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1.
Zhang J Raglione T Wang Q Kleintop B Tomasella F Liang X 《Journal of chromatographic science》2011,49(10):825-831
The regeneration of ion-pairing reagent distribution on liquid chromatography columns after gradient elution has been well recognized as the cause for long column equilibration time, a major drawback associated with gradient elution reverse phase ion-pair chromatography. To date, the majority of studies have focused on optimizing the separation conditions to shorten the equilibration time. There is limited understanding of the ion-pairing reagent distribution process between the mobile phase and stationary phase in the course of gradient elution, and subsequent column re-equilibration. The focus of this work is to gain a better understanding of this process. An ion-pair chromatographic system, equipped with a YMC ODS C(18) column and a mobile phase containing tetrabutylammonium (TBA) hydroxide as the ion-pairing reagent, was used in the study. The TBA distribution profile was established by measuring its concentration in the eluent fractions collected during the gradient cycle using different column equilibration times with an ion chromatographic method. Furthermore, the analyte retention time was evaluated as the function of the column equilibration time and TBA concentration in the mobile phase. The column equilibration and its impact on the method robustness will also be discussed. 相似文献
2.
Summary The retention behaviour of an homologous series of phosphorylated oligodeoxythymidylic acid (pd(T)5–18) oligonucleotides was studied using reversed-phase ion-pair chromatography with isocratic elution conditions. The effects
of temperature, pH, eluent ionic strength, percentage organic modifier, concentration and alkyl chain length of the ion-pairing
reagent were investigated. The retention behaviour was generally explicable by current theoretical models of ion-pair chromatography.
However, the marked effect of mobile phase pH on the retention of the oligonucleotides was unexpected, and this was ascribed
to the presence of ionisable residual silanols on the surface of the reversed-phase packing material. 相似文献
3.
Simultaneous determination of nitrite and nitrate by normal phase ion-pair liquid chromatography 总被引:1,自引:0,他引:1
Normal phase ion-pair high performance liquid chromatography has been used for simultaneous separation of nitrite and nitrate using tetraethylammonium (TEA)(+) as ion-pairing reagent. The concentration effect of (TEA)(+), buffer salt and pH of the eluent on separation is investigated. The UV detector response at various wavelengths has been optimized. The performance of the proposed method is compared with ion chromatography for quantification of the anions in potable water, wastewater and in food samples, such as spinach and lettuce. 相似文献
4.
A hydrophilic interaction chromatography (HILIC) technique has been developed and validated for determination of common denaturants
(denatonium benzoate, crystal violet and methylene blue) in denaturated alcohol formulations. Among the three different polar
stationary phases (i.e., aminopropyl, cyanoethyl and silica) studied the cyanoethyl phase provided much stronger retention
for the organic cations. It was shown that high efficiencies were reached only with anionic ion-pairing reagent that reduces
the interactions with the silanol groups. The anion ion-pairing strength under HILIC conditions was: acetate < formate < trifluoroacetate
< perchlorate. This study also investigated the effect of various experimental factors on the retention of the cyanoethyl
stationary phase, such as acetonitrile content, pH and ion-pairing anion concentration in the mobile phase. The separation
of three denaturants was achieved in about 8 min with a mobile phase containing 60% (v/v) acetonitrile and 10 mmol L−1 HClO4. The proposed method was validated and applied to the determination of danaturating agents in various Lithuanian denaturated
alcohol formulations. 相似文献
5.
A systematic study of the desorption of different ion-pairing reagents on reversed phase thin-layers
K. Kovács-Hadady 《Chromatographia》1997,45(1):81-90
Summary The absolute concentrations and the concentration distribution of different cationic ion-pairing reagents, such as tetramethylammonium
bromide, tetrabutylammonium bromide, cetyltrimethylammonium bromide and trioctylmethylammonium chloride were studied after
chromatographic development on physically and chemically bonded reversed-phase layers. The combination of the chromatographic
conditions involved three variations. Untreated layers were chromatographed with mobile phases containing the ion-pairing
reagent. Several layers were treated with the ion-pairing reagent prior to the chromatographic run, and methanol-water mixtures
were used as mobile phase. In a third set of experiments both the layer and the mobile phase contained the ion-pairing reagent.
The chromatographic behaviour of acid, neutral and basic model compounds were also studied. For the determination of different
reagents remaining on the layer after the chromatographic run, spectrophotometric, potentiometric methods and capillary electrophoresis
were used. The performance of the analytical methods was evaluated. Results obtained for the absolute concentrations and distribution
of the reagents and the retention data were compared to those obtained on silica gel layers. A discussion of the retention
mechanism is given.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
6.
Previous HPLC determination of atenolol on reversed-phase packings has often required a mobile phase containing three components: organic modifier, buffer and ion-pairing reagent or organic amine. In addition to the complexity of the eluents employed, alkyl sulphonates and organic amines in the mobile phase can reduce the life of silica-based bonded columns. A new simple, rapid and sensitive method—pseudo reversed-phase liquid chromatography/tandem mass spectrometry has been developed for the analysis of atenolol in human plasma using bare silica as the stationary phase coupled with a simple mobile phase consisted of 5% acetonitrile and 95% formate buffer. The optimization of separation is fast and easy. The assay was validated for the concentration range 1–100 ng mL?1 with a detection limit of 1 ng mL?1. Moreover, the silica column was durable with the mainly aqueous eluents. No obvious loss in performance was observed for 30,000 column volumes of eluent. 相似文献
7.
M. M. Britto Q. B. Cass I. C. S. F. Jardim C. A. Montanari H. Y. Aboul-Enein 《Chromatographia》2001,53(1-2):11-16
Summary The partition coefficients, logP
app
RPLC, for a series of propranolol analogues have been determined by reversed phase high performance liquid chromatography. The
hydrochloride salts and free base logP
app
RPLC show that charged and uncharged species can partition into the reversed phase. An extrathermodynamic relationship was found
for logP
app
RPLC measured in two different column stationary phases, C8 and PMOS, suggesting that the same set of compounds experience a similar
trend in these elution systems. The importance of using phosphate and/or MOPS buffer is due to the fact that the latter can
avoid ion-pairing partitioning, but the former does play the same role for PMOS column when the free base is considered. 相似文献
8.
Christopher J. Jones Nellymar MembrenoCynthia K. Larive 《Journal of chromatography. A》2010,1217(4):479-488
Reverse-phase ion-pair high performance liquid chromatography (RPIP-HPLC) and ultra-performance liquid chromatography (RPIP-UPLC) are increasingly popular chromatographic techniques for the separation of organic compounds. However, the fine details of the RPIP separation mechanism are still being debated. Many factors including type and concentration of the ion-pairing reagent, mobile phase pH, organic modifier, ionic strength, and stationary phase all play a role in the overall efficiency and optimization of ion-pairing separations. This study investigates the role that competition between ion-pairing reagents with different steric bulk and hydrophobicity plays in the separation of structural isomers of heparin and heparan sulfate (HS) disaccharides. In addition to providing insights into the mechanism by which RPIP-HPLC can resolve closely related disaccharides, the use of competition between ion-pairing agents could lead to new methods for the separation of larger heparin and HS oligosaccharides. This approach should also be applicable to the analysis of other compound classes, and could lead to a general approach for the chromatographic resolution of mixtures of charged analytes having similar structures. 相似文献
9.
A reversed phase ion-pair gradient liquid chromatographic method has been developed and validated for purity determination of the hydrophilic compound 2,4-disulfonic acid benzaldehyde di-sodium salt (2,4-DSAD) containing both hydrophilic and more lipophilic related impurities. Mixtures of acetonitrile-phosphate buffer containing tetrahexylammonium hydrogen sulfate as the ion-pairing reagent were used as the mobile phase. A linear gradient, which generated simultaneous change in the concentration of organic modifier, buffer concentration and the concentration of ion-pairing reagent, was applied. The method allows detection of impurities at low levels (0.01% w/w). Excellent repeatability for both retention time (RSD< or =0.3%, n = 6) and detector response (RSD = 0.03%, n = 6 for the main peak and RSD = 6%, n = 6, for an impurity at 0.01 area% level) was obtained. The method was shown to be robust for routine analysis and has been successfully transferred to the quality control laboratory. 相似文献
10.
An easy, inexpensive, and accurate method for the analysis of synthetic dyes by means of ion-pair thin-layer chromatography (IPTLC) on mixed sorbent phases containing silica gel G and barium sulfate in an aqueous ethanol system is studied. The effect of the composition of the sorbent phases has a major effect on the hundred-fold relative migration rate, as also does the effect of the ion-pairing reagent as the impregnant. Compact and sharp spot application yields very good binary and ternary separations and enables their clear identification. IPTLC has better separations on mixed sorbent phases, which are not possible on plain mixed phases in thin-layer chromatography. The method can be applied for the trace analysis of synthetic dyes in various natural and synthetic samples. 相似文献
11.
Yan Sun Laixin Luo Fang Wang Jianqiang Li Yongsong Cao 《Analytical and bioanalytical chemistry》2009,395(2):465-471
A novel method based on solid-phase extraction was studied for the extraction of amitrole (3-amino-1,2,4-triazole), and its
residue determination in apples has been developed. The samples were derivatized with 4-chloro-3,5-dinitrobenzotrifluoride
(CNBF). The derivatization conditions and the influence of elution composition on the separation were investigated. In pH
9.5 H3BO3–Na2B4O7 media, the reaction of amitrole with CNBF was complete at 60°C after 30 min. The separation of derivatized amitrole was achieved
at room temperature within 13 min by gradient elution mode with cetyltrimethylammonium bromide in mobile phase as ion-pair
reagent. The method correlation coefficient was 0.9996, in concentrations ranging from 1.66 to 415 mg L−1. The calculated recoveries of the proposed method were from 94.17% to 105.67%, and relative standard deviations were 1.57%
to 6.44% in the application to the quantitative determination of amitrole in apples. The detection limit of amitrole was 0.10 mg L−1 with a signal-to-noise ratio of 3.
Figure Residue determination of amitrole in apple by ion-pairing high-performance liquid chromatography 相似文献
12.
A method using a solid phase extraction (SPE) and ion-pair liquid chromatography-electrospray-tandem mass spectrometry (LC-ES-MS/MS) was developed for determination of amphetamine (Amp) and methamphetamine (mAmp) in urine samples. A reversed phase C18 column was utilized for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion-pairing reagent. MS2 was employed for quantitative determination. In addition, d8-amphetamine and d8-methamphetamine were used as internal standards. An Oasis HLB SPE cartridge, which has hydrophilic and lipophilic functions, was utilized for sample pre-treatment. Recoveries ranging from 97.3 to 102.1% were measured. Good linear ranges, 5-500 ng/ml, for Amp and mAmp were determined. The detection limit of each analytical compound, based on a signal-to-noise ratio of 3, was approximately 1 ng/ml. The applicability of this newly developed method was examined by analyzing several urine samples from drug users. 相似文献
13.
E. N. Shapovalova M. N. Ofitserova E. V. Savost'yanova O. A. Shpigun 《Journal of Analytical Chemistry》2001,56(2):160-165
The chromatographic behavior of heavy-metal (Pb, Cd, Cu, Hg, and Ni) complexes of unithiol was studied by ion-pair reversed-phase chromatography using new ion-pair reagents: tetrabutylphosphonium and tributylhexadecylphosphonium bromides. The dependence of the retention of metal unithiolates on the nature and concentration of ion-pair reagents, concentrations of an organic solvent and inorganic salts in the mobile phase, and the pH of the mobile phase was studied. It was found that the retention of complexes increases upon increasing the hydrophobicity and concentration of the ion-pair reagent and upon decreasing the concentrations of acetonitrile and inorganic salts (NaClO4 and NaNO3). Optimal conditions of the separation of Pb, Cd, Cu, Hg, and Ni unithiolates were selected, and the possibility of their separate determination in a mixture was demonstrated. Concentrations of metals in process water were determined. 相似文献
14.
P. Morin M. B. Amran S. Favier R. Heimburger M. Leroy 《Fresenius' Journal of Analytical Chemistry》1991,339(7):504-509
Summary Speciation and quantitative analysis of arsenical compounds are performed by using high-performance liquid chromatography (HPLC) with direct UV detection. Ion chromatography has been used to separate mixtures of arsenical compounds (arsenite, MMA, DMA, arsenate) on an anion-exchange column using phosphate buffer (1 mmol/l, pH=5.3) as eluent. Ion -pair reversed-phase chromatography has been investigated to resolve mixtures of arsenite, arsenate, MMA, DMA, arsenobetaine and arsenocholine on an octadecyl-bonded silica column using water as mobile phase (pH=7.3) and tetrabutylammonium cation as ion-pairing reagent. The influence of several parameters (pH, the ion-pairing reagent concentration or the amount of methanol in the mobile phase) has been studied to determine the best chromatographic conditions. 相似文献
15.
A simple high-performance liquid chromatographic method – ion-pair reversed- phase high performance liquid chromatography (RPIC) has been developed and employed for the analysis of zoledronic acid and its related substances in bulk material and commercial dosage forms. The mobile phase was a mixture of methanol (20%) and 5 mmol L–1 phosphate buffer (80%) containing 6 mmol L–1 tetrabutylammonium bromide, adjusted to pH 7.0 with sodium hydroxide. C8 column was used as the stationary phase. The chromatographic conditions were optimized. The active ingredient – zoledronic acid was successfully separated from its related substances, including remained imidazol-1-yiacetic acid in the synthesis of zoledronic acid and other possible impurities of oxidation and decomposition. The excipients did not interfere with the determination of zoledronic acid in commercial dosage formulations. The method was rapid, simple, accurate and reproducible. It was not only successfully employed for the assay of zoledronic acid in bulk material and pharmaceutical dosage forms but also for the determination of its related substances. 相似文献
16.
The retention properties of calcitonins on a reversed-phase column are examined using salmon calcitonin as the model compound. The effect of the concentration of organic modifier, buffer strength, pH of the mobile phase, and ion-pair reagent are studied. In the absence of an ionic modifier in the eluent the calcitonin peak shapes are not symmetrical. The addition of 0.1% trifluoroacetic acid (TFA), however, results in good peak characteristics without the need to add nonvolatile salts. The retention of the calcitonins was found to be very sensitive to the concentration of the organic modifier (acetonitrile) present in the mobile phase. A change of pH between 2 and 5 has only a slight effect of the k' of salmon calcitonin, but the k' increases significantly at higher pH values. The addition of a phosphate buffer to the mobile phase and an increase in the buffer concentration (0-0.2 M) causes a decrease in the retention of salmon calcitonin. Evidence shows that reproducible, quantitatively measurable data can be obtained using reversed-phase chromatography if the ion-pairing reagent and organic modifier concentrations are carefully controlled. The system also shows a good selectivity for the calcitonin series. Therefore, both highly selective methods (qualitative) as well as quantitative methods for analytical, pharmaceutical, and manufacturing use can be developed by adjusting the high-performance liquid chromatography (HPLC) conditions as discussed. 相似文献
17.
A highly sensitive method has been developed for the determination of titanium(IV) and iron(III) by ion-pair reversed phase liquid chromatography using sodium 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) as a precolumn chelating reagent. The metal - Tiron chelates were separated on a C18 (ODS) column; the mobile phase was a 2:8 (v/v) mixture of acetonitrile and acetate buffer (0.04 mol/L, pH 6.2) containing 2.0 × 10?3 mol/L Tiron, 0.04 mol/L tetrabutylammonium bromide, and 0.1 mol/L potassium nitrate. The detection limits for titanium(IV) and iron(III) are 0.5 and 2.0 μg/L, respectively. The method has been applied to the simultaneous determination of titanium(IV) and iron(III) in river water samples and has furnished highly precise results. 相似文献
18.
《Analytical letters》2012,45(2):328-339
A new method for nimesulide was developed using ion-pair reversed phase liquid chromatography and tetrabutylammonium hydrogen sulfate as the ion-pairing reagent. The influence of the ion pair forming reagent concentration, pH, and mobile phase composition on the retention time of nimesulide were studied. The optimum experimental conditions included a C18 column, a mobile phase of a 50/50 (v/v) mixture of acetonitrile and 15 mM phosphate buffer (pH 8.00) containing 6 mM tetrabutylammonium hydrogen sulfate, 25°C, isocratic elution, a flow rate of 1 mL/min, a run time of 10 minutes, and photodiode array detection at 404 nm. From the analysis of the results, the mechanism for the separation of nimesulide was also established. The retention time for nimesulide was 4.76 ± 0.05 min. The method was linear between concentrations of 9 µg/mL to 64 µg/mL, with limits of detection and quantification of 1.111 µg/mL and 3.390 µg/mL, respectively. The method is simple, rapid, accurate, and precise, and successfully applied for the determination of nimesulide in pharmaceutical products. 相似文献
19.
Toyohide Takeuchi Budhi Oktavia Lee Wah Lim 《Analytical and bioanalytical chemistry》2009,393(4):1267-1272
Methyl-capped poly(ethylene oxide) moieties were chemically bonded to silica gel using an amine-reactive modification reagent
and evaluated as the stationary phase for ion chromatography. In this work, primary amino groups of an aminopropylsilica packing
material were reacted with methyl-PEO12-NHS ester (succinimidyl-{[N-methyl]-dodecaethyleneglycol} ester) in phosphate buffer (pH 7.0) at room temperature. The prepared poly(ethylene oxide)-bonded
stationary was evaluated for the separation of inorganic anions, and the retention behavior of inorganic anions on the prepared
stationary phase was examined. The elution order of the investigated anions was the same as that observed in common ion chromatography.
Both cations and anions of the eluent affected the retention of the analyte anions. Ion exchange was involved for the retention
of analyte anions, although the present stationary phase does not possess any discrete ion-exchange sites. The stationary
phase was applied to the separation of trace anions contained in tap water and a rock salt. 相似文献
20.
Hsin-Chang Chen 《Talanta》2009,79(2):442-445
This paper describes the analysis of perchlorate (ClO4−) in surface water samples by a rapid and reliable ion-pair hollow-fiber liquid-phase microextraction (HF-LPME) method coupled with flow-injection electrospray ionization tandem mass spectrometry (ESI-MS-MS) technique. The effects of the type and concentration of ion-pairing reagents, extraction time, temperature and pH value on the quantitative extraction of perchlorate by ion-pair HF-LPME were investigated and optimized. Di-n-hexyl ammonium acetate (DHAA) was employed to form an extractable ion-pair complex with aqueous perchlorate. The characteristic ions [ClO4-ClO4-DHA]− at m/z 384.6 and 386.7 were observed in the ESI negative-ionization mode. The predominant product ions [ClO4]− at m/z 99 and 101 were used for quantitation and to maximize the detection selectivity and sensitivity. The limit of detection (LOD) was 0.5 μg/L. The reliability and precision of the standard addition method of ion-pair HF-LPME for the determination of trace levels of perchlorate in surface water were demonstrated. 相似文献