Andy Scheffer

Speciation Analysis of Gadolinium-Based MRI Contrast Agents in Blood Plasma by Hydrophilic Interaction Chromatography/Electrospray Mass Spectrometry

The first analytical method for simultaneous speciation analysis of five of the most important gadolinium-based magnetic resonance imaging (MRI) contrast agents in blood plasma samples was developed. Gd-DTPA (Magnevist), Gd-BT-DO3A (Gadovist), Gd-DOTA (Dotarem), Gd-DTPA-BMA (Omniscan), and Gd-BOPTA (Multihance) were separated by hydrophilic interaction liquid chromatography (HILIC) and detected with electrospray mass spectrometry (ESI-MS). Spiking experiments of blank plasma with Magnevist and Gadovist were performed to determine the analytical figures of merit and the recovery rates. The limits of detection ranged from 1 x 10 (-7) to 1 x 10 (-6) mol/L depending on the ionization properties of the individual compounds, and limits of quantification ranged from 5 x 10 (-7) to 5 x 10 (-6) mol/L. The linear concentration range comprised 2 orders of magnitude. With application of this method, blood plasma samples of 10 healthy volunteers, with Magnevist or Gadovist medication, were analyzed for Gd-DTPA and Gd-BT-DO3A, respectively. The obtained results were successfully validated with inductively coupled plasma-optical emission spectroscopy (ICP-OES).

Capillary electrophoresis with inductively coupled plasma-mass spectrometric and electrospray time of flight mass spectrometric detection for the determination of arsenic species in fish samples.

CE was coupled to inductively coupled plasma MS (ICP‐MS) and ESI‐MS to identify and quantify the arsenic species arsenobetaine (AsB), arsenite (AsIII), arsenate (AsV), and dimethylarsinic acid (DMA). A GC‐flame ionization detector (FID)‐based German standard method and ICP‐MS were used for validation of the data obtained for arsenobetaine and total arsenic, respectively. LODs obtained with the CE‐ESI‐TOF‐MS method were 1.0×10−7 M for AsB, 5.0×10−7 M for DMA, and 1.0×10−6 M for AsIII and AsV. For the CE‐ICP‐MS method, LODs were 8.5×10−8 M for AsB, 9.5×10−8 M for DMA, 9.3×10−8 M for AsIII, and 6.2×10−8 M for AsV. While CE‐ICP‐MS provided high sensitivity and better reproducibility for quantitative measurements, CE‐ESI‐MS with a TOF mass analyzer proved to be valuable for species identification. With this setup, fish samples were prepared and analyzed and the obtained data were successfully validated with the independent methods.

Quantification of Electrochemically Generated Iodine-Containing Metabolites Using Inductively Coupled Plasma Mass Spectrometry

For the risk assessment of drug candidates, the identification and quantification of their metabolites is required. The majority of analytical techniques is based on calibration standards for quantification of the metabolites. As these often are not readily available, the use of inductively coupled plasma mass spectrometry (ICPMS) is an attractive alternative for drugs containing heteroatoms. In this work, the online coupling of electrochemistry (EC), liquid chromatography (LC), and ICPMS is presented. The antiarrhythmic agent amiodarone, which contains two iodine atoms, is oxidized in an electrochemical flow-through cell under N-dealkylation and deiodination. The metabolites that are generated at different EC potentials are identified by electrospray ionization (ESI) mass spectrometry, compared to those from rat liver microsomal incubations and quantified by ICPMS. Phase-optimized LC, a recent approach for high-performance isocratic separations, is used to avoid the ICPMS calibration problems known to occur with gradient separations. The potential of the complementary use of ESI-MS and ICPMS for the qualitative and quantitative analysis of drug metabolites becomes apparent in this work.

Analysis of doped luminescent lanthanide fluoride nanoparticles by low gas flow inductively coupled plasma optical emission spectrometry

Low-flow inductively coupled plasma optical emission spectrometry is applied for the analysis of water-soluble LaF3nanocrystals doped with different lanthanide ions (Ce3+, Eu3+, Ho3+, Tb3+) for the first time. Colloidal solutions of citrate-stabilized nanoparticles (mean size 24 nm) were directly introduced into the plasma and no significant differences to digested particles were observed. The low-flow approach reduced the argon consumption of conventional instrumentation by 95% and provided limits of detection (LOD) for rare earth elements in the low microgram-per-liter range (Eu: 0.08 µg L−1, Ho: 0.18 µg L−1, La: 0.36 µg L−1, Tb: 0.56 µg L−1, Ce: 3.14 µg L−1). Relative standard deviations (RSDs) in the range of 1–2.2% with pneumatic sample introduction were obtained. The analytical performance of the low-flow torch was assessed by direct comparison with a conventional torch. Recoveries in the range of 97–104% were observed for most elements.

A new ion source design for inductively coupled plasma mass spectrometry (ICP-MS)

Based on the static high sensitivity inductively coupled plasma (SHIP) introduced by Buscher et al. (W. Buscher, A. Klostermeier, C. Engelhard, S. Evers, M. Sperling, J. Anal. At. Spectrom., 2005, 20, 308-314), a new torch design for ICP mass spectrometry was developed. The SHIP-torch, including the external air cooling system, was modified in order to allow its application as an ion source in a conventional ICP mass spectrometer. While the torch geometry was adjusted for its use in connection with the sampling interface, the principal shape of the torch remained the same as in the recently developed SHIP-OES-system. The plasma discharge was operated at 0.65 kW rf power with a total plasma gas flow rate of 1.95 L min−1 and the mass spectrum was investigated. A standard pneumatic nebuliser was used as sample introduction system and the ion signals of a multi elemental standard solution were measured for different sample carrier gas flow rates from 0.2 to 1.4 L min−1. Limits of detection were obtained for a number of elements. These results were compared to those achieved with the conventional ICP-MS setting.

Low gas flow inductively coupled plasma optical emission spectrometry for the analysis of food samples after microwave digestion.

In this work, the recently introduced low flow inductively coupled plasma optical emission spectrometry (ICP-OES) with a total argon consumption below 0.7 L/min is applied for the first time to the field of food analysis. One goal is the investigation of the performance of this low flow plasma compared to a conventional ICP-OES system when non-aqueous samples with a certain matrix are introduced into the system. For this purpose, arsenic is determined in three different kinds of fish samples. In addition several nutrients (K, Na, Mg, Ca) and trace metals (Co, Cu, Mn, Cd, Pb, Zn, Fe, and Ni) are determined in honey samples (acacia) after microwave digestion. The precision of the measurements is characterized by relative standard deviations (RSD) and compared to the corresponding precision values achieved using the conventional Fassel-type torch of the ICP. To prove the accuracy of the low flow ICP-OES method, the obtained data from honey samples are validated by a conventional ICP-OES. For the measurements concerning arsenic in fish, the low flow ICP-OES values are validated by conventional Fassel-type ICP-OES. Furthermore, a certified reference material was investigated with the low gas flow setup. Limits of detection (LOD), according to the 3σ criterion, were determined to be in the low microgram per liter range for all analytes. Recovery rates in the range of 96-106% were observed for the determined trace metal elements. It was proven that the low gas flow ICP-OES leads to results that are comparable with those obtained with the Fassel-type torch for the analysis of food samples.