Column Flow Rate Research Articles

Ultrasensitive LC-MS/MS quantitation of the N-nitroso-dabigatran etexilate impurity in dabigatran etexilate mesylate using an electrospray ionization technique.

Nitrosamine impurities, particularly nitrosamine drug substance-related impurities (NDSRIs), pose significant health risks due to their potential mutagenicity and carcinogenicity. Consequently, stringent regulatory guidelines have been established for their detection and quantification in pharmaceutical products. This study presents a simple, robust, and ultrasensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify the N-nitroso-dabigatran etexilate (NDE) impurity in the drugs and capsules of dabigatran etexilate (DEM) using an electrospray ionization technique. Using a gradient elution program, with mobile phase A consisting of 5 mM ammonium formate buffer (pH 7.0 ± 0.1) and mobile phase B 100% acetonitrile, chromatographic separation was achieved on a Sapphirus C18 HP-classic column (250 mm × 4.6 mm × 5 μm). The system utilized an Agilent 1290 infinity series LC with a 6470B LC/TQ tandem mass spectrometer, operating at a 0.6 mL min-1 column flow rate. Detection and quantitation of the N-nitroso dabigatran etexilate (NDE) impurity were performed in positive ESI mode using multi-reaction monitoring (MRM). The validation of the method adhered to the ICH Q2 (R2) guidelines, showing excellent signal-to-noise ratios for the detection and quantification limits, with linearity observed (correlation coefficient > 0.99) over a range of 18-120 ppb. Accuracy was confirmed through recovery studies, yielding satisfactory results between 80 and 120% of spiked concentrations. This validated LC-MS/MS method is suitable for routine and stability analysis of N-nitroso-dabigatran etexilate (NDE) impurities in both drug substance and finished capsules.

Interaction of lysozyme with solid supports cryogels containing imidazole functional group.

This paper details the preparation of acrylamide-based supermacroporous cryogels and their application in removing lysozyme from aqueous solutions. N-Vinyl imidazole was copolymerized with acrylamide as a comonomer to impart pseudo-specificity to the cryogels, forming poly(AAm-VIM) cryogel. Characterization studies to assess the physical and chemical properties of the synthesized cryogels involved swelling tests, Fourier Transform Infrared Spectroscopy (FTIR), elemental analysis, Field Emission Scanning Electron Microscopy (FESEM), and Thermogravimetric Analysis (TGA-DTA). To ascertain the optimal conditions for the adsorption process, pH 9.0 (TRIS buffer) was selected for lysozyme adsorption, using the parametres such as initial concentration screening, ionic strength, temperature, and column flow rate. The Langmuir and Freundlich isotherm models were analyzed to assess the adsorption parameters mathematically. The regression coefficient results indicated that lysozyme adsorption aligned more closely with the Langmuir isotherm model. The adsorption process is considered to be thermodynamically physical and spontaneous. SDS-PAGE analysis assessed the purity of lysozyme isolated from an aqueous solution using a poly(AAm-VIM) cryogel column. The inertness and regeneration capacity of poly(AAm-VIM) cryogel affinity columns were assessed using reusability studies conducted during the adsorption-desorption cycle.

Determination of the appropriate extraction method for bound aroma compounds from strawberry and analysis of aroma substances in strawberry fruits of different varieties and developmental stages.

Strawberries are rich in unique aroma substances, which include bound and free aroma compounds. Unlike the free aroma, the appropriate extraction and analytical methods for bound aroma compounds in strawberries remain unclear. In the present study, we compared three extraction methods for bound aroma compounds of strawberries and performed the single factor experiment for optimizing the hydrolysis method, process parameters, and response surface analysis. The following optimal process conditions were obtained for extracting bound aroma precursor compounds by the Cleanert PEP column: (1) column flow rate of 1mL/min; (2) dichloromethane: pentane eluent ratio of 7:1; and (3) ethyl acetate: methanol retention solution ratio of 3:1. The bound aroma precursor compounds were enzymatically hydrolyzed at 38°C for 48h and finally detected by GC-MS. The results showed that HY strawberries at red fruit stages had the most abundant aroma content and types, and different varieties had different aroma types.

Development of a QAMS Analysis Method for Industrial Lanolin Alcohol Based on the Concept of Analytical Quality by Design

The Analytical Quality by Design (AQbD) concept was adopted to establish a quantitative analysis of multi-components with a single marker (QAMS) method for industrial lanolin alcohol, targeting cholesterol, lanosterol, and 24,25-dihydrolanosterol. The potential critical method parameters (CMPs) were identified as column temperature, flow rate, and gradient. Definitive screening design and statistical modeling were employed to optimize the gradient conditions of the mobile phase, column temperature, and flow rate. The Method Operable Design Region (MODR) was determined using a risk-based quantification approach. The robustness was assessed using a Plackett–Burman experimental design, followed by methodological validation. Optimal analytical conditions were as follows: acetonitrile (B)—water (A) mobile phase system; flow rate of 1.58 mL/min; detection wavelength of 205 nm; injection volume of 10 µL; and column temperature of 37 °C. A gradient elution program was implemented as follows: 0–19.0 min, 90.5% B; 19.0–25.0 min, 90.5–100% B; and 25.0–55.0 min, 100% B. Cholesterol served as an internal standard for quantifying lanosterol and 24,25-dihydrolanosterol, with relative correction factors of 0.4227 and 0.8228, respectively. This analytical method utilized only the cholesterol reference substance as an internal standard to quantify the content of cholesterol, lanosterol, and 24,25-dihydrolanosterol in industrial lanolin alcohol. It reduced the testing costs and enhanced efficiency, making it potentially suitable for widespread adoption in lanolin alcohol processing industries.

Anion exchange-HPLC method for evaluating the encapsulation efficiency of mRNA-loaded lipid nanoparticles using analytical quality by design

Lipid nanoparticles (LNPs) are emerging nucleic acid delivery systems in the development of mRNA therapeutics such as the severe acute respiratory syndrome coronavirus 2 vaccines. However, a suitable analytical method for evaluating the encapsulation efficiency (EE) of the LNPs is required to ensure drug efficacy, as current analytical methods exhibit throughput issues and require long analysis times. Hence, we developed and validated an anion-exchange HPLC method using Analytical Quality by Design. Three critical method parameters (CMPs) were identified using risk assessment and Design of Experiments: column temperature, flow rate, and sodium perchlorate concentration. The CMPs were optimized using Face-Centered Central Composite Design. The discriminating power of the optimized HPLC method and RiboGreen assay was comparable. The main advantage of this method is that LNPs can be directly injected into the HPLC system without bursting the LNPs loaded with encapsulated poly(A). The optimized HPLC method was validated as robust, high-throughput, and sufficiently sensitive according to the ICH Q2 guidelines. We believe our findings could promote efficient LNPs-based drug development.

Comparison of nitrogen and helium as carrier gases for determination of pesticide residues in foods via gas chromatography–tandem mass spectrometry with atmospheric pressure chemical ionization

The applicability of nitrogen as an alternative carrier gas to helium for the multiresidue analysis of pesticides using gas chromatography–tandem mass spectrometry with atmospheric pressure chemical ionization (GC–(APCI)MS/MS) was examined. The methods using both carrier gases were validated for 151 pesticides in foods at a spiking level of 0.01 ppm, maintaining identical conditions for both gases, including the GC column and carrier gas flow rate. The use of nitrogen resulted in slightly broader peaks and lower peak intensities that those observed upon using helium. However, sufficient sensitivity was achieved for all target compounds because of the high sensitivity of the GC–(APCI)MS/MS method. Further, target-compound separation was not significantly affected by the carrier gas type, and no interfering peaks were observed, demonstrating the high selectivity of the nitrogen-based method, even beyond the optimum linear velocity. Finally, the analytical performance of the nitrogen-based method was comparable to those of the helium-based method. Considering cost-effectiveness of nitrogen, this method is highly valuable in the event of helium shortages and for routine pesticide residue monitoring.

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 2mL/min. The retention time of N,N-dimethylbenzamide was determined to be 8.5min. 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%.

A Robust and Reliable UPLC Method for the Simultaneous Quantification of Rosuvastatin Calcium, Glibenclamide, and Candesartan Cilexetil

Metabolic syndrome is an associated condition that occurs together and increases the risk of heart disease and diabetes. These conditions include high blood pressure, high blood sugar, and high body mass index (BMI) in terms of cholesterol and triglyceride levels. Most of the elderly population may administer three drugs to control the above conditions. Therefore, this study aims to develop an analytical assay for the precise analysis of three components and to formulate a Self-Nanoemulsifying Drug-Delivery System (SNEDDS) loaded with three drugs: Rosuvastatin Calcium (RC; antilipidemic), Glibenclamide (GB; antidiabetic), and Candesartan Cilexetil (CC; antihypertensive). A design of the experiment was developed at a level of 32, and the influence of column temperature and flow rate was studied in terms of retention time, peak area, peak asymmetry, and resolution. The assay was subjected to several studies to ensure its validation. Under the optimized conditions—column temperature at 50 °C and flow rate at 0.25 mL/min—the three drugs, RC, GB, and CC, are separated. Their retention times are 0.840, 1.800, and 5.803 min, respectively. The assay was valid in terms of linearity, accuracy, and precision. Moreover, the developed assay shows a good tolerance against any change in the condition. The assay was tested also to separate the drugs in a pharmaceutical formulation as SNEDDs. The assay successfully separates the drug with a good resolution.

Removal of low concentration of perchlorate from natural water by quaternized chitosan sphere (CGQS): Efficiency and mechanism research

In this study, an innovative approach utilizing betaine as a raw material was employed to effectively modify the surface of chitosan with quaternary ammonium groups. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) characterization showed that the quaternary ammonium groups on betaine were successfully loaded on the chitosan surface. The effects of dosage, pH, initial perchlorate concentration, temperature and co-existing anions on the removal efficiency of perchlorate were investigated. The saturated adsorption capacity of CGQS was 35.41 mg/g under natural condition. The impact of initial perchlorate concentrations and column flow rates on the column adsorption experiments were investigated, as well as natural water tests. Sterilizing performance experiments of CGQS were carried out innovatively. Under the condition of initial concentration of 0.5 mg/L, 9 BV/h (bed volume per hour), the effluent natural water was up to standard (≤0.07 mg/L) with a treatment capacity of 210 BV/g, and the sterilizing rate of CGQS was up to 97.02%. The proposed adsorption mechanisms involved surface pore adsorption, electrostatic adsorption of quaternary ammonium groups, and ion exchange between chloride and perchlorate ions. The CGQS prepared in this work had great potential for treating trace perchlorate contamination in natural water.

Comparison of Artificial Neural Fuzzy Inference System (ANFIS) and Response Surface Methodology (RSM) Model in Predicting the Outlet Flow Rate of Passive Treatment System Column

Acid mine drainage (AMD) is one of the major environmental problems the mining and mineral processing industries face. Treatment of AMD involves active and passive treatment. In the long term, passive treatment is the most effective way to treat acid mine drainage, but it can be expensive. if handled properly. Therefore, the study of flow rate in a passive treatment system is one of the important ways to identify optimum hydraulic retention time to ensure the maximum percentage of heavy metal removal can be achieved while keeping the cost to a minimum level. This study focused on developing and comparing the Response Surface Methodology (RSM) model and Artificial Neural Fuzzy Inference System (ANFIS) model to predict the outlet flow rate of the passive treatment system column based on three parameters inlet flow time, thickness of peat soil bed, and inlet flow rate. The RSM model was created by Design-Expert software whereas MATLAB created the ANFIS model with 80% of data used for the model training and 20% of the data for model testing. The models' performances were compared in terms of statistical errors (AAPE, RMSE, R2, STD, minimum error, and maximum error). It was found the ANFIS model has performed better in predicting the outlet flowrate with R2 value of 0.99 RSM model with the value of 0.97. The inlet flow rate was an insignificant parameter affecting the outlet flow rate of the passive treatment column. From the 3-D surface response plot, the highest outlet flow rate is predicted to be 524 mL/min.

Optimization of the power supply and temperature control algorithm for a second-dimension temperature programming system used in comprehensive two-dimensional gas chromatography

This study evaluates the relationship between the power supply output (voltage (V), current (I), power (W)), used for heating a second dimension (²D) column, and the maximum heating rate and temperature offset achievable by custom built ²D temperature programming system (²DTPS). The influence of the gas chromatograph (GC) oven temperature, ²D column flow rate, and ²D column dimensions when heating the ²D column were also explored. This data provided the minimum power needed for heating a ²D column (normalized to its length), based on the heating rate or temperature offset relative to the first dimension (¹D) column. During the study, optimization of the temperature control algorithm was also carried out to expand the dynamic range of the heating rate for a single power supply output (V, I), while maintaining a temperature deviation of < 0.75 °C between the measured temperature and temperature setpoint. This simplified the power supply specification recommendation to voltages which provide 1.5 A for heating rates and maximum temperature offsets below 28 °C/s and 70 °C, respectively, and 1.9 A when higher heating rates or temperature offsets were needed.

FORCED DEGRADATION STUDIES AND ASSESSMENT OF DEGRADATION PRODUCTS OF IMEGLIMIN HYDROCHLORIDE USING LC-ESI/APCI-MS

Forced degradation subjects drug substances to stress conditions, producing degradation products that are crucial for evaluating stability under accelerated conditions. Imeglimin hydrochloride is a commonly prescribed medicine for managing type 2 diabetes mellitus. This study details the forced degradation experiments and LC-MS analysis of degraded products of Imeglimin Hydrochloride under various stress conditions, offering insights into its stability and providing information on fragmentation pathways and major degradation products. The optimized mobile phase for the LC-MS method was composed of 10 mM ammonium format buffer (pH 3): methanol with a ratio of 75:25 v/v, obtained on an Xtimate C-18 column (flow rate of 0.8 ml/min), with 234 nm as the specific detection wavelength for Imeglimin Hydrochloride. The drug was subjected to stress conditions including photolysis, hydrolysis, thermal, and oxidative stress conditions. After various stress conditions were applied, the complete stability pathways and effects of these stress conditions were examined. Imeglimin hydrochloride underwent degradation when exposed to oxidative conditions at room temperature and basic conditions at elevated temperatures. However, specific degradation products were not found under acidic, thermal, and photolytic stress conditions. By comparing predicted and observed fragmentation patterns and identifying base peaks, LC-MS analysis of Imeglimin Hydrochloride revealed two new degradation products, DP1 (m/z 160.2) and DP2 (m/z 118.0) under oxidative and basic stress conditions, respectively. The developed method was validated as per the guidelines of analytical method validation.

Treatment of heavy metal ions from simulated water using adsorption process via modified iron magnetic nanocomposite

Heavy metals are considered hazardous elements because they are not biodegradable in the environment. Exposure to heavy metals leads to serious problems that affect human health and the aquatic environment. Removal of heavy metal ions from simulated water was employed for chitosan/iron nanocomposites (C-Fe2O3NPs). C-Fe2O3 was prepared from chitosan solution and iron salt. The characterization of C-Fe2O3 was carried out using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), and X-ray diffractometry (XRD). To determine the morphological structure, functional groups, and physicochemical properties. Determination of the optimum operating experimental conditions that result in the highest efficiency for heavy metal ions was investigated, such as contact duration (0–60 min), concentration (0.5, 1, 2, 3, and 5 mg/L), and adsorbent dose (0.1–0.5 g/L). Subsequently, the application of modified C-Fe2O3 in batch system for the elimination of Cu, Cr, Pb, Zn, and Se from simulated water was carried out. The results showed that EDX displayed the existence of iron, indicating the presence of iron nanoparticles. Also, the XRD and XRF showed the presence of iron oxide in the crystalline phase. The optimal conditions of the breakthrough curve, such as column height, flow rate, and contact time, were also examined. The results showed that the optimal conditions in the column system were a height of 10 cm, a flow rate of 5 mL/min, and a concentration of 3 mg/L. The kinetic information obtained was best modeled with the pseudo second-order model, and the experimental results fit the Langmuir model. High removal rates for Cu, Cr, Zn, Se, and Pb reached 99.8%, 93.8%, 98.8%, 99.8%, and 97.8%, respectively were achieved. The regeneration study indicated the good shelf life of iron magnetic NPs, which was 4.2%. In conclusion, C-Fe2O3 NPs are a potential adsorbent for heavy metal decontamination from water.

Removal of fluoride from groundwater by chemically functionalized sugarcane bagasse biochar and bagasse pellets in a fixed-bed sorption system

This study aimed to investigate the design parameters for a filter intended to remove fluoride from groundwater. Water fluoridation notably influences groundwater, particularly in arid and semi-arid areas that exacerbate the challenge of availability of safe drinking water from Groundwater resources in numerous developing nations. Experiments were conducted to determine the fluoride concentrations in groundwater sources in the arid region of Maharashtra, India. Samples were collected from seven villages in three districts of Maharashtra. This study utilized chemically functionalized sugarcane bagasse biochar adsorbent (SCBB), which is low-cost and easily accessible, to remove fluoride from groundwater in a column setup. The recommended design parameters for the packed-bed column flow rate (Q) are 100 ml min−1 and bed height (d) is 30 cm.

Simultaneous chromatographic separation of the anomers of saccharides on a polymer sulfobetaine zwitterionic stationary phase.

Simultaneous chromatographic separation of the anomers of saccharides was achieved by using a polymer zwitterionic stationary phase functionalized by acrylamide-type sulfobetaine. By optimization of separation parameters including column temperature, pH, and flow rate, the column operated in hydrophilic interaction chromatography mode exhibited excellent separation selectivity toward five monosaccharides and their anomers (including ribose, xylose, galactose, glucose, and arabinose) and two disaccharides (lactose and maltose). Baseline separation could be achieved at mild operation conditions such as 20-30°C of column temperature or typical mobile phase composition (85% acetrontrile-15% 20mM ammonium formate [NH4 FA]) with wide pH tolerance range of 2-8. This offers a rapid way to determine the configuration of α or β anomer of the saccharides.

Experimental study of airflow thermal fluctuation properties induced by liquid metal pouring based on schlieren and proper orthogonal decomposition

Understanding the thermal fluctuation characteristics of the induced airflow during liquid metal pouring processes aids in effective control of emissions from metallurgical plants. This study used schlieren and proper orthogonal decomposition (POD) to analyze the thermal fluctuation characteristics of induced airflow during continuous and discontinuous liquid column flow, within the range of Grashof numbers from 2.64 × 105–3.19 × 105, and liquid column discharge rates ranging from 2500 to 3000 mL/min. The results show that the induced airflow exhibited weak turbulence in both continuous liquid column flow (CLCF) and discontinuous liquid column flow (DLCF). Higher Grashof numbers predominantly elevate the induced airflow thermal fluctuation in CLCF, whereas increased liquid column flow rates primarily enhance the induced airflow thermal fluctuation in DLCF. The primary spatial fluctuation region of induced airflow is within a dimensionless distance (X/r') of 1 at the front side of the pouring cup; the dimensionless horizontal thermal fluctuation diameter (d') of the induced airflow around the liquid column is approximately 2.5. The fluctuation frequency of the induced airflow was mainly within the range of 0–5 Hz. The main frequency during the CLCF was greater than 1 Hz; during the DLCF it was less than 1 Hz. Additionally, the root-mean-square values of the schlieren image grayscale demonstrated the potential advantage of identifying regions with pronounced turbulence characteristics. In summary, identifying the primary location and frequency of the induced airflow with different pouring processes is beneficial for developing novel smoke-control technologies, and the experimental methods and induced airflow details are good references for further studies.

Enhancing Water Quality Management in Ornamental Fish Aquariums with Pot and Bamboo Filter Systems

The filtration of aquarium wastewater composed of a pot and bamboo is constructed for the purification of microbial activities and to reduce turbidity. The aquarium wastewater is treated with sand to reduce BOD and COD; the usage of coconut husk and vetiver act to decrease the turbidity, nitrite, and pH while raising DO level. Initially, sand was sieved to produce 12 size ranges between 180 and 2000 m. The effectiveness of each range in removing turbidity, BOD, and COD through sand beds 4 or 5 cm deep were tested. The critical size (300 &amp; 425 m) at which no solid particles could penetrate through the sand bed was observed at 3 and 4 cm in depth, respectively. Moreover, the flow of solids through sand filter beds had all particles smaller than 180 m removed from them. A 2 cm bed of sand allowed 0.2-0.5% of solids to flow through, and a 4 cm bed allowed 0.07-0.1 %. Both fine and coarse sand layers are supported by a layer of gravel. In the column approach, the thickness and flow rate of each layer were fixed. The thickness of the layers of sand and charcoal were fixed at 4 cm and 6 cm, respectively. The findings of the column analysis, the combined filter showed decreases in turbidity by 48%, COD by 52%, BOD by 30%, and increasing DO by 48%, respectively. The results reveal that absorbing nutrients can serve as bio-filters to create better conditions for fish growth. The final weight, length, and SGR of fishes in the three aquariums were significantly different after seven weeks of trial, the treated aquarium showed the highest value than the control.

Sensitivity comparison of gas chromatography-mass spectrometry with Cold EI and standard EI.

Gas chromatography-mass spectrometry (GC-MS) with Cold EI is based on interfacing GC and MS with supersonic molecular beams (SMBs) along with electron ionization of vibrationally cold sample compounds in SMB in a fly-through ion source (hence the name Cold EI). Cold EI improves all the central performance aspects of GC-MS, and in this paper, we focus on its improvement of signal-to-noise ratio (S/N) and limits of detection (LODs). We found that the harder the compound for analysis with standard EI, the greater the Cold EI gain in S/N and LOD. The lower LOD and higher S/N of Cold EI emerge from a few reasons: (a) similar ionization yield as standard EI, (b) enhanced abundance of molecular ions, (c) elimination of vacuum background noise, (d) elimination of ion source-related peak tailing and degradation, (e) ability to lower the elution temperatures via the use of high column flow rates, and (f) greater range of thermally labile and low-volatility compounds that can be analyzed. We demonstrate the superior S/N and lower LOD of Cold EI versus standard EI in a range of compounds, from the simple-to-analyze octafluoronaphthalene all the way to reserpine and an organo-metallic compound that cannot be analyzed by standard EI. These compounds include methyl stearate, cholesterol, n-C32 H66 , large polycyclic aromatic hydrocarbons, dioctyl phthalates, diundecyl phthalate, pentachlorophenol, benzidine, lambda-cyhalothrin, and methidathion. The significantly lower Cold EI LODs that can be over 1000 times better than in standard EI further result in far superior response linearity and greater measurement dynamic range.

Profiling of branched chain and straight chain saturated fatty acids by ultra-high performance liquid chromatography-mass spectrometry

Branched chain fatty acids (BCFAs) are one of the important sub categories of fatty acids (FAs) which have unique functions in nature. They are commonly analyzed by GC–MS after derivatization to methyl esters (FAMEs). On the other hand, there is a lack of isomer-selective LC-MS methods which allow the distinction of different isomers with wide coverage of carbon chain length. In this work, a systematic retention and isomer selectivity study on seven commercially available UHPLC columns (six polysaccharide columns Chiralpak IA-U, IB-U, IC-U, ID-U, IG-U and IH-U; one Acquity UPLC CSH C18 column) was performed. Various experimental factors were evaluated including column temperatures, gradient profiles and flow rates to elucidate their effects on the separation ability of homologous series of BCFAs with distinct chain lengths, different branching types and branching positions. In general, IG-U outperformed the other columns in terms of isomer selectivity especially for the short and medium-chain BCFA isomers while RP C18 showed good potential in terms of selectivity for long-chain BCFA isomers. Furthermore, after the evaluation of the chromatographic retention pattern on the various columns and method optimization, we report a methodology for untargeted isomer-selective BCFA profiling without precolumn derivatization with UHPLC-ESI-MS/MS by quadrupole-time-of-flight instrument with SWATH acquisition. The best method provides selectivity for constitutional isomers of BCFAs covering distinct chain length (C5-C20) with different branching types (methyl or ethyl) and branching positions (2Me, 3Me, 4Me, 6Me, anteiso and iso-BCFAs) with an optimized LC condition on Acquity UPLC CSH C18 column. Finally, the optimized method was applied for the BCFAs profiling in lipid extracts of Staphylococcus aureus samples. Besides, pooled human platelets and pooled human plasma were evaluated as mammalian samples for presence of BCFAs as well. The new method showed strong potential for BCFA profiling in bacterial samples including different isomers anteiso and iso-BCFAs, which could be a useful tool for related subdisciplines in metabolomics and lipidomics in particular in combination with electron-activated dissociation MS. Compared to GC, the presented isomer selective LC methods can be also of great utility for preparative purposes. Equivalent (carbon) chain length numbers were calculated for RP18 and Chiralpak IG-U and compared to those of FAMEs obtained by GC.

Modelling of Basic Yellow 28 adsorption onto activated carbon: batch and continuous process

PurposeThis study aims to model and investigate Basic Yellow 28 (BY28) adsorption onto activated carbon in batch and continuous process.Design/methodology/approachBatch adsorption experiments were carried out at 25 °C with 50 mg/L BY28 solution at pH 6 with different amounts of activated carbon. Freundlich and Langmuir adsorption isotherm models were used to model batch data. Pseudo-first-order and pseudo-second-order kinetic models were applied with linear regression. The changes of the breakthrough curve with the column height, flow rate, column diameter and adsorbent amount were examined in fixed bed column at room temperature. BY28 adsorption data were modelled by using different adsorption column models (Adams & Bohart, Thomas, Yoon & Nelson, Clark and modified dose–response) with non-linear regression.FindingsFreundlich model and pseudo-second-order kinetic model expressed the experimental data with high compatibility. Modified dose-response model corresponded to the fixed bed column data very well.Originality/valueAdsorption of Basic Yellow 28 on activated carbon in a fixed bed column was studied for the first time. Continuous adsorption process was modelled with theoretical adsorption models using non-linear regression.