Determination of atmospheric alkylamines by ion chromatography using 18-crown-6 as mobile phase additive

Gas chromatography mass spectrometer determination of dimethylamine impurity in N,N-dimethylformamide solvent by derivatization of N,N-dimethylbenzamide with benzoyl chloride agent

This study describes the development of a reliable and linear analytical method for precisely determining dimethylamine impurity in N,N-dimethylformamide solvent utilizing a benzoyl chloride derivatization reagent and a gas chromatography mass spectrometer. Benzoyl chloride was used to derivatize dimethylamine. At normal temperature, benzoyl chloride combined with dimethylamine, producing N,N-dimethylbenzamide. This method separated N,N-dimethylbenzamide using Rtx-5 amine (30 m × 0.32 mm × 1.50 μm) as the stationary phase, helium as the carrier gas, argon as the collision gas, and methanol as the diluent. The column flow rate was 2 mL/min. The retention time of N,N-dimethylbenzamide was determined to be 8.5 min. Precision, linearity, and accuracy were tested using ICH Q2 (R2) and USP<1225> guidelines. The percentage coefficient of variation (CV) for N,N-dimethylbenzamide in the system suitability parameter was 1.1%. The correlation coefficient of N,N-dimethylbenzamide was found to be >0.99. In the method precision parameter, the % CV for N,N-dimethylbenzamide was found to be 1.9%, whereas the % CV for N,N-dimethylbenzamide was 1.2% in intermediate precision. The percentage recovery of N,N-dimethylbenzamide was determined to be between 80% and 98%.

Determination of Gaseous and Particulate Secondary Amines in the Atmosphere Using Gas Chromatography Coupled with Electron Capture Detection

The aim of this study was to develop and optimize methods for the determination of gaseous and particulate (PM2.5) secondary amines (SAs) in the atmosphere using gas chromatography coupled with electron capture detection (GC-ECD) following chemical derivatization. The methods employed the liquid–liquid extraction (LLE) of pentafluorobenzenesulfonyl derivatives of the SAs before analytical samples were injected into GC-ECD. The optimized methods were applied to the determination of SAs in gaseous and particulate samples at two sites (urban and rural areas) from June to September in 2021. Gaseous samples were collected into an SPE cartridge containing a mixture of silica gel and sulfamic acid at a flow rate of 2 L·min−1 for 48 h. Particulate samples were collected onto 47 mm filters by a cyclone sampler at a flow rate of 16.7 L·min−1 for 48 h. The linearity of calibration curves, accuracy, and precision of the methods were satisfactory. In most of the field samples, dimethylamine (DMA), methylethylamine (MEA), diethylamine (DEA), and dipropylamine (DPA) were found to be the most frequently encountered compounds at the sampling sites.

Determination of ammonium and biogenic amines by ion chromatography. A review

The amount and type of chemical compounds found in food products and the environment, which are and should be controlled, is increasing. This is associated with toxicological knowledge, resulting regulations, rapid development of analytical methods and techniques, and sample preparation methods for analysis. These include, among others, ammonia derivatives such as ammonium, and amines, including biogenic amines. Their occurrence in the environment and food is related to their widespread use in many areas of life and their formation as a result of various physical and chemical changes. Analysts use various methods both classical and instrumental to theirs quantify in different matrices such as food, medicinal and environmental samples. Nevertheless, there is still a need for analytical methods with increased matrix-tolerance, selectivity, specificity, and higher sensitivity. While in the determination of ammonium, ion chromatography is a reference method. In the case of biogenic amines, its use for these purposes is not yet so common. However, given ion chromatography its advantages and rapid development, its importance can be expected to increase in the near future, especially at the expense of gas chromatography methods. This paper is a summary of the advantages and limitations of ion chromatography in this important analytical field and a literature review of the past 15 years.

Highly Efficient Separation of Methylated Peptides Utilizing Selective Complexation between Lysine and 18-Crown-6

Protein methylation is one of the most common and important post-translational modifications, and it plays vital roles in epigenetic regulation, signal transduction, and chromatin metabolism. However, due to the diversity of methylation forms, slight difference between methylated sites and nonmodified ones, and ultralow abundance, it is extraordinarily challenging to capture and separate methylated peptides from biological samples. Here, we introduce a simple and highly efficient method to separate methylated and nonmethylated peptides using 18-crown-6 as a mobile phase additive in high-performance liquid chromatography. Selective complexation between lysine and 18-crown-6 remarkably increases the retention of the peptides on a C18 stationary phase, leading to an excellent baseline separation between the lysine methylated and nonmethylated peptides. A possible binding mechanism is verified by nuclear magnetic resonance titration, biolayer interferometry technology, and quantum chemistry calculation. Through establishment of a simple enrichment methodology, a good selectivity is achieved and four methylated peptides with greatly improved signal-to-noise (S/N) ratios are successfully separated from a complex peptide sample containing 10-fold bovine serum albumin tryptic digests. By selecting rLys N as an enzyme to digest histone, methylation information in the histone could be well identified based on our enrichment method. This study will open an avenue and provide a novel insight for selective enrichment of lysine methylated peptides in post-translational modification proteomics.

Simultaneous determination of nine atmospheric amines and six inorganic ions by non-suppressed ion chromatography using acetonitrile and 18-crown-6 as eluent additive

Atmospheric amines contribute to the nucleation and initial growth of new particles as well as secondary organic aerosol formation, influencing the radiative balance of the Earth's atmosphere. In this study, we develop an ion chromatography (IC) method for separating and quantifying the nine most abundant amines (methylaminium (MMAH⁺), dimethylaminium (DMAH⁺), trimethylaminium (TMAH⁺), ethylaminium (MEAH⁺), diethylaminium (DEAH⁺), propylaminium (MPAH⁺), butylaminium (MBAH⁺), ethanolaminium (MEOH⁺), and triethanolaminium (TEOH⁺)) from six common inorganic species in atmospheric aerosols. The retention times of the amines were altered by the addition of acetonitrile to the eluent because acetonitrile can reduce the adsorption of hydrophobic amines on the stationary phase. The developed method achieved the successful separation of DEAH⁺ and TMAH⁺ from inorganic cations, which often coelute with each other in established IC methods. The interference of K⁺ on the determination of MEAH⁺ was eliminated by the complexation of K⁺ with 18-crown-6, which prolonged the retention time of K⁺. Finally, 9 target amines and 6 common inorganic cations were separated, with a resolution Rs ≥ 1.2 for DEAH⁺ and MPAH⁺ and Rs > 1.5 for other species. The detection limits varied in the range of 0.34-1.48 ng for the 9 amines and 0.19-0.56 ng for the inorganic cations. The developed method was successfully applied for the determination of low molecular weight amines and inorganic cations in PM_2.5 collected from an urban site in Shanghai and an isolated coast of Chongming Island. Eight amines were detected in the urban samples, in which MMAH⁺ and DMAH⁺ dominated. The average amine concentration in the urban aerosols was 76.3 ± 38.4 ng m^-3, which is approximately 4-fold higher than those in the marine samples collected from the coast.