Triethylammonium Acetate Buffer Research Articles

Analytical method development supported by DoE-DS approach for enantioseparation of (S,S)- and (R,R)-moxifloxacin

In this paper, method for enantiomeric purity testing of fourth-generation fluoroquinolone, moxifloxacin hydrochloride, was developed and validated. Exceptional enantioselectivity for this assay was achieved using cyclodextrin type Chiral Stationary Phase (CSP), phenylcarbamate-β-cyclodextrin CSP, and mobile phase consisted of acetonitrile and triethylammonium acetate (TEAA) buffer. Analytical Quality by Design (AQbD) methodology, comprising Design of Experiments (DoE) - Design Space (DS) approach, was used for method development. In order to select appropriate Critical Method Parameters (CMPs), risk assessment was done using combined three step strategy that involved Ishikawa diagram - CNX (Control, Noise and eXperimental) - FMEA (Failure Mode and Effect Analysis). Three CMPs were further selected and investigated in this study: acetonitrile content in the mobile phase (30–50%, v/v), triethylamine content in the TEAA buffer (0.1–1.5%, v/v) and aqueous phase pH (3.5–4.5). Monte Carlo simulations were performed and 3D-DS was computed. One point situated in the center of 3D-DS was selected as working point for method validation, with the following values of CMPs: acetonitrile content in the mobile phase set to 37% (v/v), triethylamine content in TEAA 0.8% and pH value of the aqueous phase set at 4.0. Also, 2D-DS was created (with fixed one factor – pH value of aqueous phase at 4.0) which also gave us confirmation that the selection of working conditions was suitable. The proposed enantioselective method was further on tested for its quantitative robustness, as well as for its suitability for the intended purpose through validation studies.

Synthesis and enantioseparation characteristics of a novel β-cyclodextrin chiral stationary phase based on diazotized silica in HPLC

A novel chiral selector polyacrylic acid-β-cyclodextrin (PAA-β-CD) was successfully prepared, then a facile synthesis of PAA-β-CD stationary phase based on diazotized silica was developed and characterized. Monodisperse silica microspheres were synthesized by a modified Stöber method. The obtained silica particles were functionalized by self-assembly positive charged photosensitive diazoresin (DR) and PAA-β-CD on the surface. The corresponding chiral stationary phase (CSP) was used in HPLC and the enantioseparation performance was investigated in both polar organic and reverse phase mode. Better separation abilities and excellent enantio-selectivities were obtained on PAA-β-CD CSP for antihistamine drugs in the acetonitrile and triethylammonium acetate buffer mobile phase. Abbreviations: AIBN: azodiisobutyronitrile; β-CD: b-cyclodextrin; β-CD-NH2: amino-β-CDcyclodextrin; β-CD-OTs: sulfonyl-b-cyclodextrin; CD: cyclodextrin; CSP: chiral stationary phase; DCC: dicyclohexyl carbimide; DR: diazoresin; MeOH: methanol; NMP: N-methyl pyrrolidone; PAA: polyacrylic acid; PAA-β-CD: polyacrylic acid-β-cyclodextrin; TEAA: triethylammonium acetate; TEOS: tetraethyl orthosilicate

Test purchase of new synthetic tryptamines via the Internet: Identity check by GC-MS and separation by HPLC

Over the past few years, a continuous alteration of the recreational drug market took place. Among other novel psychoactive drugs, new synthetic tryptamine derivatives appeared on the market. These compounds are mainly traded via the Internet, which has become an important marketplace for the sale of recreational drugs. The goal of our research was to check, if 13 new synthetic tryptamines obtained by test purchase via different online vendors meet the promised identity. Analysis was performed by GC-MS, using a common 30 m HP-5MS capillary column as stationary phase. Subsequently, a simple HPLC method for the separation of these tryptamines was developed. Therefore, the aim was to establish a method to separate a broad spectrum of trypamines simultaneously within short time. Measurements were performed by a LiChrospher® RP-18e column and a mobile phase consisting of 0.1% triethylammonium acetate buffer, methanol and acetonitrile. Both presented methods were found to be suitable for the identification as well as separation of tryptamines as the analysis times were short and the selectivity sufficient. Moreover, enantioseparation of 3 chiral tryptamine derivatives purchased via the Internet by HPLC-UV and an Astec® Cyclobond I™ 2000 as CSP was performed. All of them were sold as racemic mixtures.

Enantioseparation of basic chiral drugs on a carbamoylated erythromycin-zirconia hybrid monolith using capillary electrochromatography

An organic–inorganic hybrid monolithic column was prepared within the confines of a capillary via a single-step in situ sol–gel approach using zirconium tetrabutoxide as a precursor to compose the inorganic backbone and 3-triethoxysilylpropyl carbamoylated derivative of erythromycin (TEOSPC-ERY) as a co-precursor to introduce the organic chiral selector moiety in the zirconia backbone. The resulting carbamoylated ERY-zirconia hybrid monolith (ERY-ZHM) showed homogeneous morphology with well-defined through pores and was tightly connected with the inner wall of the capillary. The column was employed for capillary electrochromatographic enantioseparation of six basic chiral drugs in mobile phases (MPs) consisting of acetonitrile (ACN) and triethylammonium acetate (TEAA) buffer. The effects of composition of MP and applied voltage on chiral separation were investigated by using propranolol as a representative analyte. The highest resolution (Rs=3.33) was obtained with a MP consisting of 10/90 (v/v) ACN/TEAA buffer (10mM, pH 7), 10kV applied voltage and 25°C capillary temperature. The relative standard deviations for resolution values regarding run to run, day to day, column to column and batch to batch repeatability were 0.41%, 0.89%, 1.80% and 2.26% (for n=3), respectively, indicating satisfactory stability of columns and reproducibility of column preparation process.

Enantiomer separation of acidic chiral compounds on a quinine-silica/zirconia hybrid monolith by capillary electrochromatography

A weak anion-exchanger chiral selector, quinine-incorporated silica/zirconia hybrid monolithic (QUI-S/ZHM) capillary column was prepared by sol–gel technology. The performance of the QUI-S/ZHM column was investigated for enantioresolution of a set of acidic chiral drugs and dinitrobenzoyl (DNB)-amino acids by capillary electrochromatography in aqueous organic mobile phases composed of acetonitrile (ACN) and triethylammonium acetate (TEAA) buffer. Effects of several parameters including the ACN content, concentration and pH of the mobile phase on the chiral separation were examined. Baseline resolutions of all the compounds were obtained in the mobile phase consisting of 70:30 ACN/TEAA (10mM, pH 6) under applied voltage of −10kV at 25°C within 20min.

Evaluation of perphenylcarbamated cyclodextrin clicked chiral stationary phase for enantioseparations in reversed phase high performance liquid chromatography

In this study, perphenylcarbamated cyclodextrin clicked chiral stationary phase (CSP) was developed with high column efficiency. The characteristics of the column were evaluated in terms of linearity, limit of detection and limit of quantification. The enantioselectivity of the as-prepared clicked CSP was explored with 26 recemates including aryl alcohols, flavanoids and adrenergic drugs in reversed phase high-performance liquid chromatography. The effect of separation parameters including flow rate, column temperature, organic modifier and buffer on the enantioselectivity of the clicked CSP was investigated in detail. The correlation study of the analytes structure and their chiral resolution revealed the great influence of analytes’ structure on the enantioseparations with cyclodextrin CSP. Methanol with 1% of triethylammonium acetate buffer (pH 4) was proved to be the best choice for the chiral separation of basic enantiomers.

Determination of egg yolk xanthophylls by isocratic high-performance liquid chromatography

An isocratic HPLC method was developed for the determination of eight xanthophylls (lutein, capsanthin, zeaxanthin, canthaxanthin, β-apo-8′-carotenal, ethyl-8′-apo-β-carotene-8′-oate, citranaxanthin and β-cryptoxanthin; registered as additives in poultry feeding) in egg yolks. Optimum separation of all-E-isomers of these xanthophylls was achieved in less than 18min on a ProntoSIL C30 column at 27°C using acetone–methanol–0.5M triethylammonium acetate buffer pH 7 14:5:1 (v/v) as the mobile phase with a flow rate of 1mL/min using spectrophotometric detection at 450nm. Other mobile phases were also found suitable, including acetone–water 93:7 (v/v) and acetone–methanol 1:4 (v/v) and the influences of column temperature on the separation and addition of triethylammonium acetate buffer pH 7 to the mobile phase on enhancement of the peak areas were evaluated. Preparation of test solution from yolks included a short vortexing of 0.5g of yolk in 10mL of acetone, followed by 15min magnetic stirring under nitrogen and centrifugation. The method was validated for 5 analytes. The calibration range was between 0.04 and 2μg/mL and the mean recovery of the analytes (95%) and the intra-day precision of the method (RSD less than 5%) on three levels in triplicates were obtained. Analyses of eggs from four husbandry classes showed the presence of up to four xanthophylls (lutein, zeaxanthin, canthaxanthin and ethyl-8′-apo-β-carotene-8′-oate) and traces of β-cryptoxanthin.

Separation of benzoxazine enantiomers on β-cyclodextrin bonded chiral stationary phases

Chiral separation of benzoxazine enantiomers was studied on click chemistry based beta-cyclodextrin stationary phases under reversed-phase high performance liquid chromatographic mode. The effects of the type and percentage of the organic modifier, the concentration of triethylammonium acetate buffer (TEAA), and pH on enantioselective separation were examined and studied. It was demonstrated that acetonitrile was better for the chiral separation of benzoxazine enantiomers than methanol. It was observed that the retention time and the resolution of benzoxazine enantiomers decreased with the increase of the volume ratio of TEAA from 0.1% to 1.0%. The separation of benzoxazine enantiomers was of the maximum resolution at pH 4.1. With the optimized mobile phase of the mixture of acetonitrile and 0. 1% TEAA (pH 4.1), all the enantiomers were separated at the baseline. The chiral recognition mechanism is also discussed. The separation was probably based on the inclusion complex interaction and the hydrogen bonding between enantiomers and chiral stationary phases. This work provided the experience for the intensive study of click beta-cyclodextrin bonded stationary phases, and it also illustrated the potential of click chemistry in the preparation of beta-cyclodextrin based chiral stationary phase.

Mass Isotopomer Analysis of Metabolically Labeled Nucleotide Sugars and N- and O-Glycans for Tracing Nucleotide Sugar Metabolisms

Nucleotide sugars are the donor substrates of various glycosyltransferases, and an important building block in N- and O-glycan biosynthesis. Their intercellular concentrations are regulated by cellular metabolic states including diseases such as cancer and diabetes. To investigate the fate of UDP-GlcNAc, we developed a tracing method for UDP-GlcNAc synthesis and use, and GlcNAc utilization using (13)C6-glucose and (13)C2-glucosamine, respectively, followed by the analysis of mass isotopomers using LC-MS. Metabolic labeling of cultured cells with (13)C6-glucose and the analysis of isotopomers of UDP-HexNAc (UDP-GlcNAc plus UDP-GalNAc) and CMP-NeuAc revealed the relative contributions of metabolic pathways leading to UDP-GlcNAc synthesis and use. In pancreatic insulinoma cells, the labeling efficiency of a (13)C6-glucose motif in CMP-NeuAc was lower compared with that in hepatoma cells. Using (13)C2-glucosamine, the diversity of the labeling efficiency was observed in each sugar residue of N- and O-glycans on the basis of isotopomer analysis. In the insulinoma cells, the low labeling efficiencies were found for sialic acids as well as tri- and tetra-sialo N-glycans, whereas asialo N-glycans were found to be abundant. Essentially no significant difference in secreted hyaluronic acids was found among hepatoma and insulinoma cell lines. This indicates that metabolic flows are responsible for the low sialylation in the insulinoma cells. Our strategy should be useful for systematically tracing each stage of cellular GlcNAc metabolism.

Design and Synthesis of Cyclic ADP‐4‐Thioribose as a Stable Equivalent of Cyclic ADP‐Ribose, a Calcium Ion‐Mobilizing Second Messenger

Design and Synthesis of Cyclic ADP‐4‐Thioribose as a Stable Equivalent of Cyclic ADP‐Ribose, a Calcium Ion‐Mobilizing Second Messenger

Effects of extraction and high-performance liquid chromatographic conditions on the determination of lutein in spinach

A major factor in the direct determination of lutein in spinach extracts proved to be obtaining reproducible and stable chromatography of lutein. This was achieved on a C30 column with the mobile phase acetone–0.1M triethylammonium acetate (TEAA) buffer (pH 7) 9:1 (v/v). Extraction of 10mg of lyophilized spinach with 10mL of extraction solvent (ethanol, acetone, ethanol–ethyl acetate 1:1 (v/v), methanol–THF 1:1 (v/v)) for 15min with magnetic stirring under nitrogen resulted in equal yields of lutein. The yields were enhanced by addition of 15% of 1M TEAA buffer pH 7 to all four extraction solvents. As confirmed by recovery experiments, no loss of lutein occurred during the extraction. The relative standard deviation from triplicate extractions was less than 5%. The addition of 15% TEAA pH 7 to acetone enhanced the extraction yield of lutein also from unlyophilized spinach. The content of lutein in different spinach samples ranged from 5 to 15mg/100g of fresh weight. The first separation is reported of all the carotenoids and chlorophylls on a C18 core–shell column and the addition of 15% of 1M TEAA buffer pH 7 to acetone also enhanced the extraction yield of β-carotene compared to the yield produced by pure acetone.

A Novel Fluorescent Cell Membrane-permeable Caged Cyclic ADP-ribose Analogue

Cyclic adenosine diphosphate ribose is an endogenous Ca(2+) mobilizer involved in diverse cellular processes. A cell membrane-permeable cyclic adenosine diphosphate ribose analogue, cyclic inosine diphosphoribose ether (cIDPRE), can induce Ca(2+) increase in intact human Jurkat T-lymphocytes. Here we synthesized a coumarin-caged analogue of cIDPRE (Co-i-cIDPRE), aiming to have a precisely temporal and spatial control of bioactive cIDPRE release inside the cell using UV uncaging. We showed that Co-i-cIDPRE accumulated inside Jurkat cells quickly and efficiently. Uncaging of Co-i-cIDPRE evoked Ca(2+) release from endoplasmic reticulum, with concomitant Ca(2+) influx in Jurkat cells. Ca(2+) release evoked by uncaged Co-i-cIDPRE was blocked by knockdown of ryanodine receptors (RyRs) 2 and 3 in Jurkat cells. The associated Ca(2+) influx, on the other hand, was abolished by double knockdown of Stim1 and TRPM2 in Jurkat cells. Furthermore, Ca(2+) release or influx evoked by uncaged Co-i-cIDPRE was recapitulated in HEK293 cells that overexpress RyRs or TRPM2, respectively, but not in wild-type cells lacking these channels. In summary, our results indicate that uncaging of Co-i-cIDPRE incites Ca(2+) release from endoplasmic reticulum via RyRs and triggers Ca(2+) influx via TRPM2.

SIMULTANEOUS DETERMINATION OF PALMATINE AND BERBERINE USING CUCURBIT[7]URIL AS MOBILE PHASE ADDITIVE BY HPLC

A simple and sensitive high performance liquid chromatography-fluorescence detector (HPLC-FLD) method was developed for simultaneous determination of palmatine (PAL) and berberine (BRH). The method is based on the enhancement of the fluorescence of PAL and BRH in aqueous solution in the presence of cucurbit[7]uril (CB[7]). The chromatographic resolution of PAL and BRH was performed on a SymmetryShieldTM RP 18 column with CB[7] as the mobile phase additive. The composition of the mobile phase was (50/50, v/v) absolute methanol/0.05% (v/v) triethylammonium acetate buffer (pH 4.1) with 1.25 × 10−4 M CB[7] at a flow-rate of 0.5 mL · min−1. The linear ranges of PAL and BRH were 3–230 and 2–220 ng · mL−1, with the regression equations of Y = 594248 + 7.56 × 104X (R = 0.9993), Y = 811028 + 6.32 × 104X (R = 0.9995), respectively. The limits of detection for PAL and BRH were 1 and 0.7 ng · mL−1, respectively, with fluorescence detection at an excitation wavelength of 347 nm and an emission wavelength of 495 nm. The sensitivity of the proposed method was almost equal to previous liquid chromatography-mass spectroscopy method. The proposed method was applied to determine PAL and BRH in human plasma and Jinji capsules. The HPLC-FLD method was sensitive and convenient.

Chromatographic determination of active compounds in topical formulations

The aim of this study was to develop and validate new methods for the determination of active compounds in topical gels. The method for the determination of nonoxinol-9 and trimecaine hydrochloride in lubricant gel by HPLC with UV detection was described. Separation was carried out using a Discovery ZR-PBD analytical column (150 × 4.6 mm, 5 μm), and a mobile phase composed of a mixture of triethylammonium acetate buffer (pH 9; 50 mM) and methanol (22 : 78, v/v). Determination of terpinen-4-ol in lubricant gel was achieved by GC with a flame ionization detector (FID). An Alltech-AT-624 (0.32 mm ID × 30 m, 1.8 μm film thickness) fused-silicacapillary column and helium as the carrier gas, at a flow rate of 28 cm s−1, were employed. The analysis time was less than 7.5 min for HPLC and 5 min for GC analyses. Both methods were successfully applied to the analysis of pharmaceuticals.

Analysis of hesperetin enantiomers in human urine after ingestion of blood orange juice by using nano-liquid chromatography

Hesperetin (HT) is a flavanone abundantly found in citrus fruits. It has been reported that HT possesses significant antioxidant, anticancer, anti-inflammatory and analgesic activities. This explains the necessity of developing new methods more powerful and sensitive for analyzing HT in biological fluids. Taking into account the chiral nature of HT, the study of the stereospecific kinetics of in vitro and in vivo metabolism and tissue distribution could be a useful tool for further understanding stereoselective biotransformations in human body. A simple nano-liquid chromatographic method for the determination of the enantiomeric composition of hesperetin in human urine was developed. Chiral separation was achieved using a 100 μm I.D. capillary, packed with phenyl-carbamate-propyl-β-cyclodextrin stationary phase, employing a mobile phase composed by a mixture of triethylammonium acetate buffer (1%, v/v, pH 4.5) and water/methanol (30:70, v/v) at room temperature. The detection was done by using on-column UV detector at 205 nm. Calibration curves were linear in the studied concentration range from 0.25 to 25 μg/mL ( r 2 > 0.999). Precision assay was <4.5% and was within 3% at the limit of quantification (0.5 μg/mL). The recovery of 7-ethoxycoumarin (IS), R- and S-hesperetin was greater than 82.48%, utilizing a liquid–liquid extraction procedure. The developed method was successfully applied to the determination of hesperetin enantiomers in urine samples obtained from a male volunteer, after the ingestion of 1 L of a commercial blood orange juice.

Enantioseparation of a novel “click” chemistry derived native β-cyclodextrin chiral stationary phase for high-performance liquid chromatography

A novel native β-cyclodextrin chiral stationary phase was prepared via “click” chemistry with cuprous iodide–triphenylphosphine complex as the catalyst and applied for enantioseparation of Dns-amino acids, substituted phenyl and phenoxy group modified propionic acids, flavonoids, and some pharmaceutical compounds such as nimodipine, propranolol, brompheniramine and bendroflumethiazide in reversed-phase high-performance liquid chromatography. The studied analytes could be resolved under different separation conditions. The resolution of Dns-DL-Leu could reach 5.08 using a mobile phase consisting of 1% (w/w) triethylammonium acetate buffer (pH 4.11) and methanol (50:50 v/v). The effects of buffer pH and the content of organic modifier on enantioseparation of Dns-amino acids by this novel chiral phase were being investigated. The separation results demonstrate that click chemistry, a versatile reaction, affords a facile approach towards the preparation of stable chiral stationary phases.

Perphenylcarbamoylated β‐cyclodextrin bonded‐silica particles as chiral stationary phase for enantioseparation by pressure‐assisted capillary electrochromatography

Perphenylcarbamoylated beta-cyclodextrin bonded-silica particles (5 microm) were packed into 75-mum fused-silica capillaries, and used for the enantiomer separation of neutral and basic solutes by pressure-assisted capillary electrochromatography. Triethylammonium acetate and phosphate buffer were employed as the BGEs. A cathodic EOF was observed with these two BGEs. Seven chiral analytes were successfully resolved into their enantiomers under optimized conditions, and five of them could be baseline-separated within 12 min due to their high electrophoretic mobility. Better results were achieved with phosphate buffer as the BGE. The effects of organic content and pH on the enantioseparation were also investigated.

Synthesis and chromatographic properties of α-Schiff bases (6-imino)-β-cyclodextrin bonded silica for stationary phase of liquid chromatography

Two new chiral stationary phases (CSPs), 6-deoxyisopropylimino-β-cyclodextrin bonded on the silica gel (YBCDs) and heptakis[2,6- o-diamyl-6-deoxyisopropylimino]-β-cyclodextrin bonded on the silica gel (WYBCDs), were prepared. The chromatographic properties of two CSPs (YBCDs and WYBCDs) were tested. Good resolutions for disubstituted benzene isomers were obtained with YBCDs. l- and d-amino acids mixtures were well separated on both YBCDs and WYBCDs. The influence of pH of aqueous triethylammonium acetate buffer (TEAA) was also studied on the two CSPs. Experimental results show that WYBCDs enhances the retention of amino acids. It is proposed that the amylation modification above the cyclodextrin (CD) partially occludes the mouth of the CD cavity and sterically influences the formation of inclusion complexes, leading to the change in solute retention.

Competitive reactions of a ruthenium arene anticancer complex with histidine, cytochrome c and an oligonucleotide

The ruthenium arene anticancer complex [(eta(6)-bip)Ru(en)Cl][PF(6)] (1) (bip is biphenyl, en is ethylenediamine) reacted slowly with the amino acid L-histidine (L-His) in aqueous solution at 310 K. Two L-His adducts of 1 were separated by high-performance liquid chromatography and identified by electrospray ionisation mass spectrometry and NMR: an imidazole N(delta)-bound complex [(eta(6)-bip)Ru(en)(N(delta)-L-His)](2+), and an N(epsilon)-bound complex [(eta(6)-bip)Ru(en)(N(epsilon)-L-His)](2+). At 310 K, after 24 h only about 22% of complex 1 (2 mM) reacted with L-His, and of the unreacted 1, 59% had hydrolysed. In the presence of 100 mM NaCl, approximately 90% of 1 remained unreacted. In aqueous solution or triethylammonium acetate (TEAA) buffer (pH 7.6), (15)N-labelled 1 reacted with cytochrome c to give two monoruthenated protein adducts. The reaction reached equilibrium within 2 h by which time approximately 50% of cytochrome c was ruthenated. On the basis of [(1)H, (15)N] NMR data, one adduct may have Ru bound to the N-terminus, and the other to a carboxylate group on the protein. In TEAA buffer and at 310 K, more than 90% of the 14-mer oligonucleotide d(TATGTACCATGTAT) reacted with 2 mol Eq of 1 to give rise to monoruthenated and diruthenated oligonucleotide adducts. The presence of cytochrome c (1 mol Eq) or L-His (4 mol Eq) had little effect on the course of the reaction with the oligonucleotide. In cells, DNA (or RNA) may be a favoured reaction site for this Ru anticancer complex.

Enhanced mass detection of oligonucleotides using reverse-phase high-performance liquid chromatography/electrospray ionization ion-trap mass spectrometry.

A new method providing enhanced sensitivity for the analysis of oligonucleotides using an on-line coupled system of reversed-phase high-performance liquid chromatography (RP-HPLC) and electrospray ionization ion-trap mass spectrometry (ESI-MS) has been developed. The presented method allows the use of the standard gradient elution of 0.1 M triethylammonium acetate (TEAA) buffer (adjusted to pH 7.0 with acetic acid) and acetonitrile that is typically used for the separation of oligonucleotides in RP-HPLC. An added feature of this method is the ability to combine and mix additional 0.1 M imidazole in acetonitrile after the separation column for improved ESI-MS performance. This is similar to the post-column reaction method in liquid chromatography (LC) and the liquid sheath flow method in LC/ESI-MS, both of which offer the advantage of not compromising the chromatographic separation conditions. The application of this new method is demonstrated to afford improved sensitivity for the analysis of oligonucleotides (20-50 mer) via on-line coupled HPLC/ESI-MS analysis and purification systems.