Automated on-line in-tube solid-phase microextraction-assisted derivatization coupled to liquid chromatography for quantifying residual dimethylamine in cationic polymers

Quantification of dimethylamine in low concentration particulate matter by reducing the concentration of 9-fluorenylmethyl chloroformate

This study presents a refined method that uses liquid chromatography with a fluorescence detector (LC-FD) to quantify trace amounts of dimethylamine in particulate matter (PM). This method was optimized to prioritize simplicity, cost-effectiveness and practicality. To ensure accurate and reliable analysis, strict protocols and procedures were followed to minimize cross-contamination. Separate workspaces were designated for preparing control blanks and sample treatments in one area and standard solutions in another, thus mitigating the risk of cross-contamination. An evaluation was conducted on different concentrations of 9-fluorenylmethyl chloroformate to derivatize dimethylamine. The results showed that a concentration of 3 μg mL-1 was effective in derivatizing dimethylamine concentrations up to 300 ng mL-1. Increasing the concentration of the derivatization reagent from 2.9 to 7.3 μg mL-1 resulted in slightly elevated dimethylamine levels in blank measurements. Also, during the preparation of standards at low concentrations, high analytical coefficients of variation were observed. This highlights the importance of checking for potential sources of contamination. Method precision and quantification limits were evaluated through blank analysis, yielding values of approximately 20% and 20 ng mL-1, respectively, consistent with chromatographic determination for environmental analysis. The suitability of the method for environmental analysis was demonstrated by analyzing eight PM2.5 samples. The concentrations of methylamine and dimethylamine were found to range from 0.8 to 3 ng m-3 and 1.4 to 7.1 ng m-3, respectively, in accordance with the literature. Comparison with concurrent carbonyl measurements revealed similar concentration profiles. Both types of analyses can be performed using affordable methodologies that involve prior derivatization using a reduced concentration of the derivatization reagent.

Carbonized Aramid Fiber as the Adsorbent for In-Tube Solid-Phase Microextraction to Detect Estrogens in Water Samples

Carbonized aramid fiber was prepared as a new type of adsorbent for in-tube solid-phase microextraction. The surface structure, chemical composition, and graphitization degree of the resulted fiber was determined and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectrometry. The prepared fiber was packed in a stainless-steel tube instead of the sample loop of a six-port and tested for the extraction of five environmental estrogen hormones coupled with high-performance liquid chromatography. Several parameters affecting the estrogens’ extraction including the sampling volume, sampling rate, NaCl content, and desorption time were investigated in detail. The extraction tube with carbonized aramid fiber exhibited remarkable extraction performance towards five estrogen targets. The analysis method was established, and it exhibited a wide linear range (0.5–10.0 μg/L) with good linearity (correlation coefficient ≥0.9906), low limits of detection (0.011–0.13 μg/L), and high enrichment factors (178–1335) for the five analytes. Relative standard deviations (n = 3) for intraday (≤4.8%) and interday (≤4.0%) tests indicated that the extraction material had satisfactory repeatability. Bisphenol A released from a polycarbonate (PC) bottle was quantitatively detected with a concentration of 8.3 μg/L. The relative recoveries spiked at 5 and 10 μg/L were investigated, and the results were in the range of 74.3–121% for real water samples.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Simultaneous HPLC-MS determination of 8-hydroxy-2'-deoxyguanosine, 3-hydroxyphenanthrene and 1-hydroxypyrene after online in-tube solid phase microextraction using a graphene oxide/poly(3,4-ethylenedioxythiophene)/polypyrrole composite

The exploration of monohydroxy polycyclic aromatic hydrocarbons and 8-hydroxy-2'-deoxyguanosine (8-OHdG) produced by oxidative stress and DNA damage is a powerful and non-invasive tool to study the health risk of exposure to polycyclic aromatic hydrocarbons (PAHs). A nanocomposite prepared from graphene oxide, poly(3,4-ethylenedioxythiophene) and polypyrrole was electrodeposited on the internal surface of a stainless-steel tube for online in-tube solid phase microextraction (IT-SPME) of 8-OHdG, 3-hydroxyphenanthrene and 1-hydroxypyrene from urine. The coating possesses excellent chemical and mechanical stability, high extraction efficiency, good resistance to matrix interference, and a long lifespan. An online IT-SPME-high performance liquid chromatography-mass spectrometry method was developed for the determination of these three metabolite biomarkers in human urine. Figures of merit include (a) enrichment factors of 30-48; (b) low limits of detection (4-41 pg·mL^-1 at S/N = 3); (c) wide linear ranges (0.05-50 ng·mL^-1); (d) good recoveries from spiked samples (71.6-109.5%); and (e) acceptable repeatability (2.3-14.6%). The method offers the advantages of low cost, simplicity, sensitivity, rapidity and automation. Graphical abstract Schematic illustration of online in-tube solid phase microextraction using graphene oxide/poly(3,4-ethylenedioxythiophene)/polypyrrole composites as adsorbent in a stainless-steel (SS) tube for the enrichment and simultaneous determination of 8-hydroxy-2'-deoxyguanosine, 3-hydroxyphenanthrene and 1-hydroxypyrene prior to HPLC-MS analysis.

A novel gaseous dimethylamine sensor utilizing cataluminescence on zirconia nanoparticles

A novel cataluminescence (CTL) sensor using ZrO2 nanoparticles as the sensing material was developed for the determination of trace dimethylamine in air samples based on the catalytic chemiluminescence (CL) of dimethylamine on the surface of ZrO2 nanoparticles. The CTL characteristics and the different factors on the signal intensity for the sensor, including nanomaterials, working temperature, wavelength and airflow rate, were investigated in detail. The CL intensity on ZrO2 nanoparticles was the strongest among the seven examined catalysts. This novel CL sensor showed high sensitivity and selectivity to gaseous dimethylamine at optimal temperature of 330 degrees C. Quantitative analysis was performed at a wavelength of 620 nm. The linear range of CTL intensity vs concentration of gaseous dimethylamine was 4.71 x 10(-3) to 7.07 x 10(-2 )mg L(-1) (r = 0.9928) with a detection limit (3sigma) of 6.47 x 10(-4) mg L(-1). No or only very low levels of interference were observed while the foreign substances such as benzene, hydrochloric acid, methylbenzene, chloroform, n-hexane and water vapor were passing through the sensor. The response time of the sensor was less than 50 s, and the sensor had a long lifetime of more than 60 h. The sensor was successfully applied to the determination of dimethylamine in artificial air samples, and could potentially be applied to analysis of nerve agents such as Tabun (GA).