A boronic acid-modified C60 derivatization reagent for the rapid detection of 3-monochloropropane-1,2-diol using matrix-assisted laser desorption/ionization-mass spectrometry.

RATIONALE: 3-Monochloropropane-1,2-diol (3-MCPD) is a well-known contaminant formed in food thermal processing, which could be found in a variety of foodstuffs. Due to its potential carcinogenicity, it was essential to quickly develop a rapid and high-throughput analytical method to monitor 3-MCPD in foodstuffs, which is described in this study. METHODS: 3-MCPD was extracted from foodstuffs and then was derivatized with a boronic acid-modified C60 (B-C60 ) through the boronic acid-diol reaction. Microwave heating was used to accelerate the derivatization reaction. Mass spectrometry (MS) analysis was conducted using matrix-assisted laser desorption/ionization-MS (MALDI-MS). The application of the method was validated using various smoked food samples. RESULTS: The chemical derivatization of 3-MCPD with B-C60 enabled the addition of a C60 -tag to 3-MCPD. High-throughput analysis of the sample within 0.5 h was realized. A good linear range from 0.02 to 1.5 µg mL-1 for 3-MCPD was obtained, with a detection limit of 0.005 µg mL-1 . The recoveries in spiked foodstuffs ranged from 85.4% to 115.1% with relative standard deviations of 2.0%-14.2%. This method was successfully applied to detect 3-MCPD in smoked foodstuffs. CONCLUSIONS: A quantitative method was developed for the detection of 3-MCPD in foodstuffs using B-C60 derivatization combined with MALDI-MS strategy. This proposed method may serve as a potential platform for the rapid and high-throughput analysis of 3-MCPD in foodstuffs for the purpose of food safety control.

C60-based chemical labeling strategy for the determination of polyamines in biological samples using matrix-assisted laser desorption/ionization mass spectrometry.

Bioactive polyamines play important roles in many biological processes such as gene expression, cell growth, protein synthesis, and signal transduction. Accurate determination of polyamines is helpful for studying their biological functions. Herein, a C60-based chemical labeling strategy was proposed for the determination of polyamines (putrescine, cadaverine, spermidine, and spermine) in biological samples using matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). An N-hydroxysuccinimide ester functionalized C60 (NHS-C60) was used as a labeling reagent and the m/z of the labeled polyamines reached up to more than 900 Da, which avoided matrix interferences in the low m/z region. In addition, as NHS-C60 derivatives, mono- and bis-substituted polyamines were produced simultaneously, which benefited the qualitative analysis of polyamines. The analytical method was validated using NHS-C60 labeled polyamines in cells and mice feces samples. Good linearities were obtained with correlation coefficients ranging from 0.9786 to 0.9982. The limits of quantification were in the range of 0.68-1.48 pmol. Good reproducibility and reliability of our proposed method were confirmed by intra- and inter-day precisions ranged from 2.8 to 16.6%, and the recoveries ranged between 81.8 and 119.9%. Finally, the proposed method was applied to determine polyamines in cells and mice feces. Three polyamines were detected in the cells, and the contents of cadaverine and spermidine in the feces of high-fat diet mice were found to be significantly lower than those in the normal diet mice. The results show that the proposed NHS-C60 labeling coupled with MALDI MS strategy is suitable for the determination of polyamines in biological samples.

Preparation of zirconium arsenate-modified monolithic column for selective enrichment of phosphopeptides.

Protein phosphorylation is a crucial posttranslational modification for the regulation of many different biological functions. Selective enrichment of phosphopeptides from the complex biological samples is an essential step for the mass spectrometry analysis of protein phosphorylation. In this study, an arsenate functionalized monolithic column was first prepared by a single-step copolymerization of p-methacryloylaminophenylarsonic acid and ethylene dimethacrylate. Then the metal ions Zr4+ were attached onto the prepared monolithic column via metal-chelate complex formation by Zr4+ and arsenate groups. The obtained monolithic column was employed as a new sorbent for the phosphopeptide enrichment via immobilized metal affinity chromatography. Phosphopeptides analysis was realized by polymer monolith microextraction using this monolithic column coupled to both matrix-assisted laser desorption/ionization mass spectrometry and liquid chromatography-electrospray ionization tandem mass spectrometry. The proposed method exhibited a high selectivity for phosphopeptide enrichment in complex matrices, and was applied to the analysis of phosphopeptides in human serum and tryptic digests of rat brain proteins. Four phosphopeptides could be selectively captured from human serum and 2608 endogenous phosphopeptides were identified from the tryptic digests of rat brain proteins, indicating a satisfactory performance of this method for the enrichment of phosphopeptides from complex biological samples.

On-Site and Quantitative Detection of Trace Methamphetamine in Urine/Serum Samples with a Surface-Enhanced Raman Scattering-Active Microcavity and Rapid Pretreatment Device.

Here, it reports a high-throughput detection method for reliably quantitative analysis of illegal drugs in complex biological samples by means of a surface-enhanced Raman scattering (SERS) active microcavity and rapid pretreatment device. Based on the well-made hemispherical microcavities that regularly distributed on a glass array, the quality-controllable microcavity device is fabricated by the compact self-assembly of core-shell nanopeanuts (CSNPs) onto the inside surface. Both the CSNPs with a quantifiable internal standard signal of crystal violet acetate anchored inside their gap and the well-made microcavity referred to the physical amplification of the microscale groove surface will do well in trace analysis, which will allow us to realize the accurately quantitative SERS analysis of targeted analytes spread on the bottom area of the microcavity array. As an example, 0.8 nM malachite green and 160 ppb methamphetamine (MATM) have been successively detected in a wide range as standard, while even 0.01 ppm MATM mixed in the urine/serum samples has been efficiently tested by the microcavity device equipped with a rapid pretreatment device (manual monolithic column syringe needle). All of the above suggest that the SERS-active microcavity equipped with a rapid pretreatment device has potential in the on-site quick test of trace amounts of illegal drugs in bodily fluid samples or other field analysis of food sanitation, environmental safety, and public health.

Development of C60-based labeling reagents for the determination of low-molecular-weight compounds by matrix assisted laser desorption ionization mass spectrometry (II): Determination of thiols in human serum.

Perturbation of thiol homeostasis in biological fluids are thought to be associated with several diseases, and reliable analytical methods for the determination of low molecular weight (LMW) thiols in human plasma or serum are thus required. In this study, a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method is described for high throughput determination of four LMW thiols (glutathione, cysteine, homocysteine and cysteinylglycine) in human serum. It is based on the use of a bromoacetyl functionalized C60 (Br-C60) as a derivatization reagent to label thiols. The Br-C60 labeling can add an 832-Da tag to thiols, which moves thiol signals to high mass region and effectively avoids the signal interference generated by the traditional MALDI matrix below 800 Da. The labeling can be completed within 5 min under microwave-assisted condition. Thereby, the Br-C60 labeling based MALDI-TOF MS analytical method can achieve high throughput analysis of LMW thiols in serum. Good linearities of the method for the thiols in human serum were obtained in the range of 0.5-500.0 µM with correlation coefficient (R) greater than 0.9960. The limit of detection is in the range of 0.07-0.18 µM for the investigated thiols in human serum with relative standard deviations of lower than 13.5% and recoveries ranging from 81.9 to 117.1%. Using the method, four thiols in microliter serum samples of breast cancer (BC) patients were determined. The result showed that the contents of the four thiols in BC serum samples significantly changed compared to the healthy control (HC).

Preparation of polymer monolithic column functionalized by arsonic acid groups for mixed-mode capillary liquid chromatography.

A mixed-mode polymer monolithic column functionalized by arsonic acid groups was prepared by single-step in situ copolymerization of monomers p-methacryloylaminophenylarsonic acid (p-MAPHA) and pentaerythritol triacrylate (PETA). The prepared poly(p-MAPHA-co-PETA) monolithic column has a homogeneous monolithic structure with good permeability and mechanical stability. Zeta potential measurements reveal that the monolithic stationary phase holds a negative surface charge when the mobile phase resides in the pH range of 3.0-8.0. The retention mechanisms of prepared monolithic column are explored by the separation of selected polycyclic aromatic hydrocarbons (PAHs), nucleosides, and three basic compounds. The results indicate that the column functions in three different separation modes associated with reversed-phase chromatography based on hydrophobic interaction, hydrophilic interaction chromatography, and cation-exchange chromatography. The column efficiency of prepared monolithic column is estimated to be 70,000 and 76,000 theoretical plates/m for thiourea and naphthalene, respectively, at a linear flow velocity of 0.85 mm/s using acetonitrile/H2O (85/15, v/v) as the mobile phase. Furthermore, an analysis of the retention factors obtained for the PAHs indicates that the prepared monolithic column exhibits good reproducibility with relative standard deviations of 2.9%, 4.0%, and 4.7% based on run-to-run injections, column-to-column preparation, and batch-to-batch preparation, respectively. Finally, we investigate the separation performance of the proposed monolithic column for select phenols, sulfonamides, nucleobases and nucleosides.