This study describes a method for the quantification of trace-level benzene, toluene, ethylbenzene, and xylene in cellulose acetate tow by heart-cutting multidimensional gas chromatography with mass spectrometry in selected ion monitoring mode. As the major volatile component in cellulose acetate tow samples, acetone would be overloaded when attempting to perform a high-resolution separation to analyze trace benzene, toluene, ethylbenzene, and xylene. With heart-cutting technology, a larger volume injection was achieved and acetone was easily cut off by employing a capillary column with inner diameter of 0.32 mm in the primary gas chromatography. Only benzene, toluene, ethylbenzene, and xylene were directed to the secondary column to result in an effective separation. The matrix interference was minimized and the peak shapes were greatly improved. Finally, quantitative analysis of benzene, toluene, ethylbenzene, and xylene was performed using an isotopically labeled internal standard. The headspace multidimensional gas chromatography mass spectrometry system was proved to be a powerful tool for analyzing trace volatile organic compounds in complex samples.

The total saccharides content of Lycium barbarum L. is very high, and a high temperature would result in saccharide decomposition and the emergence of a large amount of water. Moreover, the volatile compounds from the fruit of L. barbarum L. are rather low in concentration. Hence, it is difficult for a conventional headspace method to study the volatile compounds from the fruit of L. barbarum L. Since headspace-trap gas chromatography with mass spectrometry is an excellent method for trace analysis, a headspace-trap gas chromatography with mass spectrometry method based on low-temperature (30°C) enrichment and multiple headspace extraction was developed to explore the volatile compounds from the fruit of L. barbarum L. The headspace of the sample was extracted in 17 cycles at 30°C. Each time, the compounds extracted were concentrated in the trap (Tenax TA and Tenax GR, 1:1). Finally, all the volatile compounds were delivered into the gas chromatograph after thermal desorption. With the method described above, a total of 57 compounds were identified. The identification was completed by mass spectral search, retention index, and accurate mass measurement.

In this study, ion mobility separation coupled with tandem mass spectrometry (IM-tandem MS) was utilized to investigate the ionization behaviors of two amino acids including leucine and isoleucine. Under the electrospray ionization (ESI) mode, two protonation sites in each molecular sturcture caused two forms of protomer. One arose from the amino being protonated (amino-protomer) and the other from the carboxyl being protonated (carboxyl-protomer). In the two-dimensional (drift time, m/z) spectrum, the protomers had the same mass, but the distinguishable drift times and fragmentation patterns. For the characterization purpose, the theoretical collision cross section (CCS) values of the protomers were calculated and proven to be consistent with the experimental. Moreover, the quantified relationship between the amino acids and their protomers was evaluated. It showed that the abundance of the carboxyl-protomer was proportional to the concentration of the amino acid, whereas that of the amino-protomer did not have the same trend. Under the atmospheric pressure chemical ionization (APCI) mode, only the carboxyl-protomer was observed. In addition, the amino-protomer and the cluster ions observed under ESI were absent completely. The results demonstrate that the ionization mode impacts heavily on the ionization behaviors of leucine and isoleucine not only on the form of therir protomers but also on the quantified relationship.

A method for rapid identification and quantification of phthalate plasticizers in beverages was developed. A number of 15 phthalate plasticizers which covered all the phthalates concerned in the US Consumer Product Safety Improvement Act (CPSIA), European Union legislations and Chinese national standards (GB) were analyzed. By a combined solid-phase micro-extraction (SPME) and direct analysis in real time mass spectrometry (DART-MS) approach, phthalates at sub-ng·mL⁻¹ levels can be qualitatively and quantitatively analyzed in a short time. The use of ultrahigh-resolving power and the accurate mass measurement capacity naturally provided by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) minimizes the matrix interferences and thus enables the evaluation of phthalates in a complex matrix without extensive sample handlings or preparations. The limits of quantification (LOQs) were estimated to be at 0.3–5.0 ng·mL⁻¹, lower than the Maximum Residue Limit (MRL) regulated by the European Union legislations (2007/19/EC) in foods, beverages, food packaging and toys (0.3–30 ng·mL⁻¹). This rapid and easy-to-use SPME-DART-FT-ICR-MS method provided a relatively high-throughput and powerful analytical approach for quick testing and screening phthalates in beverages and water samples to ensure food safety.

In the traditional research of volatile compounds, some trace-level compounds could not be identified by gas chromatography-mass spectrometry. Target and post-targeted methods were applied in the investigation of trace-level volatile compounds in fresh turf crop (Lolium perenne L.) based on gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry. According to literatures published, a target analysis was performed by using retention index, accurate masses of characteristic ions and second-stage mass spectra (MS² spectra). And a series of experiments showed that low electron impact energy was beneficial to the improvement of the abundances of low abundance molecular ion peak. Enhancing the abundances of low abundance molecular ion peak was beneficial to qualitative analysis. Totally, 60 volatile compounds were identified, the great majority compounds of which were benzeneacetaldehyde (14.8%), 2,5-dimethyl-pyrazine (9.6%), and hexanal (9.3%). Identification was complied by mass spectral search, retention index and accurate masses of characteristic ions.

Pd-catalyzed oxidative coupling reaction was of great importance in the aromatic CH activation and the formation of new CO and CC bonds. Sanford has pioneered practical, directed CH activation reactions employing Pd(OAc)₂ as catalyst since 2004. However, until now, the speculated reactive Pd(IV) transient intermediates in these reactions have not been isolated or directly detected from reaction solution. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to intercept and characterize the reactive Pd(IV) transient intermediates in the solutions of Pd(OAc)₂-catalyzed oxidative coupling reactions. In this study, the Pd(IV) transient intermediates were detected from the solution of Pd(OAc)₂-catalyzed oxidative coupling reactions by ESI-MS and the MS/MS of the intercepted Pd(IV) transient intermediate in reaction system was the same with the synthesized authentic Pd(IV) complex. Our ESI-MS(/MS) studies confirmed the presence of Pd(IV) reaction transient intermediates. Most interestingly, the MS/MS of Pd(IV) transient intermediates showed the reductive elimination reactivity to Pd(II) complexes with new CO bond formation into product in gas phase, which was consistent with the proposed reactivity of the Pd(IV) transient intermediates in solution.