. All have in common that they need no or less sample preparation and & Oliver J. Schmitz oliver.schmitz@uni-due.de 1 ionize the analytes under atmospheric conditions.…”

“…This, on one hand, leads to short analysis times, reduces the needed solvents and simplifies the analysis. But on the other hand, ion suppression is increased in comparison to classical chromatographic separation techniques [10,11]. To reduce the ion suppression, an ambient ion source named direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI) has been developed in our group [11].…”

“…This ion source can reduce the ion suppression due to the subsequent evaporation of the analytes according to their vapor pressure. It has been successfully applied to various samples such as Chinese drugs [11] and plasticizers [12]. Also quantification, which is still challenging with other types of ambient ion sources, is possible with this ion source as shown for coumarin in different cinnamon samples [13].…”

Non-destructive plasticizer screening using a direct inlet probe-atmospheric pressure chemical ionization source and ion trap mass spectrometry

“…The direct inlet probe–atmospheric pressure chemical ionization (DIP‐APCI) ion source developed in our laboratory consists of a commercially available temperature‐programmed push rod coupled to a homemade APCI ion source. The vaporization of sample components due to the programmed heating of the push rod leads to a partial separation of sample components as a result of their different vapor pressures, which reduces ion suppression and simplifies the evaluation of the resulting mass spectra due to the fact that not all components of the sample are present in the source at the same time. For use in routine analysis, DIP‐APCI‐MS analysis can also be automated using a CombiPal autosampler.…”

“…We have previously coupled the temperature‐programmed push rod to a different homemade APCI ion source for use with a high‐resolution quadrupole time‐of‐flight (QTOF) mass spectrometer from Agilent . Here, we report the newly developed coupling of the DIP‐APCI ion source to a Bruker Daltonik amaZon speed ion trap mass spectrometer.…”