Search

Stroke is a major cause of mortality and long-term disability worldwide. The study of biomarkers and pathogenesis is vital for early diagnosis and treatment of stroke. In the present study, a continuous-flow normal-phase/reversed-phase two-dimensional liquid chromatography-quadrupole time-of-flight mass spectrometry (NP/RP 2D LC-QToF/MS) method was employed to measure lipid species in human plasma, including healthy controls and lacunar infarction (LI) patients. As a result, 13 lipid species were demonstrated with significant difference between the two groups, and a "plasma biomarker model" including glucosylceramide (38:2), phosphatidylethanolamine (35:2), free fatty acid (16:1), and triacylglycerol (56:5) was finally established. This model was evaluated as an effective tool in that area under the receiver operating characteristic curve reached 1.000 in the discovery set and 0.947 in the validation set for diagnosing LI patients from healthy controls. Besides, the sensitivity and specificity of disease diagnosis in validation set were 93.3% and 96.6% at the best cutoff value, respectively. This study demonstrates the promising potential of NP/RP 2D LC-QToF/MS-based lipidomics approach in finding bio-markers for disease diagnosis and providing special insights into the metabolism of stroke induced by small vessel disease. Graphical abstract Flow-chart of the plasma biomarker model establishment through biomarker screening and validation.

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane lipids that are widely used as valuable paleoenvironmental proxies. The recently discovered 6-methyl brGDGTs improved the accuracy of the proxies for temperature “methylation branched tetraethers (MBT)” and soil pH “cyclization branched tetraethers (CBT)”. However, the calibration uncertainties are still substantial for brGDGT-derived proxies (e.g., 5 °C for MBT′5ME). Here we report a series of novel 7-methyl brGDGT isomers that co-eluted with the known 5- and 6-methyl brGDGTs in commonly applied normal phase high performance liquid chromatography (HPLC). Using an optimized HPLC gradient the novel 7-methyl brGDGTs could be structurally characterized and quantified. Their mean relative abundance was in the range of 6% of the total brGDGTs in Chinese and Cameroon lake sediments. The 7-methyl brGDGT IIa7 correlates with sediment pH (R2 = 0.44, root-mean-square error = 0.26 pH unit), a result that motivates the re-analysis of brGDGTs in soils and sediments to further reassess brGDGT-based proxies and to determine the source of 7-methyl brGDGTs. In addition to the 7-methyl brGDGTs, we identified two novel pentamethylated brGDGTs based on the mass spectra of its ether-cleaved hydrocarbon products.

We investigate the interplay of superradiant phase transition (SPT) and energy band physics in an extended Dicke-Hubbard lattice whose unit cell consists of a Dicke model coupled to an atomless cavity. We found in such a periodic lattice the critical point that occurs in a single Dicke model becomes a critical region that is periodically changing with the wavenumber $k$. In the weak-coupling normal phase of the system we observed a flat band and its corresponding localization that can be controlled by the ground-state SPT. Our work builds the connection between flat band physics and SPT, which may fundamentally broaden the regimes of many-body theory and quantum optics., 9 pages, 5 figures, published version

Modelling the retention behaviour of solutes in liquid chromatography, based on the composition of the mobile phase is a common task in the chromatographic practice. Along the development of liquid chromatography (LC), several models have been proposed to help in understanding the retention mechanisms, and especially, allow the prediction of retention times with optimisation purposes. Particular models are used for different LC modes, such as normal phase (NPLC), reversed phase (RPLC), hydrophilic interaction (HILIC), and micellar (MLC). In this work, a general equation is proposed that includes a parameter (the elution degree, g), which characterises the way the elution strength varies with the modifier concentration. The elution degree adopts the value g = 1 when the system follows the linear solvent strength (LSS) model, where the elution strength is constant. When g 1, the elution strength decreases, and for g 1, it increases with the modifier concentration. The proposed equation was applied to experimental retention data obtained for several chromatographic systems in RPLC, HILIC, MLC, and microemulsion LC. It was found that values in the 1 g 2 range are most usual. The general behaviour of the proposed equation was studied for isocratic and gradient elution. A general expression to calculate the compression factor of chromatographic peaks in gradient elution was also developed. It is shown that an increasing g value makes retention factors close to zero more difficult, since the elution strength decreases as the modifier concentration increases. For this reason, the larger the g value, the harder it is to reach significant peak compression. In contrast, an elution mode with g 1 would yield increased elution strength with the modifier concentration, giving rise to significant peak compression.

Chiral considerations are found to be very much relevant in various aspects of forensic toxicology and pharmacology. In forensics, it has become increasingly important to identify the chirality of doping agents to avoid legal arguments and challenges to the analytical findings. The scope of this study was to develop an liquid chromatography-mass spectrometry (LCMS) method for the enantiomeric separation of typical illicit drugs such as ephedrines (ie, 1S,2R(+)-ephedrine and 1R,2S(-)-ephedrine) and pseudoephedrine (ie, R,R(-)-pseudoephedrine and S,S(+)-pseudoephedrine) by using normal phase chiral liquid chromatography-high-resolution mass spectrometry technique. Results show that the Lux i-amylose-1 stationary phase has very broad and balancing-enantio-recognition properties towards ephedrine analogues, and this immobilized chiral stationary phase may offer a powerful tool for enantio-separation of different types of pharmaceuticals in the normal phase mode. The type of mobile phase and organic modifier used appear to have dramatic influences on separation quality. Since the developed method was able to detect and separate the enantiomers at very low levels (in pico grams), this method opens easy access for the unambiguous identification of these illicit drugs and can be used for the routine screening of the biological samples in the antidoping laboratories.

We provide a description of a diagrammatic Monte Carlo algorithm for the resonant Fermi gas in the normal phase. Details are given on diagrammatic framework, Monte Carlo moves, and incorporation of ultraviolet asymptotics. Apart from the self-consistent bold scheme, we also describe a non-self-consistent scheme, for which the ultraviolet treatment is more involved., Revised and extended version

Reaction monitoring is crucial in order to guide pharmaceutical chemical processes towards successful outcomes. Many drug substances require the application of water/additive-free solvents to guide process efforts which are intrinsically incompatible with reversed phase liquid chromatography (RPLC) conditions. Sub/supercritical fluid chromatography (SFC) helps to overcome many of these challenges delivering unmatched speed, with low cost, high-efficiency and an additive-free environment ideal for reaction monitoring of species chemically susceptible to water. Herein, we provide several examples where traditional RPLC fails or delivers sub-optimal performance in monitoring processes. These examples include using additive-free SFC-UV and SFC-MS methodologies to overcome difficulties associated with: 1) on-column RPLC hydrolysis, 2) improving normal phase liquid chromatography, replacing capillary zone electrophoresis methods, and 3) avoiding the use of tedious pre-column derivatization procedures.

We investigate strong-coupling properties of a two-dimensional ultracold Fermi gas in the normal phase. In the three-dimensional case, it has been shown that the so-called pseudogap phenomena can be well described by a (non-self-consistent) $T$-matrix approximation (TMA). In the two-dimensional case, while this strong coupling theory can explain the pseudogap phenomenon in the strong-coupling regime, it unphysically gives large pseudogap size in the crossover region, as well as in the weak-coupling regime. We show that this difficulty can be overcome when one improve TMA to include higher order pairing fluctuations within the framework of a self-consistent $T$-matrix approximation (SCTMA). The essence of this improvement is also explained. Since the observation of the BKT transition has recently been reported in a two-dimensional $^6$Li Fermi gas, our results would be useful for the study of strong-coupling physics associated with this quasi-long-range order., Comment: 7pages, 4 figures, Proceedings of QFS2016

International audience; Cyclofructans (CF) are cyclic oligosaccharides consisting of a crown ether core with pendent fructofuranose units. These unique macrocycles were reported recently to be powerful chiral selectors. Derivatized and bonded to silica, CFs make excellent chiral selectors for HPLC. In this study, several new derivatives of cyclofructan 6 (CF6) were prepared by introducing aromatic moieties with electron-withdrawing chloro and nitro groups and an electron-donating methyl group. Their enantioselectivities were evaluated in the normal phase mode in comparison to the commercially available cyclofructan columns (LARIHC CF6-P, LARIHC CF6-RN, and LARIHC CF7-DMP). In several cases, the columns prepared in this work showed improved enantioselectivity over the existing commercially available stationary phases. Furthermore, an evaluation of the number and position of chloro and methyl groups on the phenyl substituents of CF6 is discussed in terms of their ability to alter enantioselectivity.

Thin-layer chromatography (TLC) combined with densitometry was used to determine the limit of detection (LOD) and quantification (LOQ) of estradiol hemihydrate. Average values of both LOD and also LOQ were determined on the basis of the standard deviation of the response and slope of special calibration curve in accordance with the procedure required by validation guidelines. Influence of chromatographic conditions, such as different sorbents and various mobile-phase compositions on determining of LODs and LOQs of examined steroid by normal phase TLC (NP-TLC) and reversed-phase (RP-TLC) techniques, was estimated. Of all chromatographic plates and mobile phases used, those that gave the best results (the lowest LOD and LOQ value) using NP-TLC system are silica gel 60 F254 plates developed with mobile phase consisted of dichloromethane–ethyl acetate (8:2, v/v). In the case of RP-TLC method, a mixture of methanol–water (9:1, v/v) as mobile phase enabled detection of estradiol hemihydrate at the lowes...

Micro-thin-layer chromatography in two dimensional (2D-mTLC) mode in normal and reversed phase systems by use of diol bonded stationary phase was applied to make fingerprints of 11 species of Mentha genus and two finished pharmaceutical products. Nonaqueous eluents (propan-2-ol or ethyl acetate dissolved in n-heptane) were used in normal phase systems. Mixtures of acetonitrile with water were used in reversed phase chromatographic systems. Optimization of one dimensional systems was performed by determining of RF vs. composition of mobile phases dependencies for standards occurring in various species of Mentha. Most selective eluents were chosen to optimize two-dimensional systems by creating RF in normal-phase (NP) systems vs. RF in reversed-phase (RP) systems correlations. 2D-mTLC on diol polar bonded stationary phase were optimized to separate phenolic compounds and make fingerprints of examined plant materials and this method was never applied earlier in the chromatographic analysis.

The goal of this study was to develop new chiral stationary phases (CSPs) with high chiral recognition capability and high compatibility with the so-called "nonstandard solvents". Seven new chitosan bis(phenylcarbamate)-(N-cyclobutylformamide) derivatives were synthesized from chitosan with high degree of deacetylation as a starting material. The corresponding chiral stationary phases (CSPs 1-7) were prepared with the chitosan derivatives as chiral selectors (CSs). The enantioseparation capability of CSPs 1-7 was evaluated by high performance liquid chromatography with nineteen analytes. In comparison with the CSPs of cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and amylose tris(3,5-dimethylphenylcarbamate) (ADMPC), the prepared CSPs generally demonstrated excellent enantioseparation capability, particularly for the CSP derived from chitosan bis(3-chloro-4-methylphenylcarbamate)-(N-cyclobutylformamide). Moreover, the CSPs in the present study could separate some analytes better, making them complementary for enantioseparations with the CSPs of CDMPC and ADMPC. The tolerability of the CSP with the best enantioseparation capability to organic solvents was investigated. The results showed that it could work in pure ethyl acetate, pure chloroform, and a normal phase containing 70% tetrahydrofuran, which are prevented from enantioseparation by the coating type CSPs of CDMPC and ADMPC. As these chitosan derivatives were almost insoluble in most organic solvents, the corresponding CSPs can work in a wide range of mobile phases. In addition, the influence of the position and electron effects of methyl and chloro groups introduced onto the CSs and the composition of mobile phases on enantioseparation was also discussed.

Ceramide 2-aminoethylphosphonate (CAEP) is a type of phosphonosphingolipids with potential trophic activity. In this work, complicated CAEP species from different aquatic products were comprehensively identified and semi-quantified by utilizing normal phase liquid chromatography/Q-Exactive mass spectrometry (NPLC/Q-Exactive-MS). We elucidated the fragment schemes of CAEP molecules and found the presence of methylated CAEP (Me-CAEP) species. Remarkably, quantitative results revealed that Loligo chinensis had the highest CAEP content of 4.9 ± 0.4 mg/g dry weight and the most complex molecular species composition, whereas Asterias amurenis had the lowest CAEP content of 1.9 ± 0.6 mg/g dry weight. The most common molecule was CAEP (d19:3–16:0). Additionally, statistical analysis revealed that five aquatic products can be effectively distinguished from their CAEP species; thus, CAEP molecules can play an important role in identifying processed products from aquatic products.

Prothioconazole is a type of broad-spectrum triazole thione fungicide developed by the Bayer Company. Prothioconazole-desthio is the main metabolite of prothioconazole in the environment. In our study, enantiomeric separation of prothioconazole and prothioconazole-desthio was performed on various chiral stationary phases (CSPs) by high-performance liquid chromatography (HPLC). It was found that polysaccharide CSPs showed better ability than brushing CSPs in enantiomeric separation. The successful chiral separation of prothioconazole could be achieved on self-made Chiralcel OD, commercialized Chiralcel OJ-H and Lux Cellulose-1. Chiralpak IA, Chiralpak IB, Chiralpak IC, Chiralcel OD, Chiralpak AY-H, Chiralpak AZ-H, and Lux Cellulose-1 realized the baseline separation of prothioconazole-desthio enantiomers. Simultaneous enantiomeric separation of prothioconazole and prothioconazole-desthio was performed on Lux Cellulose-1 using acetonitrile (ACN) and water as mobile phase. In most cases, low temperature favored the separation of two compounds. The influence of the mobile phase ratio or type was deeply discussed. We obtained larger Rs and longer analysis time with a smaller proportion of isopropanol (IPA) or ethanol and more water content at the same temperature. The ratio of ACN and water had influences on the outflow orders of prothioconazole-desthio enantiomers. This work provides a new approach for chiral separation of prothioconazole and prothioconazole-desthio with a discussion of chiral separation mechanism on different CSPs.

A simple, specific, precise, sensitive and rapid normal phase-Ultra Fast Liquid Chromatography (NP-UFLC) method was developed for determination of venlafaxine hydrochloride enantiomers in pharmaceutical formulation. The method was developed on a Lux amylase 2 column (150 x 4.0 mm I.D., particle size 5 μ) with the mobile phase was n-hexane and ethanol (97:3 v/v); in 0.1 % diethyamine using UV detector was fixed at 254 nm with a flow rate was 1 ml/ min. The retention time (tR) of both enantiomer were found to be 4.1±0.2 min and 4.8±0.3 min, respectively. The linearity over the concentration range of 5-30 μg/ ml for venlafaxine. The intra-day and inter-day coefficient of variation of the assay method were found to be 0.293 to 1.760 and 0.319 to 0.210 respectively for enantiomer 1 and 2, with high accuracy and precision results. The proposed NP-UFLC method is suitable for analysis of venlafaxine hydrochloride enantiomers in pharmaceutical dosage forms. The validated NP-UFLC method was developed for the quantification of venlafaxine in tablet dosage form.

In this work, the enantiomeric separation of ten anticholinergic drugs was first examined on two derivative polysaccharide chiral stationary phases (CSPs), i.e., Chiralpak ID and Chiralpak IA in the normal phase mode. Except for scopolamine hydrobromide, the remaining nine analytes could be completely separated with good resolutions using both columns under the optimized mobile phase conditions. And the enantiomeric discrimination ability of the studied CSPs towards nine analytes was in the order of Chiralpak ID > Chiralpak IA. The influences of organic modifier types, alcohol content, and base/acid additives on the enantiomeric separation were evaluated and optimized. According to the experimental results, the effect of the structures of analytes on enantiomeric separation was discussed. Additionally, the chiral recognition mechanisms were proposed based on the thermodynamic analysis of the experimental data.

Palm oil has been known to be the richest source of tocotrienols, a compound belonging to the vitamin E family. Besides tocotrienol, other tocols that are present in palm oil includes the tocopherol and tocomonoenol (α-T, α-T1, α- T3, β-T3, γ-T3, and δ-T3). The tocols are much sought after natural products due to their powerful antioxidative and anticancer properties. However, analysis of the tocols have always been a subject of debate due to discrepancy in techniques, instrumentations, reference materials for calibration as well as the baseline separation of all tocols components in the oil. This paper reports on a comprehensive normal phase chromatographic method using high performance liquid chromatography (HPLC) that is able to separate all the tocols in palm oil to baseline resolution with good repeatability where the presence of α-T1 is reported and accounted for. Results from inter laboratory crosscheck proved that the method is robust, repeatable and reliable.

We investigate the behavior of transport coefficients for \(2+1\) dimensional strongly coupled system using Einstein-Maxwell gravitational theory. The dependence of conductivity on chemical potential is shown using soft wall model. Numerical results for ac and dc conductivity indicating normal phase of strongly coupled system has also been shown.

The screening conditions of an existing column and mobile phase selection strategy for chiral compounds in normal-phase high performance liquid chromatography (NP-HPLC) were tested for their applicability on Chiralpak IC, which is a chiral stationary phase (CSP) made by immobilising cellulosic tris (3,5-dichlorophenyl-carbamate) on silica gel. In this study, the applicability of the optimization steps of the existing separation strategy was examined using 36 compounds representing the three possible resolution situations that occur after screening. The cumulative number of separated compounds is 27 (75.0 %), and the cumulative number of baseline separated compounds is 19 (52.8 %).

Purpose Single-shot imaging by spatiotemporal encoding (SPEN) can provide higher immunity to artifacts than its echo planar imaging–based counterparts. Further improvements in resolution and signal-to-noise ratio could be made by rescinding the sequence's single-scan nature. To explore this option, an interleaved SPEN version was developed that was capable of delivering optimized images due to its use of a referenceless correction algorithm. Methods A characteristic element of SPEN encoding is the absence of aliasing when its signals are undersampled along the low-bandwidth dimension. This feature was exploited in this study to segment a SPEN experiment into a number of interleaved shots whose inaccuracies were automatically compared and corrected as part of a navigator-free image reconstruction analysis. This could account for normal phase noises, as well as for object motions during the signal collection. Results The ensuing interleaved SPEN method was applied to phantoms and human volunteers and delivered high-quality images even in inhomogeneous or mobile environments. Submillimeter functional MRI activation maps confined to gray matter regions as well as submillimeter diffusion coefficient maps of human brains were obtained. Conclusion We have developed an interleaved SPEN approach for the acquisition of high-definition images that promises a wider range of functional and diffusion MRI applications even in challenging environments. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

We report results of spin diffusion measurements in normal phase of liquid 3He confined in nafen. Nafen is a new type of aerogel and it consists of Al2O3 strands, which are nearly parallel to one another at macroscopic distances. We examine two samples of nafen with different porosities using spin echo techniques. Spin diffusion of 3He along and across the strands was measured. The aerogel alignment is evident from observed spin diffusion anisotropy. A theory describing this effect is developed and compared with the experiment.

Convenient procedure for in situ cyclization of hydrazinecarbodithioate potassium salts to 1,3,4-oxadiazole-2(3 H )-thiones under normal phase micellar media catalysis promoted by sodium dodecyl sulfate (SDS) as an anionic surfactant is reported. The main advantages of this procedure is to provide shorter reaction time for the completion of cyclization, scale-up synthesis is possible and the oxadiazoles were obtained in high to excellent yields (87-100%), making the protocol an alternative addition to the available methods.

A rapid, simple to use and low-cost thin-layer chromatographic procedure in normal phase system with densitometric detection at 246 nm was carefully validated according to the International Conference on Harmonisation (ICH) guidelines for assay of clobetasol propionate in topical solution containing clobetasol propionate in quantity 0.50 mg/mL. The adopted thin-layer chromatographic (TLC)-densitometric procedure could effectively separate clobetasol propionate from its related compound, namely clobetasol. It is linear for clobetasol propionate in the range of 0.188 ÷ 5 µg/spot. The limit of detection (LOD) and limit of quantification (LOQ) value is 0.061 and 0.186 µg/spot, respectively. Accuracy of proposed procedure was evaluated by recovery test. The mean recovery of studied clobetasol propionate ranges from 98.7 to 101.0%. The coefficient of variation (CV, %) obtained during intra-day and inter-day studies, which was less than 2% (0.40 ÷ 1.17%), confirms the precision of described method. The assay value of clobetasol propionate is consistent with the pharmacopoeial requirements. In conclusion, it can be suitable as a simple and economic procedure for routine quality control laboratories of clobetasol propionate in topical solution.

Retention indices for 67 polycyclic aromatic sulfur heterocycles (PASHs) and 80 alkyl-substituted PASHs were determined using normal-phase liquid chromatography (NPLC) on an aminopropyl (NH2) stationary phase. The retention behavior of PASH on the NH2 phase is correlated with the number of aromatic carbon atoms and two structural characteristics have a significant influence on their retention: non-planarity (thickness, T) and the position of the sulfur atom in the bay-region of the structure. Correlations between solute retention on the NH2 phase and T of PASHs were investigated for three cata-condensed (cata-) PASH isomer groups: (a) 13 four-ring molecular mass (MM) 234 Da cata-PASHs, (b) 20 five-ring MM 284 Da cata-PASHs, and (c) 12 six-ring MM 334 Da cata-PASHs. Correlation coefficients ranged from r = −0.49 (MM 234 Da) to r = −0.65 (MM 334 Da), which were significantly lower than structurally similar PAH isomer groups (r = −0.70 to r = −0.99). The NPLC retention behavior of the PASHs are compared to similar results for PAHs.

The gap parameter of the standard BCS model is replaced by the order parameter of the modified Ginzburg–Landau theory. Using this new form of the BCS model, the energy, entropy, and heat capacity of $$^{93,94,95}$$ Mo nuclei are calculated. The results are compared with the experimental data and standard BCS results. Since the order parameter does not drop to zero at a critical temperature, our results for thermal properties are free of singularities. We have shown that the heat capacity as a function of temperature behaves smoothly and it is highly in agreement with the experimental heat capacity, while heat capacity behaves singularly and discontinuously in the standard BCS model. A smooth peak in the heat capacity is observed which is interpreted as a signature of the transition from the superfluid to the normal phase.

We revised the large-$N$ expansion for a three-dimensional Bose system with short-range repulsion in normal phase. Particularly, for the model potential that is characterised only by the $s$-wave scattering length $a$ the full numerical calculations of the critical temperature in the $1/N$-approximation as a function of the gas parameter $an^{1/3}$ are performed. Additionally to the well-known result in the dilute limit we estimated analytically the leading-order strong-coupling behavior of the Bose-Einstein condensation transition temperature. It is shown that the critical temperature shift of the non-ideal Bose gas grows at small $an^{1/3}$, reaches some maximal value and then falls down becoming negative., 6 pages, 3 figures

Retention indices for 124 polycyclic aromatic hydrocarbons (PAHs) and 62 methyl-substituted (Me-) PAHs were determined using normal-phase liquid chromatography (NPLC) on a aminopropyl (NH2) stationary phase. PAH retention behavior on the NH2 phase is correlated to the total number of aromatic carbons in the PAH structure. Within an isomer group, non-planar isomers generally elute earlier than planar isomers. MePAHs generally elute slightly later but in the same region as the parent PAHs. Correlations between PAH retention behavior on the NH2 phase and PAH thickness (T) values were investigated to determine the influence of non-planarity for isomeric PAHs with four to seven aromatic rings. Correlation coefficients ranged from r = 0.19 (five-ring peri-condensed molecular mass (MM) 252 Da) to r = −0.99 (five-ring cata-condensed MM 278 Da). In the case of the smaller PAHs (MM ≤ 252 Da), most of the PAHs had a planar structure and provided a low correlation. In the case of larger PAHs (MM ≥ 278 Da), nonplanarity had a significant influence on the retention behavior and good correlation between retention and T was obtained for the MM 278 Da, MM 302 Da, MM 328 Da, and MM 378 Da isomer sets.

The enantioseparation of a series of six azulene-centered 1,5-diol enantiomers was studied employing two cellulose-based chiral stationary phases under normal phase conditions (isopropanol/hexanes). The separations were generally quite good on Chiralcel-OD-H, with α values ranging from 1.2 to 8.4 (average 4.0) and resolution values of 0.4–8.3 (average 4.7). Only one of the six enantiomer pairs was not well resolved, but was well separated on Lux cellulose 2 (α 1.4, Rs 8.7). It was observed that the enantioseparations of the RS/SR diastereomers (ave α = 7.8, Rs = 8.2) were dramatically better than that of the corresponding RR/SS diastereomers (ave α = 2.1, Rs = 3.0) on Chiralcel-OD-H. The better-resolved diastereomer pairs correspond to the more strongly retained diastereomers on silica gel. The enantiomers of two benzene 1,5-diols were much more poorly separated on both stationary phases, suggesting that the unusual polarity of the azulene ring enhances critical interactions with these phases.

Metabolomics is currently being adopted as a tool to understand numerous clinical pathologies. It is essential to choose the best combination of techniques in order to optimize the information gained from the biological sample examined. For example, separation by reverse-phase liquid chromatography may be suitable for biological fluids in which lipids, proteins and small organic compounds coexist in a relatively nonpolar environment, such as serum. However, urine is a highly polar environment and metabolites are often specifically altered to render them polar suitable for normal phase/hydrophilic interaction liquid chromatography. Similarly, detectors such as high-resolution mass spectrometry (MS) may negate the need for a pre-separation but specific detection and quantification of less abundant analytes in targeted metabolomics may require concentration of the ions by methods such an ion trap MS. In addition, the inherent variability of metabolomic profiles need to be established in appropriately large sample sets of normal controls. This review aims to explore various techniques that have been tried and tested over the past decade. Consideration is given to various key drawbacks and positive alternatives published by active research groups and an optimum combination that should be used for urinary metabolomics is suggested to generate a reliable dataset for baseline studies. Copyright © 2014 John Wiley & Sons, Ltd.

Simultaneous preparation of naturally rare catechins, EGC and EC, has been realized by tannase-mediated biotransformation combining high speed counter current chromatography. In addition, simultaneous preparation of the four catechins, EGCG, ECG, EGC, and EC in green tea extract has also been achieved by HSCCC under the normal phase and the reversed phase modes. The identity of the catechins was determined by HPLC-DAD-ESI-MS and quantification of the catechins was performed by HPLC-DAD. In a typical HSCCC separation, 27.2 mg 98.8% EGCG, 14.1 mg 94.7% EGC, and 9.3 mg 97.5% EC were obtained. This new method is efficient, time-saving and valuable for biological studies.

Mono-dispersed poly(ethylene glycols) (PEGs) are of great value in the development of biopharmaceuticals. However, tedious synthesis limits the availability of mono-dispersed PEGs. To address this issue, a fluorous synthesis of mono-dispersed PEGs, discretely PEGylated surfactants and 19 F magnetic resonance imaging (MRI) agents has been developed. During the synthesis, both fluorous and normal phase silica gel-based solid-phase extractions were successfully employed to simplify the purifications. This synthesis provided an easy access to valuable mono-dispersed PEGs and related molecules for biomedical application on multi-gram scales.

A simple, rapid, accurate and precise HPLC method was developed and validated for the simultaneous quantification of prifinium bromide and paracetamol combination in pharmaceutical dosage form. The separation was achieved on a normal phase-nitrile (CN) column. The mobile phase consisted of 30 mM ammonium acetate buffer–acetonirtile (50%:50%, v/v) at pH = 6.5. The UV detection was carried out at a wavelength of 254 nm. A linear response was observed over a concentration range 3–50 μg/mL for prifinium bromide and paracetamol. The limit of detection for prifinium bromide was 0.75 μg/mL and its limit of quantification was 2.30 μg/mL. For paracetamol, the limit of detection was 0.64 μg/mL while its limit of quantification was 1.60 μg/mL. The method was validated for linearity, accuracy, precision and robustness. The validated method was applied to the analysis of prifinium bromide and paracetamol in commercial Riabal ® Compound tablets.

Recently, a multilaboratory validation (MLV) of AOAC Official Method 2012.24 for the determination of cocoa flavanols and procyanidins (CF-CP) in cocoa-based ingredients and products determinedthat the method was robust, reliable, and transferrable. Due to the complexity of the CF-CP molecules, this method required a run time exceeding 1 h to achieve acceptable separations. To address this issue, a rapid resolution normal phase LC method was developed, and a single-laboratory validation (SLV) study conducted. Flavanols and procyanidins with a degree of polymerization (DP) up to 10 were eluted in 15 min using a binary gradient applied to a diol stationary phase, detected using fluorescence detection, and reported as a totalsum of DP 1–10. Quantification was achieved using (-)-epicatechin-based relative response factors for DP 2–10. Spike recovery samplesand seven different types of cocoa-based samples were analyzed to evaluate the accuracy, precision, LOD, LOQ, and linearity of the method. The within-day precision of the reported content for the samples was 1.15–5.08%, and overall precision was 3.97–13.61%. Spike-recovery experiments demonstrated recoveries of over 98%. The results of this SLV were compared to those previously obtained in the MLV and found to be consistent. The translation to rapid resolution LC allowed for an 80% reduction in analysis time and solventusage, while retaining the accuracy and reliability of the original method. The savings in both cost and time of this rapid method make it well-suited for routine laboratory use.

A normal phase on-line OPLC-UV technique was adopted for separation and quantification of colchicine alkaloid in G. superba. The analyzed and developed method was rapid and specific, and selective separation was observed with high peak purity. Validation parameters prove the selectivity and reproducibility of the method and thus can be applied for estimation of a targeted marker in Gloriosa, in various pharmaceutical formulations and also to check phyto-geographical variations among species.