Selection of Internal Standards for Quantitative Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis Based on Correlation Coefficients
Abstract:Matrix-assisted laser desorption/ionization
mass spectrometry (MALDI
MS) has shown its great success in the qualitative analysis of a wide
range of organic and biological molecules. However, its application
in quantitative analysis is still limited by the difficulty in the
availability of isotope-labeled internal standards. The present work
investigates the relationship between the correlation coefficient
of the peak intensities of analyte and candidate internal standard
ions and the linearity of possible quan… Show more
“…This indicated that the S-CDs were composed of C, H and O atoms in the m/z range of 100 to 380, especially the pronounced peak at m/z 225 was observed. While the S-CDs conjugated with CP (CP@CDs-200) showed the mass-charge ratio (m/z) especially at 215, 248, 322 and 354, which revealed that CP was loaded onto the surface of S-CDs [ 56 ]. Figure 13.…”
Carbon dots (CDs) are a new class of nanomaterials exhibiting high biocompatibility, water solubility, functionality, and tunable fluorescence (FL) property. Due to the limitations of batch hydrothermal synthesis in terms of low CDs yield and long synthesis duration, this work aimed to increase its production capacity through a continuous flow reactor system. The influence of temperature and time was first studied in a batch reactor for glucose, xylose, sucrose and table sugar precursors. CDs synthesized from sucrose precursor exhibited the highest quantum yield (QY) (175.48%) and the average diameter less than 10 nm (~6.8 ± 1.1 nm) when synthesized at 220°C for 9 h. For a flow reactor system, the best condition for CDs production from sucrose was 1 mL min
−1
flow rate at 280°C, and 0.2 MPa pressure yielding 53.03% QY and ~ 6.5 ± 0.6 nm average diameter (6.6 mg min
−1
of CDs productivity). CDs were successfully used as ciprofloxacin (CP) nanocarrier for antimicrobial activity study. The cytotoxicity study showed that no effect of CDs on viability of L-929 fibroblast cells was detected until 1000 µg mL
−1
CDs concentration. This finding demonstrates that CDs synthesized via a flow reactor system have a high zeta potential and suitable surface properties for nano-theranostic applications.
“…This indicated that the S-CDs were composed of C, H and O atoms in the m/z range of 100 to 380, especially the pronounced peak at m/z 225 was observed. While the S-CDs conjugated with CP (CP@CDs-200) showed the mass-charge ratio (m/z) especially at 215, 248, 322 and 354, which revealed that CP was loaded onto the surface of S-CDs [ 56 ]. Figure 13.…”
Carbon dots (CDs) are a new class of nanomaterials exhibiting high biocompatibility, water solubility, functionality, and tunable fluorescence (FL) property. Due to the limitations of batch hydrothermal synthesis in terms of low CDs yield and long synthesis duration, this work aimed to increase its production capacity through a continuous flow reactor system. The influence of temperature and time was first studied in a batch reactor for glucose, xylose, sucrose and table sugar precursors. CDs synthesized from sucrose precursor exhibited the highest quantum yield (QY) (175.48%) and the average diameter less than 10 nm (~6.8 ± 1.1 nm) when synthesized at 220°C for 9 h. For a flow reactor system, the best condition for CDs production from sucrose was 1 mL min
−1
flow rate at 280°C, and 0.2 MPa pressure yielding 53.03% QY and ~ 6.5 ± 0.6 nm average diameter (6.6 mg min
−1
of CDs productivity). CDs were successfully used as ciprofloxacin (CP) nanocarrier for antimicrobial activity study. The cytotoxicity study showed that no effect of CDs on viability of L-929 fibroblast cells was detected until 1000 µg mL
−1
CDs concentration. This finding demonstrates that CDs synthesized via a flow reactor system have a high zeta potential and suitable surface properties for nano-theranostic applications.
“…The quantification of PS and PET MNPs was further conducted using the internal standard method widely applied by an extensive list of published works. , Figure a illustrates the normalized signal intensities with variation in concentrations of LM-PS and LM-PET microplastics, which shows a nearly linear correlation ( R 2 = 0.90) between the signal intensity and concentration for PS but a nonlinear behavior for PET. When plotted as P normalization versus ln[polymer concentration], the results in Figure b show that the data of both polymers fit a logarithmic regression with acceptable coefficients of determination ( R 2 > 0.96).…”
Micro(nano)plastics
(MNPs) are widely acknowledged as global environmental
threat while determination methods for MNPs are still lacking and
becoming a growing concern. This study provides a novel method for
MNPs identification/quantification by matrix-assisted laser desorption/ionization–time-of-flight
mass spectrometry (MALDI–TOF MS). Factors affecting the measurement
were optimized, including laser energy, matrix (M), analyte (A), cationization
agent (C), and MAC volume ratio. Under the optimal conditions, the
peaks representative of polystyrene (PS) and polyethylene terephthalate
(PET) were identified, and the mass differences were consistent with
the molecular weight of the corresponding oligomer. A quantitative
correlation was built between normalized signal intensity and ln[polymer
concentration] with a correlation coefficient above 0.96 for low-molecular-weight
polymers and 0.98 for high-molecular-weight polymers. Furthermore,
two types of environmental MNP samples were prepared, including aviation
cup particles as fresh plastics and aged MNPs extracted from river
sediment. By using MALDI–TOF MS, the PS-related MNPs (in both
aviation cup and sediment) consisted of C8H8 and C16H16O oligomers, while the PET-related
MNPs (only found in sediment) were identified with repeated units
of C10H8O4 and C12H12O4. According to the quantitative correlation
curve, the contents of PS and PET MNPs were quantified as 8.56 ±
0.04 and 28.71 ± 0.20 mg·kg–1, respectively,
in the collected sediment. This study is the first attempt to propose
a quantification method with the employment of MALDI–TOF MS
for aged MNPs analysis in environmental samples, which can not only
supply an effective method for MNP analysis but also inspire future
studies on the in situ distribution and transformation of MNPs in
environmental and biological samples.
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