Use of computerized pattern recognition in the study of the cuticular hydrocarbons of imported fire ants. II. Comparison of the cuticular hydrocarbon patterns between different colonies of Solenopsis richteri

Gas chromatography (GC) data obtained from the cuticular hydrocarbons of the black imported fire ants are treated by methods of pattern recognition. Based on a recently described sample preparation procedure, GC data are normalized to eliminate slight variations in chromatographic conditions, and converted to the proper format for discriminant analysis by computer. The results of several methods of data treatment and display are discussed, based on the chemometrics system package, ARTHUR.     

Use of computerized pattern recognition in the study of the cuticular hydrocarbons of imported fire ants. I. Introduction and characterization of the cuticular hydrocarbon patterns of Solenopsis invicta and S. richteri

A method is described in which gas chromatographic (GC) data obtained from cuticular hydrocarbons are treated by methods of pattern recognition. Based on a recently described sample preparation procedure, GC data are normalized to eliminate slight variations in chromatographic conditions and converted into the proper format for discriminant analysis by computer. The results of several methods of data treatment and display are discussed, based upon the chemometric system package, ARTHUR. The approach has the advantage of largely removing operator bias.     

Effect of different extraction procedures on the yield and pattern of Se-species in bacterial samples

Investigations are described to extract Se-species from a bacterial sample. The five extraction methods investigated were: hot water, protease, lysozyme, lysozyme-protease, and HCl hydrolysis. The extraction efficiency was determined by comparing the total amounts of selenium in the sample after pressure digestion with the amounts extracted by the different methods described. Efficiencies were found to be only 1% (hot water), ca. 8% (protease, HCl hydrolysis) or ca. 12% (lysozyme, lysozyme-protease). The Se-peak patterns were compared after investigating the extracts with strong anion exchange chromatography-inductively coupled plasma mass spectrometry (SAX-ICP-MS). Most promising were the lysozyme-assisted procedures, which showed the highest diversity of species. Here, in the protease-lysozyme approach, the protease seemed to break down species that had been extracted by lysozyme from the bacterial wall (murein sacculus). The other approaches seemed not to extract many species. Hot water extraction was completely unsuitable, extracting only low amounts of a single, unknown species.     

On-line procedures for the phase-transfer-catalyzed dansylation of phenolic steroids — Application to biological samples

Summary Commercially available equipment from two manufacturers served to set up an automated system for the precolumn phase-transfer-catalyzed dansylation of phenolic steroids, using ethynyl estradiol (EE) and estradiol (E) as model compounds. Using different mixing techniques, the on-line determination of EE and E in 200l untreated urine samples was achieved at a rate of 3–8 analyses per hour. Detection limits were calculated to be 3–5 ng/ml. Calibration curves in urine were linear over two orders of magnitude with r=0.999 (n=5) for EE and r=0.999 (n=6) for E. The repeatability of the determination of EE in urine (1g/ml) was 3.9% (RSD; n=20) and of E (1.5l/ml) 3.8% (RDS; n=10). The use of plasma instead of urine in the on-line procedures was not possible due to rapid formation of emulsions, but E and EE were determined in 100l plasma samples using a mild off-line mixing procedure in 10min. Detection limits were calculated to be ca 10ng/ml.A reaction detector, based on a solvent-segmented system, was developed for the on-line post-column dansylation of phenols and was coupled with a reversed-phase LC system. The highly selective system showed excellent linearity over at least two orders of magnitude with r=0.9999 (n=6) for both phenol and 2,5-dimethylphenol. The reproducibility was good with RSD values of around 2%. Detection limits for loop injections from standard solutions were calculated to be between 4 and 11ng.     

Determination of histamine, methylhistamines and histamine-o-phthaldialdehyde complexes by two high-performance liquid chromatographic procedures. Application to biological samples

Two high-performance liquid chromatographic procedures were proposed to measure histamine. The first, with UV detection and a strong acid cation exchanger (Partisil 10, SCX Whatman), made it possible to isolate histamine and some methylated derivatives. The second, with a C18 sorbent (mu Bondapak, Waters, 10 microns particle size) eluted with ion-pairing phases, made it possible to isolate the histamine-o-phthaldialdehyde complexes. This last procedure allied with a chromatographic purification step gave lower or identical amounts of histamine than those described in human urine (16 +/- 7 micrograms per 24 h), canine whole blood (1.5 +/- 1 ng/ml) and human gastric juice (2.3 +/- 1.4 ng/ml). The two procedures gave the concentration of a histamine-like compound isolated from the antral mucosa.     

Water-compatible molecularly imprinted polymer for the selective recognition of fluoroquinolone antibiotics in biological samples

A novel water-compatible molecularly imprinted polymer (MIP), prepared with enrofloxacin (ENR) as the template, has been optimised for the selective extraction of fluoroquinolone antibiotics in aqueous media. The results of a morphological characterisation and selectivity tests of the polymer material for ENR and related derivatives are reported. High affinity for the piperazine-based fluoroquinolones marbofloxacin, ciprofloxacin, norfloxacin and ofloxacin was observed, whereas no retention was found for nonrelated antibiotics. Various parameters affecting the extraction efficiency of the polymer have been optimised to achieve selective extraction of the antibiotics from real samples and to reduce nonspecific interactions. These findings resulted in a MISPE/HPLC-FLD method allowing direct extraction of the analytes from aqueous samples with a selective wash using just 50% (v/v) organic solvent. The method showed excellent recoveries and precision when buffered urine samples fortified at five concentration levels (25–250 ng mL⁻¹ each) of marbofloxacin, ciprofloxacin, norfloxacin, enrofloxacin and sarafloxacin were tested (53–88%, RSD 1–10%, n = 3). Moreover, the biological matrix of the aqueous samples did not influence the preconcentration efficiency of the fluoroquinolones on the MIP cartridges; no significant differences were observed between the recovery rates of the antibiotics in buffer and urine samples. The detection limits of the whole process range between 1.9 and 34 ng mL^–1 when 5-mL urine samples are processed. The developed method has been successfully applied to preconcentration of norfloxacin in urine samples of a medicated patient, demonstrating the ability of the novel MIP for selective extraction of fluoroquinolones in urine samples.     

Bioanalytical procedures and recent developments in the determination of opiates/opioids in human biological samples

The use and abuse of illegal drugs affects all modern societies, and therefore the assessment of drug exposure is an important task that needs to be accomplished. For this reason, the reliable determination of these drugs and their metabolites in biological specimens is an issue of utmost relevance for both clinical and forensic toxicology laboratories in their fields of expertise, including in utero drug exposure, driving under the influence of drugs and drug use in workplace scenarios. Most of the confirmatory analyses for abused drugs in biological samples are performed by gas chromatographic–mass spectrometric methods, but use of the more recent and sensitive liquid chromatography–(tandem) mass spectrometry technology is increasing dramatically. This article reviews recently published articles that describe procedures for the detection of opiates in the most commonly used human biological matrices, blood and urine, and also in unconventional ones, e.g. oral fluid, hair, and meconium. Special attention will be paid to sample preparation and chromatographic analysis.     

涡流色谱技术在生物样品分析中的应用

生物样品的复杂性使其在进行分析测定前必须经过处理。传统的样品前处理方法(如液-液萃取、固相萃取等)耗时长且操作繁琐。涡流色谱作为在线萃取技术,可以实现生物样品直接进样,减少了样品处理步骤,有效富集纯化了分析物,是一种高通量、高选择性的生物样品前处理方法。为此,本文介绍了涡流色谱技术的原理及优势,并总结了不同涡流柱的特点及其在生物样品分析领域中的应用情况。     

Recognizing chromatographic peaks with pattern recognition methods III. Application of the algorithm for peak recognition in trace analysis

Summary The application of a newly developed peak recognition algorithm is shown. This algorith is based on the KNN method, one of the pattern recognition methods. It is shown that peaks with a S/N-ratio down to one can be safely recognized. This is also possible if the baseline has not only detector noise, but has other disturbances, e.g., noise signals which are generated by a reaction detector. The recognition ability of the algorithm is demonstrated by a standard chromatogram with three different concentrations and with two different sampling rates. The improvement against the classical algorithm is demonstrated. Some properties of the algorithm are discussed.     

Assessment of oil contamination in the marine environment by pattern recognition analysis of paraffinic hydrocarbon content of mussels

Data on the paraffinic hydrocarbon content of mussels (Mytilus edulis and M. califomianus) were analyzed statistically in an attempt to assess oil contamination of several aquatic areas of the greater Puget Sound basin in the State of Washington. The mussels were collected quarterly over a period of two years from ten locations. Fundamental statistical treatment of the data did not reveal meaningful trends. Application of pattern recognition techniques to the hydrocarbon data set allowed the mussel samples to be successfully classified into groups, from areas near known sources of potential pollution or from areas remote from known pollution. Several samples however, could not be grouped consistently as either from contaminated or uncontaminated sites. In addition, the mussels from a particular area could be separated as to season of sampling. Seasonal variation in levels of individual paraffinic hydrocarbons were greater than annual changes. The n-C₁₆ hydrocarbon concentration was the most useful of the 34 features studied for establishing possible oil contamination of the areas. The n-C₁₆ hydrocarbon content was also used successfully to detect oil spills and to define uncontaminated locations in Puget Sound.     

Comparison of sample digestion procedures for the determination of arsenic in certified marine samples using the FI-HG-AAS-technique

 High-pressure digestion and a closed-vessel microwave heated system, both employing a mixture of nitric acid and hydrogen peroxide as digesting agent, were tested for decomposing the certified samples of BCR 278 mussel tissue (Mytilus edulis) and of BCR 422 cod muscle to determine arsenic by use of FI-HG-AAS. While the microwave system is insufficient to mineralize arsenic in marine samples (arsenic recoveries of 13±10% in BCR 278, 2±1% in BCR 422; n=4), high-pressure ashing at 300 °C results in recovery percentages of 56±15% (n=4) in mussel tissue (BCR 278) and of 25±10% (n=4) in cod muscle (BCR 422). A dry ashing procedure is given as a reference digestion, yielding complete recoveries of arsenic for both materials. The nitrite interference arising during measurement can be entirely overcome by using an amino sulfuric acid concentration of about 350 mmol/L in the solutions for measurement. Received: 30 April 1996/Revised: 12 July 1996/Accepted: 16 July 1996     

Comparison of heating extraction procedures for Al, Ca, Mg, and Mn in tea samples.

A focused-microwave-assisted procedure was adopted for the extraction of Al, Ca, Mg, and Mn in tea leaves. The efficiency of extraction was evaluated using diluted acids and a water-soluble alkaline tertiary-amines solution. The extraction procedure was implemented in 5 min. A conventional hot-plate digestion procedure was employed for a comparison. A colorless digest was obtained for all tea samples and the total contents determined for each analyte were employed for estimating the efficiency of extraction. Tea infusions were also prepared. Subsequent determinations of Al, Ca, Mg, and Mn were carried out using flame atomic absorption spectrophotometry (FAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). In most cases, quantitative, or at least semi-quantitative, extractions were attained for Ca, Mg, and Mn. Lower recoveries were attained to Al, which seems to be related to compounds that bind this element in the sample matrix. Large variations in the trace-element composition of teas were observed; these results are discussed with reference to both extraction media and type of tea.     

Preliminary study of the effects of some physical parameters on the stability of methylmercury in biological samples.

The effects of storage conditions (long-term storage of wet samples in a deep-freeze or thermal cycling), freeze-drying and gamma-irradiation at 1 and 5 Mrad on the stability of methylmercury in some biological samples were investigated. Methylmercury was determined by volatilization separation followed by gas chromatography and by ion-exchange separation of inorganic and organic species followed by measurement by cold vapour atomic absorption spectrometry (CVAAS). Total mercury was determined by CVAAS. Biological samples studied included fish and shellfish tissues, human hair and blood samples and appropriate reference materials. From the preliminary results obtained it can be concluded that fresh and dried fish muscle and fish certified reference materials show good stability with time and against temperature cycling. Shellfish and blood should not be repeatedly frozen and unfrozen otherwise possible losses of methylmercury can occur. Losses of methylmercury of up to 30% from wet mussels occurred on prolonged storage in a deep-freeze. Gamma-irradiation reduced the methylmercury content of the fish and shellfish only for hake (Merluccius merluccius). Further experiments should be carried out to confirm this and to investigate if this effect is species dependent. Apparent losses of methylmercury on freeze-drying of blood need to be reconfirmed on further samples.     

Gas--liquid chromatographic evaluation of lofemizole in biological samples for pharmacokinetic investigations. Comparison of two analytical methods

The present paper reports the analytical conditions allowing lofemizole, a new non-steroidal anti-inflammatory drug, to be evaluated in biological fluids for pharmacokinetic and bioavailability investigations. The first approach led to an N-methyl derivative of lofemizole which could be successfully analysed by gas--chromatography employing a flame-ionization detector, reaching a sensitivity of 2 micrograms/ml. The second approach led to the N-(2-chlorobenzoyl) derivative of lofemizole which was suitable for pharmacokinetic investigation using gas--liquid chromatography with electron-capture detection, and reaching a much higher sensitivity of 10 ng/ml of plasma. Recovery of the extraction, reproducibility and specificity were all satisfactory with both methods. Since the first method employing flame-ionization detection was suitable for pharmacokinetic investigations in animal species, this paper describes both methods on a comparative basis.     

Comparison of single and sequential extraction procedures for the study of rare earth elements remobilisation in different types of soils

With the continual increase in the utilisation of rare earth elements (REE) for industrial and agricultural purposes, research into the environmental and biogeochemical behaviour of REE had attracted much interest in recent times. This study principally describes the distribution of REE in four different types of soils like lateritic soil (S-1), in situ natural soil (S-2), soil contaminated by mining activity (S-3) and accidentally polluted soil (S-4) utilizing the optimised BCR sequential extraction procedure and partial extractions with various types of single extractants such as unbuffered salt solutions 0.1 M NaNO₃, 0.01 M CaCl₂, 1 M NH₄NO₃; complexing agents 0.005 M DTPA and 0.05 M EDTA; acid solutions 0.43 M CH₃COOH and 1 M HCl. Comparison of the sum of the four BCR fractions, which included an aqua regia attack on the residue, with the pseudo-total aqua regia digest values to assess the accuracy of the BCR partioning approach has been undertaken. Partial extraction results with several single extractants have also been reported for all the REE elements including yttrium which have been analysed by the optimised BCR procedure. Results obtained after 24 h extraction with each of the single extractant have also been discussed. The extraction with 1 M HCl during 24 h yielded similar quantities of REE as those released under the combined steps of 1, 2 and 3 of the BCR sequential extraction for all the four different type of soil samples indicating that this reagent can be used successfully to estimate the total extractable contents of REE in various types of soil samples.     

Comparison of different methods for the determination of volatile organic compounds in water samples

The aim of this work was to compare the characteristics of three methods, membrane inlet mass spectrometry (MIMS), purge-and-trap gas chromatography-mass spectrometry (P&T) and static headspace gas chromatography (HSGC), for the determination of volatile organic compounds in water samples as used in routine analysis. The characteristics examined included linear dynamic ranges, detection limits of selected environmentally hazardous volatile organic compounds (e.g. toluene, benzene and trichloroethene) in water, required analysis time and reproducibility of the analytical methods. The MIMS and P&T methods had the lowest detection limits for all the tested compounds, ranging from 0.1 to 5 mug 1(-1). Linear dynamic ranges using the MIMS method were about four orders of magnitude and using the P&T method about two orders of magnitude. Detection limits of the HSGC method were 10-100 times higher than those of the other two methods, but the linear dynamic ranges were larger, even up to six orders of magnitude. The analysis time per sample was shortest for the MIMS method, from 5 to 10 min, and ranged around from 35 to 45 min for the HSGC and P&T methods. The reproducibilities of the methods were of the same order of magnitude, in the range of 1-13%. Agreement between the analytical results obtained for spiked samples and for environmental water samples by the three different methods was very good.     

Appraisal of different electrothermal atomic absorption spectrometric methods for the determination of strontium in biological samples

A comparative study of various potential chemical modifiers (La, Mg, Pd, Ni, Ta, Lu, Sm, Eu, Ho, Er, Tm and Tb) as well as of different background correction procedures (deuterium and Zeeman effect) and atomization techniques (wall and platform) for the direct determination of strontium in biological samples was carried out. Two instruments, one with deuterium and the other with Zeeman effect background corrections have been used to perform the experiments. Although La, Mg, Pd, Ta and Lu had a positive effect, lanthanum alone provided the best performance for the determination of strontium in whole blood, urine and bone digests using wall atomization without deuterium background correction. However, neither chemical modifier produced any significant improvement in sensitivity when Zeeman effect background correction with integrated platform atomization was used. Under the optimized conditions, the characteristic masses were 0.82 and 2.20 pg and the detection limits (3σ) were 0.13 and 0.30 μg l⁻¹ with wall atomization and with Zeeman effect background correction respectively. Recovery studies and analysis of standard reference materials certified for strontium were performed to assess the accuracy. The results for the determination of strontium in real samples with wall atomization and lanthanum as chemical modifier, agreed well with those obtained with Zeeman effect background corrector with a precision typically between 0.5 and 3%. Both procedures can be recommended, and the choice will depend on instrument availability.     

High-performance liquid chromatographic procedures for the determination of temafloxacin in biological matrices.

A simple and precise high-performance liquid chromatographic procedure has been developed for the determination of temafloxacin and its trace level metabolites in biological matrices. Plasma samples are ultrafiltered after addition of an internal standard in a displacing reagent containing sodium dodecyl sulfate and acetonitrile. Plasma ultrafiltrates or diluted urines are chromatographed on a reversed-phase analytical column, using an ion-pair chromatographic mobile phase and fluorescence detection. The chromatographic system allows resolution and quantitation of temafloxacin's oxidative metabolites, which collectively account for less than 2% of the administered dose. The mean intra-assay coefficient of variation for determination of temafloxacin concentrations in plasma ranging from 0.05 to 10.0 micrograms/ml was 0.7%. The procedure was implemented at four laboratories for the analysis of over 12,000 samples from clinical studies. Inter-assay coefficients of variation estimated from routine analyses of quality control samples in these studies averaged 4% or lower for concentrations in the 0.15-10 micrograms/ml range. The limit of quantitation of the procedure is approximately 10 ng/ml; inter-assay coefficients of variation at 15 ng/ml averaged under 9%. Calibration curves were reproducible and highly linear, with correlation coefficients typically averaging over 0.9995. An alternative, more complex procedure, involving methylene chloride extraction, which extends the detection limits to below 1 ng/ml, is also described.