We report a novel, fast, and automatic SPME-based method capable of extracting a small molecule-drug conjugate (SMDC) from biological matrices. Our method relies on the extraction of the drug conjugate followed by direct elution into an electrospray mass spectrometer (ESI-MS) source for qualitative and quantitative analysis. We designed a tool for extracting the targeting head of a recently synthesized SMDC, which includes acetazolamide (AAZ) as high-affinity ligand specific to carbonic anhydrase IX. Specificity of the extraction was achieved through systematic optimization. The design of the extraction tool is based on noncovalent and reversible interaction between AAZ and CAII that is immobilized on the SPME extraction phase. Using this approach, we showed a 330% rise in extracted AAZ signal intensity compared to a control, which was performed in the absence of CAII. A linear dynamic range from 1.2 to 25 μg/ml was found. The limits of detection (LOD) of extracted AAZ from phosphate-buffered saline (PBS) and human plasma were 0.4 and 1.2 μg/ml, respectively. This with a relative standard deviation of less than 14% (n = 40) covers the therapeutic range.
The mechanisms of the reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry (MALDI) are studied. In MALDI mass spectra, ions cationized by copper mostly contain Cu(I) even if Cu(II) salts are added to the sample. It was found that Cu(II) was reduced to Cu(I) by gas-phase charge exchange with matrix molecules, which is a thermodynamically favorable process. Under some conditions, large amounts of free electrons are present in the plume. Cu(II) can be even more efficiently reduced to Cu(I) by free electron capture in the gas phase. The matrices studied in this work are nicotinic acid, dithranol, and 2,5-dihydroxybenzoic acid. 相似文献
Ambient mass spectrometry—mass spectrometric analysis with no or minimal effort for sample preparation—has experienced a very
rapid development during the last 5 years, with many different methods now available for ionization. Here, we review its range
of applications, the hurdles encountered for its quantitative use, and the proposed mechanisms for ion formation. Clearly,
more effort needs to be put into investigation of matrix effects, into defining representative sampling of heterogeneous materials,
and into understanding and controlling the underlying ionization mechanisms. Finally, we propose a concept to reduce the number
of different acronyms describing very similar embodiments of ambient mass spectrometry. 相似文献
The development of analytical techniques suitable for sensitive, high-throughput, and nondestructive food analysis has been
of increasing interest in recent years. In this study, mass-spectral fingerprints of various cheese products were rapidly
recorded in the mass range of m/z 50–300 Da without any sample pretreatment, using neutral desorption extractive electrospray ionization mass spectrometry
(ND-EESI-MS) in negative ion mode. The results demonstrate that both volatile and nonvolatile analytes on greasy cheese surfaces
can be directly sampled by a neutral desorption gas beam. The influence of the neutral desorption gas flow on the analyte
signal was systematically investigated. Under optimized experimental conditions, reproducible results were obtained using
ND-EESI-MS. Principal component analysis was applied to differentiate a total of 49 individual cheese samples (four different
types), which were purchased from three different supermarkets. All samples were successfully classified according to their
types; but distributors and sensory properties were not distinguishable from the spectra data. The principal components 2,
3, and 4 scores showed an excellent capacity of distinguishing types of cheese. Molecular markers of interest can be identified
using tandem mass spectrometry and matching the data with those from reference compounds. The experimental data show that
ND-EESI-MS is able to sensitively and directly detect analytes on greasy surfaces without chemical contamination, providing
a convenient method for high-throughput food analysis with a high degree of safety. 相似文献
Single-cell metabolomics is an emerging field that addresses fundamental biological questions and allows one to observe metabolic
phenomena in heterogeneous populations of single cells. In this review, we assess the suitability of different detection techniques
and present considerations on sample preparation for single-cell metabolomics. Although targeted analysis of single cells
can readily be conducted using fluorescent probes and optical instruments (microscopes, fluorescence detectors), a comprehensive
metabolomic approach requires a powerful label-free method, such as mass spectrometry (MS). Mass-spectrometric techniques
applied to study small molecules in single cells include electrospray MS, matrix-assisted laser desorption/ionization MS,
and secondary ion MS. Sample preparation is an important aspect to be taken into account during further development of methods
for single-cell metabolomics. 相似文献
By gently bubbling nitrogen gas through beer, an effervescent beverage, both volatile and non-volatile compounds can be simultaneously sampled in the form of aerosol. This allows for fast (within seconds) fingerprinting by extractive electrospray ionization mass spectrometry (EESI-MS) in both negative and positive ion mode, without the need for any sample pre-treatment such as degassing and dilution. Trace analytes such as volatile esters (e.g., ethyl acetate and isoamyl acetate), free fatty acids (e.g., caproic acid, caprylic acid, and capric acid), semi/non-volatile organic/inorganic acids (e.g., lactic acid), and various amino acids, commonly present in beer at the low parts per million or at sub-ppm levels, were detected and identified based on tandem MS data. Furthermore, the appearance of solvent cluster ions in the mass spectra gives insight into the sampling and ionization mechanisms: aerosol droplets containing semi/non-volatile substances are thought to be generated via bubble bursting at the surface of the liquid; these neutral aerosol droplets then collide with the charged primary electrospray ionization droplets, followed by analyte extraction, desolvation, ionization, and MS detection. With principal component analysis, several beer samples were successfully differentiated. Therefore, the present study successfully extends the applicability of EESI-MS to the direct analysis of complex liquid samples with high gas content.
Figure
By gently bubbling nitrogen gas through beer, both volatile and non-volatile compounds can be simultaneously sampled in the form of aerosol for further analysis, allowing fast chemically fingerprinting using extractive electrospray ionization mass spectrometry (EESI-MS). 相似文献
Solvent polarity plays an important role in electrospray ionization-mass spectrometry (ESI-MS), one of the most widely used
analytical methods for biochemistry. To have a comprehensive understanding of how solvent polarity affects ESI-MS measurements,
we systematically investigated the polarity change in the ESI plume formed from an ethanol solution using laser-induced fluorescence
(LIF) spectroscopy. Two solvatochromic dyes (i.e., dyes whose fluorescence emission is sensitive to solvent polarity), Nile
red and DCM (4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran), were used as probes. The peak emission wavelengths
of these two dyes exhibited significant red shifts (8–12 nm) when the measuring spot was moved away from the spray tip and
in radial direction in the plume, indicating a dramatic polarity change during shrinking of the droplets. The emission intensities
were also measured with a polarity-insensitive dye as a reference. The results are consistent with the peak wavelength measurements.
Two key mechanisms responsible for the change of solvent polarity in the plume were considered, water entrainment from the
surrounding air and solvent evaporation. Furthermore, quantitative analysis of the solvent polarity change was performed by
using the Lippert-Mataga polarity parameter Δf. The value of Δf reached 0.305–0.307 at the periphery of the ESI plume, which means that the solvent polarity in the smaller droplet is close
to that of a mixture of 30% water and 70% ethanol (Δf = 0.307), even though the bulk solvent was ethanol containing less than 1% water as an impurity. 相似文献