The separations using pure water as a mobile phase in liquid chromatography using polar-embedded stationary phases (original) (raw)
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Journal of Chromatography A, 2004
The solvation parameter model is used to characterize the retention properties of a 3-aminopropylsiloxane-bonded (Alltima amino), three 3-cyanopropylsiloxane-bonded (Ultrasphere CN, Ultremex-CN and Zorbax SB-CN), a spacer bonded propanediol (LiChrospher DIOL) and a multifunctional macrocyclic glycopeptide (Chirobiotic T) silica-based stationary phases with mobile phases containing 10 and 20% (v/v) methanol-water. The low retention on the polar chemically bonded stationary phases compared with alkylsiloxane-bonded silica stationary phases arises from the higher cohesion of the polar chemically bonded phases and an unfavorable phase ratio. The solvated polar chemically bonded stationary phases are considerably more hydrogen-bond acidic and dipolar/polarizable than solvated alkylsiloxane-bonded silica stationary phases. Selectivity differences are not as great among the polar chemically bonded stationary phases as they are between the polar chemically bonded phases and alkylsiloxane-bonded silica stationary phases.
Journal of the Brazilian Chemical Society, 2022
Poly(ethylene oxide-co-dimethylsiloxane) was thermally immobilized on silica particles-Si(PEO)-to separate small polar compounds with water-rich mobile phases. Poly(ethylene oxideco-dimethylsiloxane) content on Si(PEO) stationary phase was optimized using a central composite design. Infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis morphologically and structurally characterized the optimized material. Separation of standard test mixtures showed that the Si(PEO) phase had a typical reversed-phase elution order. However, the Si(PEO) phase retained polar compounds better than C 18 or aqueous C 18 phases under waterrich mobile phases. Under this condition, small changes in the acetonitrile fraction resulted in a marked increase in the retention of some polar drugs on the Si(PEO) phase. A typical condition observed in per aqueous liquid chromatography separations, a more environmentally friendly liquid chromatography approach. On the other hand, hydrophobic compounds showed lower mass transfer rates due to their low solubility in the aqueous mobile phase. Thus, the Si(PEO) phase was more suitable and efficient for separating polar or hydrophilic compounds.
Sains Malaysiana, 2021
Poly(ethylene oxide) (PEO) bonded stationary phase has been synthesized by a single and simple step reaction. Poly(ethylene glycol monomethyl ether p-toluene sulfonate) (tosylated-PEO, molecular weight 900, n ≈ 18) was chemically bonded to 3-aminopropyl silica (TSKgel NH2-60, 5 µm particle size, and 60 Å mean pore diameter). The prepared stationary phase was able to separate polar compounds such as phenolics and nucleobases in capillary liquid chromatography. The retention and separation of phenolics and nucleobases could be achieved under isocratic elution condition. Nucleobases such as thymine, adenine, uracil, uridine, cytidine and toluene and phenolics (phenol, pyrocatechol, pyrogallol) were baseline separated in less than 6 min using 98% acetonitrile and less than 7 minutes using 80% acetonitrile, respectively. We demonstrated that the retention of nucleobases as analyte decreased with decreasing eluent concentration. The retention of these polar compounds was believed to be ba...
Suitability of stationary phase for LC analysis of biomolecules
Critical Reviews in Food Science and Nutrition, 2019
Biologically active compounds such as carotenoids/isoprenoids, vitamins, steroids, saponins, sugars, long chain fatty acids, and amino acids play a very important role in coordinating functions in living organisms. Determination of those substances is indispensable in advanced biological sciences. Engineered stationary phase in LC for the analysis of biomolecules has become easier with the development of chromatographic science. In general, C 18 column is being used for routine analysis but specific columns are being used for specific molecule. Monolithic columns are found to have higher efficiency than normal column. Among recent introduction, triacontyl stationary phases, designed for the separation of carotenoid isomers, are widely used for the estimation of carotenoids. In comparison to conventional C 18 phases, C 30 phases exhibited superior shape selectivity for the separation of isomers of carotenoids. It is also found useful for better elution and analysis of tocopherols, vitamin K, sterols, and fatty acids. Vitamin K, E, and their isomers are also successfully resoluted and analyzed by using C 30 column. Amino bonded phase column is specifically used for better elution of sugars, whereas phenyl columns are suitable for the separation and analysis of curcuminoids and taxol. Like triacontyl stationary phase, pentafluorophenyl columns are also used for the separation and analysis of carotenoids. Similarly, HILIC column are best suited for sugar analysis. All the stationary phases are made possible to resolute and analyze the target biomolecules better, which are the future of liquid chromatography. The present article focuses on the differential interaction between stationary phase and target biomolecules. The applicability of these stationary phases are reported in different matrices.
Shape selectivity in embedded polar group stationary phases for liquid chromatography
Analytical and Bioanalytical Chemistry, 2009
Seven columns with embedded polar functionality were evaluated for use in liquid chromatography with a focus on molecular shape recognition. Tests based on Standard Reference Material 869b Column Selectivity Test Mixture for Liquid Chromatography and the Tanaka test indicate that only two of the phases are slightly shape selective at 20°C. The shape recognition characteristics of the phases appear to be directly related to the density of the embedded polar ligands and the temperature of the separation, consistent with trends observed with conventional hydrocarbon phases.
ELECTROPHORESIS, 2006
co-[3-(methacryloylamino)propyl]-trimethylammonium} as a stationary phase for capillary electrochromatography A cationic polyacrylamide-based stationary phase was synthesized and characterized for CEC. The stationary phase was prepared by radical copolymerization of N-isopropylacrylamide (NIPAAm) and (3-(methacryloylamino)propyl)trimethylammonium chloride (MAPTA), producing a copolymer attached to 5 mm porous silica particles. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to characterize the copolymer. Under capillary electrochromatographic conditions, the poly-NIPAAm-co-MAPTA stationary phase showed to be stable in a wide pH range. The amino groups in the MAPTA provided an anodic EOF for CEC separation. The electroosmotic mobility changed less than 10% when the pH of the mobile phase was changed from 2 to 12. The run-to-run RSD of analyte migration time was less than 1.5% (n = 3), and the RSD of peak area was less than 3% (n = 3). The day-today RSD for migration time was less than 2% (n = 3). The polar groups present in the stationary phase contributed to the selectivity of the phase providing for hydrophilic interactions. In the separation of a series of neutral and acidic compounds, the stationary phase shows a mixed-mode separation mechanism with both hydrophobicity and hydrophilicity contributing to the separation.
Separation Science Plus, 2019
Stationary phase development for hydrophilic interaction chromatography is rapidly gaining attention due to its versatile application in the separation of diversified solutes. Considering the hydrogen bonding property of urea, we designed and synthesized double-alkylated L-lysine derived urea containing short and long chain systems for use as stationary phases in hydrophilic interaction chromatography after immobilizing onto silica. The compounds were characterized by elemental analysis, NMR, and Fourier transform infrared spectroscopy. The compounds were further investigated by thermogravimetric analysis and diffuse reflectance infrared Fourier transform spectroscopy after immobilization onto silica. The effect of chain length in hydrophilic interaction chromatography, the phases were used for the separation of nucleic acid bases, nucleosides, and sulfa drugs. Enhanced selectivity was observed for both phases. However, the L-lysine-derived urea-containing phase with short alkyl chains showed better separation ability than did the phase with longer alkyl chains. The former also showed better performance in terms of other chromatographic parameters such as efficiency, resolution, and asymmetry as compared to the latter.
The role of organic modifiers on polar group selectivity in reversed-phase liquid chromatography
Journal of Chromatography A, 1978
The influence of the organic modii?ers methanol (MeOH), acetonitrile (AN) and tetrahydrofuran (THF) on polar group selectivity in reversed-phase liquid chromatography has been studied. In order to elucidate polar group e&c&+, we have Erst explored the influence of the surface coverage of bonded phase on selectivity. Using a series of synthesized n-octyl bonded phases, we have been able to observe significant differences in group contribution with bonded phase coverage, the largest differences arising from MeOH-Hz0 as mobile phase and the least from THF-Hz0 as mobile phase. The importance of using phases that minimize accessible silanol groups in order to study the influence of the mobile phase has been emphasiid. We have selected a high coverage n-octyl phase that is silanized for these studies. In order to examine polar group effects, we have normalized the methylene group increment in the MeOH-H20, AN-H,0 and THF-H,O binary phases. As the hydrophobic selectivity is thus roughly normalized, meanitigful relative polar group contributions are observed. Plots of log k' (THF-H,O) vs. log k' (MeOH-H20) reveal particularly striking polar group differences. The practical usefulness df the plots is shown in the peak reversal of solute mixtures with the two mobile phases. Further studies reveal that polar group selectivity can be poGerfully controlled using ternary phases of MeOH-THF-HLO. Thus, the choice of mobile phase can greatly influence separation in reversed-phase liquid chromatography. INI-FtODUClTON At present reversed-phase liquid chromatography (RPLC) using n-al?+ bonded phases is the most frequently selected separation mode in high-performance liquid chromatography (HPLC). It is well-known that RPLC is an excellent method to separate substances based on size or alkyl group structure, as a conseqtience of hydrophobic or solvophobic interactions1-5. What may not be suf6ciently realized is that RPLC can also be a highly selective method for separation based on polar group differences. It is known that hydrophobic selectivity in RPLC is a sensitive function of * To whom reprint requests should be sent. N. TANAKA, H. GOODE=, B. L. KARGER the mobile phase, more specZcally the type and amount of organic modifier mixed with water1sz*5. We should also note that the role of the mobile phase has been studied in the past using open-bed technique+'. The composition of the mobile phase can play a significant role on (1) reten: tion; (2) hydrophobic group seIectivity and (3) polar group selectivity-That mobile phase control can be a potentially powerful tool for the optimization of separation has been demonstrated in a recent paper, dealing with binary and ternary phases'. However, it is clear that an understanding of the role of mobile phase composition on retention and selectivity is difficult to achieve because of several facrors. First, as coyectly pointed out by Karch et al., a well-defined and reproducible stationary phase IS required before one can begin to understand mobile phase or bonded phase eff&tsg. Second, without app ro p riate normalization, both hydrophobic and polar group selectivity can simultaneously change with organic modiGer type and composition. Third, there is a Iack of a full understanding of the mechanism of retention with bonded pha&l~loJ1. We have undertaken an examination of the role of organic modifier(s) on selectivity in RPLC. As we have already explored to some extent hydrophobic se-lectivity2, our main emphasis will be on polar group selectivity-In this paper we wish to report our initial efforts in this direction_ We first examine in detail the role of the quality of the bonded phase on retention and group selectivity of non-ionic polar substances, as well as to a limited extent ionic substances. We next turn to a comparison of binary solvents in terms of polar group selectivity. For this study, we have normalized the hydrophobic selectivity in order to examine more meaningfully polar group selectivity. Large variations in polar group selectivity are observed when various organic modifiers are used. Indeed, complete reversals in elution order for selected substances from one mobile phase to another can be found. Polar group selectivity under normalized hydrophobic conditions is also examined in ternary phases, and _&n&ant changes with composition are again seen. It is clear that mobile phase composition can significantly control separation in RPLC. IixPERIMENTAL Equipment i An HPLC instrument was setup from Waters Assoc. (Milford, Mass., U.S.A.) components, consisting of a M6OOOA solvent delivery system, U6K injector, R401 refractive index detector and M4lO absorbance monitor operated at 254 nm. The columns were maintained at 30 t 0.1" by submerging them in a water bath. Co?umns The packing consisted of 5-pm Hypersil (Shandon Southern, Sewickley, Pa., U.S.A.). Chemical bonding was performed with octyldimethylchlorosilane (Silar Labs., Scotia, N-Y., U.S.A.), using conditions similar to those of Hemetsberger et aZ_12_ Silaxiization after bonding was done in a similar fashion using hexamethyldisilazine and trimethylchlorosilane (Silar Labs.). The stationary phase was packed into columns of 15 cm x 4.6 mm I.D. tubing (Analabs, North Haven, Corm., U.S.A.) using conventional high-pressure slurry techniques.