Multiresidue Analysis of Some Insect Growth Regulators by Reversed-Phase High-Performance Liquid Chromatography

Abstract

A general procedure has been developed for the analysis of 8 different insect growth regulators (IGRs) by using reversed-phase high-performance liquid chromatography with gradient solvent systems. The method has been used to identify and separate 8 insect growth regulators from a mixture of the standards. The method has been evaluated with different column conditions and under different solvent systems. Best resolution was obtained by using a double column and methanol/water gradient system.     

High Performance Liquid Chromato-Graphic Method For The Determination Of Permethrin Deposits In A Forestry Spray Trial

Abstract

A convenient and sensitive reversed-phase high performance liquid Chromatographie method has been developed for the determination of perraethrin [3-phenoxybenzyl (±)- cis,trans -3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] insecticide. Various isocratic and gradient mobile phases, consisting of acetonitrile:water (CH₃CN:H₂O) and methanol:water (CH₃OH:H₂O) solvent systems at two flow rates, were tested to separate and quantify the Isoners of permethrin using octadecylsilyl (ODS) (Regis 5μ m) and octylsilyl (OS) (RP-8, 10 μ m) bonded columns. The optimal mobile phase for perraethrin using the ODS column was 70:30 (v/v) CH₃CN:H₂O mixture at flow rates of either 1.0 or 1.5 mL/min. The measurement was done with a UV detector at 200 nm and 50°C. The OS column gave a less satisfactory separation than the ODS. Gradient elution systems examined did not improve the iso-meric separation of perraethrin. Using the method developed, deposit levels obtained on various sampling units during a perraethrin spray trial were analyzed after elution or extraction followed by necessary column cleanup. Minimum levels of detection for permethrin varied from 1 to 3 ng depending on the nature of the sampler used.     

A Novel Reverse Phase HPLC Method to Separate and Quantify Androstenedione and Its Stereospecific Hydroxyaromatic Derivatives

Abstract

Reverse - phase High Pressure Liquid Chromatography with a gradient elution on a LiChrocart 250-4 LiChrospher 100 RP-18 column has been used to separate and quantify 7 α-hydroxyandrostenedione (7α-OHA), 6β-hydroxyandrostenedione (6β- OHA), 16α-hydroxyandrostenedione (16α - OHA), 2 β - hydroxyandrostenedione (2 β - OHA), testosterone (T) and androstenedione (A). These steroids are the major products of androstenedione hydroxylation by adult rat liver microsomes. Separation was achieved in 30 minutes by using a linear gradient of acetonitrile (CH³CN) and water in increasing amounts from 30% to 60% of the first solvent (CH₃CN).

This new method compares very favourable with other methods already reported for studying microsomal hydroxylations of androstenedione in different positions of the steroidal skeleton.     

Indirect Fluorescent Visualization Of Aliphatic Amines

Abstract

2-Amino-5-methylbenzenesulfonic acid has been investigated as an indirect fluorescent visualization reagent in reversed phase ion pair chromatography. Aliphatic amines coelute as a negative peak which can be quantitated. Using a solvent of 1 mM 2-amino-5-methyl-benzenesulfonic acid, 0.05 M acetic acid, pH = 5.0 buffer and a C₁₈ column, butylamine was quantitated. The calibration curve was linear from 1.0 M to 2.5 × 10^?3M with a minimum detectable concentration of 1.01 × 10^?3M with a 20 μl injection loop.     

HPLC Laser Fluorometric Determination of Amines in Beer

Abstract

A method has been developed for the rapid and accurate determination of the predominant aliphatic amines in beer. Chromatography was performed on a reverse phase C₁₈ column using an acetonitrile-water solvent gradient. Chromatographic detection was facilitated by pre-column derivatization with 7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) which fluoresces under visible light (in this case an argon ion laser operating at 488 nm) after reaction with an amine. Response was linear over four decades of concentration with detection limits at approximately five picograms injected.     

Rapid and Simple Technique for the Quantitation of Polyamines in Biological Samples

Abstract

A rapid and simple technique has been developed to quantify putrescine, spermidine, and spermine in biological tissue. The method, based upon several published procedures, involves protein precipitation with perchloric acid followed by dansylation with 5-dimethylamino-1-naphthalenesulfonyl chloride (dansyl chloride). After extraction on a Waters C₁₈ Sep-Pak cartridge, the samples are analyzed by high pressure liquid chromotography using a step solvent change and a 3μ C₁₈ reverse phase column. The chromotographic conditions allowed complete analysis of the three polyamines within 10 min with a total run time of 13 min (sample injection and re-equilibrium of column). Standard curves were linear up to 1 μg polyamine and the coefficient of variation for the assay ranged from 4% at l μg polyamine per sample to 11% at 50 ng polyamine per sample. The assay is therefore both rapid and simple. Moreover, unlike other available methods, the present technique does not require duel pumps, ion pairing agents, solvent extraction or a gradient control system. The concentrations of putrescine, spermidine and spermine in rat lung, liver and kidney are reported.     

A Rapid Isolation of Human Chorionic Gonadotropin and Its Subunits by Reversed-Phase High Performance Liquid Chromatography

Abstract

A rapid isolation of human chorionic gonadotropin and its subunits from a commercially available concentrate of human urine has been achieved using reversed-phase high performance liquid chromatography. With μBondapak C₁₈ columns and a gradient employing aqueous trifluoroacetic acid as one solvent and dilute trifluoroacetic acid in acetonitrile as the other, complete separation can be accomplished in one day whereas standard column chromatographic procedures take about two weeks. Specific radioimmunoassays, polyacrylamide gel electrophoresis, and amino acid analyses were used to identify and characterize chromatographic peaks.     

A Simple Solvent Programmer for Liquid Chromatography. I

Abstract

Equations have been derived from which the dimensions of a solvent gradient generator, coupled to open tubular, micro-packed, semi-micro packed or conventional HPLC columns, may be calculated for a desired gradient volume. Packed and open-tubular generators have been considered. Calculations, using the derived equations, predict that a generator of particular dimensions is needed for each column type. These dimensions are practically feasible for all column types except the conventional column.     

A Sensitive Gas Chromatograph Detector for Nitrosamines

Abstract

A GC method using a flame thermionic detector (FTD) with a RbSO₄ source to determine nitrosamines is described. The method is sensitive enough to be used for a preliminary screening of foodstuffs for the presence of volatile nitrosamines. The lowest detection limit is 0.1 ng for DMNA, DENA, or DPNA, with a linear range of 0.1 ? 100 ng determinable. The method has a favorable stability; the factors affecting its sensitivity, e.g. the H₂ flow rate, column temperature and the solvent used, have been studied.     

Wine Phenolics: Optimization Of HPLC Analysis

Abstract

Without previous extraction wine phenolics could be analysed by RP-HPLC via direct injection of the wine samples into the column. In order to optimize the analytical procedure the results obtained with two different columns of slightly different polarity and three different gradient elution systems have been compared.

The separated phenolics were further tentatively identified by means of their retention times and UV spectra which were recorded with a Photodiode Array detector     

Semi-Preparative High Performance Liquid Chromatographic Separation of Carbon-14 Labeled Avermectin B1a from a Mixture of Avermectins

Abstract

A semi-preparative high performance liquid chromatographic method has been developed to separate carbon-14 labeled avermectin B_1a from a fermentation mixture of carbon-14 labeled avermectins, i. e., avermectins A₁a, A₁b, A₂a, A₂b, B₁a, B₁b, B₂a, and B₂b. Two HPLC systems were employed for the separation: I. A Whatman M20, Partisil 10, normal phase column and a solvent system of 10% ethanol in isooctane (v/v), and II. A Whatman M20, Partisil 10, ODS-3, reverse phase column and a solvent system of acetonitrile/methanol/water (56:18:26, v/v/v); the flow rate was 18 ml/ min. Avermectin separations were monitored using ultraviolet detection (254 nm). Further analyses of avermectin B₁a were done using analytical HPLC and TLC/radioassay to check compound purity and identity.     

Structural determination of two lipids isolated from the sea urchin <Emphasis Type="Italic">Echinometra lucunter</Emphasis>

Specimens of the sea urchin Echinometra lucunter were collected at Dakar (Senegal). Fresh sea urchins were exhaustively treated with CHCl₃–MeOH 1:1 (v/v). After evaporation of solvent the oily residue (1, 92 g) was passed through an RP 18 column. The CHCl₃ soluble fraction has been analyzed through spectroscopic means (NMR, electrospray ionization mass spectrometry). It has been shown to contain the two sterol derivatives lucunterperacetate (1) and peroxylucunterine (2).     

Improved Separation of Closely Related Metal Ions by Centrifugal Partition Chromatography

Abstract

Centrifugal Partition Chromatography (CPC) has been used for the analytical scale separations of adjacent trivalent lanthanides. The stationary phase was 0.1 M Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) in heptane and the mobile phase was water at the appropriate pH. Baseline separations of the adjacent lanthanides were achieved with an observed column efficiency of 320 /pm 40 theoretical plates. The column efficiency decreased with flow rate, i.e., the normal Van Deemter behavior was observed. The distribution ratios (D) of selected trivalent lanthanides at different pH values were in general in good agreement with the values determined by batch solvent extraction method. The D obtained with CPC differed markedly from the solvent extraction values inn certain cases resulting in a dependence of separation factor (α) of adjacent lanthanides on pH. This anomaly is under further investigation. The number of theoretical plates, selectivity and resolution of adjacent lanthanides obtained with the current system is ssignificantly better than previously reported. We have demonstrated for the first time, that a mixture of light and heavy lanthanides can been efficiently separated in a single run by CPC, by using gradient pH elution.     

Water-mediated,green, and efficient synthesis of bisquinolones under catalyst-free conditions

Water-mediated, green, and efficient synthesis involving condensation of 4-hydroxy-1-methylquinoline-2(1H)-one (3) with different aromatic and heterocyclic aldehydes (4a–n) leading to 3,3′-(arylmethylene)-bis-(4-hydroxy-1-methylquinolin-2(1H)-one) 5(a–n) under catalyst-free conditions is described. This reaction has an easy workup without using column chromatography and provides excellent yields of the products in shorter reaction times. It does not require any catalyst and uses water as the medium which is the greenest solvent. 3 required in this work was itself obtained by condensation of N-methylaniline (1) with malonic acid (2) in the presence of POCl₃ using a previously reported procedure.     

Method for Gradient Elution in Micro-Flow Liquid Chromatography

This paper describes a new method for gradient elution at low flow rate. By adjusting the solvent composition flowing into a dynamic mixer, we can program the concentration of solvent, B, inside a dynamic mixer to form a time-resolved solvent gradient delivered to the column. The input gradient is related to the output gradient by the equation, B_in = B_out + τ × dB_out/dt, in which τ is the gradient response time constant at specified flow rate, and B_in and B_out are input and output concentration of solvent B, respectively.     

Simple and rapid screening procedure for pesticides in water using SPE and HPLC/DAD detection

An HPLC method, using a photodiode array detector (DAD) has been developed for the simultaneous screening of pesticides. A solid phase extraction system (SPE) has been combined, off-line, with the HPLC/DAD to isolate, recover and quantify pesticides from water samples at ppb levels. The pesticides are eluted from a Hypersil C₁₈ column 5 μm applying a solvent elution programme with two steps, isocratic and gradient mode, in reverse phase. Full UV spectra from 200 to 400 nm are recorded on-line during the analysis and may be compared to stored spectra. The method has been applied to the determination of pesticides in real water samples.     

High-Performance Liquid Chromatography of 2′-5′Oligoadenylates and Related Oligonucleotides

Abstract

HPLC has been used for the analysis and separation of the components of p_x (A2′p)_n A (x = 1 to 3, n = 1 to ≥4). Weak anion exchange columns give excellent resolution, but their instability in phosphate buffers makes them impractical for routine use. Reverse phase chromatography using C18 columns provides a satisfactory alternative method. For preliminary analysis of crude material, ammonium phosphate pH7.0 with a linear 1:1 methanol/H₂O gradient gives a good basic separation of the individual oligomers. Resolution of the 5′ mono-, di-and triphosphorylated oligomers or of the nonphosphorylated components can be obtained using ammonium phosphate pH6.0 and potassium phosphate pH6.5 buffers respectively. The C18 columns are very stable and any one column will give retention times reproducible within 0.2%.     

Reverse-Phase High-Performance Liquid-Chromotographic DAD Method for Simultaneous Determination of Five Isoflavones in Millettia nitida var. hirsutissima

Abstract

A reverse-phase high-performance liquid-chromatographic photodiode array detection (DAD) method has been developed and validated for the simultaneous determination of five isoflavones in Millettia nitida var. hirsutissima: hirsutissimiside B, sphaerobioside, lanceolarin, formononetin, and afromosin. The method utilized a C₁₈ column (4 µm, 250 × 4.6 mm) with an acetonitrile and aqueous H₃PO₄ gradient and ultraviolet detection at 259 nm. The recovery of the method is 94.1–105.9%, and linearity (r > 0.9996) is obtained for all the isoflavones.     

Rapid HPLC Methods for the Separation and Quantitation of a Mono-, Di-, and Tri-Saccharides Mixture and Applications

Abstract

A simple, rapid method has been developed for the separation and quantitation of mono-, di-, and tri-saccharides. The method utilizes a 30cmx 3.9mm i.d. Microbondapak NH₂ column, refractive index detection and water-acetonitrile elution. Two chromatographic systems are described. The isocratic mode was necessary to develop a procedure. 20 Carbohydrate's retention times were evaluated. To optimize the separation of nine water-soluble sugars, a gradient mode flow-programming was used. Separation was achieved within 28 minutes. The low detection limit (4 micrograms) of the above chromatographic procedure and its different possibilities could be of great interest to the analyst. The method has been successfully applied to quantify the major carbohydrates found in two types of commercial honey.     

A review of: “HPLC of Biological Compounds-A Laboratory Guide,by William S. Hancock & James T. Sparrow, (Volume 26 of the Chromatographic Science Series,Jack Cazes,Editor), Marcel Dekker,Inc., New York,NY, 1984, 361 pp., £39.75 (US)”.

Abstract

The analytical and preparative separation of the saturated, monoene, diene and triene constituents of cardanol and cardol have been achieved by reverse phase HPLC on a C₁₈ column using gradient elution.