High-performance Liquid Chromatographic Behaviour Research Articles

Usefulness of thin-layer chromatography for the prediction of high-performance liquid chromatographic retention behavior of new 1,2,4-triazole and thiosemicarbazide derivatives

The purpose of this paper was to assess the suitability of thin-layer chromatography (TLC) as a pilot method for high-performance liquid chromatography (HPLC). The new 1,2,4-triazole and thiosemicarbazide derivatives were analyzed by use of reversed-phase (RP)-TLC and RP-HPLC techniques, applying octadecyl silica adsorbents and aqueous-organic mobile phases. Organic modifiers: methanol and acetonitrile were used at appropriate concentrations providing optimal retention factors. For both techniques, retention coefficient k in column chromatography and the retardation factor RF expressing retention in TLC were determined. The experimentally measured parameters were presented in a logarithmic scale as log k and RM, respectively. The constructed relationships between log k and RM allowed determining the possibility of TLC for anticipating HPLC retention behavior.

Preparation of a new 1,3-alternate-calix[4]arene-bonded HPLC stationary phase for the separation of phenols, aromatic amines and drugs

We have synthesized the 1,3-alternate 25,27-dioctyloxy-26,28-bis-[3-aminopropyloxy]-calix[4]arene and then immobilized onto γ-chloropropylsilica gel (CPS). The high-performance liquid chromatographic behavior of some aromatic hydrocarbons, phenolic compounds, aromatic amines and drug compounds was studied on this 1,3-alternate-calix[4]arene-bonded silica gel stationary phase (CIMS). The effect of organic modifier content and pH of the mobile phase on retention and selectivity of these compounds were investigated. According to chromatographic data, it can be concluded that the selectivity of CIMS for analytes ascribes to various interactions between CIMS and the analytes, such as hydrophobic interaction, hydrogen bonding interaction, π–π interaction and inclusion interaction.

Structure–retention and mobile phase–retention relationships for reversed-phase high-performance liquid chromatography of several hydroxythioxanthone derivatives in binary acetonitrile–water mixtures

The reversed-phase high-performance liquid chromatographic (RP-HPLC) behavior of some newly synthesized hydroxythioxanthone derivatives using binary acetonitrile–water mixtures as mobile phase has been examined. First, the variation in the retention time of each molecule as a function of mobile phase properties was studied by Kamlet–Taft solvatochromic equations. Then, the influences of molecular structure of the hydroxythioxanthone derivatives on their retention time in various mobile phase mixtures were investigated by quantitative structure–property relationship (QSPR) analysis. Finally, a unified model containing both the molecular structure parameters and mobile phase properties was developed to describe the chromatographic behavior of the systems studied. Among the solvent properties, polarity/polarizability parameter ( π *) and hydrogen-bond basicity ( β), and among the solute properties, the most positive local charge (MPC), the sum of positive charges on hydrogen atoms contributing in hydrogen bonding (SPCH) and lipophilicity index (log P) were identified as controlling factors in the RP-HPLC behavior of hydroxythioxanthone derivatives in actonitrile–water binary solvents.

Application of Humic Acid Bonded‐Silica as a Hydrophilic‐interaction Chromatographic Stationary Phase in Separation of Polar Compounds

In this paper, humic acid bonded silica (HAAS) stationary phase was prepared through the spacer of aminoalkyl silanes. The high performance liquid chromatographic behavior of several polar compounds, including four alkaloids and clenbuterol, was studied on HAAS. The effect of mobile phase variables such as organic solvent content, buffer pH, and ionic strength on their chromatographic behavior was investigated. The retention mechanism of tested compounds on the stationary phase was elucidated. The results indicate that the HAAS stationary phase behaved as hydrophilic interaction chromatographic packing, using high content organic solvent as mobile phase, and the stationary phase showed good separation selectivity for four alkaloids and clenbuterol.

High-performance Liquid Chromatography of Some Alkaloids on n-Octadecylphosphonic Acid-modified Magnesia-Zirconia Stationary Phase

The high-performance liquid chromatographic behavior of some alkaloids was studied on an n-octadecylphosphonic acid-modified magnesia-zirconia (C 18PZM) stationary phase. The effects of the mobile phase variables such as the methanol content, the ionic strength, and the pH on their chromatographic behavior were investigated. The retention mechanism of the alkaloids in the stationary phase was elucidated. The results indicate that both hydrophobic and cation-exchange interactions contribute to the retention of the alkaloids under most chromatographic conditions. The inherent Brönsted-acid sites and the adsorbed Lewis-base anionic buffer constituents on the accessible ZM-surface Lewis-acid sites play a role in the retention of ionized solutes by cation-exchange interaction. However, at high pH, the retention of the alkaloids depends mainly on the hydrophobic interactions between the solutes and the support. A satisfactory separation of the alkaloids was achieved with the mobile phase of pH 10.1. The C 18PZM seems to be an excellent alternative to the silica-based reversed-phase stationary phase for the separation of strongly basic solutes.

Characterization ofin vitro metabolites of toad venom using high-performance liquid chromatography and liquid chromatography–mass spectrometry

The characterization of the in vitro metabolites of toad venom, which has been widely used as a traditional Chinese drug, Ch'an Su, has been completed. Toad venom contains bufotoxins (such as marinobufotoxin; marinobufagin 3-suberoylarginine ester) and bufogenins (such as marinobufagin and bufalin) as the main cardiac steroids. An in vitro experiment using the rat or human liver cytosolic fraction disclosed that marinobufotoxin produced marinobufagin, but not its 3-hemisuberate. Marinobufagin was subjected to the enzyme reaction using the rat or human liver microsomal fraction together with NADPH and NAD, which produced 3-dehydromarinobufagin and 3-epimarinobufagin. Marinobufagin produced its 3-sulfate upon treatment with the rat or human liver cytosolic fraction and 3'-phosphoadenosine 5'-phosphosulfate. Bufalin was also subjected to the above enzyme reactions and showed almost the same results except for the result that the hydroxylation occurred at the 5beta-position. On the other hand, small amounts of marinobufagin 3-glucuronide were obtained only by treatment with the human liver microsomal fraction and uridine 5'-diphosphoglucuronic acid. The structures of these metabolites were confirmed using authentic samples regarding their high-performance liquid chromatographic behavior and/or liquid chromatography-mass spectrometry analysis.

High‐performance liquid chromatography of some basic drugs on a n‐octadecylphosphonic acid modified magnesia‐zirconia stationary phase

The high-performance liquid chromatographic behavior of some basic drugs was studied on a n-octadecylphosphonic acid modified magnesia-zirconia (C18PZM) stationary phase. The effect of mobile phase variables such as methanol content, ionic strength, and pH on their chromatographic behavior was investigated. The retention mechanism of basic drugs on the stationary phase was elucidated. The results indicate that both hydrophobic and cation-exchange interactions contribute to solute retention under most chromatographic conditions. The inherent Brönsted-acid sites and also the adsorbed Lewis base anionic buffer constituents on accessible ZM surface Lewis acid sites play a role in the retention of ionized solutes by cation-exchange interaction. However, especially at high mobile phase pH, the retention of basic drugs depends mainly on hydrophobic interactions between solutes and support. Separations of the basic drugs on the C18PZM phase by a predominantly reversed-phase retention mode were very promising. The mixed-mode retention feature on this phase, as a result of the adsorbed Lewis base anionic buffer constituents acting as sites for cation-exchange, could also be very useful, e.g. for enhancing the chromatographic selectivity of such analytes. The C18PZM seems to be an excellent alternative to silica-based reversed-phase stationary phase for the separation of strongly basic solutes.

High-performance liquid chromatography of sulfonamides and quinolones on p- tert-butyl-calix[6]arene-bonded silica gel stationary phase

The high-performance liquid chromatographic behavior of some sulfonamides and quinolones was studied on a p- tert-butyl-calix[6]arene-bonded silica gel stationary phase. The effect of mobile phase variables such as methanol content, ionic strength and pH on their chromatographic behavior was investigated. The retention behavior of sulfonamides on the stationary phase was compared with that on both Zorbax C 18-bonded silica gel and γ-(ethylenediamino)propyltriethoxylsilane-bonded silica gel (diamino-bonded phase). The retention mechanism of sulfonamides and quinolones on the stationary phase was also discussed. The results indicate that the stationary phase behaves as a reversed-phase packing and its separation selectivity is much better than that of not only Zorbax C 18 phase but also diamino-bonded phase. Some sulfonamides and quinolones were separated on the stationary phase, but the separation of sulfonamides is far more successful.

HPLC OF SOME NUCLEOSIDES AND BASES ON p-tert-BUTYL-CALIX[6]ARENE-BONDED SILICA GEL STATIONARY PHASE

The high-performance liquid chromatographic behavior of some nucleosides and bases was studied on a new p-tert-butyl-calix[6]arene-bonded silica gel stationary phase. The effect of mobile phase variables, such as ionic strength, methanol content, and pH on their chromatographic behavior was investigated. Some nucleosides and bases were successfully separated on the new stationary phase. Their retention behavior was compared with that on both Zorbax C18 phase and-(ethylenediamino)propyltriethoxylsilane-bonded silica gel. The results indicate that the new stationary phase behaves as a reversed-phase packing, but its hydrophobicity is much weaker than that of Zorbax C18 phase. The retention mechanism on the new stationary phase was also discussed.

Isolation and identification of a phenolic antioxidant from Aloe barbadensis

A potent antioxidative compound has been isolated from a methanolic extract of Aloe barbadensis Miller using a combination of column and thin-layer chromatography. The antioxidant activity of this substance was similar to that of α-tocopherol as assessed in vitro using rat brain homogenates. On the basis of electrospray ionization and electron-impact ionization mass spectra in combination with reversed-phase, high-performance liquid chromatographic behavior, this compound has been identified as 8- C-β- d -[2- O-( E)-coumaroyl]glucopyranosyl-2-[2-hydroxy]propyl-7-methoxy-5-methylchromone.

Ion-Pair High-Performance Liquid Chromatographic Retention Behavior of Copper(II)–1-Oxa-4,7,10,13- tetraazacyclopentadecane Complex

The ion-pair high-performance liquid chromatographic retention behavior of copper(II)–1-oxa-4,7,10,13-tetraazacyclopentadecane (Cu(II)–OTACP) complex is discussed with data from indirect spectrophotometric detection on the μBondapak CN column. The mobile phase was acetonitrile solution (MeCN:H2O 20:80) containing sodium dodecyl sulfate (SDS) as ion-pairing reagent and sodium 1-naphthalenesulfonate (SNS) as detection reagent. The effects of the concentration of SDS and OTACP added to the sample solution to form the Cu(II)–OTACP complex on the capacity factor of the complex, k′, are illustrated. As a consequence of the study, it was found that two peaks anticipated for the 1:1 and 1:2 mole ratio complexes appeared, and the peak anticipated for the 1:2 mole ratio complex could be used to determine the Cu(II) ion. The method has been applied in the determination of Cu(II) ion in waste water and serum.

High-Performance Liquid Chromatography of some Bases and Nucleosides on Alkylphosphonate-Modified Magnesia-Zirconia Column

ABSTRACT The high-performance liquid chromatographic behavior of some bases and nucleosides was studied on a new reversed-phase stationary phase, alkylphosphonate-modified magnesia-zirconia. The effect of mobile phase variable such as methanol content, ionic strength and pH on their behavior was investigated. It was found that the retention behavior of the bases and nucleosides on the new stationary phase is similar to that on ODS stationary phase. The retention mechanism on the new stationary phase was also discussed. The separation of some bases and nucleosides was accomplished on the new stationary phase.

Reversed Phase High Performance Liquid Chromatographic Separation of Esterquats with Indirect Spectrophotometric Detection

The reversed phase high performance liquid chromatographic (RP-HPLC) elution behavior of the basic esters and esterquats is discussed with data from indirect spectrophotometric detection. Three kinds of basic esters were synthesized by esterification of triethanolamine (TEA) with palmitic acid of three mole ratios (1:1.35, 1:2.00, and 1:3.00). Esterquats were prepared from quaternization of the basic esters with dimethyl sulfate (DMS). As a result, it was found that capacity factor(k′)values of mono-, di-, and triester of the basic esters and esterquats were significantly increased and the elution order reversed as the percentage of 1-propanol (1-PrOH) in mobile phase is increased from 75% to 80%. The RP-HPLC separation and determination of the basic esters and esterquats were also accomplished. Tetraphenylphosphonium bromide (TPPBr) was used as the detection reagent.

Normal-phase and reversed-phase high-performance liquid chromatographic behaviour and particle beam mass spectrometric characterization of alkyne-substituted iron–carbonyl clusters

The chromatographic behaviour of seven iron–carbonyl compounds substituted with alkynes R 2C 2 was studied both in normal-phase and reversed-phase chromatography. Several kinds of stationary phases were considered, including silica, CN, C 18 and phenyl columns. Positive-ion and negative-ion chemical ionization mass spectra of the compounds obtained with a particle beam MS system in flow injection analysis are reported. LC–MS experiments were performed for confirmation purposes and in order to check the integrity of the analytes after the LC separation.

RP-HPLC study of redox equilibria in vanadium-PAR binary and ternary systems: Direct determination of vanadium in steel

The reversed-phase high-performance liquid Chromatographic (RP-HPLC) behaviour of the binary chelates of V(V) and V(IV) with 4-(2-pyridylazo) resorcinol (PAR) and ternary chelates of vanadium with PAR and auxiliary ligands: hydrogen peroxide, hydroxylamine, tartrate and citrate were studied using a C18 column. The complex double-peak chromatograms of V(IV)/V(V)-PAR systems were studied and the origin of each peak was proved. Vanadium in ternary systems with PAR and hydrogen peroxide was found exclusively in V(V)-H2O2-PAR complex (single peak on the chromatogram) despite its initial oxidation state. The double role of hydroxylamine (complex agent and reductor) in vanadium systems with PAR was confirmed: in the V(V) system three species were identified (V(V)-PAR, V(V)-NH2OH-PAR and V(IV)-PAR), but in the V(IV) system only two: V(IV)-PAR and V(V)-NH2OH-PAR. Citrate and tartrate giving single peak were found as auxiliary ligands in ternary V(V) systems of analytical importance. Due to its masking potential towards iron (III) ions, citrate was chosen as the most suitable third component of a ternary vanadium system with PAR, to form the basis of an RP-HPLC method for direct determination of V in steel.

High performance liquid chromatographic behaviour of several barbiturates on a newly developed high purity silica column

A simple isocratic reversed phase HPLC method for the separation of a series of barbiturates is described. The column used is a newly developed synthetic silica known as Symmetry Clg (Waters Corp., Milford, MA, USA) and the mobile phase consists of 50 mM KH2PO4 (pH 4.55): acetonitrile water (20:30:50:). The barbiturates studied are monitored by UV detection at 225 nm. Detailed methodology and the advantage of the Symmetry C18 reversed phase is presented.

Prediction of the Retention Behavior of lonizable Compounds in Reversed-Phase LC Using Factor-Analytical Modeling

Principal component factor analysis (PCFA) and target transformation factor analysis (TTFA) are used to examine the reversed-phase high-performance liquid chromatographic retention behavior of some neutral, basic, and acidic organic compounds in water-methanol-acetonitrile solvent systems at pH 7, 5, and 3. The ratios of the pairs of HA/A – (acid) or B/BH + (base) are controlled by the buffered mobile phases, and this permits the factor analytical model to be extended to ionic compounds. Four factors are sufficient to reproduce the data within an error margin of 3%.

Reversed-Phase LC Retention Prediction in Water-Methanol-THF Using Factor-Analytical Modeling

A factor-analytical retention prediction model is used to analyze the reversed-phase high-performance liquid chromatographic retention behavior of 23 organic compounds in solvent systems of water-methanol-tetrahydrofuran ranging from 0 to 70% water. Principal component factor analysis and target transformation factor analysis are the methods used. The retention data are reproduced using three factors ; there is a reproduction error of 2.2% in capacity factors from 0.08 to 95.1. This model is further tested by extrapolating the retention prediction to new compounds and solvents.

Reversed-Phase High-Performance Liquid-Chromatographic Behavior of Phthalic Acid and Terephthalic Acid in the pH Region around the Second pKa Values

Abstract In a reversed-phase high-performance liquid-chromatographic analysis phthalic acid and terephthalic acid were observed as two clearly separated peaks with a mobile phase of pHs around the second pKa values involving the monoanion and dianion species.

Prediction of High-Performance Liquid Chromatographic Retention Data of Carboxamides and Oxadiazoles

Abstract Regression models that predict the high-performance liquid chromatographic retention behavior of carboxamides and oxadiazoles were proposed. A new intermolecular interaction parameter was developed that combines dispersion interaction and total water solvation shell surface energy ratio of structural(o, m, p) isomers to form nonpolar bonding constant descriptor. Also resonance effect constant and field effect constant were used as electronic descriptor. A three-variable model indicated high multiple correlation(R>0.996) between the observed and the calculated values.