Separation of Thiamin,Thiamin Antagonists and Their Phosphate Esters by High-Performance Liquid Chromatography

Abstract

Methods are presented for the separation of the phosphate esters of thiamin, oxythiamin or pyrithiamin and the separation of thiamin and oxythiamin by high-performance liquid chromatography. Detection by means of a UV monitor and fluorometer with a post-column oxidation system is described which allows for selective detection of thiochrome, pyrichrome and their respective phosphate esters. Anion exchange and ion-pair reverse phase chromatography are the chromatographic modes of separation.     

Extraction and Quantitation of Polyolefin Additives

Abstract

The extraction and subsequent separation and quantitation of polymer additives in polyolefins has proven to be a challenge for the analytical chemist. There have been several workers over the years who have investigated the separation of additives in polyolefins (1–7), but the extraction and recovery (at > 90%) in reasonable times has been most difficult. the Soxhlet extraction technique has been used for many years, but suffers in that it takes over twelve hours to extract most of the additives used in polyolefin formulations. Some workers have used the ultrasonic bath (7), but not very much work has been done with the microwave oven. We have investigated some ways to extract the additives from polyolefins, namely, microphye oven and ultrasonic bath techniques for high density polyethylene (HDPE), low density polyethylene (LDPE), and polypropylene. We have concentrated on identifying and quantitating recoveries for typical polyolefin

antioxidants, 20 such as Irganox 1010, Irgafors 68, and Cyasorb UV 531. the extraction times are typically 20 minutes for the microwave oven and 30–60 minutes for the ultrasonic bath with 90+% recoveries being obtained. Both normal phase isocratic (used when phosphites are present) and reverse phase gradient LC techniques are discussed. We have also extracted the slip agent, erucamide, from LDPE, using reverse phase, at 200nm.     

Comparative Enantioseparation of Seven Amino Alcohols on Teicoplanin‐Based Chiral Stationary Phases

Abstract

The macrocyclic antibiotics represent a relatively new class of chiral selectors in separation science and teicoplanin‐based chiral stationary phases (CSP) have been used successfully in a number of applications in high‐performance liquid chromatography. In the present studies, we self‐prepared two bonded CSPs–teicoplanin (TE) and teicoplanin phenyl isocyanate (TE‐Phe). Seven amino alcohols, propranolol, bisoprolol fumarate, atenolol, salbutamol, isoproterenol, metoprolol, and labetalol were enantioseparated on both self‐made CSPs using methanol as mobile phase and acetic acid (HOAc) and triethylamine (TEA) as mobile phase additives. On both CSPs, the different enantioseparation behavior of analytes with different structure was compared. The influence of the concentration of mobile phase additives (HOAc and TEA) on the enantioseparation was investigated. In all conditions, the retention factors (k′) of seven analytes on TE‐Phe CSP were larger than that on TE CSP. However, the separation factors (α) and resolutions (Rs) on TE‐Phe CSP were smaller than that on TE CSP. The results indicated that the derivatized TE‐Phe CSP is not efficient as original teicoplanin CSP. Our observations also suggested that, for teicoplanin‐based CSPs, π‐π interactions and dipole‐dipole between solutes and CSPs mainly contribute to the retention of solutes on CSPs while hydrogen bonding and steric interactions play important roles in the chiral recognition for teicoplanin‐based CSPs.     

High Performance Size Exclusion Liquid Chromatography of Small Molecular Weight Peptides from Protein Hydrolysates Using Methanol as a Mobile Phase Additive

Abstract

The separation of low molecular weight peptides according to their molecular weight has been a challenge. The earlier works using chaotropic additives in the mobile phase such as SDS or guanidium chloride failed to give a linear response for the semilogarithmic graph of molecular weight versus retention time. Here we report a mobile phase composition suited to the size exclusion separation of the peptides of molecular weight between 6000 and 250 on a TSK-SW 2000     

Comparison of Reversed Stationary Phases for the Chromatographic Separation of Inorganic Analytes Using Hydrophobic Ion Mobile Phase Additives

Abstract

Alkyl-modified silica (RSi) and polystyrenedivinylbenzene (PRP-1) stationary phases are compared for the chromatographic separation of inorganic analyte anions and cations using hydro-phobic ions of opposite charge as mobile phase additives. Tetra-alkylammonium salts were used for anion separations and alkyl sulfonate salts for cation separations. Two major equilibria influence the retention of analyte ions on PRP-1. These are: retention of the hydrophobic ion on PRP-1 and an ion exchange selectivity between the hydrophobic counterion and the analyte ion. When using RSi retention is also influenced by ion exchange at residual silanol groups, which act as weak cation exchange sites. Mobile and stationary phase variables that influence analyte retention are identified. Optimization of these provides favorable eluting conditions for the separation of inorganic ionic analytes. Of particular interest is the potential use of PRP-1 and RSi columns for the separation of inorganic cations; conditions for the separation of alkali metals and alkaline earths are discussed.     

PREPARATION AND CHARACTERIZATION OF POLYSULFONE AND POLYETHERSULFONE MEMBRANES FOR CALCIUM (Ca2+) AND MAGNESIUM (Mg2+) SEPARATION BY COMPLEXATION ULTRAFILTRATION

ABSTRACT

Asymmetric ultrafiltration membranes were synthesized from locally available polysulfone and polyethersulfone polymers using aprotic solvents and organic additives by the phase inversion method. The membranes were characterized in terms of pure water permeability, separation behavior with respect to polyethylene glycols of various molecular weights and electrolytes. The suitability of using polyethyleneimine (PEI) for selective removal of calcium and magnesium salts by an ultrafiltration process was studied in terms of optimum polymer loading at reasonable permeate flux, irreversible adsorptive fouling of the macromolecular ligand on the polymer as functions of solution pH and ionic strength, and metal ion separation as a function of concentration and pressure. Direct electron microscopic observation of fresh, as well as fouled, membranes are presented.     

Separation of enantiomers and diastereomers of 4-hydroxy-2H-1,4-benzoxazin-3(4H)-one derivatives by capillary electrophoresis

Summary A high performance capillary electrophoresis (HPCE) procedure for the enantioseparation of the methyl acetals3 and4 of the natural products DIBOA1 and DIMBOA2, respectively, has been developed using borate buffers (pH 9–10 range), cyclodextrins as chiral additives and addition of up to 20% methanol. A mixture of GDIBOA5 and GDIMBOA6 of natural origin was also clearly separated. HPCE proved to be superior to HPLC by the first separation of GDIBOA5 and three of its diastereomers resulting from a synthetic approach to this acetalglucoside.     

Chiral Separations: A Comparison of Hplc and TLC

Abstract

Comparisons are made for separations attained in normalphase HPLC and TLC involving N-carbobenzyloxy-glycyl-L-proline and (+/?)?10-camphorsulfonic acid as chiral mobile phase additives/chiral counter ions (CMA). Possible reasons for differences in stereoselectivity of β-cyclodextrin CMA and chiral stationary phases (CSP) are discussed. In addition, differences in solubility and proposed separation mechanisms for native cyclodextrins (CD) versus derivatized CD are discussed. Inherent differences in high performance liquid chromatographic (HPLC) and thin-layer chromatographic (TLC) methods are outlined. The pros and cons of using HPLC and TLC are considered.     

Chromatographic Separations of Oligovinylpyridines. II. HPLC Separations of Radically and Anionically Oligomerized 2- and 4-Vinylpyridines

Abstract

HPLC-separations of oligomers obtained by radical and anionic oligomerization of 2- and 4-vinylpyridine by means of gradient elution are reported. The eluent systems used were pentane/methanol and nitrous oxide/methanol. Elution is shown to occur more rapidly with 2-vinylpyridine oligomers. Using nitrous oxide/methanol, separation with respect to degree of oligomerization was enhanced compared to pentane/methanol. Differences in the elution behavior of 2- and 4-vinylpyridine oligomers are ascribed to differences in interactions of the respective oligomer molecules with the stationary and the mobile phase, caused by the different position of the nitrogen atom in these two oligomer types.     

Determination of preservatives in soft drinks by capillary electrophoresis with ionic liquids as the electrolyte additives

A capillary electrophoresis method for separating preservatives with various ionic liquids as the electrolyte additives has been developed. The performances for separation of the preservatives using five ionic liquids with different anions and different substituted group numbers on imidazole ring were studied. After investigating the influence of the key parameters on the separation (the concentration of ionic liquids, pH, and the concentration of borax), it has been found that the separation efficiency could be improved obviously using the ionic liquids as the electrolyte additives and tested preservatives were baseline separated. The proposed capillary electrophoresis method exhibited favorable quantitative analysis property of the preservatives with good linearity (r² = 0.998), repeatability (relative standard deviations ≤ 3.3%) and high recovery (79.4–117.5%). Furthermore, this feasible and efficient capillary electrophoresis method was applied in detecting the preservatives in soft drinks, introducing a new way for assaying the preservatives in food products.     

Separation of carrier-free 90Y from 90Sr using flat sheet supported liquid membranes containing multiple diglycolamide-functionalized calix[4]arenes

Abstract

Five diglycolamide-appended calix[4]arene (C4DGA) ligands, viz. C4DGA with no substituent (L-I), n-propyl (L-II), 3-pentyl (L-III), n-octyl (L-IV) and both side (L-V) substituents were evaluated for the separation of carrier free ⁹⁰Y from a ⁹⁰Y–⁹⁰Sr mixture using the flat sheet supported liquid membrane technique. Based on the results of earlier batch studies, the transport properties of the C4DGA ligands towards Y(III) and Sr(II) were monitored at two different feed acidities. The transport rates were significantly lower for 6 M HNO₃ as compared to 3 M HNO₃ as the feed. After 6 h, the observed trend of Y(III) transport with the C4DGA ligands using a feed of 3 M HNO₃ was: L-I ~ L-III > L-V > L-IV > L-II which changed to L-III > L-I > L-IV > L-V > L-II for 6 M HNO₃ as the feed. With 3 M HNO₃ as feed, >97% Y(III) transport was obtained with L-I and L-III in 6 h. Comparative Sr(II) transport was negligible resulting in high decontamination factors. In a one-step separation process, using L-I as the carrier ligand, pure ⁹⁰Y was obtained as the respective complex with either EDTA or DOTA. The highlights of this liquid membrane-based separation method comprise: its easiness, one-step separation, low ligand inventory, relatively pure product and continuous method.     

Ionic liquids as additives in high performance liquid chromatography: Analysis of amines and the interaction mechanism of ionic liquids

As novel solvents, ionic liquids have many applications in synthesis, catalysis and analytical separation, i.e. extraction and chromatography separation. In this paper, some amines including benzidine, benzylamine, N-ethylaniline and N,N′-dimethylaniline are separated using ionic liquids as additives for the mobile phase in high performance liquid chromatography (HPLC). The effects of the length of alkyl chain or counterions on different ionic liquids and their concentrations on the separation of these analytes are performed. The differences between ionic liquids and tetrabutylammonium bromide (TBA) on the separation of o-, m-, p-phthalic acids are compared and the results show that ionic liquids are ion-pair reagents in essence, although their hydrophobicity and hydrogen bonding also play important roles.     

Determination Of Chlorpromazine And Its Sulfoxide And 7-Hydroxy Metabolites By Ion-Pair High Pressure Liquid Chromatography

Abstract

An ion-pair HPLC approach with ordinary silica has been applied, with detection by ultraviolet absorption, to the assay of plasma for chlorpromazine and its sulfoxide on the one hand, and for 7-hydroxychlorpromazine (an active metabolite) on the other hand. The respective sample-preparation procedures entail extraction of the plasma with heptane at strongly alkaline pH, or else with diethyl ether at a less alkaline pH and with ensuing back-extraction and re-extraction. For each of the compounds, levels as low as 10 ng. ml^?1 are measurable. The conditions adopted are such that specificity and reproducibility are satisfactory although chlorpromazine and its various metabolites, especially 7-hydroxychlorpromazine, are chemically unstable and, moreover, are readily lost onto glass. With the unorthodox separation system adopted, adsorption rather than partition appears to be the dominant mechanism.     

Ion-Interaction Chromatographic Separation of Free Amino Acids

Abstract

An extensive study of the HPLC separation of 20 free amino acids by the addition of alkanesulfonate salts to the mobile phase was previously reported (1). This paper describes modifications in the procedure that improves the separation and resolution of the 20 free amino acids. Mobile phase variables (type and concentration of alkanesulfonate salt, organic modifier concentration, mobile phase pH, and mobile phase ionic strength), and stationary phase variables (particle size, type of packing) which can affect amino acid separation, resolution and selectivity were studied. Two stationary phases were compared, the 5 μm Hamilton PRP-1 and Phase Separations 3 μm, ODS-2. Longer chain alkanesulfonate salts (octane and decanesulfonate salts) were evaluated as mobile phase additives. A mobile phase gradient of increasing per cent organic modifier was necessary for separating complex mixtures of polar and nonpolar-basic amino acids. It is now possible to separate 19 of 20 free amino acids with this ion-interaction chromatographic procedure.     

Effect of additive length and chemistry on the morphology of blends of conjugated thiophenes and fullerene derivative acceptor molecules

Small molecule additives have been shown to increase the device efficiency of conjugated polymer (donor) and fullerene derivative (acceptor) based organic solar cells by modifying the morphology of the device active layer. In this paper we conduct a systematic study of how additives affect the donor‐acceptor morphology using molecular dynamics simulations of blends of thiophene‐based oligomers, mimicking poly(3‐dodecylthiophene) (P3DDT) or poly(2,2′:5′,2”‐3,3”‐didocyl‐terthiophene) (PTTT), and fullerene derivatives with additives of varying length and chemical functionalization, mimicking experimentally used additives like methyl ester additives, diiodooctane, and alkanedithiols. We find that functionalization of additives with end groups that are attracted to acceptor molecules are necessary to induce increased donor‐acceptor macrophase separation. In blends where acceptors intercalate between oligomer alkyl side chains, functionalized additives decrease acceptor intercalation. Functionalized additives with shorter alkyl segments increase acceptor macrophase separation more than additives with same chemical functionalization but longer alkyl segments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1046–1057     

A Simple Novel Method for the Analysis of Lubricating Oil Additives by the Use of Sep-Pak Cartridges

In combination with the use of SEP-PAK cartridges and computerized difference infrared spectroscopic technique, a simple novel method for analyzing lubricating oil additives was developed. The present method involves solvent extraction and the use of SEP-PAK C₁₈ for separating polar additives from residual base oil, followed by the use of SEP-PAK Silica for further elution. With the aid of infrared data station, components of the polar additives were identified. The present method is definitely much more rapid and efficient than the conventional column separation method, and the separation efficiency of this simple method is comparable to that of using flash chromatographic technique.     

Reversed-Phase High Pressure Liquid Chromatography Separation of Deuterated Compounds of Biological Importance from Their Protio Analogs

Abstract

A rapid and a practical HPLC method with UV-VIS detection was developed for the separation and analysis of deuterated carotenoids from their protio analogs. Four different chromatography systems were developed. The results showed that with reversed-phase C₁₈ columns it was possible to baseline resolve fully deuterated carotenoids from the nondeuterated analogs. In all instances the deuterated compound eluted ahead of its protio analog indicating that van der Waals forces are operational during the separation process. Specificity, sensitivity, and reproducibility make these methods particularly suitable in plant chemistry for semi-preparative purification processes and methodologies.     

Normal Phase TLC Separation of Enantiomers Using Chiral Ion Interaction Agents

Abstract

A method for the thin layer chromatographic (TLC) separation of enantiomers and diastereomers involving the use of chiral ion interaction agents is described. Several aromatic amino alcohols were resolved by TLC on diol and/or high performance silica gel plates using a mobile phase containing (1R)-(-)- ammonium-10-camphorsulfonate or N-benzoxycarbonyl-glycyl-L-proline (ZGP). Many of these chiral aromatic amino alcohols are of pharmacological importance as α- and β-adrenergic blockers, adrenergic compounds, and anti-glaucoma agents. A comparison was made between various N-CBZ-amino acid derivatives as chiral counter ions/chiral mobile phase additives (CMAs). These separations could not be achieved on other normal phase TLC stationary phases including microcrystalline cellulose, alumina and ordinary silica gel plates.     

Separation of abietane-type diterpenoids from Clerodendrum kaichianum Hsu by high-speed counter-current chromatography using stepwise elution

High-speed counter-current chromatography (HSCCC) was successfully used for the separation of abietane-type diterpenoids from the medicinal plant C. kaichianum, which were not separated in our previous study using preparative HPLC. The HSCCC separation employed the lower phases of n-hexane–ethyl acetate–methanol–water (HEMW) 4:5:4:5 and HEMW 4:5:5:4 as the mobile phase for stepwise elution while the upper phase of HEMW 4:5:4:5 was used as the stationary phase. HSCCC separation yielded 90.5 mg of compound 1(kaichianone A), 137.7 mg of compound 2 (kaichianone B), 125.0 mg of compound 3 (teuvincenone E), and 227.6 mg of compound 4 (taxusabietane A) with purities of 95.3%, 97.2%, 97.8%, and 98.6%, respectively, as determined by HPLC. Compounds 1–2 are two new abietane-type diterpenoids while Compounds 3–4 are known abietane-type diterpenoids, analyzed by ESIMS and NMR data. The results demonstrated that HSCCC can be an excellent alternative for other separation methods. The two new compounds showed significant cytotoxicity against ileocecal carcinoma HCT-8 and breast adenocarcinoma MCF-7 cells.     

Investigation of deep eutectic solvents as additives to β‐CD for enantiomeric separations of Zopiclone,Salbutamol, and Amlodipine by CE

The enantioseparation of chiral drugs via CE was first investigated using β‐CD as chiral additive and deep eutectic solvents (DESs) as auxiliary additive. The results showed that improved separation of tested chiral drugs was obtained in the presence of DESs and β‐CD compared to the single β‐CD separation system. With the optimized condition, resolutions of DESs applied β‐CD separation system for rac‐Zopiclone, rac‐Salbutamol, and rac‐Amlodipine increased 3–4.2 times as single β‐CD separation system. The resolutions reached 4.74, 6.37, and 9.67, respectively. The results demonstrate that DESs are viable additives to CD system in CE for the separation of the chiral drugs.