Application of flowerlike MgO for highly sensitive determination of lead via matrix-assisted laser desorption/ionization mass spectrometry

Research progress on nanomaterial-based matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis

Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a novel soft ionization bio-mass spectrometry technology emerging in the 1980s, which can realize rapid detection of non-volatile, highly polar, and thermally unstable macromolecules. However, the analysis of small molecular compounds has been a major problem for MALDI-TOF MS all the time. In the MALDI analysis process based on traditional matrices, large numbers of interference peaks in the low molecular weight area and "sweet spots" phenomenon are produced, so the detection method needs to be further optimized. The promotion of matrix means the improvement of MALDI performance. In recent years, many new nanomaterial-based matrices have been successfully applied to the analysis of small molecular compounds, which makes MALDI applicable to a wider range of detection and useful in more fields such as pharmacy and environmental science. In this paper, the newly developed MALDI matrix categories in recent years are reviewed initially. Meanwhile, the potential applications, advantages and disadvantages of various matrices are analyzed. Finally, the future development prospects of nanomaterial-based matrices are also prospected.

A New Binary Matrix for Specific Detection of Mercury(II) Using Matrix-Assisted Laser Desorption Ionization Mass Spectrometry

The development of simple, low-cost, and specific detection method for mercury (Hg(II)) ions in aqueous media using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is a challenge due to matrix interferences and acidity that destroy weak interactions. Herein, a new binary matrix consists of mefenamic acid, and thymine (T) is applied for simple and specific detection of Hg(II) in aqueous solution and blood sample. Mass spectra show metal-to-ligand ratio of 1:2 (Hg(II):T) in which Hg(II) ions are bound to two T molecules and two water molecules, i.e., [Hg(T)₂(H₂O)₂]. The method is simple and fast, and requires cheap reagents. In addition, the spectra show extremely specific signals for Hg(II) ions and insignificant signals in case of other competing metal ions. The concept of our protocol can be applied for other metals. The new matrix may be used for the analysis of small molecules with minimal interferences peaks.

Microscale flower-like magnesium oxide for highly efficient photocatalytic degradation of organic dyes in aqueous solution

Flower-like MgO microparticles with excellent photocatalytic performance in degradation of various organic dyes were synthesized by a facile precipitation method via the reaction between Mg²⁺ and CO₃²⁻ at 70 °C.

Determination of copper and lead in tequila by conventional matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and partial least squares regression

RATIONALE

Quantification of small molecules by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is challenging yet attractive, due to micro-scale procedural simplicity, high throughput and lack of memory effects. Since these features are important while analyzing trace elements in quality control schemes, MALDI-TOFMS was used for the determination of copper (Cu) and lead (Pb) in tequila with quantification carried out by partial least squares regression (PLS2) and by univariate calibration (UC).

METHODS

In the proposed procedure, Bi(III) was added as internal standard (IS), diethyldithiocarbamate complexes were formed (pH 7.4) and extracted into chloroform; after solvent evaporation and re-constitution in acetonitrile, the sample was co-crystallized with α-cyano-4-hydroxycinnamic acid on a steel target. From the acquired mass spectra, UC was performed using IS-normalized signals of the monoisotopic ions of analytes, and the m/z range 350-513 was used for PLS2. Accuracy was tested by recovery experiments and by inductively coupled plasma (ICP)-MS analysis.

RESULTS

When compared with direct analyte signal measurements, application of IS yielded enhanced analytical performance using either UC or PLS2; the method quantification limits were: 11.1 μg L^-1 , 23.4 μg L^-1 for Cu and 89.8 μg L^-1 , 97.1 μg L^-1 for Pb, respectively. In tequila, MALDI-TOFMS and ICP-MS provided consistent results for Cu (165-2599 μg L^-1 ); Pb was not detected in any sample by MALDI-TOFMS, yet recoveries obtained after standard addition were indicative of acceptable accuracy (400 μg L^-1 Pb added; recoveries: 91.2-108% for UC and 98.8-120% for PLS2).

CONCLUSIONS

New experimental evidence has been provided supporting the inclusion of trace metals quantification within a range of MALDI-TOFMS applications. Slightly better results were obtained for UC as compared with PLS2 yet both methods can be recommended for testing the compliance of Cu and Pb levels with Official Mexican Norm. Of note, while using PLS2, there is no need for signal integration nor for IS normalization.