Dimensional Liquid Chromatography Research Articles

Modulation optimization when using a splitter pump after the first dimension in comprehensive two- dimensional liquid chromatography

The rapid growth in the use of two dimensional liquid chromatography (2D-LC) applied to the analysis of moderately to highly complex mixtures, has been fueled by continuous improvements in performance and robustness of the instrument components, as well as the ease-of-use of software necessary for controlling the 2D-LC instrument hardware, and analysis of the large data files that result from this type of work.This work has focused on the evaluation of the performance of an online full comprehensive mode (LC×LC), when an active modulation is implemented using a flow splitter pump placed after the 1D effluent. Two different types of splitting pumps were evaluated: a binary ultra-high pressure liquid chromatography (UHPLC) pump and a high precision syringe pump. We analyzed the performance (reproducibility in peak area and retention times and the 2D peak dispersion) as a function of the location of the active pump Before or After the modulation valve, and the influence of connecting tubes (based on internal diameter and length) necessary between the interface, waste, and the splitting pump. The effect on the flow direction on the filling and flushing of the injection loops at the modulation valve was also analyzed for each pump.In this study, we demonstrate that flow-splitting LCxLC assembly can be performed using either a UHPLC binary pump or a simple syringe pump. Flow splitting after the first dimension is a straightforward strategy to: (i) independently select the 1D column and flow rates with respect to the second dimension; (ii) consciously dilute the eluate according to the solvent characteristics of the second dimension, thereby avoiding 2D peak distortions; and (iii) adapt the injected amount to the second column according to the relative concentration of the components in a complex sample. However, careful consideration of the system setup is necessary. It is demonstrated how experimental results can be significantly affected in terms of peak broadening and reproducibility if optimization of the interface is not taken into account.In addition, under the optimized conditions, the reproducibility in peak area and dispersion in the 2D dimension were evaluated as a function of the amount of sample transferred in terms of percentage of filled loop.

Investigation of the phytochemical profiling and antioxidant, anti-diabetic, anti-inflammatory, and MDA-MB-231 cell line antiproliferative potentials of extracts from Ephedra alata Decne

Ephedra is one of the many medicinal herbs that have been used as folk/traditional medicine in Jordan and other countries to cure various illnesses. Plants of this genus are well known for their antioxidant and antibacterial properties. In this study, three different solvents were used to obtain Ephedra extracts. When evaluated, the Ephedra alata Decne ethanolic extract reportedly had the greatest levels of total phenolic compounds (TPC) and total flavonoid compounds (TFC). The aqueous extracts displayed the highest antioxidant activity in the DPPH and ABTS assays, demonstrating their considerable capacity to neutralize free radicals. However, when evaluated using the FRAP method, the acetone extracts showed the strongest antioxidant activity, indicating their high reducing power. LC–MS/MS, a potent method of analysis that combines the liquid chromatographic separation properties with mass spectrometry detection and identification capabilities, was used in this study to detect and measure phytochemical content of a total of 24 phenolic compounds and 16 terpene compounds present in the extracts of Ephedra alata Decne. Various concentrations of these chemicals were found in these extracts. The extracts’ inhibitory effects on albumin denaturation and alpha-amylase activity were also assessed; the findings demonstrated the potentials of these extracts as anti-inflammatory and anti-diabetic medicines, with the acetone extract having the lowest IC50 values in the concomitant tests (306.45 µg/ml and 851.23 µg/ml, respectively). Furthermore, the lowest IC50 value (of 364.59 ± 0.45 µg/ml) for the 80% ethanol extract demonstrated that it has the strongest antiproliferative impact regarding the MDA-MB-231 breast cancer cell line. This finding indicates that this particular extract can be potentially used to treat cancer.

Temperature-responsive comprehensive two-dimensional liquid chromatography coupled to high resolution mass spectrometry for the elucidation of the oxidative degradation processes of chemicals of environmental concern

This study explores the possibilities offered by temperature-responsive liquid chromatography (TRLC) based comprehensive 2-dimensional liquid chromatography in combination with reversed-phase liquid chromatography (RPLC) for the analysis of degradation products formed upon oxidative treatment of persistent organic pollutants, in this case exemplified through carbamazepine (CBZ). The TRLC×RPLC combination offers the possibility to overcome peak overlap and incomplete separation encountered in 1D approaches, while the transfer of the purely aqueous mobile phase leads to refocusing of all analytes on the second dimension column. Consequently, this allows for about method-development free and hence, easier LC×LC. The study focuses on the oxidative degradation of CBZ, a compound of environmental concern due to its persistence in water bodies. The TRLC×RPLC combination effectively separates and identifies CBZ and its degradation products, while offering improved selectivity over the individual TRLC or RPLC separations. This allows gathering more understanding of the degradation cascade and allows real-time monitoring of the appearance and disappearance of various degradation products. The compatibility with high-resolution mass spectrometry is last shown, enabling identification of 21 CBZ-related products, nine of which were not previously reported in CBZ degradation studies. The approach's simplicity, optimization-free aspects, and ease of use make it a promising tool for the analysis of degradation pathways in environmental contaminants.

Grb2 Expression in Acute Spinal Cord Injury After Methylprednisolone Intrathecal Injection in Rats.

This study aims to investigate the effect of methylprednisolone (MP) intrathecal injection on a rat model of acute spinal cord injury (ASCI). Allen's frame was used to establish a rat model of ASCI. MP and normal saline were intrathecally injected to Sprague-Dawley rats at 0, 3, 6, 8, 12, and 24 hours after ASCI, and injured spinal cord tissues were sterilely extracted after 24 hours of treatment. Isobaric tags for relative and absolute quantitation (iTRAQ) were coupled with 2-dimensional liquid chromatography tandem mass spectrometry to separate and identify differentially expressed proteins. The expression of growth factor receptor-bound protein 2 (Grb2) was downregulated in the MP groups at 0 hours (iTRAQ ratio = 0.996), 3 hours (iTRAQ ratio = 0.737), 8 hours (iTRAQ ratio = 0.763), and 24 hours (iTRAQ ratio = 0.908) after injury compared with that in the control groups. No significant difference in Grb2 expression was observed between the control groups at 6 and 12 hours after ASCI. Standardized MP intrathecal injection after ASCI treatment reduces Grb2 activation in a rat ASCI model. Further studies should determine whether or not the same effect can be observed in human ASCIs.

A novel multi-hyphenated approach to screen and character the xanthine oxidase inhibitors from saffron floral bio-residues

Recently, the incidence of hyperuricemia increased with patient rejuvenation, searching for new xanthine oxidase (XOD) inhibitors from natural products becomes important. In our previous work, a flavonoid extract of saffron floral bio-residues (SFB) was found to alleviate hyperuricemia via inhibiting XOD. In this study, an integrated approach combining two-dimensional liquid chromatography, surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC) was developed to online screen and character the potential XOD inhibitors from SFB. The two-dimensional liquid chromatography consisted of affinity chromatography and reverse phase chromatography (2D-AR), in which an XOD column, an inactive XOD column, and a control column were used in the first dimensional liquid chromatography to avoid phenomena of “false positive” and “missing screen of compounds with weak affinity to XOD” that often occur in the screening process, and a C18 column was used in the second dimensional liquid chromatography to separate the mixed XOD binders. Four flavonoid glycosides, i.e., quercetin-3-O-sophoroside (QS), kaempferol-3-O-sophoroside (KS), kaempferol-3-O-rutinoside (KR), and kaempferol-3-O-glucoside (KG), were thus successfully screened and identified from SFB extract by the 2D-AR method. The affinity of QS, KS, KR, KG, kaempferol (aglycone of KS, KR and KG), and quercetin (aglycone of QS) binding to XOD was investigated using SPR method, with KD ranged from 4.8 μM to 47.6 μM. The inhibitor constant (KI) of KS, KR, KG, quercetin and kaempferol were 4.92 mM, 1.11 mM, 0.294 mM, 4.93 μM and 3.27 μM, respectively, determined using ITC method. Finally, the anti-XOD activities of KS, the most abundant flavonoid in SFB extract, and kaempferol in hyperuricemia mice were verified, which suggested that the multi-hyphenated approach established herein can be applied for screen and character the XOD inhibitors in natural products.

The Association Between Clozapine Plasma Concentration, CYP2D6 (*10, *2) Polymorphisms and Risk of Adverse Reactions.

The aim of this article was to study the relationships between the risk of adverse reactions, plasma concentration, and cytochrome P450 2D6 rs1065852 (*10) and rs16947 (*2) polymorphisms for clozapine. The steady-state clozapine plasma concentration of 100 Chinese inpatients with schizophrenia was determined using 2-dimensional liquid chromatography. The polymorphisms of cytochrome P450 2D6 (*10 and *2) were determined using fluorescent in situ hybridization protocols. The decreased percentages of white blood cells and neutrophils and the elevated percentages of creatine kinase, alanine aminotransferase, and aspartate transferase in patients treated with clozapine for 6 months were linearly associated with clozapine plasma concentration. Compared with the corresponding groups, the clozapine plasma concentrations of individuals with the *10TT genotype and individuals with the *2CC genotype were the highest (P < .05). The decreased percentages of white blood cells and neutrophils and elevated percentages of creatine kinase, alanine aminotransferase, and aspartate transferase for patients with the *10TT genotype were significantly higher than those for patients with the *10CC and *10CT genotypes (P < .05). The decreased percentages of white blood cells and neutrophils and increased percentages of creatine kinase, alanine aminotransferase, and aspartate transferase for patients with the *2CC genotype were significantly higher than those of the other groups (P < .05). The therapeutic reference range of clozapine for Chinese patients with schizophrenia was defined as 102.5-483.1 ng/mL. This study demonstrated that the determination of cytochrome P450 2D6 polymorphisms and therapeutic drug monitoring of clozapine might be beneficial for identifying patients with a higher risk of adverse reactions.

A plasma proteomic approach in patients with heart failure after acute myocardial infarction: insights into the pathogenesis and progression of the disease.

The pathogenesis of disease progression targets for patients with heart failure after acute myocardial infarction was investigated by using plasma proteomics. The plasma proteomes of acute myocardial infarction patients with (MI-HF) and without (MI-WHF) heart failure were compared. Each group consisted of 10 patients who were matched for age and sex. The peptides were analyzed by 2-dimensional liquid chromatography coupled to tandem mass spectrometry in a high definition mode. Parallel reaction monitoring (PRM) verified the selected target proteins. We identified and quantified 2,589 and 2,222 proteins, respectively, and found 117 differentially expressed proteins (DEPs) (≥1.5-fold), when the MI-HF and MI-WHF groups were compared. Of these 51 and 66 were significantly up-regulated and down-regulated, respectively. The significant DEPs was subjected to protein-protein interaction network analysis which revealed a central role of the NF-κB signaling pathway in the MI-HF patients. PRM verified that MB, DIAPH1, VNN1, GOT2, SLC4A1, CRP, CKM, SOD3, F7, DLD, PGAM2, GOT1, UBA7 and HYOU1 were 14 proteins which were highly expressed in MI-HF patients. These findings showed a group of proteins related to the NF-κB signaling pathway in the pathogenesis of patients with poor outcomes after experiencing MI-HF. These proteins may be useful candidate markers for the diagnosis of MI-HF as well as help to elucidate the pathophysiology of this major cause of mortality in older patients.

Survey of Acetylation for Thermoanaerobacter tengcongensis.

Non-histone protein acetylation is involved in key cellular processes both in eukaryotes and prokaryotes. Acetylation in bacteria is used to modify proteins involved in metabolism and allow the bacteria to adapt to their environment. TTE (Thermoanaerobacter tengcongensis) is an anaerobic, thermophilic saccharolytic bacterium that grows at extreme temperature range between 50 and 80℃. The annotated TTE proteome contains less than 3000 proteins. We analyzed the proteome and acetylome of TTE using 2DLC-MS/MS (2-dimensional liquid chromatography mass spectrum). We evaluated the ability of mass spectrometry technology to cover a relatively small proteome as much as possible. And we also observed wide spread of acetylation in TTE, which changed under different temperatures. A total of 2082 proteins were identified, which accounts for about 82% of the database. A total of 2050 (~ 98%) proteins were quantified in at least one culture condition and 1818 proteins were quantified in all 4 conditions. The result also consisted 3457 acetylation sites corresponding to 827 distinct proteins, which covered 40% of the proteins identified. Bioinformatics analysis reported that proteins related to replication, recombination, repair, and extracellular structure cell wall biogenesis had more than half members acetylated, while energy production, carbohydrate transport, and metabolism related proteins were least acetylated. Our result suggested that acetylation affects the ATP-related energy metabolism and energy-dependent biosynthesis process. Comparing the enzymes related with lysine acetylation and acetyl-CoA (acetyl-coenzyme A) metabolism, we suggested that the acetylation of TTE took a non-enzymatic mechanism and affected by abundance of acetyl-CoA.

Less Configuration and More Dimensionality: Preparative Heart-Cut Multidimensional Liquid Chromatography Based on Trapping Arrays.

The resolving power of multiple dimensional liquid chromatography (mD-LC) is multiplicative as it adds dimensions. However, the issue in creating a preparative mD-LC system is that the higher the dimensionality, the more complicated the system configuration. Thus, we presented a new configuration of preparative mD-LC using one set of LC modules and trapping array-based multiple heart-cut interfaces. A preparative two-dimensional liquid chromatography (2D-LC) separation of herbal medicine formulation produced 40 compounds with a purity of >90%. During the separation process, the interface stores the fractions and allocates positions for the fractions from a different dimension; LC draws the fraction from the interface, makes nD separation, and sends isolated fractions to the interface. By repeating this process, we achieved variable dimensionality of LC separations. We also presented a preparative 3D-LC separation of herbal medicines to validate the principle of "less configuration and more dimensionality". Thus, we can explore the higher dimensional preparative separations. The developed preparative mD-LC displayed exceptional power in the isolation of various compounds and has great potential in the application of natural products.

Comprehensive profiling of conjugated fatty acid isomers and their lipid oxidation products by two-dimensional chiral RP×RP liquid chromatography hyphenated to UV- and SWATH-MS-detection

This research reports on the development of a comprehensive two-dimensional liquid chromatography (2D-LC) method hyphenated to inline DAD-UV and ESI-QTOF-MS/MS-detection for the separation of conjugated polyunsaturated fatty acid isomers and structurally related (saturated, unconjugated, oxidized) compounds. In pharmaceutical lipid formulations conjugated fatty acids can be found as impurities, generated by oxidation of polyunsaturated fatty acids. Due to the structural complexity of resultant multi-component samples one dimensional liquid chromatography may be suboptimal for quality control and impurity profiling. The screened reversed-phase columns showed a lack of selectivity for the conjugated fatty acid isomers but the resolutions improved with the shape selectivity of the stationary phases (C18- < C30- < cholesteryl-ether-bonded). Further enhanced selectivity for the non-chiral conjugated FAs could be achieved with amylose/cellulose-based chiral stationary phases (CSPs) which harbor cavities for selective inclusion depending on E/Z configurations of the double bonds of the analytes. Amylose-based CSPs showed higher selectivity for conjugated fatty acids than the cellulose-based polysaccharide CSPs. Hyphenating the chiral and reversed-phase columns in a comprehensive 2D-LC-setup was favorable since they showed orthogonality and good compatibility, because both were operated under RP-conditions. The chiral dimension (1D) mainly separated the different isomers, while the reversed-phase dimension (2D) separated according to number of double bonds and degree of oxidation. Using this setup, advanced structural annotation of unknowns was possible based on UV-, MS1- and MS2-spectra. Data-independent acquisition (by SWATH) enabled differentiation of positional isomers of oxidized lipids by characteristic MS2-fragments and elucidation of co-eluted compounds by selective extracted ion chromatograms of fragment ions (MS2 EICs).

Determination of Afatinib in Human Plasma by 2-Dimensional Liquid Chromatography

Introduction: A simple, sensitive, rapid, and practical 2-dimensional liquid chromatography (2D-LC) method was developed and validated for the quantification of a 500-μL afatinib sample extracted from human plasma. Methods: The plasma samples were pretreated with acetonitrile for protein precipitation. The mobile phase consisted of a first-dimensional mobile phase (acetonitrile, methanol, and 25 mmol/L ammonium phosphate in a ratio of 25:25:50, V/V/V) and a second-dimensional mobile phase (acetonitrile and 10 mmol/L ammonium phosphate in a ratio of 25:75, V/V). The average recovery of the plasma samples was stable and reproducible (98.56%–100.02%). Results: The analyte was sufficiently stable for handling and analysis. The calibration curve was linear, ranging from 10.93 to 277.25 ng/mL with regression equation y = 804.60 x – 4,169.87 (R² = 0.999). The relative standard deviations for accuracy and precision studies were within ±2.30% and <3.41%, respectively (intra- and interday). Finally, the validated method was successfully employed to determine the drug levels in plasma from the patients treated with afatinib. In clinical assessment, the patients with gastric cancer were orally administered with 30 or 40 mg per day of afatinib, which resulted in large plasma concentrations, ranging from 5.52 to 45.16 ng/mL. Conclusion: The results indicated that this method was useful for the therapeutic drug monitoring of afatinib and suitable for the assessment of the risks and benefits of chemotherapy in patients with non-small cell lung cancer.

Middle-up quantification of therapeutic monoclonal antibodies in human plasma with two dimensional liquid chromatography high resolution mass spectrometry: Adalimumab as a proof of principle

Next generation human therapeutic monoclonal antibodies (t-mAbs) are harder to quantify with the widely used bottom-up tryptic digestion method. Due to their homology with endogenous immunoglobulins, there is a lack of unique and stable ‘signature’ peptides that can be targeted. Middle-up two dimensional liquid chromatography high resolution mass spectrometry (2D-LC-HRMS), targeting the entire light chain, was examined as an alternative. Adalimumab (ADM) was successfully quantified in human plasma after Melon® Gel sample purification, followed by orthogonal separation on a weak cation exchange (WCX) and reversed phase column. Charge and hydrophobicity were used to separate ADM from the polyclonal immunoglobulin background. HRMS with its high resolution and exact mass was able to isotopically resolve the ADM light chain and to provide another separation dimension on the basis of mass to charge ratio. Using the targeted single ion monitoring (T-SIM) with multiplex (MSX) option, three ADM light chain precursors, 2341.80, 2129.00, and 1951.68 m/z, and one internal standard precursor 2146.39 m/z, were measured simultaneously. The Melon® Gel sample purification was found to be very efficient in removing plasma proteins that would otherwise interfere with chromatographic separation and ionization. The linearity of the method for the analysis of ADM was excellent (R2=0.999) between 1 – 128 mg/L with an LLOQ signal to noise ratio (S/N) of 10. Within-run and between-run precision and accuracy were in concordance with the EMA guideline. Cross-validation of the 2D-LC-HRM method with the standard peptide LC-MS/MS method showed a good agreement (R2 = 0.86) between the methods. However, there was a bias present, possibly due to charge variant ADM formation over time. Since the presented 2D-LC-HRMS method is able to measure only the native form of ADM, it is able to provide a measure of the active form of ADM in patients.

Evaluation of different internal standardization approaches for the quantification of melatonin in cell culture samples by multiple heart-cutting two dimensional liquid chromatography tandem mass spectrometry

We evaluate here different analytical strategies for the chromatographic separation and determination of N-acetyl-5-methoxytryptamine (MEL) and its oxidative metabolites N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), N1-acetyl-5-methoxykynuramine (AMK) and cyclic 3-hydroxymelatonin (c3OHM) in cell culture samples. Two dimensional liquid chromatography (2D-LC) in the multiple heart-cutting mode was compared with regular 1D chromatographic separations of MEL and its oxidative metabolites. Our results showed that the use of trifluoroacetic acid (TFA) as mobile phase modifier was required to obtain a satisfactory resolution and peak shapes particularly for c3OHM. As TFA is not compatible with ESI ionization the application of the MHC mode was mandatory for a proper chromatographic separation. We evaluate also different internal standardization approaches based on the combined use of a surrogate standard (5-methoxytryptophol) and an internal standard (6-methoxytryptamine) for MEL quantification in cell culture samples obtaining unsatisfactory results both by 1D- and 2D-LC-ESI-MS/MS (from 9 ± 2 to 186 ± 38%). We demonstrate that only the application of isotope dilution Mass Spectrometry through the use of an in house synthesized 13C isotopically labelled analogue provided quantitative MEL recoveries both by using 1D- and 2D-LC-ESI-MS/MS (99±1 and 98±1. Respectively) in androgen-insensitive human prostate carcinoma PC3 cells.

Multiple heart-cutting two dimensional liquid chromatography and isotope dilution tandem mass spectrometry for the absolute quantification of proteins in human serum

We evaluate here the combination of two-dimensional liquid chromatography (2D-LC) in the multiple heart cutting mode and isotope dilution tandem mass spectrometry for the direct analysis of tryptic digests of serum samples. As a proof of concept, we attempt the quantification of proteotypic peptides of Apolipoprotein AIV (APOA4), Complement C3 (C3) and Vitronectin (VTN) which have been previously identified as potential candidate biomarkers of glaucoma. Using this 2D-LC strategy, analyte enrichment steps are avoided and the sample preparation involved after enzymatic digestion amounted to a simple centrifugation, evaporation of the supernatant and reconstitution in the 1D mobile phase. A mobile phase not compatible with the ESI source (10 mM KH2PO4 at pH 2.7) was used in the first dimension as it provided a satisfactory chromatographic resolution of the peptides and a high buffering capacity avoiding changes in retention times when analyzing complex matrices like human serum. We also demonstrate that using coeluting labelled analogues of the target peptides, protein concentrations were not affected by slight retention time shifts affecting the amount of target peptides transferred to the second dimension. Satisfactory results were obtained when analyzing fortified serum samples (recoveries from 98 to 113%). Precisions in the range of 1–9% RSD were obtained when replicating the analysis of a pooled serum sample. The comparative analysis of serum samples from n = 94 control subjects and n = 91 patients diagnosed with primary open-angle glaucoma did not show significant differences in the APOA4, VTN and C3 concentrations in contrast with previous studies using immunoassays.

2-Dimensional ultra-high performance liquid chromatography and DMT-MM derivatization paired with tandem mass spectrometry for comprehensive serum N-glycome characterization

Glycosylation is a prominent co- and post-translational modification which contributes to a variety of important biological functions. Protein glycosylation characteristics, particularly N-glycosylation, are influenced by changes in one's pathological state, such as through the presence of disease, and as such, there is great interest in N-glycans as potential disease biomarkers. Human serum is an attractive source for N-glycan based biomarker studies as circulatory proteins are representative of one's physiology, with many serum proteins containing N-glycosylation. The difficulty in comprehensively characterizing the serum N-glycome arises from the absence of a biosynthetic template resulting in great structural heterogeneity and complexity. To help overcome these challenges we developed a 2-dimensional liquid chromatography platform which utilizes offline weak anion exchange (WAX) chromatography in the first dimension and hydrophilic interaction liquid chromatography (HILIC) in the second dimension to separate N-glycans by charge, corresponding to degree of sialylation, and size, respectively. Performing these separations offline enables subsequent derivatization with 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) for sialic acid linkage determination and the identification of sialic acid linkage isomers. Subsequent tandem mass spectrometry analysis revealed the identification of 212 complete and partial N-glycan structures including low abundant N-glycans containing acetyl and sulphate modifications. The identifications obtained through this platform were then applied to N-glycans released from a set of stage 3 gastric cancer serum samples obtained from patients before (pre-op) and after (post-op) tumour resection to investigate how the serum N-glycome can facilitate differentiation between the two pathological states.

Fast determination of vitamin A, vitamin D and vitamin E in food by online SPE combined with heart-cutting two dimensional Liquid Chromatography

An automatic method combing online solid phase extraction (SPE) and heart-cutting two dimensional Liquid Chromatography (2DLC) was developed for the simultaneous determination of vitamins A, vitamin D and four vitamins E homologues in foodstuff. In this method, the target analytes were released from their coated state of lipoprotein after saponification. Then the saponified solution was directly injected into the constructed system combining online SPE and heart-cutting 2DLC for enrichment, purification, separation and quantification. Online dilution was incorporated into the online SPE process to weaken the solvent effect on the first-column separation. The analysis of vitamins A and four E homologues were carried out by using PFP as the first column. The analysis of vitamin D was performed by using PAH as the second column. The results showed good linearity (R2>0.9999) of the analytes and good reproducibility (RSD < 2 %, n = 5). The limit of quantification of vitamin A, D2, D3 and α-, β-, γ-, δ-vitamin E (calculated by S/N = 10:1) were 0.030, 0.013, 0.014, 0.51, 0.33, 0.31 and 0.33 ng, respectively. The spiked recoveries ranged from 93.29 % to 103.66 %. The proposed method greatly simplifies the analytical workflow and improves the efficiency.

Multiple Heart-Cutting Two-Dimensional Liquid Chromatography: Recent Developments and Applications

Background: Over the last few decades, there has been a growing interest in Two- Dimensional Liquid Chromatography (2D-LC). This advanced technology has become a relevant solution for solving all the analytical challenges encountered in the pharmaceutical industry. The primary purpose of this review is to give a brief account of the developing techniques notable in 2D-LC. Methods: Review of recent literature on advanced separation techniques for complex mixtures revealed that 2D-LC is the most widely used technique in the pharmaceutical laboratory for the separation of complex samples. Among the various techniques used in 2D-LC, comprehensive 2D-LC and heart-cutting 2D-LC are highly used techniques. To enhance the resolution, further development has been made to heart-cutting 2D-LC called multiple heart-cutting 2D-LC, which has recently become a very popular technique in the pharmaceutical industry. Therefore research articles mentioning the use of multiple heart-cutting 2D-LC for separation of complex mixtures were reviewed. Results: The most crucial benefit of multiple heart-cutting 2D-LC is its reduced effort in method development and also the storage of multiple sample sections for further analysis. The multiple heartcutting 2D-LC is suited, preferably for method development and impurity analysis of pharmaceutical substances, fine chemicals and offers better peak separation, which is otherwise not possible by comprehensive 2D-LC. Conclusion: The advantage of two-dimensional liquid chromatography over one-dimensional liquid chromatography is its high resolving power. Further improvement in resolution was achieved by using the advanced multiple heart-cutting 2D-LC which appears to have an imperative role in pharmaceutical and food analysis.

Recent Advances and Developments in Hyphenated Techniques and their Applications

Background: A hyphenated technique is blend or coupling of two distinctive analytical methods like chromatographic and spectral methods with appropriate interface.&#x0D; Objective: This article describes about the various hyphenated techniques, a brief note on their instrumentation and working principles that are used in the current setup of industries. Like-wise their remarkable improvement and efficiency over the past decade. The techniques like single quadrupole inductively coupled mass spectrometry (ICP-Q-MS), ICP- Triple quadrupole mass spectrometry (ICP-QQQ), Liquid chromatography-Two -dimensional Gas chromatography mass spectrometry (LC-GCXGC-MS/MS), Two dimensional liquid chromatography (2D-LC), Fourier transform near infrared spectroscopy (FT-NIR) ,etc. are considered as recent improvements in this trend.&#x0D; Conclusion: This development in the hyphenated techniques supports in different scientific fields, biomedical research, food and drug analysis. In addition to this improvement produced remarkable dimensional changes in the natural product analysis and elemental specifications.

Pushing the limits of native MS: Online SEC-native MS for structural biology applications

Native mass spectrometry (nMS) is now widely applied to investigate non-covalently assembled biomolecule complexes. nMS requires the use of near-neutral pH and volatile buffers to preserve the native state of proteins. However, buffer exchange into nMS-compatible solvent is usually performed manually, which results in a time-consuming and tedious process, thus appearing as a major drawback for nMS analysis. Conversely, online coupling of size exclusion chromatography (SEC) to nMS affords a fast-automated and improved desalting, but also provides an additional dimension of separation for complex protein mixtures. We illustrate here the benefits of SEC-nMS compared to manual offline desalting for the characterization of a wide variety of biological systems, ranging from multiprotein assemblies, protein–ligand and protein–nucleic acid complexes, to proteins in a detergent environment. We then highlight the potential of the coupling to further integrate ion mobility while preserving the native conformations of proteins, allowing for rapid collision cross section measurement and even collision-induced unfolding experiments. Finally, we show that online SEC coupling can also serve as the basis for multidimensional non-denaturing liquid chromatography (LC) workflows, with the SEC acting as a fast desalting device, helping to achieve first dimension LC separation in optimal chromatographic conditions while being compatible with further nMS analysis.

Chromatographic analysis of bio-oil formed in fast pyrolysis of lignocellulosic biomass

Abstract Fast pyrolysis of lignocellulosic biomass is one of the most promising methods of the production of renewable fuels. However, an optimization of the conditions of bio-oil production is not possible without comprehensive analysis of the composition of formed products. There are several methods for the determination of distribution of products formed during thermal decomposition of biomass with chromatography being the most versatile among them. Although, due to the complex structure of bio-oil (presence of hundreds chemical compounds with different chemical character), an interpretation of the obtained chromatograms is not an easy task. Therefore, the aim of this work is to present an application of different chromatographic methods to the analysis of the composition of the mixture of products formed in high temperature decomposition of lignocellulosic feedstock. It includes pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), two dimensional gas (GC x GC) or liquid chromatography (LC x LC) and initial fractionation of bio-oil components. Moreover, the problems connected with the analysis of bio-oils formed with the use of various fast pyrolysis reactors and capabilities of multivariate analysis are discussed.