Chromatographic Separation System Research Articles

Separation and purification of heavy rare earth elements by a silica/polymer-based β-aminophosphonic acid resin from chloride media

High-purity heavy rare earths (HREs) are important for promoting the development of cutting-edge materials, but their efficient separation and purification still face significant challenges. Here, a silica/polymer-based β-aminophosphonic acid resin (HEHAEP/SiO2-P) was prepared by vacuum impregnation for the separation of HREs from chloride media. At pH = 2.0, the separation factors (SF) for Er/Ho, Tm/Er, Yb/Tm and Lu/Yb were 2.35, 3.62, 3.14 and 1.23, respectively, surpassing those of some other reported impregnating resins. The maximum adsorption capacity of HEHAEP/SiO2-P for Ho, Er, Tm, Yb and Lu were 33.5, 34.6, 37.0, 38.3 and 43.2 mg/g, respectively. The adsorption process was characterized as homogeneous monolayer chemisorption, driven by entropy in a spontaneous endothermic reaction. Complete desorption of the adsorbed HREs was achieved using 4.0 mol/L HNO3. Employing our strategy, as exemplified by Tm, high-purity Tm2O3 (99.997 %) was obtained by HEHAEP/SiO2-P resin in the column chromatography separation system. FT-IR and XPS analysis demonstrated that both P-OH and PO groups participated in the coordination reaction during the HREs adsorption.

Development of an analytic method for organosulfur compounds in Welsh onion and its use for nutritional quality analysis of five typical varieties in China

A reliable, simple, and sensitive method capable of quantifying six organosulfur compounds (OSCs) was established. The samples were extracted by water containing 3 % formic acid with a simple vortex, ultrasound, and centrifugation step, and the solutions were analyzed by ultra-high-performance liquid chromatography separation system coupled with a triple-quadrupole mass spectrometry (UHPLC − MS/MS). Then the method was applied for the analysis of six OSCs in five varieties of two types Welsh onions in China, and the moisture content, reducing sugar, total polyphenols, and 21 free amino acids were also analyzed to study the characters of these Welsh onions intensively. Multivariate statistical analysis was used to investigate the differences in OSCs and free amino acids profiles among the samples. This study showed that enzymatic inhibition method combined with UHPLC − MS/MS is an effective technique to analyze OSCs in Welsh onion, and could be valuable for the routine quantitation of OSCs in other foods.

Rapid and sensitive dilute-and-shoot analysis using LC-MS-MS for identification of multi-class psychoactive substances in human urine

The emergence of new psychoactive substances currently exceeding a thousand is rapidly changing substance prevalence patterns and straining the methods used for detection, most of which are suitable only for a single class of substances. This study presents a rapid and facile dilute-and-shoot system operated in conjunction with an optimized liquid chromatographic separation system for the high-sensitivity detection of substances across a range of substance classes with 3 isotopes used only. The proposed method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) is able to identify 68 substance and their metabolites in urine samples as small as 50 μL. Optimal chromatographic conditions including 95% water/methanol ratio with 0.1% added formic acid and a prolonged LC gradient run-time (15 min) improved the peak shape of polar compounds and enhanced signal strength by 5%. Under 4-fold dilution, all analytes were within 80–120% of tolerance response levels, indicating that the matrix effect was insignificant. In experiments, the limit of detection (LOD) ranged from 0.05 to 0.5 ng mL−1, while the coefficient of determination (R2) was > 0.9950. The retention time shift of each peak remained at < 2% with an inter-day relative standard deviation (RSD) of 0.9–14.9% and intra-day RSD of 1.1%− 13.8%. The rapid dilute-and-shoot presents a high-sensitivity, significant stability, robustness and reproducibility without serious interference. To demonstrate the effectiveness of the system, 532 urine samples were collected from suspected drug abusers, and the proposed method was used for rapid analysis. Of these samples, 79.5% contained between one and twelve analytes, and 12.4% tested positive for new psychoactive substances, mostly derivatives of amphetamine and synthetic cathinones. The study presents a high-sensitivity analytic system that is capable of detecting substances from multiple classes and can be used for effective monitoring of substance prevalence in urine.

Determination of trace perfluorinated compounds in environmental water samples by dispersive solid- phase extraction-high performance liquid chromatography-tandem mass spectrometry using carbon nanotube composite materials

In this work, carbon nanotubes (CNTs) on silica rod (SiO2) composite materials were prepared to extract six perfluorinated compounds (PFCs) in real environmental water samples by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The as-synthesized sorbents, hereafter referred to as CNT@SiO2, were employed for dispersive solid-phase extraction (d-SPE). Perfluoroheptanoic acid (PFHpA), perfluorohexane sulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctane sulfonate (PFOS), and perfluorodecanoic acid (PFDA) were selected as target analytes. The main extraction parameters were systematically optimized using the single-factor optimization method. The optimum adsorption parameters were as follows: adsorption time of 30 min, sorbent amount of 10 mg, pH 6 and NaCl concentration of 1.7 mol/L for sample solution, and 4 mL acetone as desorption solvent, desorption for 4 min. LC-triple quadrupole MS was conducted to quantify the selected PFCs in water samples. The mobile phase was 5 mmol/L ammonium acetate and methanol, the flow rate was set to 0.4 mL/min, the column temperature was set to 40 ℃, and the injection volume was 5.0 μL. The chromatographic separation system was equipped with a Kinetex C18 column (100 mm×2.1 mm, 1.7 μm). The mass spectrometer was operated with negative electrospray ionization in multi-reaction monitoring mode. CNT@SiO2 was prepared in five batches and used as the d-SPE sorbent, and the relative standard deviations (RSDs) of the PFC recoveries among these five batches ranged from 4.9% to 9.3%. The reusability of the CNT@SiO2 sorbent was assessed. After eight d-SPE cycles using the same sorbent, the RSDs of the PFC recoveries were 3.7%-8.2%. These results indicated that the sorbent had good stability and reusability for d-SPE. Excellent results were achieved under optimal extraction conditions. The method validation results indicated that the linear ranges were 0.4-1000 ng/L for PFNA, PFOS, and PFDA, 0.9-1000 ng/L for PFHpA, 0.7-1000 ng/L for PFHxS, and 0.6-1000 ng/L for PFOA. The correlation coefficients were 0.973-0.997. The limit of detection (LOD) and limit of quantification of the method were 0.10-0.26 ng/L and 0.33-0.87 ng/L, respectively. At 20 ng/L, the RSDs of the intra- and inter-day precisions were 2.73%-7.75% and 3.38%-8.21%, respectively. At 100 ng/L, the RSDs of the intra- and inter-day precisions were 2.95%-8.46% and 4.16%-9.14%, respectively. Finally, at 500 ng/L, the RSDs of the intra- and inter-day precisions were 2.51%-7.48% and 3.59%-9.63%, respectively. The developed method was applied to analyze six PFCs in tap water, barreled drinking water, and river water samples. PFOA and PFOS were determined in tap water at mass concentrations of 5.6 and 8.7 ng/L, respectively. No PFCs were found in barreled drinking water and river water. Satisfactory recoveries of 72.1%-109.6% at low, middle, and high spiking levels were also obtained. In conclusion, the d-SPE-LC-MS/MS method based on CNT@SiO2 composite sorbents is accurate and sensitive. The results of this study demonstrate that CNT@SiO2 is a good choice for the rapid and effective determination of PFCs from water samples. Further exploration of the use of CNT@SiO2 sorbents for the extraction and determination of trace organic pollutions in environmental samples is in progress.

A Streamlined High-Throughput Plasma Proteomics Platform for Clinical Proteomics with Improved Proteome Coverage, Reproducibility, and Robustness.

Mass spectrometry-based clinical proteomics requires high throughput, reproducibility, robustness, and comprehensive coverage to serve the needs of clinical diagnosis, prognosis, and personalized medicine. Oftentimes these requirements are contradictory to each other. We report the development of a streamlined High-Throughput Plasma Proteomics (sHTPP) platform for untargeted profiling of the blood plasma proteome, which includes 96-well plates and simplified procedures for sample preparation, disposable trap column for peptide loading, robust liquid chromatographic system for separation, data-independent acquisition in tandem mass spectrometry, and DIA-NN, FragPipe, and in-house peptide spectral library-based data analysis. Using the optimized platform at a throughput of 60 samples per day, over 600 protein groups including 57 FDA-approved biomarkers can be consistently identified from whole human plasma, and more than 85% of the detected proteins have 100% completeness in quantitative values across 300 samples. The balance achieved between proteome coverage, throughput, and reproducibility of this sHTPP platform makes it promising in clinical settings, where a large number of samples are to be measured quickly and reliably to support various needs of clinical medicine.

Electrohydrodynamic viscous fingering of leaky dielectric fluids in a channel

Viscous fingering is a commonly observed interfacial instability during fluid displacement, where a fingerlike shape is formed at the fluid interface when a more viscous fluid is displaced by a less viscous fluid. In this study, a hybrid numerical model based on the lattice Boltzmann method and finite difference method is developed for investigating the control of viscous fingering of leaky dielectric fluids confined in a channel using electrohydrodynamics. Extensive simulations are carried out for studying the effects of the strength and direction of the electric field as well as the fluid properties, including the permittivity ratio and conductivity ratio, on viscous fingering. It is shown that a horizontal electric field, i.e., when the direction of the electrical field is perpendicular to the direction of fluid motion, can either promote or suppress the viscous fingering, depending on the permittivity ratio and conductivity ratio. For a vertical electric field, the extent of promotion of viscous fingering first decreases and then increases with the increase in conductivity ratio at a constant permittivity ratio. Also, various interfacial morphologies, such as broad fingers and thin jets, are observed under different fluid properties. A phase diagram for both the horizontal and vertical electric field is established based on the simulations with different permittivity and conductivity ratios to characterize the interfacial morphologies. This study offers insight into the electrohydrodynamic effects on the viscous fingering of leaky dielectric fluids, which could facilitate the control of multiphase flow in various applications, such as enhanced oil recovery and coupled chromatographic systems for separation.

Analytical reversed‐phase high‐performance liquid chromatography method development for silodosin and solifenacin in bulk and marketed formulation using analytical quality by design approach

AbstractA reliable HPLC method for the simultaneous estimation of Silodosin and Solifenacin was developed using the quality by design approach. In this study, the main goal was to find a dependable chromatographic system for acceptable component separation. The peaks were sharp within a reasonable run time. For the risk measurement related to the study, critical quality attributes were evaluated. To create an analytical design and a control strategy, the quantitative relationship between critical materials attributes and critical quality attributes was built utilizing the Box‐Behnken design. The optimum and ideal mobile phase ratio selected as per the quality by design approach was acetonitrile:methanol:buffer (50:20:30, v/v/v) which has a pH 4.5 flow rate of 1 ml/min. The buffer system used in this mobile phase was potassium dihydrogen orthophosphate. The retention time for Silodosin and Solifenacin determined was 3.626 and 5.754 min. respectively at λmax = 210 nm. The R2 value calculated for Silodosin and Solifenacin was 0.9994 and 0.9982, respectively. The related standard deviation was less than 2% for the developed method showing good reproducibility and recovery. A simple, precise, and repeatable high‐performance liquid chromatography method for regular quality control testing was developed simultaneously by applying a quality by design approach.

Novel chromatographic purification of succinic acid from whey fermentation broth by anionic exchange resins.

Replacement of the petroleum-based refineries with the biorefinery is regarded as an essential step towards a "zero" waste (circular) economy. Biobased succinic acid (SA) is listed by the United States Department of Energy among the top ten chemicals with the potential to replace chemicals from petroleum synthesis with renewable sources. Purification of bio-based succinic acid from fermentation by-products such as alcohols, formic acid, acetic acid and lactic is a major drawback of fermentative SA production. This study addresses this issue through a novel chromatographic separation using three distinct anionic resins: Amberlite IRA958 Cl (strong base anion exchange resin), Amberlite HPR 900 OH (strong base anion exchange resin) and Amberlyst A21 (week base anion exchange resin). The influence of process variables such as flow rate (0.18 BV/h, 0.42 BV/h and 0.84 BV/h), eluent concentration (1%, 5% and 10% HCl) and temperature (20, 30 and 40°C) were investigated. The results indicated SA separation efficiency of 76.1%, 69.3% and 81.2% for Amberlyst A21, Amberlite HPR 900 OH and Amberlite IRA958 Cl, respectively. As the regenerant HCl concentration increased from 1 to 10%, calculated succinic acid separation efficiencies decreased from 80.3 to 70.7%. Notably, as the regenerant strength increased from 1 to 10%, the total amount of organic acids desorbed from the resin sharply increased. At operation temperatures of 20, 30 and 40°C, SA separation efficacies were 81.2%, 73.9% and 76.4%, respectively. The insights from this study will be of great value in design of chromatographic separation systems for organic acids.

Integration of offline two-dimensional chromatography and mass defect filtering-based precursor ion list data acquisition for targeted characterization of diterpenoid alkaloids in the lateral roots of Aconitum carmichaelii

The hyphenated technique of offline two-dimensional (2D) chromatography with high resolution mass spectrometry (MS) was an efficient tool for separation and characterization of components in complex systems such as herbal medicines, especially those co-eluting components or isomers. In this study, we constructed the ultra-performance convergence chromatography (UPC2) × reversed phase (RP) chromatographic separation system and developed a mass defect filtering (MDF)-based precursor ion list (PIL) acquisition method to improve the selectivity and sensitivity of this technique, and the systematic characterization of diterpenoid alkaloids in the lateral roots of Aconitum carmichaelii (namely “Fuzi” in Chinese) was used as an example. The constructed offline 2D separation system showed a good orthogonality of 0.77. Besides, the in-house databases for known and predicted C19- and C20-diterpenoid alkaloids were established by molecular design in Compound Discoverer software for MS data matching and filtering, and two MDF windows were further constructed to screen out more potential diterpenoid alkaloids with novel structures and to obtain the PIL (mass range: even values between 298 and 1020 Da, parent mass width: ±100 mDa) for data acquisition by calculating the m/z values of potential ions using mass range and corresponding mass defect in the MDF windows. In addition, an integrative structure interpretation strategy was developed by integrating elemental composition analysis, ring double bond analysis, neutral loss filtering, diagnostic ion filtering and database matching, etc. As a result, a total of 659 components in the lateral roots of A. carmichaelii were exposed and characterized, including 526 potential new compounds. This strategy showed significant advantages in improving the coverage and selectivity of screening, and could also be applied in systematic characterization of components in other herbal medicines.

A zirconia-based column chromatography system optimized for the purification of IgM from hybridoma culture supernatants

By using EDTPA-modified zirconia particles that selectively adsorb immunoglobulins in a column, we developed a chromatography separation system for efficient concentrating and purifying of IgM from hybridoma culture supernatants. Hybridoma culture supernatants containing IgMs were diluted 3-fold with 10 mM phosphate buffer (pH 7.0) and passed through the column. During this process, zirconia particles selectively adsorbed these IgMs, and most of the contaminating proteins flowed out into the flow-through. The adsorbed IgMs were easily eluted with a small volume of 400 mM phosphate buffer (pH 8.0), and high-concentration IgM solutions were prepared. Subsequent simple processing using a Capto™ Core 400 cartridge column provided highly purified IgM. The operation is easy, and the activity of IgM is maintained because the purification process is performed using only neutral ranges of phosphate buffers. Here, we showed that anti-globoside and anti-CDw75 IgM purified by this method can be used to stain cervical cancer and Burkitt lymphoma cells that specifically express these respective tumor-associated carbohydrate antigens.

Preparation of a novel silica-based N-donor ligand functional adsorbent for efficient separation of palladium from high level liquid waste

In this work, a novel silica-based N-donor ligand functional adsorbent (SiVpC) is prepared by in situ polymerization for the efficient separation of palladium from high level liquid waste (HLLW). The as-prepared SiVpC adsorbent is characterized by SEM-EDS, TGA, and BET. The effects of nitric acidity, SiVpC adsorbent dosage, time, temperature, and palladium ion concentration on the adsorption are investigated. Among the 12 typical fission product metal ions (Ru, Rh, La, Y, Pr, Ce, Sm, Nd, Gd, Eu, Zr, Mo) existing in HLLW, SiVpC adsorbent can selectively adsorb palladium (SFPd/other metals = 137.6) in 0.5 M HNO3 solution. The adsorptio kinetics of Pd(II) are consistent with the pseudo-second-order model, reaching equilibrium within 120 min. The maximum adsorption capacity is 38.4 mg/g in 0.5 M HNO3, and the adsorption process is consistent with the Langmuir model. The adsorbed palladium can be completely desorbed with 0.5 M HNO3-0.5 M Thiourea. Furthermore, SiVpC adsorbent remains good performance after five adsorption–desorption cycles, which indicates good reusability. The adsorption mechanism of SiVpC adsorbent on palladium is analyzed by FT-IR and XPS that N-containing functional groups on the ligand are coordinated with palladium, which is also further verified by DFT calculations. In addition, through the column chromatography separation system, SiVpC adsorbent can efficiently adsorb palladium from HLLW and the adsorbed palladium can be desorbed with 0.5 M HNO3-0.5 M thiourea solution, which has great application potential.

Assessing Chemical Migration from Plastic Food Packaging into Food Simulant by Gas and Liquid Chromatography with High-Resolution Mass Spectrometry.

Some components of plastic food packaging can migrate into food, and whereas migration studies of known components are required and relatively straightforward, identification of nonintentionally added substances (NIAS; unknowns) is challenging yet imperative to better characterizing food safety. To this aim, migration was investigated across 24 unique plastic food packaging products including plastic wrap, storage bags, vacuum bags, and meat trays. Gas and liquid chromatography separation systems coupled with Orbitrap mass analyzers were used for comprehensive nontargeted screening of migrants. Tentative identifications of features were assigned by searching commercial databases (e.g., NIST, MZCloud, ChemSpider, Extractables and Leachables) and filtering results based on mass accuracy, retention time indices, and mass spectral patterns. Several migrants showed elevated levels in specific food packaging types, particularly meat trays and plastic wrap, and varying degrees of migration over the 10 days. Eleven putative migrants are listed as substances of potential concern or priority hazardous substances. Additionally, migration amounts of an Irgafos 168 degradation product determined by semiquantitation exceeded proposed theoretical maximum migration values.

High-Performance NMHC Detection Enabled by a Perylene Bisimide-Cored Metallacycle Complex-Based Fluorescent Film Sensor.

Non-methane hydrocarbons (NMHCs) can serve as precursors of ozone and photochemical smog, and hence their highly efficient detection is of great importance for air quality monitoring. Here, we synthesized a new fluorescent perylene bisimide (PBI)-cored metallacycle complex through coordination-driven self-assembly and used it for the production of a fluorescent film sensor. The unique rectangular structure of the developed fluorophore endows the sensor with enhanced sensing performance and discriminability to n-alkanes (C5-10). Specifically, the experimental detection limits for n-pentane, n-hexane, and n-decane are 39, 7, and 1.4 mg/m3, respectively, and the corresponding linear ranges are from 39 to 2546, 7 to 1745, and 1.4 to 85 mg/m3, respectively. Moreover, the sensing is fully reversible. In tandem with a gas chromatographic separation system, the film sensor showed comparable detection ability for the n-alkanes with a commercial flame ionization detector (FID), while the film sensor needs no hydrogen; it occupies a much smaller size (30 × 30 × 44 mm3) and consumes less energy (0.215 W). Further studies demonstrated that the developed sensor can be used for on-site and real-time quantification of NHMCs, laying the foundation for developing into a portable detector.

Rapid Separation of Photofissioned Uranium Products via a Single-Pass Multiplexed Chromatographic Fission Product Separation System.

Current state-of-the-art fission product separations frequently involve multiple independent separation columns and sample manipulation processes; to couple these processes together, multiple evaporation and transposition steps are often required. The addition of these steps results in lengthy separation times, increased analysis costs, the potential for sample loss, and release of radioactive contamination. We report a new semiautomated method for the rapid separation of U, Zr, Mo, Ba, Sr, Te, and lanthanide fission products from irradiated uranium samples. Chemical yields for U, Zr, Ba, Sr, Te and the lanthanides from less than 3-day old uranium fission product samples are consistently greater than 90%, while those of Mo are greater than 70%. This method minimizes the use and addition of oxidation and reduction reagents that often cause issues with retention and separation. Uranium dissolution and fission product separations using this single-pass method are achievable in under 2 h, representing a significant improvement over traditional gravimetric uranium fission product separation procedures.

Miniaturized all-in-one nanoGIT+active system for on-surface metabolization, separation and effect imaging

Sample components can not only be changed but also activated or inactivated via enzymatic or metabolic reactions. Identifying such activity conversions is the challenge. Up to now, the instrumental complexity and required bioanalytical effort have hindered progress in understanding such mechanisms. The newly developed all-in-one nanoGIT+active system substantially extends, and at the same time, miniaturizes the state-of-the-art technology. It combines all relevant steps on the same adsorbent surface. On-surface metabolization, immediate separation, multi-imaging, and effect-directed detection is performed as all-in-one system. Such a compact, miniaturized nanomolar system was exemplarily developed for well-known food systems. The proof-of-concept showed not only the miniaturized simulation of the coordinated processes of all digestion segments, but also bioactivity changes. The results presented as images were easily understandable. The conversions on surface were verified by comparison with state-of-the-art in vitro assays (analyzed by the same method). With new bioanalytical tools, new insights will open up. Activity changes and effects on metabolization pathways can now be identified more comprehensively and cost-/time-efficiently, if compared to status quo procedures (requiring in vitro digestion assays, column chromatographic separation systems, multiple detectors and in vitro effect-directed assays). This is attractive for nutritional, health and pharmaceutical science, drug development, medicinal research and for lean laboratories.

The Effect Analysis of Carrier Gas Flow Rate on the Rapid Gas Chromatographic Separation System.

Odor pollution did not only disturb the human normal life but also aroused the attention of environmental researchers and environmental protection departments. Therefore, the research on odor detecting method and instrument is important to theory and application. On this basis, the self-developed microfluidic chip capillary column is used in our odor detecting system. In this paper, lead the chip column into the chromatography separation system, with its small size, high efficiency, easy integration, and other characteristics to replace the original traditional column. The chip column was used in many gas experiments for several typical VOCs. At different carrier gas flow rates, the baseline value, toluene response, and toluene and methyl sulfide mixed gas separation were compared to verify the experiment to determine the optimal carrier gas flow rate in accordance with its response and separation degree. Under the premise of ensuring column efficiency as high as possible, it is determined that the optimal carrier gas flow rate is 6 ml/min. This paper shows the most proper carrier gas flow rate of our odor detecting system with the self-developed microfluidic chip capillary column.

A robust affinity chromatography system based on ceramic monoliths coated with poly(amino acid)‐based polymeric constructs

AbstractTraditional chromatographic separation systems are disadvantaged by low flow rates, a high pressure drop across the column, low capacity and poor reusability. Searching for more efficient separation systems we introduced the use of a ceramic monolith as robust support in bioseparations. A coating consisting of l‐asparagine as ligand, poly(l‐lysine) as spacer arm and a commercial poly(ethylene acrylic acid) film forming copolymer network (Michem 4983‐40R) was developed as a coating for these ceramic monoliths. Poly(l‐lysine) was synthesized by ring‐opening polymerization of ε‐trifluoroacetyl‐l‐lysine N‐carboxyanhydride and coupled to a commercial film‐forming poly(ethylene acrylic acid) network. This construct was then ‘decorated’ with l‐asparagine via the terminal amino functional groups of poly(L‐lysine) and coated onto the ceramic monolith to selectively bind l‐asparaginase. Adsorption/elution experiments showed reversible binding between l‐asparagine and l‐asparaginase, and the subsequent release of l‐asparaginase, and between 83% and 94% of the active enzyme was recovered by elution with d‐asparagine and NaCl solutions. The functional activity of the eluted l‐asparaginase was verified by a Nessler's assay. While traditional separation processes (adsorption and elution) using gel bead packings take many hours, the ceramic monolith system achieves the same of level of separation in about 1 h. This new system served as a proof of concept for its application in protein separation and purification. This work paves the way to a better understanding of the use of ceramic monoliths as stationary phase coated with a stable polymer construct for more robust and efficient supports in affinity chromatography. © 2020 Society of Industrial Chemistry

Automated extraction chromatographic radionuclide separation system for analysis of 90Sr in seawater

After the Fukushima Dai-ichi nuclear power plant disaster, the demand for a rapid method for the detection of environmental radioactivity increased drastically. Since the development of extraction chromatography using resins, analytical methods have advanced significantly in terms of simplicity and required labor. Herein, a home-made automated separation system that is applicable radio-extraction chromatographic separation techniques is reported. A simple, rapid, and high-throughput method was developed using this home-made automated separation system to analyze radiostrontium in seawater in emergency and routine situations. For emergency situations, radiostrontium in seawater is pre-concentrated on a cation exchange resin and consecutively purified using the Sr-resin. Fifty minutes are required for the purification of 90Sr in four samples (100 ml). The minimum detectable activity (MDA) for 90Sr is 0.2 Bq kg−1 at 100 min counting, with a recovery of 70% and counting efficiency of 95% in the scintillation mode. For routine monitoring, 90Y that is in equilibrium with 90Sr is first separated from the sample matrix using DGA. Treatment of 30 L of each seawater sample requires ~2 h. The MDA for this method is 0.3 mBq kg−1 at 400 min counting with a recovery of 70% and counting efficiency of 67% in the Cerenkov mode. By employing the developed method, the measured 90Sr in seawater collected from the coastal area of Korea is 0.92 ± 0.18 mBq kg−1, which is comparable to that reported previously. The measurements were obtained using a liquid scintillation counter, and the entire separation process was performed by employing the home-made separation system.

Simultaneous quantification of N‐butylthiophosphoric triamide and dicyandiamide in urea formulation by liquid chromatography with tandem mass spectrometry

A new liquid chromatography with tandem mass spectrometry method employing a mixed-mode zwitterionic stationary phase was developed for simultaneous determination of urease inhibitor (N-butylthiophosphoric triamide) and nitrification inhibitor (dicyandiamide) in urea fertilizer. Molecular modeling based on density functional theory calculations was employed to provide an insight into the interaction mechanism of urea, dicyandiamide, and N-butylthiophosphoric triamide with zwitterionic stationary phase in chromatographic separation system. The detection of analytes was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode using positive electrospray ionization. The ion transitions monitored were m/z 85→68 for dicyandiamide and m/z 168.2→74 for N-butylthiophosphoric triamide, respectively. The standard calibration curves of dicyandiamide and N-butylthiophosphoric triamide were linear over the range of 1.0 ̶ 15ppm (coefficient of determination=0.9984), 0.05 ̶ 1ppm (coefficient of determination=0.9995), with limit of detection of 25 and 5ppb, respectively. The recoveries of low, middle, and high concentrations were from 96.7 to 105.8% for N-butylthiophosphoric triamide and 94.4 to 105.8% for dicyandiamide with accuracy (relative error %) of ≤5.8% and ≤5.8%, the precision (coefficients of variation) was ≤2.0% and ≤2.9%, respectively. The validated method was successfully applied on real urea samples to determine N-butylthiophosphoric triamide and dicyandiamide simultaneously.

Silver ion chromatography for peak resolution enhancement: Application to the preparative separation of two sesquiterpenes using online heart-cutting LC-LC technique

Silver ion chromatography, utilizing columns packed with silver ions bonded to silica gel, has proved to be an invaluable technique for the analysis of some positional isomers. In this work, silver ion chromatography by combination with online heart-cutting LC-LC technique for the preparative separation of two sesquiterpenes positional isomers from a natural product was investigated. On the basis of the evaluation that silver ion content impacts on the separation, the laboratory-made silver ion columns, utilizing silica gel impregnated with 15% silver nitrate as column packing materials, were used for peak resolution improvement of these two isomers and the preparative separation of them in heart-cutting LC-LC. The relationship among the maximal sample load, flow rate and peak resolution in the silver ion column were optimized, and the performance of the silver ion column was compared with conventional C18 column and silica gel column. Based on the developed chromatographic conditions, online heart-cutting LC-LC chromatographic separation system in combination with a silica gel column and a silver ion column that was applied to preparative separation of these two isomers from a traditional Chinese medicine, Inula racemosa Hook.f., was established. The results showed that the online heart-cutting LC-LC technique by combination of a silica gel column and a silver ion column for the preparative separation of these two positional isomers from this natural plant was superior to the preparative separation performed on a single-column system with C18 column or silica gel column.