Aqueous Methanol Mobile Phase Research Articles

Relationships of Enantioselective Retention of Chiral Oxazolopyrroloquinolones on a Stationary Phase with Grafted Ristocetin А Antibiotic from Aqueous Methanol Solutions

The mechanisms of retention and separation of the enantiomers of chiral oxazolopyrroloquinolones on a stationary phase with graftеd macrocyclic antibiotic ristocetin A under conditions of high-performance liquid chromatography with aqueous methanol mobile phases have been studied. The retention factor was found to decrease monotonically when the CH3OH concentration in the mobile phase increased to 90 vol %; then it slightly increased as the composition of the mobile phase approached pure methanol. The thermodynamics of adsorption of oxazolopyrroloquinolones in different regions of this dependence was studied. A mathematical model has been proposed; it describes well the experimental data and allows for analyte solvation in the mobile phase and competitive adsorption (with mobile phase components) on a chiral selector. The results were compared with previously obtained data for water–acetonitrile mobile phases. The reasons for the observed differences were discussed.

Mouse pharmacokinetics and metabolism of the phenylurea thiocarbamate NSC 161128

NSC 161128, a phenylurea thiocarbamate, displays activity against the NCI60 anti-cancer cell line panel and xenograft models. The metabolite N-methyl-N'-phenylurea (M10) has been detected in animal plasma; however, detection and quantification of other putative NSC 161128 metabolites have not been undertaken. The purpose of this study was to characterize the pharmacokinetics and metabolism of NSC 161128 in mice and under in vitro conditions. An LC-MS/MS assay was developed to evaluate stability and in vitro metabolism of NSC 161128 in liver microsomes and S9 fractions. Single-dose pharmacokinetic profiles for NSC 161128 and its metabolite M10 were obtained following intraperitoneal (I.P.) administration. A sensitive and specific positive ionization LC-MS/MS method for measuring NSC 161128 and its metabolites was developed. HPLC separation was achieved under gradient elution using an aqueous methanol mobile phase containing 0.05% formic acid and 0.05% ammonium hydroxide. The assay was linear over the range 1.0-1000ng/mL. NSC 161128 was stable in aqueous solution and tissue culture media, but not in plasma, where rapid degradation of NSC 161128 to the metabolite M10 was observed. Following I.P. administration of a 200mg/kg dose to male CD1 mice, the peak plasma concentration of NSC 161128 was 255ng/mL after 5min with a plasma half-life of 138min. Potential bioactivation of NSC 161128 was explored using mouse S9. An analytical LC-MS/MS method was successfully developed for the detection and quantification of NSC 161128 and its metabolites. These results increase the understanding of NSC 161128 pharmacokinetic and metabolic properties.

Simultaneous Determination of Fifteen Polyphenols in Fruit Juice Using Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry Combining Dispersive Liquid-Liquid Microextraction.

Polyphenols are secondary metabolites of plants and used as effective antioxidants in dietary supplements, whose main sources are fruits, vegetables, and grains. To clarify the content and distribution of polyphenols in different fruit species samples accurately, a rapid and sensitive ultrahigh-pressure liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method combining dispersive liquid-liquid microextraction (DLLME) was developed for quantitative determination of fifteen polyphenol compounds in fruit juice. In this method, the targets were first extracted from 1 g of fruit juice sample using 10 mL of 80% ethanol solution by ultrasonic-assisted extraction (UAE). Then, 1.0 mL of UAE extracted solution, 60 μL of n-octanol and 2.0 mL of H2O were performed in the following DLLME procedure. A C18 reversed-phase column, ZORBAX SB (100 × 4.6 mm, 3.5 μm), was proposed under gradient elution with 0.1% formic acid aqueous solution and methanol mobile phases for the determination of 15 polyphenols, allowing us to obtain polyphenolic profiles in less than 23.0 min. Under the optimum conditions, the enrichment factors ranged from 162 to 194. The results showed that the 15 polyphenols had linear correlation coefficients (R2) more than 0.99. The limits of detection (LODs) were between 18.3 and 103.5 ng/g, and the average recoveries were between 96.9 and 116.3% with interday relative standard deviations (RSDs) ranging from 4.4 to 8.2% in all cases. The method was successfully applied to the analysis of real fruit juice samples and presented itself as a simple, rapid, practical, and environment-friendly technique.

New Evidence of the Bidentate Binding Mode in 3-MBA Protected Gold Clusters: Analysis of Aqueous 13-18 kDa Gold-Thiolate Clusters by HPLC-ESI-MS Reveals Special Compositions Aun(3-MBA)p, (n = 48-67, p = 26-30).

Gold clusters protected by 3-MBA ligands (MBA = mercaptobenzoic acid, –SPhCO2H) have attracted recent interest due to their unusual structures and their advantageous ligand-exchange and bioconjugation properties. Azubel et al. first determined the core structure of an Au68-complex, which was estimated to have 32 ligands (3-MBA groups). To explain the exceptional structure-composition and reaction properties of this complex, and its larger homologs, Tero et al. proposed a “dynamic stabilization” via carboxyl O–H––Au interactions. Herein, we report the first results of an integrated liquid chromatography/mass spectrometer (LC/MS) analysis of unfractionated samples of gold/3-MBA clusters, spanning a narrow size range 13.4 to 18.1 kDa. Using high-throughput procedures adapted from bio-macromolecule analyses, we show that integrated capillary high performance liquid chromatography electrospray ionization mass spectrometer (HPLC-ESI-MS), based on aqueous-methanol mobile phases and ion-pairing reverse-phase chromatography, can separate several major components from the nanoclusters mixture that may be difficult to resolve by standard native gel electrophoresis due to their similar size and charge. For each component, one obtains a well-resolved mass spectrum, nearly free of adducts or signs of fragmentation. A consistent set of molecular mass determinations is calculated from detected charge-states tunable from 3− (or lower), to 2+ (or higher). One thus arrives at a series of new compositions (n, p) specific to the Au/3-MBA system. The smallest major component is assigned to the previously unknown (48, 26); the largest one is evidently (67, 30), vs. the anticipated (68, 32). Various explanations for this discrepancy are considered. A prospective is given for the various members of this novel series, along with a summary of the advantages and present limitations of the micro-scale integrated LC/MS approach in characterizing such metallic-core macro-molecules, and their derivatives.

Influence of pressure on the retention of resorcinarene-based cavitands

The thermodynamics of the retention mechanism of resorcinarene-based cavitands in RPLC as well as the nature of the binding sites have been studied recently. In the present study, the influence of pressure on the retention of the cyclic tetramers on alkylsilyl and polar-embedded C8 and C18 stationary phases is investigated using aqueous methanol mobile phase. The pressure effect for cavity-shaped molecules has been scarcely studied so far. We observed that the retention factors of the analytes increased with the increase of the average column pressure (1–400 bar) when using restricting capillary tubes. The calculated molar volume changes were negative, between −ΔVm = 5–19 mL/mol on all types of stationary phases. Comparing the different stationary phases, we found that the molar volume changes for both the apolar and more polar analytes were twice larger on the Hypersil BDS (base deactivated silica) than on the XTerra columns and they were independent of the length of the alkyl chains of the stationary phases.

Liquid Chromatography for Analysis of Metformin in Myrmeleon sp.

Myrmeleon sp is a typical of insect larva which has been used in Indonesia for diabetes treatment. However, there is no sufficient scientific report explaining the bioactive compounds in this insect. Based on our preliminary research, this insect contained metformin, i.e. one of bioactive compounds for the treatment of type-2 diabetes. Therefore, this study is focused on the development of separation technique using high performance liquid chromatography (HPLC) on a reverse phase C-18 column with UV detection to identify and quantify metformin in methanol extract of Myrmeleon sp. Several parameters of HPLC method were optimized with respect to high resolution of separation and accurate determination of metformin. Satisfied separation was obtained under gradient elution mode using aqueous methanol mobile phase varied from 50-90 % of methanol with flow rate of 0.5 mL/min and detection wavelength of 233 nm. The method performed total separation for all compounds in less than 11 minutes. Spiking technique was chosen for metformin identification and quantitation. Metformin in extract Myrmeleon sp was eluted at retention time (t R ) of 4.095 minutes, similarly with retention time of standard metformin of 4.092 minutes. The quantity of metformin in Myrmeleon sp can be simply determined by comparing the additional area of standard metformin with area of metformin from extract Myrmeleon sp . The results confirmed that methanol extract of Myrmeleon sp contained anti-diabetes compound of metformin of 0.58 mg/g Myrmeleon sp larvae with acceptable coefficient variation of 5.56 %.

Determination of polyphenolic profiles by liquid chromatography-electrospray-tandem mass spectrometry for the authentication of fruit extracts.

Liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) was applied to the analysis and authentication of fruit-based products and fruit-based pharmaceutical preparations. A Kinetex C18 reversed-phase column under gradient elution with 0.1% formic acid aqueous solution and methanol mobile phases was used for the simultaneous determination of 26 polyphenols, allowing an acceptable separation in less than 22min. Instrumental quality parameters such as limits of detection (LOD, values between 12 and 14μg/L for 19 of the 26 analyzed polyphenols), linearity (r (2) > 0.991), run-to-run and day-to-day precisions (relative standard deviation (RSD) values lower than 9.9 and 13.5%, respectively), and accuracy (relative errors lower than 8%) were established. A simple extraction method, consisting of a sample sonication with acetone/water/hydrochloric acid (70:29.9:0.1 v/v/v) and centrifugation, was proposed. Two calibration procedures, external calibration using standards prepared in water and standard addition, were evaluated for polyphenol quantification in several grape and cranberry fruits and processed fruit products. For a 95% confidence level, no statistical differences were observed between the two calibration methods (p values between 0.06 and 0.95), denoting that external calibration was suitable enough for the quantitative analysis of polyphenols in fruit-based products. The proposed LC-ESI-MS/MS method was then applied to the analysis of polyphenols in 23 grape-based and cranberry-based natural products and pharmaceutical preparations. Polyphenolic concentration data was then analyzed by principal component analysis (PCA) to extract information of the most significant profile data contributing to authentication of natural extracts according to their fruit of origin.

Mouse pharmacokinetics and metabolism of the curcumin analog, 4-piperidinone,3,5-bis[(2-fluorophenyl)methylene]-acetate(3E,5E) (EF-24; NSC 716993).

Curcumin, a keto-enol constituent of turmeric, has in vitro and in vivo antitumor activity. However, in vivo potency is low due to poor oral absorption. The mono-carbonyl analog, 3,5-bis[(2-fluorophenyl)methylene]-4-piperidinone acetate (EF-24, NSC 716993), exhibited broad-spectrum activity in the NCI anticancer cell line screen and potent antiangiogenesis activity in a HUVEC cell migration assay. The purpose of this study was to characterize the preclinical pharmacology of EF-24 in mice. EF-24 plasma stability, protein binding, pharmacokinetics, and metabolism were characterized utilizing an LC/MS/MS assay. An LC/MS/MS assay incorporated protein precipitation with methanol, reverse-phase HPLC separation under gradient elution using an aqueous methanol mobile phase containing 0.1 % formic acid, and positive electrospray ionization detection of the m/z 312 > 149 transition for EF-24. The assay was linear over the range 7.8-1,000 nM. Plasma protein binding was >98 % with preferential binding to albumin. EF-24 plasma disposition in mice after i.v. administration of a 10 mg/kg dose was best fit to a 3-compartment open model. The terminal elimination half-life and plasma clearance values were 73.6 min and 0.482 L/min/kg, respectively. EF-24 bioavailability was 60 and 35 % after oral and i.p. administration, respectively. NADPH-dependent metabolism of EF-24 loss in liver microsomal preparations yielded several metabolites consistent with EF-24 hydroxylation and reduction.

The simultaneous determination of vitamins A, E and β-carotene in bovine milk by high performance liquid chromatography–ion trap mass spectrometry (HPLC–MSn)

Bovine milk is considered to be a good dietary source of vitamins A, E and β-carotene. This paper describes a robust method for the simultaneous determination of these compounds using high performance liquid chromatography–ion trap mass spectrometry (HPLC–MSn) as the determinative step. The compounds were separated with a 5 μm Polaris 2.1 × 150 mm C18-A column and an aqueous-methanol mobile phase and the levels determined using the MS2 fragments (vitamin A, m/z 213 and m/z 199, vitamin E m/z 165 and β-carotene m/z 413). The HPLC–MSn was operated in the positive ion APCI mode. The method was validated using repeatability studies, duplicate analyses, recovery experiments, proficiency study data and comparison with previously validated high performance liquid chromatographic ultraviolet/visible (HPLC–UV/Vis) and fluorescence (HPLC–Fl) procedures used in our laboratory. Expanded measurement uncertainties were similar for HPLC–MSn, HPLC–UV/Vis and HPLC–Fl, e.g. vitamin A 45 μg/100 ml, HPLC–MSn ±8%, HPLC–UV ±9%; vitamin E 150 μg/100 ml, HPLC–MSn ±11%, HPLC–Fl ±9%; β-carotene 12 μg/100 ml, HPLC–MSn ±18%, HPLC–Vis ±21%.

Selectivity Tests of Stationary Phases for Reversed-Phase HPLC

The retention and selectivity properties of 17 columns for reversed-phase HPLC were characterized using classical Galushko, Engelhardt, and Walters chromatographic tests; homologous alkylbenzene and LFER tests in aqueous acetonitrile and aqueous methanol mobile phases; and, finally, isomeric naphthalene disulfonic acids (NDSA) tests. The column properties were compared using the chemometric approach—cluster analysis. The results of simple hydrophobicity and silanol activity tests using relative retention of phenol, aniline, isomeric toluidines, and other compounds strongly depend on the mobile phase. The results of the alkylbenzene methylene and phenyl selectivity tests take into account the effects of the composition of the two-component aqueous-organic mobile phase. The LFER tests distinguish the selective polar interactions of the stationary phase. The alkylbenzene and LFER tests allow column characterization with respect to the column hydrophobicity and polar selectivity in a medium composition range of aqueous-organic mobile phases, but the results strongly depend on the type of the organic solvent (acetonitrile or methanol) and cannot be extrapolated to highly aqueous mobile phases. The NDSA tests performed in highly aqueous mobile phases take into account the effects of column hydrophobicity and ionic exclusion. The results are not affected by the solvation of stationary phase by organic solvents and can be used to characterize the column properties in highly aqueous mobile phases.

Microchip electrospray: Cone-jet stability analysis for water–acetonitrile and water–methanol mobile phases

Changes in mobile phase composition during high performance liquid chromatography (HPLC) gradient elution coupled to mass spectrometry (MS) sensitively affect electrospray operation modes. In this work, we identify the influences of dynamic changes in bulk conductivity on the cone-jet stability island for aqueous acetonitrile and aqueous methanol mobile phases commonly used in reversed-phase HPLC. Bulk conductivities of the mobile phases were varied by adding different amounts of formic acid. A commercial microchip-HPLC/ESI-MS configuration was modified to enable in situ electrospray diagnostics by frequency analysis of the microchip emitter current and spray imaging. This approach facilitated the detection of different spray modes together with their onset potentials. The established spray modes are described and the differences in onset potentials and stability regions explained by the physicochemical properties of the electrosprayed liquid.

Quantitative assessment of xanthone derivatives inSwertia chirata(Wall.) by RP-HPLC with UV detection

The chromatographic profile of xanthones found in Swertia chirata was studied by HPLC using a C18 reversed phase column and aqueous methanol mobile phase using UV absorption at 260 nm. RP-HPLC method was developed and validated for the determination of two xanthone derivatives, 2, 8-dihydroxy-1, 6-dimethoxyxanthone (SR1) and 1, 2, 6, 8-tetrahydroxyxanthone (SR2) in leaves and rhizomes of S. chirata. The HPLC fingerprints of four batches of herbal samples from different regions of Uttarakhand Himalaya showed similar chromatographic patterns. The retention time of markers peak in the HPLC fingerprint were determined as an important parameter for identification. In this herb, SR1 and SR2 were quantitatively determined using a validated reversed phase HPLC method. The bioactives of S. chirata were quantified and their variation was studied in cultivated and wild species with season and altitude to infer about prime of potency and proper harvesting period. The limit of detection obtained for the analytes were in the range of 0.86–2.24 ppm and the maximum concentration of xanthones was found in cultivated plants.

Chromatographic behaviour of steroidal saponins studied by high-performance liquid chromatography–mass spectrometry

The chromatographic behaviour of steroidal saponins found in Anemarrhena asphodeloides, Asparagus officinalis, Convallaria majalis, Digitalis purpurea and Ruscus aculeatus was studied by HPLC–MS using a C-18 reversed-phase column and aqueous acetonitrile or aqueous methanol mobile phase gradients, with or without the addition of 1% acetic acid. The behaviour was compared to that of triterpene saponins found in Aesculus hippocastanum, Centella asiatica, Panax notoginseng and Potentilla tormentilla. Inclusion of methanol in the mobile phase under acidic conditions was found to cause furostanol saponins hydroxylated at C-22 to chromatograph as broad peaks, whereas the peak shapes of the spirostanol saponins and triterpene saponins studied remained acceptable. In aqueous methanol mobile phases without the addition of acid, furostanol saponins chromatographed with good peak shape, but each C-22 hydroxylated furostanol saponin was accompanied by a second chromatographic peak identified as its C-22 methyl ether. Methanolic extracts analysed in non-acidified aqueous acetonitrile mobile phases also resolved pairs of C-22 hydroxy and C-22 methoxy furostanol saponins. The C-22 methyl ether of deglucoruscoside was found to convert to deglucoruscoside during chromatography in acidified aqueous acetonitrile, or by dissolving in water. Poor chromatography of furostanol saponins in acidified aqueous methanol is due to the interconversion of the C-22 hydroxy and C-22 methoxy forms. It is recommended that initial analysis of saponins by HPLC–MS using a C-18 stationary phase is performed using acidified aqueous acetonitrile mobile phase gradients. The existence of naturally-occurring furostanol saponins methoxylated at C-22 can be investigated with aqueous acetonitrile mobile phases and avoiding methanol in the extraction solvent.

An assessment of the retention behaviour of polycyclic aromatic hydrocarbons on reversed phase stationary phases—Thermodynamic behaviour on C18 and phenyl-type surfaces

The thermodynamic retention behaviour of a linear series of polycyclic aromatic hydrocarbons (PAHs) was investigated on C18 and selected phenyl-type reversed-phase stationary phases, namely C18, C18 Aqua, Propyl-phenyl and Synergi polar-RP stationary phases, using methanol mobile phases. The Propyl-phenyl stationary phase, despite having the lowest surface coverage, was found to exhibit significantly larger enthalpic interactions to the other Phenyl-type phase (Synergi polar-RP) even though this had a much higher surface coverage. This indicated that stronger interactions between the PAHs and the stationary phase ligands were occurring on the Propyl-phenyl phase. Evaluation of the elution band profile of the PAHs in the aqueous methanol mobile phase revealed fairly symmetrical bands for the C18, C18 Aqua and Synergi polar-RP, but severe peak tailing on the Propyl-phenyl phase. A change in mobile phase from methanol to acetonitrile improved the peak shape of the PAHs on the Propyl-phenyl phase, leading to the assumption that unfavourable π–π interactions were occurring between the electron-rich PAHs and the electron-rich phenyl rings of the Propyl-phenyl phase.

Behaviour of sulphonated azodyes in ion-pairing reversed-phase high-performance liquid chromatography

Ion-pairing reversed-phase high-performance liquid chromatography (RP-HPLC) operation conditions were studied to obtain information useful for development and optimization of separation methods suitable for HPLC/MS analysis of dyes. The retention of eight sulphonated azodyes with widely differing structures (1–5 acid groups, molecular weight range 350–1220) was measured in mobile phases containing various ion-pairing reagents in aqueous-methanolic mobile phases. The effects of the type and of the concentration of ammonium acetate, tetrabutylammonium hydrogen sulphate and five di- and tri-alkylammonium acetate ion-pairing reagents on the chromatographic behaviour of dyes were compared in mobile phases with varying concentrations of methanol. Structural effects on the retention of dyes were studied in detail. The retention scale based on lipophilic and polar indices can be used for optimization of mobile phase for HPLC/MS of dyes and, on the other hand, may provide some information on the structure of unknown dyes.

Application of liquid chromatography–mass spectrometry to the investigation of poisoning by Oenanthe crocata

Liquid chromatography-mass spectrometry (LC-MS) analysis of methanol extracts of Oenanthe crocata roots revealed that oenanthotoxin co-eluted with another major polyalkyne, 2,3-dihydro-oenanthotoxin, using the existing high performance liquid chromatography (HPLC) method (isocratic elution from C18 with aqueous methanol) for investigating Oenanthe poisoning. Positive ES or APCI gave [(M+H)-H(2)O](+) and its methanol adduct as major ion species for oenanthotoxin, whereas 2,3-dihydro-oenanthotoxin formed [M+H](+) and its methanol adduct. The two polyalkynes could be chromatographically resolved on C18 by gradient elution with aqueous acetonitrile. This provides superior analysis for oenanthotoxin using HPLC with photodiode array (PDA) detection alone, but for LC-MS/MS aqueous acetonitrile was less suitable due to poor ionisation and, with APCI, an increase in the relative abundance of a [M-1](+) species, which could confuse compound assignment. HPLC-PDA and LC-MS/MS methods using an aqueous acetonitrile or aqueous methanol mobile phase, respectively, were successful when applied to the analysis of the stomach contents of a pony suspected to have eaten O. crocata. Relevant product ion spectra, by ion trap MS/MS, accurate mass data and complete sets of (1)H and (13)C NMR spectral assignments are given for the two compounds.

Simultaneous determination of tretinoin and clindamycin phosphate and their degradation products in topical formulations by reverse phase HPLC.

A new HPLC method based on reverse phase separation and photodiode-array detection has been developed for the simultaneous determination of tretinoin and clindamycin phosphate, and their degradation products in topical formulations. The method has been shown to be stability indicating, accurate, and precise for two different formulation vehicles. Separation was achieved on a reverse phase C18 column (Lichrospher, RP18, 5 microm, 25 cm x 4.6 mm ID, Phenomenex, USA) using a simple gradient with aqueous-acetonitrile and aqueous-methanol mobile phases. The method recovery averaged 100.3% for tretinoin and 99.6% for clindamycin phosphate at a concentration range between 80% and 120% of the label claim. The method can be applied to assess the stability of tretinoin and clindamycin phosphate in pharmaceutical formulations containing tretinoin and clindamycin phosphate individually or in combination as active drugs.

Application of pseudo-reversed-phase systems to the purification and isolation of biologically active taxoids from plant material

Silica and aqueous methanolic mobile phases have been optimized for the purification of crude yew extracts. From the recoveries measured for 10-deacetylbaccatin Ill and paclitaxel it was found that 20% methanol in water elutes all taxoids from the adsorbent and that non-polar materials remain in the starting band; this enables preparation of the samples before HPLC analysis. Partial separation of the taxoid fraction was achieved by elution with pure water then 6:4 methanol-water. Such systems on a large scale can be used for preparative separation of taxoids. Partially separated fractions are re-chromatographed in a normal-phase system consisting of silica with a non-aqueous mobile phase. This procedure enables isolation of 10-deacetylbaccatin Ill from the fraction.

HPLC determination of chlorobenzenes, benzenesulphonyl chlorides and benzenesulphonic acids in industrial waste water

An HPLC method has been developed for the determination of chlorobenzenes, benzenesulphonyl chlorides, benzenesulphonic acids and related compounds in industrial waste water. The separation and determination of diphenylsulphone, 1,4-dichlorobenzene, 1,2,3,4-tetrachlorobenzene 1,2,3,5-tetrachlorobenzene and pentachlorobenzene was performed in reversed-phase system with octadecylsilica gel stationary phase and aqueous-methanolic mobile phase. Successful separation of ionic and polar compounds as water pollutants such as: benzenesulphonamide, benzenesulphonic acid, 1,3-benzenedisulphonic acid, 4-chlorobenzenesulphonic acid, 2,5-dichlorobenzenesulphonyl chloride, 2,3,4-trichlorobenzenesulphonyl chloride and 2,4,5-trichlorobenzenesulphonyl chloride requires addition of a salt (sodium sulphate) to the mobile phase. Addition of a buffer or of an ion-pair reagent to aqueous-methanolic mobile phases did not yield satifactory improvement in separation selectivity nor of peak shape. Polar and ionic compounds diphenylsulphone and chlorobenzenes, were separated and determined by a two-step, reversed-phase LC method. On-line sample enrichment on an adsorption column packed either with octadecyl silica or with aminopropyl silica connected to an LC column improved the limits of detection of the pollutants.

HPLC behavior and hydrophobic parameters of some anilides

The chromatographic behavior ofpara substituted anilides of 2,2-dimethylpropanoic, benzoic and α-phenyl acetic acid has been studied by reversed-phase high performance liquid chromatography. HPLC was performed on a C-18 column with various aqueous methanol mobile phases. The influence on the retention of anilide type and additional substituents in the molecule is discussed.