Liquid Chromatography Detection Research Articles

Selective solid-phase extraction of atrazine from agricultural environmental water samples using high permeability nanoporous carbon derived from melamine-based polybenzoxazine followed by HPLC-UV

ABSTRACT For the first time, a highly permeable nanoporous carbon derived from melamine-based polybenzoxazine (NPC-PBZ-m) was used as the solid-phase extraction sorbent for trace analysis of atrazine (ATZ) herbicide in environmental water samples as a pre-treatment to enhance detection for high-performance liquid chromatography. Extraction performance was investigated using an agricultural field matrix-water sample. The parameters affecting the solid-phase extraction efficiency were carefully investigated. The optimisation conditions were determined as 200.0 mg of sorbent with an adsorption flow rate of 10.0 mL min−1, an elution flow rate of 1.0 mL min−1, and an elution volume of 3.0 mL. Moreover, it was not necessary to adjust the pH of the sample. Under these optimised extraction conditions, good linearity between 5.00 and 30.0 µg L−1 was achieved along with a limit of detection (LOD) of 1.25 µg L−1 and a limit of quantification (LOQ) of 3.79 µg L−1. Furthermore, the reusability of the NPC-PBZ-m column was found up to 8 cycles making it a new cost-effective material for herbicide enrichment. Finally, this developed method was successfully applied to analyse ATZ in water samples from rice fields, fish farms, and natural canal water, with 98–117% relative recoveries. These results indicate that NPC-PBZ-m with our proposed method is feasible and demonstrates its potential application as an effective adsorbent for herbicide enrichment.

Screening method for chromatographic analysis of diarylheptanoids in alder bark extracts

An experimentally proven novel analytical approach for chromatographic analysis of diarylheptanoids in grey alder (Alnus incana) and black alder (Alnus glutinosa) bark matrices was established. A method for qualitative and quantitative determination of oregonin (dominant diarylheptanoid) and semiquantitative analysis of related diarylheptanoids from alder bark using a photodiode array (PDA) detector coupled to a high-resolution mass spectrometer (QTOF-MS) was developed. A comparison of different liquid chromatography detectors (UV, MS and ELS) showed that only a combination of them is applicable for comprehensive analysis of multicomponent extracts. A total of sixteen different diarylheptanoids were simultaneously identified and semi-quantified in alder bark extracts. This is the first report of the method for individual and total diarylheptanoid determination in alder bark extracts, discussed in detail. The liquid chromatography complex is suggested as a tool for the reliable identification and quality control of the diarylheptanoids containing extracts isolated from the Alnus species and their dominant component - oregonin. The semiquantitative methodology established, and the dominant compound quantification provided means for assessing comparative sample complexities.

β-Ketoenamine-linked covalent organic framework absorbent for online micro-solid phase extraction of trace levels bisphenols in plastic samples.

Covalent organic frameworks with tunable porous crystallinity and outstanding stability have exhibited fascinating pretreatment performance as ideal extraction media. Herein, the β-ketoenamine-linked TpPa-1 synthesized by 1,3,5-triformylphloroglucinol and paraphenylenediamine was employed as the absorbent for online micro-solid phase extraction of trace bisphenols combined with high-performance liquid chromatography detection. A series of characterizations indicated that the TpPa-1 possessed large surface areas, high stability, and hydrophobicity. The main experimental parameters affecting the extraction efficiency were optimized in detail. Compared with four commercial sorbents, the TpPa-1 exhibited superior enrichment capacity for extracting bisphenols. Under the optimum conditions, the established method demonstrated a wide linear range and high sensitivity with the limit of detection ranging from 0.05-0.06 μg/L. Furthermore, the developed method was successfully applied to determine bisphenols in plastic samples. Bisphenol A was actually detected in a transparent box with a concentration of 0.31 μg/g, and the recoveries of the four bisphenols in the plastic samples were 80.5-116% with the relative standard deviation less than 9.2%. Such performance was attributed to recognition affinity, including the π-π affinity, hydrophobic effect, and hydrogen bond. These results demonstrated that TpPa-1 possessed great potential to be an excellent pretreatment medium for online separation and analysis of trace analytes in complex samples.

Bisphenol and Phthalate Migration Test from Mexican Meat Packaging Using HPLC-DAD Technique

The objective of this work was to analyze the bisphenols’ and phthalates’ (PAEs) migration from meat packages (of sausages, Winnies, and ham found in Mexican markets) to a water simulant. The determination of these compounds was realized by high performance liquid chromatography (HPLC) and diode array detection (DAD) at a wavelength of 254 nm. The mobile phase utilized was a mixture of acetonitrile:H2O (70 : 30). Elution was performed isocratically at a temperature of 25°C and at a flow rate of 1 mL min−1. The LOQs obtained for BPA, DEP, BADGE, DBP, BisDMA, DHP, DOP, and PA in µg mL−1 were 0.53, 2.09, 0.85, 1.45, 5.81, 1.03, 3.12, and 29.6, respectively. Calibration curves exhibited an adequate determination coefficient for all compounds (R2 >0.999). Excellent accuracy and precision in measurements (% RSD) were achieved. The recovery study showed good applicability of the method (percentage recovery 80% to 106%). The BPA, BADGE, DBP, and DOP concentrations found in samples exceeded the simulant migration limits (SMLs) established by the European Union. The contribution of the current investigation was to provide information related to the presence of bisphenols and PAEs in the package of meat products, highlighting the health risks associated with their exposure.

The Beauty of the Quadrupole Mass Analyzer

The quadrupole mass analyzer is now available to many analytical chemists as a detector for high performance liquid chromatography (HPLC) and gas chromatography (GC), thanks to its increasingly accessible price point. Although it’s not vital to understand the working details of these detectors, insight into their design and operation can help enormously when planning, optimizing, or troubleshooting analytical methods.

Preparation of molecularly imprinted polymers based on covalent organic frameworks and their application to selective recognition of trace norfloxacin in milk

诺氟沙星(NFX)作为一种常见的喹诺酮类兽药,被广泛应用于畜牧业中,但其会残留在动物体内,进而对人体健康造成危害,为此有许多国家和组织均对NFX残留量进行了严格限制。为实现对复杂体系中痕量NFX残留的准确与可靠分析,该文制备了一种以共价有机框架(COFs)为载体的分子印迹聚合物(MIPs)。首先,在室温条件下,以金属三氟酸盐为催化剂,对苯二甲醛和3,3'-二氨基联苯为原料快速合成了“席夫碱”型共价有机框架(DP-COF)。然后将NFX、甲基丙烯酸、乙二醇二甲基丙烯酸酯与DP-COF混合,利用偶氮二异丁腈引发聚合反应,即可得到DP-COF@MIPs。整个制备过程条件温和,耗时仅5 h。采用场发射扫描电镜、傅里叶红外光谱、X射线衍射仪、BET比表面积测试仪等对其进行了表征。结果证实成功制备出了DP-COF@MIPs,该材料表面粗糙,拥有介孔范围的孔径(17.79 nm)。通过吸附实验、重复使用性实验对材料性能进行评估,结果表明该材料表观吸附容量高达41.57 mg/g,对NFX具有良好的特异性和选择性识别能力,且重复使用率令人满意。结合HPLC-UV-Vis,实现对牛奶样品中痕量NFX的检测。在3个加标水平下(0.03、0.1、0.3 mg/L),平均回收率为88.8%~92.9%,相对标准偏差小于1.7%。结果表明,该方法可以实现在复杂基质中对兽药残留高选择性、高灵敏度及准确性的检测。

Determination of 1,1-Dimethylhydrazine in Water with High Pressure Liquid Chromatography and Spectrophotometric Detection Using Micellar Catalysis

Determination of 1,1-Dimethylhydrazine in Water with High Pressure Liquid Chromatography and Spectrophotometric Detection Using Micellar Catalysis

High-performance liquid chromatographic detection of selected phenolic acidsin wine

The aim of this study was to develop a method for identification and quantification of phenolic acids in different wine samples. The simple reversed-phase HPLC-UV method for simultaneous determination of p-coumaric and ferulic acid was developed. The method was validated and working range, linearity, repeatability, accuracy, limit of quantitation LOQ and limit of detection LOD were determined. The linearity of the method was tested in concentration ranges 0.1-1 mg L-1 and 1-10 mg L-1. The correlation coefficients (r2) were greater than 0.996 and quality coefficients (QC) ≤ 5%. Detection limit for both compounds was 0.01 mg L-1. The method is precise (RSD

Electroanalytical characterisation of nitrosamines in different mobile phases as supporting electrolytes

N-nitrosamines (N-NAs), hazardous food contaminants, were submitted to an extensive electrochemical characterization of N-NAs in various mobile phases used as the supporting electrolyte and with metal and carbonaceous electrodes, in order to develop sensitive electrochemical detection methods to be applied in their post-column analysis. N-NAs (N-nitrosodiethylamine, N-nitrosomorpholine, N-nitrosopyrrolidine, and N-nitrosodiphenylamine) with both different structural characteristics and physico-chemical/reactivity properties were used as model compounds. Preliminary experiments by cyclic voltammetry at platinum (PtEs), gold (AuEs) and glassy carbon electrodes (GCEs) were performed to investigate their electrochemical behavior.The best performances were obtained either by AuEs in 20 mM methanesulfonic acid mobile phases (MSA) operating with pulsed amperometric detection (PAD) technique or by GCEs in organic mobile phases with direct current cathodic detection (DCCD) the latter proposed for the first time for the detection of N-NAs.The detection schemes were characterized in flow injection analysis (FIA) by the evaluation of some important performance parameters, such as limit of detection and response repeatability.For all the investigated N-NAs, PAD at AuEs in MSA and DCCD at GCEs in organic mobile phases showed detection limits in the range 0.8–1.2 µM and 0.4–1.2 µM respectively with RSDs of about 4%, showing the potential of the proposed electrochemical detection methods as an excellent alternative to the current N-NAs post-column detection in liquid chromatography.

Novel solid-phase extraction filter based on a zirconium meta-organic framework for determination of non-steroidal anti-inflammatory drugs residues

In this study, a zirconium-based metal-organic framework UiO-66-NH2 modified cotton fiber (CF@UiO-66-NH2) was fabricated for the extraction of five common NSAIDs, namely ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen. UiO-66-NH2 was synthesized and immobilized on the surface of cotton fiber using an environmentally friendly aqueous synthesis method. The prepared CF@UiO-66-NH2 composite of 50 mg was loaded into a 13 mm recessed filter for use as a solid-phase extraction (SPE) adsorbent material. The filter was then used to enrich NSAIDs in fish and shrimp muscle tissues followed by ultra-high performance liquid chromatography (UPLC) detection. Several key parameters were evaluated and optimized, including adsorption flow rate, pH value of sample, desorption flow rate, and the formic acid content of the eluent. Under optimized conditions, linear ranges of ketoprofen, naproxen, flurbiprofen, diclofenac sodium, and ibuprofen were 2.0–300.0 ng/mL, 1.4–280.0 ng/mL, 3.0–400.0 ng/mL, 1.0–500.0 ng/mL, and 14.0–560.0 ng/mL, respectively. The detection limits ranged from 0.12 ng/mL to 3.50 ng/mL with recoveries in the range of 72.95–116.99%, RSDs < 9.90%. The results demonstrated that the homemade filters based on CF@UiO-66-NH2 exhibited good reproducibility, stability and adsorption property for the determination of trace-level NSAIDs in complex matrix.

In Vivo Monitoring of Acetylcholine Release from Nerve Endings in Salivary Gland.

Simple SummaryStimulation of the parasympathetic nervous system results in the secretion of saliva. Previous studies have demonstrated acetylcholine content in homogenate obtained from salivary glands. Acetylcholine in homogenate, however, includes that stored in the cells, as well as that released in the interstitial fluid. The activity of the parasympathetic nervous system is mainly determined by the amount of acetylcholine released. We established an in vivo microdialysis method for monitoring the acetylcholine released from nerve endings in the salivary glands in rats. The results of the present study demonstrated that acetylcholine levels in the dialysate reflect acetylcholine levels in the interstitial fluid of the submandibular gland, and that an increase in the acetylcholine level in the dialysate depends predominantly on the release of acetylcholine from the parasympathetic nerve endings.A microdialysis technique was used to monitor acetylcholine levels in the local interstitial fluid in rat submandibular glands, with the aim of determining parasympathetic nerve activity in vivo. The dialysis probe housed a 10 × 0.22 mm semipermeable membrane (molecular weight cutoffs: 50,000 Da). When the probe was perfused at 2 μL/min in vitro, the mean relative recovery of acetylcholine was 41.7% ± 2.5%. The dialysis probes were implanted in the submandibular glands of anesthetized rats and perfusion with Ringer’s solution, at 2 μL/min, was performed. Acetylcholine concentrations in the dialysate were measured by high-performance liquid chromatography and electrochemical detection. The results revealed the following: (1) that mixing Eserine with Ringer’s solution allowed acetylcholine in the salivary glands to be quantified; (2) that acetylcholine concentrations in the dialysate were highly variable and unstable over the first 120 min after probe implantation, but reached a nearly stable level (4.8 ± 2.7 nM) thereafter in the presence of 100 µM of Eserine; and (3) that electrical stimulation of the chorda tympani nerve, or perfusion with high potassium Ringer’s solution, significantly increased acetylcholine concentrations in the dialysate. These results indicate that the present microdialysis technique offers a powerful tool for detecting changes in parasympathetic activity within the salivary glands.

Automated Programmable Generation of Broad pH Range Volatile Ionic Eluents for Liquid Chromatography.

Many of the universal detectors in liquid chromatography, including mass spectrometry, must completely volatilize the chromatographic eluent first before further processing and detection of the analytes. A basic requirement is that the eluent does not contain a nonvolatile dissolved component. However, separation of biomolecules must be conducted in mostly aqueous media of compatible pH and ionic strength if their biological activity must survive the separation process. Combinations of ammonia with acetic and formic acids are commonly used as eluent for this purpose but generally maximum concentrations that can be tolerated are relatively low. Further, buffering is good only over a limited pH range. We describe a system where the eluent is generated in an automated pressure-programmed manner from high-purity gaseous NH3 and CO2 through gas-permeable membrane devices. This can be aided by the prior presence of formic/acetic acids in the mobile phase to extend the attainable low pH limit. We outline the fundamental pH, ionic strength, and buffer intensity considerations and demonstrate the application of such eluents in the separation of amino acids, proteins, and monoclonal antibodies. We also demonstrate the use of dissolved CO2 as an ion-pairing agent in the separation of chiral amines.

New Determination Method of Two Bioactive Saponins in Lysimachia capillipes Hemsl. by Quantitative Analysis of Multi-Components by Single-Marker

Capilliposide B (CPS-B) and Capilliposide C (CPS-C), as the key components in Lysimachia capillipes Hemsl., increasingly aroused the interest and research concern of many researchers due to the good bioactivities. Nowadays, the reference standards of CPS-B and CPS-C yield were very limited. Due to the deficit of reference standards, the determination could be difficult to carry out, and the quality control and evaluation would be restrained afterwards. To solve this urgent problem, a quantitative analysis of multi-components by single-marker (QAMS) method was proposed and established based on high-performance liquid-chromatography tandem evaporative light-scattering detector. In this QAMS method, the content of the two bioactive components could be calculated by buddlejasaponin IV, which is applied as an external standard and readily obtained. And the methodological experiments were evaluated and indicated accuracy, stability and feasibility of this QAMS method. Therefore, in this study, this built method would properly meet the requirement of determination of CPS-B, CPS-C and quality control of the L. capillipes Hemsl. plant.

Application and Research of Analytical Chemistry Technology in Food Safety Testing

Food safety problems occur frequently, and the food safety problems of major enterprises are continuously reported. Therefore, food safety quality and how to test food safety have become the focus of people’s attention. The technical testing of food safety is mainly achieved through chemical means, but with the continuous development of science and technology, the disadvantages of chemical testing technology continue to appear, so how to improve the chemical testing technology has become a difficult problem to be overcome in the technical field. The thesis focuses on various chemical technologies in food safety testing, such as electrochemical immunosensors, liquid chromatography detection, pigment rapid testing instruments, nucleic acid aptamers, etc., and selects several items for detailed description.

Selective Extraction and Determination of Citrinin in Rye Samples by a Molecularly Imprinted Polymer (MIP) Using Reversible Addition Fragmentation Chain Transfer Precipitation Polymerization (RAFTPP) with High-Performance Liquid Chromatography (HPLC) Detection

Citrinin (CIT) is a mycotoxin naturally in many foods that causes carcinogenic and mutagenic effects in the human body. A novel method was developed for the selective quantification of citrinin in rye samples. Citrinin-imprinted spheres were fabricated through reversible addition fragmentation chain transfer (RAFT) precipitation polymerization (RAFTPP) in the presence of 2-hydroxymethacrylate (HEMA, functional monomer), ethylene glycol dimethacrylate (EGDMA, cross-linker), citrinin (template), 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CTA, RAFT agent), azobisisobutyronitrile (AIBN, initiator), and acetonitrile (ACN, porogen). The imprinted polymers were shown to be spherical with a high surface area and a porous structure. The rebinding properties of citrinin to the imprinted spheres were also examined in detail. The maximum adsorption capacity, equilibration time, and imprinting factor were 38.6 mg g−1, 90 min, and 3.89, respectively. In addition, the citrinin-imprinted spheres were regenerated at least 10 times without change in the adsorption capacity. The citrinin-imprinted particles were used to selectively remove and determine the analyte in rye extract. The calibration relationship was linear between 1 and 100 µg kg−1 with a limit of detection of 0.35 µg kg−1. The method also had high recoveries (98 to 100.0%) and low relative standard deviations (less than 4.1%). Therefore, the imprinted spheres are suitable for the selective determination of citrinin in rye extracts.

Development of ultrasound-assisted centrifugal extraction and online solvent concentration coupled with parallel countercurrent chromatography for the preparation of purified phytochemicals: Application to Lycium ruthenicum

To improve the preparation efficiency of natural products, new techniques for extraction and concentration of natural products have been established. Based on this, an on-line technology to improve the yield and preparation efficiency of natural products have been established. In this study, a novel method to extract natural products from crops and plants, termed ultrasound-assisted centrifugal extraction (UACE), was developed as a supplement to a new online solvent concentration (OSC) technique. These techniques were coupled with parallel countercurrent chromatography (PCCC) and evaluated in the automated preparation of phytochemicals from Lycium ruthenicum. The UACE device comprises an extraction chamber and a solution separation chamber and offers the advantages of higher extraction efficiency, fewer impurities, and conduciveness to sample processing. The OSC device comprises a spray nozzle, concentrating cylinder, and hot-blast air nozzle. The mechanical parameters of the UACE and OSC were optimized, and the operation mode of online UACE combined with OSC and PCCC was described. Raw plant materials were extracted with a two-phase extractant comprising petroleum ether‒ethyl acetate‒ethanol‒water (2:2:1:6, v/v/v/v), and the aqueous and organic phases were then concentrated by OSC. After extraction and online concentration, the concentrate was separated. During PCCC separation, the on-line extraction, and concentration were still conducted. When the first cycle of the UACE/OSC/PCCC was completed, the second cycle was initiated, and so on. As a result, six target compounds with purities exceeding 97.03 % (high performance liquid chromatography detection at 250 nm) were successfully separated using the countercurrent chromatography solvent systems comprising n-heptane‒ethyl acetate‒acetonitrile‒water (20:4:17:1, v/v/v/v) and n-butanol–ethyl acetate–water (55:21:70, v/v/v). Compared with conventional extraction methods, the proposed method offers the advantages of efficiency, automation, high-purity separation of the analytes, and systematic preparation of natural products from crops.

The influence of anesthetics on neurotransmitters in the nervous system of Sepia pharaonis

Anesthesia is a stress mitigation technique widely used during transportation and short-term human manipulation, such as labeling and measurement of body parameters of aquatic animals. This is because anesthetics affect the content of neurotransmitters, exerting various effects on the body. This study determined optimal anesthetic concentration for cuttlefish by measuring the anesthetic and recovery duration of Sepia pharaonis. This was assessed with Nuclear magnetic resonance (NMR) combined with high performance liquid chromatography (HPLC) detection of nervous system metabolites and specific changes in the content of six neurotransmitters. Successful anesthetization of cuttlefish was observed with ethanol concentration (10–30 mL L−1). The cuttlefish recovered after anesthesia, with the longest exposure time being 60 min at a concentration of 10 mL L−1 ethanol. Likewise, the cuttlefish also reached a sedative state at a concentration below 5 mL L−1 ethanol, but with a maximum exposure time of 270 min. We concluded that the action of ethanol attributed to the 10–20% increase of glycine and tyrosine using NMR and HPLC analysis. We postulate the anesthetic role of ethanol in cuttlefish led to increased inhibitory neurotransmitters gamma-Aminobutyric acid, (GABA) and Glycine (Gly) while it reduced the levels of excitatory neurotransmitters acetylcholine (Ach), dopamine (DA) and 5-hydroxytryptamine (5-HT).However, cuttlefish recovery from anesthesia was probably due to rising Ach and Glutamate (Glu) levels.

LC–NMR for Natural Product Analysis: A Journey from an Academic Curiosity to a Robust Analytical Tool

Liquid chromatography (LC)–nuclear magnetic resonance (NMR) combines the advantage of the outstanding separation power of liquid chromatography (LC) and the superior structural elucidating capability of nuclear magnetic resonance (NMR). NMR has proved that it is a standout detector for LC by providing maximum structural information about plant originated extracts, particularly on the isolating ability of isomeric (same molecular formula) and/or isobaric (same molecular weight) compounds as compared to other detectors. The present review provides an overview of the developmental trends and application of LC–NMR in natural product analysis. The different LC–NMR operational modes are described, and how technical improvements assist in establishing this powerful technique as an important analytical tool in the analysis of complex plant-derived compounds is also highlighted. On-flow, stop-flow and loop-storage modes, as well as the new offline mode LC–solid phase extraction (SPE)–NMR and capillary LC (capLC)–NMR configurations which avoid the ingestion of expensive deuterated solvents throughout the experiment, are mentioned. Utilization of cryogenic probe and microprobe technologies, which are the other important promising approaches for guaranteeing sensitivity, are also described. Concluding remarks and future outlooks are also discussed.

Editorial: Improved Methods Using Spectrophotometric Detection In Liquid Chromatography

LC – HPLC is an actual a separation technique for follow investigation. It depends on the association of an analyte with a stationary phase (column with particles) and a mobile phase (liquid eluent or a combination of eluents). Mass Spectrometry (MS) is the insightful instrument to gauge the structure of an example. The MS creates valuable data about the sub-atomic weight and the construction of analytes and helps in the explanation of obscure mixtures

Enhancement of functional characteristics of blueberry juice fermented by Lactobacillus plantarum

Lactic acid bacteria with various probiotic functions and excellent fermentation characteristics are widely used in food production, which not only enhance flavor, but also improve functional quality. In this research, Lactobacillus plantarum J26 was selected as the fermented strain in blueberry juice, and the basic indexes, nutritional functional properties, antioxidant capacity and enzyme inhibition were tested to judge the fermentation process influences to blueberry matrix. The results showed that the total amount of phenolic substances increased by 43.42% after fermentation. Four kinds of anthocyanins were found through High Performance Liquid Chromatography (HPLC) detection. Then the scavenging abilities of DPPH, superoxide anion radical and hydroxyl radical were estimated to determine the antioxidant activities of fermented blueberry juice. Moreover, the effect of oxidative damage was also analyzed in the model of Caco-2 cells. Finally, the inhibition of α-glucosidase and α-amylase were both detected in fermented blueberry juice. To sum up, these findings suggested that L. plantarum J26 could be used as fermented strain in the blueberry juice to improve the functional activities.