Optimized separation of pesticide enantiomers by chiral high-performance liquid chromatography

Summary A computer-assisted method is described for optimization of multi-component, mobile phase selection for separating enantiomers of four pesticides in normal-phase HPLC. The method is based on the triangle, solvent-selection concept using a statistical scanning method. The optimization of the separation over the experimental region is based on a special polynomial estimation from seven experimental runs, and resolution (R_s) is used as the selection criterion. Excellent agreement was obtained between predicted and experimental data.     

Chiral separation and determination of ofloxacin enantiomers by ionic liquid-assisted ligand-exchange chromatography

A simple and accurate method for the separation and determination of ofloxacin enantiomers was developed by ionic liquid-assisted ligand-exchange high performance liquid chromatography. Both achiral and chiral ionic liquids were tested for their efficiency of ofloxacin enantiomeric separation. The effects of ligands, concentration of metal ion, organic modifier, pH of the mobile phase, and temperature were also investigated and evaluated. Optimal conditions were obtained on a conventional C(18) column, where the mobile phase consisted of methanol/water (20 : 80, v/v) (containing 4.0 mmol L(-1) amino acid ionic liquid and 3.0 mmol L(-1) copper sulfate) at a flow rate of 0.5 mL min(-1). Under this condition, the ofloxacin enantiomers could be baseline separated within 14 minutes; the proposed method was used to analyze different commercial ofloxacin medicines.     

Chiral separation of two pairs of enantiomers of tadalafil by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the chiral separation of a new selective phosphodiesterase 5 inhibitors, tadalafil and its three isomers. The chiral separation was performed on a Chiralpak AD column. The mobile phase was hexane-isopropyl alcohol (1:1, v/v). UV detection was at 220 nm. Baseline chiral separation for the four isomers was obtained within 30 min. Each of the resolutions of the two pairs enantiomers were more than 2.0. The limits of quantitation were 0.60, 0.90, 1.20, and 1.80 ng for (6R, 12aS), (6R, 12aR), (6S, 12aS), and (6S, 12aR) isomers, respectively. Relative standard deviation of the method was below 2% (n=5). The method is suitable in quality control.     

Direct separation of drug enantiomers by high-performance liquid chromatography with chiral stationary phases

The development of chiral stationary phases for HPLC has resulted in renewed interest in methods for the separation of drug enantiomers. This paper provides a brief overview of some of the more recent approaches to the direct resolution of drug enantiomers by HPLC with particular emphasis on their quantification in biological fluids.     

Analytical and semipreparative separation of the enantiomers of new acetylcholinesterase inhibitors by high-performance liquid chromatography

Summary The resolution of the enantiomers of new acetylcholinesterase inhibitors by high-performance liquid chromatography (HPLC) was investigated on stationary phases containing cellulose tris-(3,5 methylphenylcarbamide) (Chiralcel OD). The effects of the mobile phase on retention, enantioselectivity and resolution were also studied. Ethanol and isopropanol were tested as organic modifiers and the influence of diethylamine was investigated. The effect of temperature on chiral separations was also studieded.     

Isocratic separation of some purine nucleotide, nucleoside, and base metabolites from biological extracts by high-performance liquid chromatography.

Separation of ATP, ADP, AMP, adenine, adenosine, cAMP, ITP, IDP, IMP, hypoxanthine, inosine, cIMP, the guanine series, NAD, NADPH, xanthine, 3-methylxanthine, theobromine, theophylline, and caffeine was accomplished using high-performance liquid chromatography with a microparticulate reversed-phase column. Under isocratic conditions all compounds could be eluted with reasonable resolution and retention time. Quantitation by peak height for several of the compounds was used to the 10-ng level.     

Quantitative analysis of three chiral pesticide enantiomers by high-performance column liquid chromatography

Methods for the enantiomeric quantitative determination of 3 chiral pesticides, paclobutrazol, myclobutanil, and uniconazole, and their residues in soil and water are reported. An effective chiral high-performance liquid chromatographic (HPLC)-UV method using an amylose-tris(3,5-dimethylphenylcarbamate; AD) column was developed for resolving the enantiomers and quantitative determination. The enantiomers were identified by a circular dichroism detector. Validation involved complete resolution of each of the 2 enantiomers, plus determination of linearity, precision, and limit of detection (LOD). The pesticide enantiomers were isolated by solvent extraction from soil and C18 solid-phase extraction from water. The 2 enantiomers of the 3 pesticides could be completely separated on the AD column using n-hexane isopropanol mobile phase. The linearity and precision results indicated that the method was reliable for the quantitative analysis of the enantiomers. LODs were 0.025, 0.05, and 0.05 mg/kg for each enantiomer of paclobutrazol, myclobutanil, and uniconazole, respectively. Recovery and precision data showed that the pretreatment procedures were satisfactory for enantiomer extraction and cleanup. This method can be used for optical purity determination of technical material and analysis of environmental residues.     

Separation of pyrethroid enantiomers by chiral high-performance liquid chromatography

The separation of enantiomers of pyrethroid insecticides has been systematically studied using a commercially available Pirkle type 1-A chiral-phase high-performance liquid chromatography column. Useful resolution was obtained for compounds with a variety of acid and alcohol moieties, and containing one to four chiral centres. The chromatographic behaviour of the diastereomers of some of these insecticides on a cyano-bonded column was also examined.     

Preparative separation of lithospermic acid B from Salvia miltiorrhiza by polyamide resin and preparative high-performance liquid chromatography

Adsorption on polyamide resin was investigated as a means of separating lithospermic acid B (LAB) from a crude extract of the roots of the traditional Chinese medicine Salvia miltiorrhiza Bunge ("Danshen"). Variables affecting adsorption capacity (solution pH, contact time on resin, initial LAB concentration) were studied. Adsorption was strongly dependent upon the initial concentration of LAB and pH. In all conditions, the polyamide resin gave optimal adsorption of LAB at an initial concentration of 2.66 mg/mL and pH <3.0. The adsorption isotherm correlated well with the Langmuir-type adsorption isotherm. Maximal adsorption capacity was calculated to be 380 mg/g at pH 2.0 and 25°C. LAB purity of 85.30% could be obtained by polyamide resin adsorption followed by elution with 70% ethanol solution, and the recovery was 87.1%. After preparative HPLC, the maximum HPLC purity obtained was 99.28% with a recovery of 75.2%. This method provides an efficient and low-cost method for LAB purification for industrial applications.     

Determination of tertatolol enantiomers in biological fluids by high-performance liquid chromatography.

A stereospecific high-performance liquid chromatographic method for the quantification of (-)- and (+)-tertatolol in plasma and urine is described. The method involves solid-phase extraction followed by derivatization with S(+)-naphthylethylisocyanate to form the urea derivative, which is more sensitive to fluorescence detection. The separation of the diastereomeric derivatives was performed by reversed-phase high-performance liquid chromatography. Fluorimetric detection (lambda excitation = 220 nm, lambda emission = 320 nm) allows the quantification of tertatolol enantiomers down to 6 ng/ml. The assay was used to study the pharmacokinetic profile of tertatolol enantiomers following oral administration of racemic tertatolol; preliminary results suggest enantioselective absorption and/or disposition of tertatolol.     

Determination of [S,S']-ethylenediaminedisuccinic acid by high-performance liquid chromatography

A new high-performance liquid chromatography (HPLC) method for the determination of ethylenediaminedisuccinic acid (EDDS) is presented. Free EDDS(4-) and EDDS complexes with divalent metals undergo conversion to the Fe(III) complex in the presence of Fe(III)Cl(3). Fe(III)EDDS is separated by HPLC on an ion exchange column using (NH(4))(2)SO(4) eluent with detection at 258 nm. The detection limit is 0.01 microM. The method is applied to natural waters and soil solution samples. A background of natural water results in a reduction in EDDS peak area. The method is suited for EDDS analysis in samples with well-defined, simple matrices such as those used in laboratory experiments or biodegradation studies.     

The separation of nonapeptides by reversed-phase high-performance liquid chromatography.

The separation properties of five nonapeptides on commercial reversed-phase materials have been investigated and the effects of pH, salt concentration and solvent composition have been studied. With appropriate variation of the pH and salt concentration in the mobile phase, it is possible to resolve all of the peptides investigated and their by-products. Mixtures of water and organic solvents (acetonitrile, dioxan, methanol and n-propanol) have been used. The choice of the organic solvent does not strongly influence the separation pattern. The simplicity, speed and quality of the separations and the favourable detection limits (ca. 30 ng) at 220 nm render this technique suitable to routine quantitative analysis.     

Direct separation of 2-hydroxy acid enantiomers by high-performance liquid chromatography on chemically bonded chiral phases

Summary The resolution of 2-hydroxy acid enantiomers by the principle of ligand exchange chromatography on chemically modified silica gel is described. The phases were synthezised by fixing L-amino acids via 2-glycidoxypropyl-trimethoxysilane to silica gel. The highest enantioselectivity for 2-hydroxy acids was obtained by using L-hydroxyproline as fixed ligand and Cu(II) as complexing agent. A number of aromatic as well as aliphatic 2-hydroxy acids could be resolved on this sorbent. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Preparative separation of sphingolipids and of individual molecular species by high-performance liquid chromatography and their identification by gas chromatography-mass spectrometry

Six fractions containing tri- to pentaglycosylceramides were isolated from the green, fresh water alga Chlorella kessleri, grown heterotrophically, by using preparative high-performance liquid chromatography (HPLC). Up to twelve fractions were obtained by further reversed-phase HPLC of each glycosylceramide. The use of a polar capillary column with Supelcowax 10 as the stationary phase allowed an excellent separation of the individual molecular species of ceramides, even though the separation did not occur when the ceramides differed only in the position of the amide bond. The individual molecular species (even if present in mixtures) were identified by gas chromatography-chemical ionization mass spectrometry. The evidence for a complete structure was obtained by enzyme splitting with alpha- and beta-galactosidases (the sequence of monosaccharides) and by negative ionization fast atom bombardment mass spectrometry. More than 400 molecular species of glycosylceramides were identified.     

Determination of betaxolol enantiomers by high-performance liquid chromatography. Application to pharmacokinetic studies

A high-performance liquid chromatographic (HPLC) method is described for the determination of (R)- and (S)-enantiomers of betaxolol in blood and other biological fluids. Separation of the enantiomers is performed after preparation of diastereomeric derivatives with the chiral reagent R(-)-naphthylethylisocyanate by reversed-phase HPLC. Fluorimetric detection allows the quantification of betaxolol enantiomers down to 0.5 ng/ml. This method was used to evaluate the pharmacokinetic profile of the betaxolol enantiomers in three subjects following one single oral dose (20 mg) of racemic betaxolol. No significant difference was observed in blood levels of the isomers.     

高效液相色谱法拆分硅氟唑对映体

在纤维素-三-(3,5-二甲基苯基氨基甲酸酯)(Chiralcel OD-H)手性柱上对硅氟唑对映体的分离进行了研究.考察了流动相中改性剂的种类和浓度、流速以及柱温对分离效果的影响,并对手性拆分机制进行了讨论.实验结果表明:5种醇改性剂中,异丙醇的改性效果最佳,当异丙醇含量为2%时,分离度(Rs)达最大值10.19;在...     

Optimization separation of five phosphoamidothioate enantiomers using a series of silica and chiral column by high-performance liquid chromatography

A computer-assisted method is described for optimization of multi-component,mobile phase selection for separation of five phosphoamidothioate enantiomers with a series of silica and chiral columns in normal phase HPLC.The method is based on the triangular solvent selection concept using a statistical scanning method.The optimization of the separation over the experimental region is based on a special polynomial estimation from seven experimental runs,and resolution (Rs) is used as the selection criterion.Excellent agreement was obtained between predicted and experimental data.     

Preparative high-performance liquid chromatographic separation of naphthodianthrones from St. John's Wort

St. John's Wort (Hypericum perforatum), a perennial flowering plant, has been used medicinally for thousands of years and has most recently been identified as an effective treatment for mild to moderate depression and neuralgic disorders. This work presents a procedure for the isolation of naphthodianthrones from St. John's Wort by an accelerated extraction and separation of marker compounds by preparative high-performance liquid chromatography (HPLC) with photodiode array detection. The accelerated extraction method minimizes the extraction time and increases the yield, and the marker compounds obtained by preparative HPLC are of 98% purity. The compounds are characterized by liquid chromatography-mass spectrometry (electrospray ionization) and NMR spectra.