Chromatographic Trace Research Articles

Gas chromatographic trace analysis of underivatized nitrophenols

A method for the gas chromatographic trace analysis of underivatized nitrophenols in ground-water is presented. Using a highly de-activated separation system a satisfactory precision for their quantitative GC analysis could be achieved by avoiding condensation of the solvent and by fast injection of the sample. The reproducibility of the peak areas of eleven nitrophenols in ethylacetate was 0.992.

Isolation, purification, and biological activity of mono- and dihydroxylated paclitaxel metabolites from human feces.

Three metabolites of the cytotoxic drug paclitaxel (Taxol) were isolated and purified from the feces of cancer patients receiving the agent as an intravenous infusion. The procedures involved sample homogenization in water followed by liquid-liquid extraction with diethyl ether and high-performance liquid chromatography (HPLC). Approximately 1-3.5 mg of each metabolite was obtained from 100 g of feces. As judged from the chromatographic traces of analytical HPLC with ultraviolet (UV) detection at 227 nm, the purity of each compound was > 97%. On-line photodiode-array detection demonstrated that the UV spectrum of the isolated compounds closely resembles that of the parent drug. Mass spectrometry provided evidence that these metabolites are mono- and dihydroxy-substituted derivatives, namely, 6 alpha-hydroxypaclitaxel, 3'-p-hydroxypaclitaxel, and 6 alpha, 3'-p-dihydroxypaclitaxel. The two 6 alpha-hydroxy-substituted metabolites were shown to have lost their cytotoxicity in in vitro clonogenic assays using the A2780 human ovarian carcinoma and the CC531 rat colon-carcinoma tumor cell lines. In addition, the metabolites showed reduced myelotoxic effects as compared with paclitaxel in an in vitro hemopoietic progenitor toxicity assay. Our procedure for the isolation and purification of paclitaxel metabolites in milligram quantities should be useful for testing the biological activities of these compounds and for the preparation of calibration standards essential for pharmacokinetics studies.

ミツバの香気の特性ならびにその香気特性に及ぼす栽培培地と品種の影響

The effects of cultivation methods (soil vs solution culture) and cultivar variations on the characteristic aroma of Japanese hornwort (Cryptotaenia japonica Hassk., JH) were examined by flame ionization chromatography (FID) and organoleptic evaluation.Culture solution containing [Ca (NO3)2•4H2O] : 1000mg, [KNO3] : 800mg, [MgSO4•7H2O] : 500mg, (NH4H2PO4) : 150mg, and Fe?EDTA : trace in 1000ml water was defined as 1 unit solution.Injection of the head space gas yielded twelve peaks on the chromatographic tracing; the largest one was at 4 min. 30 sec. retention time (RT). Using the TCD detector and organoleptic evaluation, this peak, which corresponded to the aroma of JH, is attributed to a monoterpene (M. W. 136) based on a GC-MS analysis.Organoleptically, the aroma from 6 cultivars did not show obvious differences in quality. However, the aromas of 'Yanagawa 1 goh', 'Kanto-masumori', and 'Kantomasumori (B) ' were slightly stronger than those of 'Yanagawa 2 goh', 'Osaka-shiroguki', and 'Kansai-shiroguki'.Organoleptic evaluations showed that the aroma emanating from JH grown in soil culture was stronger than those plants grown hydroponically. The aroma of JH grown in 3 unit culture solution was stronger than that collected from plants grown in the standard (1 unit) culture solution. The main peak on gas chromatographic tracings derived from emanations of JH grown in soil culture was the tallest followed by that from JH grown in 3 unit solution culture; the peak derived from the emanation of JH grown in the 1 unit solution culture was shortest.

Selective and sensitive detection of organic contaminants in water samples by on‐line trace enrichment–gas chromatography–mass spectrometry

AbstractLiquid chromatographic (LC) type trace enrichment is coupled online with capillary gas chromatography (GC) with mass spectrometric (MS) detection for the analysis of aqueous samples. A volume of 1–10 ml of an aqueous sample is preconcentrated on a trace‐enrichment column packed with a polymeric stationary phase. After cleanup with HPLC‐grade water the precolumn is dried with nitrogen and subsequently desorbed with ethyl acetate. A fraction of 60 μl is introduced on‐line into a diphenyltetramethyldisilazane‐deactivated retention gap under partially concurrent solvent evaporation conditions and using an early solvent vapor exit. The analytes are separated and detected by means of GC–MS. The potential of the LC–GC–MS system for monitoring organic pollutants in river and drinking water is studied. Target analysis is carried out with atrazine and simazine as model compounds; the detection limits achieved under full‐scan and multiple ion detection conditions are 30 pg and 5 pg, respectively. Identification of unknown compounds (non‐target analysis), is demonstrated using a river water sample spiked with 168 pollutants varying in polarity and volatility.

Collisional fragmentation of glycopeptides by electrospray ionization LC/MS and LC/MS/MS: methods for selective detection of glycopeptides in protein digests.

Mass spectrometric methods of glycopeptide-specific detection in liquid chromatography/electrospray mass spectrometry (LC/ESMS) of glycoprotein digests are explored using a variety of glycopeptide models and then applied to soluble complement receptor type I, a 240-kDa glycoprotein containing 25 potential sites of N-glycosylation. The most specific method, requiring a triple quadrupole, involves monitoring of sugar oxonium fragment ions during precursor-ion scan ESMS/MS. Signals derived from nonglycosylated peptides are virtually eliminated, resulting in a total-ion current chromatographic trace of only the glycopeptides present in the digest. The corresponding mass spectra yield molecular weight and glycopeptide microheterogeneity information. An alternative and complementary approach that we term collisional-excitation scanning also involves fragmentation of glycopeptides to sugar oxonium ion fragments but does not involve any mass-selection process, permitting the experiment to be performed on a single quadrupole instrument. The resulting total ion chromatogram is similar to the UV chromatogram (215 nm), but a selected-ion chromatogram for carbohydrate-specific ions such as the N-acetylhexosamine oxonium ion (m/z 204) produces a glycopeptide-specific trace. Although there can sometimes be peptide interferences in the spectra of the indicated glycopeptide-containing chromatographic peaks, this latter approach permits peptide mapping to be performed on the same data set that also indicates the location of glycopeptides in the chromatogram. Both methods are suitable for detection of glycopeptides with all common classes of oligosaccharides in either N- or O-linkage to the peptide.

Gas chromatographic determination of carbamate pesticides after flash-heater methylation with trimethylsulfonium hydroxide

A simple and quick on-line derivatization method for the gas chromatographic trace analysis of 13 carbamate pesticides in water is described. Sample preparation consisted of solid-phase extraction with RP C18 cartridges. Trimethylsulfonium hydroxide solution was added to the concentrated eluate, and an aliquot of the mixture was injected in a programmed temperature vaporizer (PTV) at 60 o C.After solvent purging and a subsequent heating step, carbamate pesticides underwent methylation in the PTV, and the derivatives were separated, detected, and quantitated using high-resolution gas chromatography/mass spectrometry

The atomic emission detector in gas chromatographic trace analysis

The atomic emission detector for element-selective detection in gas chromatography shows high selectivities for many elements vs. carbon, coupled with a large dynamic range and relatively low limits of detection. In this work we report on our experience with the detector with respect to the response in dependence on the chemical form of the element monitored, the limit of detection, the selectivity vs. carbon and efforts to improve the limit of detection by varying the flow rate of the make-up gas. Applications discussed include the quantification of a dibenzodioxin/dibenzofuran standard solution, dual-isotope monitoring and the determination of elemental ratios in organic compounds. The work centers on the elements carbon, sulphur, chlorine, bromine and oxygen.

Drying step for introduction of water-free desorption solvent into a gas chromatograph after on-line liquid chromatographic trace enrichment of aqueous samples

Two procedures are described which effect the rigorous removal of water from the liquid chromatographic (LC) precolumn during the on-line LC trace enrichment-capillary gas chromatography (GC) of aqueous samples, thereby preventing the deterioration of the performance of the retention gap and, thus, the loss of analytes. After LC preconcentration of an aqueous sample on a polymer-packed precolumn , the ethyl acetate used for desorption is led to the GC system either via a small cartridge containing a drying agent (anhydrous sodium sulphur or silica) or after removal of residual water from the precolumn by means of a 30-min nitrogen purge. Regeneration of the drying agents by electric heating permits re-use of the cartridges for about 20 runs. For both procedures, experiments with a series of s-triazine herbicides and several volatile test compounds showed that analyte losses are negligible, even at the sub-ppb level and the repeatability is satisfactory.

Determination of tranquilisers and carazolol residues in animal tissue using high-performance liquid chromatography with electrochemical detection

A multi-residue method for the determination of tranquiliser residues in animal tissue is described. The procedure may be used to determine residues of the tranquilisers acepromazine, azaperone, chlorpromazine, haloperidol, propionylpromazine, xylazine, the metabolite of azaperone, azaperol, and the β-adrenoreceptor blocking agent carazolol. Existing methods of analysis for tranquilisers are based on ultraviolet and fluorescence detection and have been used for pig kidney analysis. Determination in this method was by high-performance liquid chromatography with electrochemical detection in the screen mode. The enhanced selectivity offered by the electrochemical detector allowed determination in liver extracts, which often give rise to more interferences on chromatographic traces when using conventional methods of detection. The method offers up to a ten-fold improvement in limits of determination over methods using ultraviolet and fluorescence detection. Recoveries and coefficients of variation have been determined in the range 2–25 μg/kg in pig kidney and liver. This electrochemical detection method has been used to measure residues in routine surveillance programmes.

Toxicosis in sheep following ingestion of natural gas condensate.

Thirty of 200 ewes died or were euthanatized during a 21-day period following a 1-day accidental exposure to natural gas condensate, a complex mixture of hydrocarbons obtained during collection of natural gas from wells. Despite access to potable well water, the poisoned ewes willingly consumed toxic doses of condensate that contaminated surface water. Eight animals died without premonitory signs; the remainder became ill over the course of a few days to 3 weeks. The principal cause of mortality was aspiration pneumonia, but myocardial degeneration and necrosis, renal tubular damage, gastritis, enteritis, and meningeal edema and hyperemia were also observed. Gas chromatographic analysis identified chemical traces of the hydrocarbons in the tissues, and "fingerprinting," the process of matching chromatographic tracings, provided forensic proof of the contamination source. Atomic absorption spectroscopy and cholinesterase analyses were performed to eliminate the possibility of toxicosis by heavy metal contaminants or other constituents. This appears to be the first reported incidence of natural gas condensate toxicity involving sheep or other ruminants. Although the available literature presents a suggestive pattern of clinical signs and pathologic lesions of petroleum product poisoning, diagnostic investigations should employ detailed analytic examination because each source of petroleum hydrocarbons contains unique sets of components that may produce different toxic effects.

Chromatographic trace analysis of some organic compounds in the environment using derivatization—sorption concentration techniques : I. Gas chromatographic analysis of acrylates in air

Derivatization-sorption concentration techniques for the gas chromatographic analysis of acrylates are described. Acrylates are accumulated and derivatized in the trapping absorber. The sorption and derivatization yield of thioethers is 71 ± 2.6%. Two different procedures are recommended: (1) direct selective derivatization—sorption, and (2) universal sorption of all organic compounds in the first step, followed by a thermal desorption and selective derivatization in the second step.

LC for Sample Preparation in Coupled LC-GC: A Review

In chromatographic trace analysis, most of the working time is spent in preparing the sample; the methods involved are largely inefficient, often rather primitive. (HP)LC could replace a good part of this pre-separation, clean-up or sample enrichment work. It offers high separation efficiency, a wide range of selectivities, and accurate control through on-line detection. LC work is reviewed that is related to on-line LC-GC, showing the wealth of possibilities available for LC sample preparation. The present problems are discussed, hoping to motivate colleagues getting involved in the development of advanced sample preparation techniques.

Selective determination of trace levels of phenol in river water using electrochemical concentration modulation correlation chromatography

Electrochemical concentration modulation (ECM) was used as a sample introduction technique in the correlation chromatographic (CC) trace determination of phenol in water. The linearity and sensitivity of the method were tested and detection limits were calculated. The selectivity of the technique was confirmed by comparison with loop injection experiments using several detection methods. In preliminary experiments is was found taht ECM—CC, in combination with fluorescence detection, is selective and sensitive enough to be used for the monitoring of the phenol concentration in river water at the draining points for drinking water production.

Application of Fourier transformation in high resolution gas chromatographic trace analysis

The fast Fourier transformation (FFT) method was used to increase the signal-to-noise ratio (S/N) in high resolution gas chromatographic trace analysis. A new procedure has been devised for FFT smoothing of chromatograms with a very low S/N. The proposed FFT smoothing procedure allows improvement of S/N by a factor of twenty with a very low error of the peak area recovery.

Sampling device for a simple, fast calibration technique in gas chromatographic trace analysis of gas phases and vapor phases

AbstractIn order to accommodate continually changing tasks in the [μl/l]–[nl/m3] ranges of gas chromatographic trace analysis of gas phases and vapor phases, a simple and time‐saving calibration technique is presented which renders unnecessary conventional test mixtures of the abovementioned concentration ranges.This new method is based on the simulation of such mixtures at the inlet of the GC unit with the aid of commercially available multiway sampling valves of various volumes by means of partial pressure sampling.

Thermal instability of germacrone: implications for gas chromatographic analysis of thermally unstable analytes

The rearrangement of germacrone (1) to β-elemenone (2) is common during gas chromatographic (GC) analysis, with the conversion taking place in the injector port at temperatures above 250 °C as well as on the column. While production of 2 in the injector is evident from the gas chromatographic trace, 2 produced from 1 during its migration down the column is difficult to detect because of the diffuse nature of the chromatographic peak produced by this process. A mathematical model and kinetic parameters (A = (1.35 ± 0.03) × 10−3s−1; Ea = 137 ± 4 kJ mol−1) determined from the reaction in solution can be used to estimate the degree of conversion of 1 to 2 for chromatographic runs (including temperature-programmed analyses). The results of these calculations verify that substantial amounts of 1 are converted to 2 under conditions that are commonly used for the analysis. The method for modeling thermally induced rearrangements in nonisothermal processes represents the first approach to quantitatively assessing their importance in GC analyses of thermally labile substances. Keywords: kinetics, gas chromatography, thermal rearrangement, germacrone, β-elemenone.

A high-performance liquid chromatography method for the analysis of picomole amounts of oligosaccharides

A method for the high-performance liquid chromatography separation of tritium-reduced, acetylated oligosaccharides is described. Their highly sensitive detection in column eluant is facilitated by the use of a flow radioactivity detector. The method differentiates some structural isomers and provides resolution of high-mannose oligosaccharides comparable or superior to that of other high-performance liquid chromatography methods. The detection limit is 0.3 pmol of oligosaccharide. For the detection of radioactive oligosaccharides this method is much less laborious than scintilation counting of collected peak fractions. Generation of a continuous chromatographic trace offers a particular advantage in the detection of partially resolved peaks and the visualization of peak shape. A study of some of the factors influencing acetylation and reduction has led to the development of a robust analytical method.

Physicochemical quantities in catalytic reactions measured simultaneously by gas chromatography

A small volume of reactant, 1-butene, is injected onto a catalytic bed and is allowed to diffuse away from it together with the product butane, along a narrow empty chromatographic tube; the latter is connected perpendicularly to the middle point of another similar tube through which hydrogen flows as reactant and carrier gas, transferring both 1-butene and butane to the detector through an analytical column. By using the reversed-flow GC technique, extra peaks are obtained in the chromatographic trace, sampling the concentration of both the readtant and product at the junction of the two tubes as a function of time. These concentrations are the result of the diffusion of the substances along the narrow empty tube, modified by the adsorption-desorption rates and the rate of the catalytic reaction.

An automated high-performance liquid chromatographic trace enrichment method for the determination of metoclopramide in serum and its application to a bioequivalence human volunteer study

An automated trace enrichment method for metoclopramide is described. Serum was injected on to a short column packed with PLRP-S 100A (a polymeric reversed-phase material). The unwanted components were washed off with borate buffer (pH 9.8) before switching to a Spherisorb ODS column for the separation. The limit of detection in serum samples was 2 ng/ml. The method was used in a pharmacokinetic study to compare the bioavailability of two formulations of the drug.

Improvement of chemical instability of digitoxin in aqueous solution by complexation with .BETA.-cyclodextrin derivatives.

Inclusion complexation of digitoxin with β-cycIodextrin (β-CyD) derivatives, such as 2, 6-di-Omethyl-β-CyD (DM-β-CyD), 2, 3, 6-tri-O-methyl-β-CyD (TM-β-CyD), hydroxypropyl-β-CyD (HPβ-CyD, substitution degree 4.3) and hydroxyethyl-β-CyD (HE-β-CyD, substitution degree 4.0) was studied by the solubility method. The apparent 1: 1 stability constant (Kc) of the complexes in water at 25 -C was in the order of DM-β-CyD (84000 m-1)> HP-β-CyD (18000 m-1) =HE-β-CyD (17000 m-1) =β-CyD (17000 M-1)> TM-β-CyD (5600 M -1). From the high-performance liquid chromatographic tracing of each of the four components (digitoxin, bisdigitoxoside, monodigitoxoside, digitoxigenin) in the reaction mixtures, the individual hydrolysis rate constants (K1-K6) were determined by the non-linear least-squares method.β-CyDs suppressed the hydrolysis rates of digitoxin species in an acidic medium (pH 1.2), particularly the appearance of digitoxigenin, the final hydrolysis product, and the inhibitory effect was generally in the order of DM-β-CyD >β-CyD=HP-β-CyD=HE-β-CyD> TM-β-CyD. By analyzing the concentration dependency of the hydrolysis rate, DM-β-CyD was found to decelerate the appearance rate of digitoxigenin more than 2400 times.