Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection

Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 2³ factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120 μg kg⁻¹, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006 μg kg⁻¹. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.     

Determination of selected polychlorinated biphenyls in water samples by ultrasound-assisted emulsification-microextraction and gas chromatography-mass-selective detection

Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 2³ factorial experimental design. The optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ng L⁻¹ (for PCB153) to 30 ng L⁻¹ (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 μg L⁻¹ and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples.     

Nanogram level quantitation of oxycodone in human plasma by capillary gas chromatography using nitrogen-phosphorus selective detection.

A sensitive and specific capillary gas chromatographic assay is reported for the quantitation of oxycodone in human plasma. The technique involves a single extraction of oxycodone and internal standard (hydrocodone) from plasma by toluene containing 1% isopropanol. Separation is achieved on a methyl silicone (HP-1) fused-silica capillary column (25 m x 0.2 mm I.D., 0.33 microns film thickness) and detection is by nitrogen-phosphorus selective mode. The minimum quantifiable limit is 1.8 ng/ml using 2 ml of plasma. The method is applicable to characterize the plasma profile of oxycodone in humans after a single oral 5-mg oxycodone hydrochloride tablet.     

Simultaneous determination of the prodrug zofenopril and its active drug in plasma by capillary gas chromatography-mass-selective detection

After oral administration of zofenopril, the active sulfhydryl angiotensin-converting enzyme inhibitor is released. Zofenopril is currently under clinical investigation as an antihypertensive. Blood samples are reacted with N-ethylmaleimide, immediately after collection, processed into plasma and stored frozen for subsequent analysis. After addition of two internal reference standards, one each for the prodrug and the active compound, the plasma samples are purified by a combination of liquid-liquid and solid-phase extractions. The dried methylated extracts are reconstituted with tetramethylbenzene and chromatographed by automated splitless injection on a fused-silica capillary column, connected to a mass-selective detector. The analytes and the internal reference standards are chromatographically resolved and a common fragment ion is monitored for the analytes. A limit of quantitation of approximately 1 ng/ml of plasma is achieved.     

Fast urinary screening for paracetamol using on-line microwave assisted hydrolysis and spectrophotometric detection

A fully automated urinary screening system for paracetamol and its metabolites is proposed. The method comprises on-line acid microwave assisted hydrolysis of the drug to p-aminophenol followed by reaction with o-cresol in alkaline medium. The indophenol blue dye formed can be continuously monitored at 620 nm. The detection limit achieved, 0.1 microgram ml-1, allows a high dilution of the samples, thus reducing potential interferences from the sample matrix (mainly protein degradation during urine hydrolysis). The proposed screening system also possesses an adequate selectivity, as the major interferent, epinephrine, is tolerated at concentrations higher than those that could be found in the positive urine samples. The reproducibility, expressed as relative standard deviation, was 3.0% and the sample frequency 20 h-1. The reliability of the method was established at five concentrations (between 0.5 and 4 times the detection limit). Finally, it was applied to the screening of several human urine samples. The results obtained were compared with those provided by batch acid hydrolysis, and were similar in all instances.     

用台式色谱-质谱仪同时进行原油芳烃色谱和色谱-质谱分析

 摘要：用HP6890GC/5973MSD仪器,一次进样同时测定原油、烃源岩抽提物中芳烃馏分的芳烃色谱和色谱-质谱信息,效果良好,在有机地球化学研究工作中很有实用价值,方法具有高效、经济等优点。     

Characterisation and quantitation of morphine in urine using high-pressure liquid chromatography with fluorescence detection.

A simple and rapid method for the identification and quantitation of morphine in urine samples is described. The procedure, which involves conversion of the drug a fluorescent product followed by liquid chromatography, is shown to be highly sensitive and specific. Levels down to 0.01 mug/ml of morphine can be quantitatively detected in urine. A large number of drugs have been tested and shown not to interfere.     

Routine determination of urinary free catecholamines by high-performance liquid chromatography with electrochemical detection

A simple and reliable high-performance liquid chromatographic method is described for the routine determination of the free catecholamines (norepinephrine, epinephrine and dopamine) in urine. The catecholamines are isolated from urine samples using small affinity chromatography columns prepacked with immobilised m-aminophenylboronic acid, separated by ion-pair reversed-phase liquid chromatography and quantified by electrochemical detection. Total analysis, including sample preparation time, is achieved in less than 30 min with analytical recoveries of 92-96% for all three catecholamines. Long-term stability and reproducibility of the liquid chromatographic system is attained by selection of optimised conditions for chromatographic separation with a formate mobile phase and produces detection limits of 1.4, 1.8 and 2.2 nmol/l for norepinephrine, epinephrine and dopamine, respectively, in urine samples and day-to-day coefficients of variation of less than 6%. Furthermore, the affinity isolation gels can be reused a minimum of ten times providing a rapid and cost-effective means of sample preparation.     

Identification of urinary acylcarnitines using gas chromatography-mass spectrometry: preliminary clinical applications.

Many disorders of organic acid metabolism are associated with abnormalities in the levels of acylcarnitines excreted in urine. Profiling of urinary acylcarnitines allows diagnosis and characterisation of many acidurias and acidemias, monitoring dietary treatment of such patients, and elucidation of the metabolism of some exogenous acidic compounds. Urine (ca. 0.5 ml) was subjected to a simple work-up by ion-exchange chromatography, and the isolated acylcarnitines were derivatized by cyclization in 35 min to give volatile lactones that are compatible with gas chromatography-mass spectrometry using electron or chemical ionization. The feasibility of this new and affordable procedure has been confirmed by identifying urinary acylcarnitines in cases of medium-chain acyl-coenzyme A dehydrogenase deficiency, propionic acidemia and isovaleric acidemia.     

Highly sensitive routine method for urinary 3-hydroxybenzo[a]pyrene quantitation using liquid chromatography-fluorescence detection and automated off-line solid phase extraction

Many workers and also the general population are exposed to polycyclic aromatic hydrocarbons (PAHs), and benzo[a]pyrene (BaP) was recently classified as carcinogenic for humans (group 1) by the International Agency for Research on Cancer. Biomonitoring of PAHs exposure is usually performed by urinary 1-hydroxypyrene (1-OHP) analysis. 1-OHP is a metabolite of pyrene, a non-carcinogenic PAH. In this work, we developed a very simple but highly sensitive analytical method of quantifying one urinary metabolite of BaP, 3-hydroxybenzo[a]pyrene (3-OHBaP), to evaluate carcinogenic PAHs exposure. After hydrolysis of 10 mL urine for two hours and concentration by automated off-line solid phase extraction, the sample was injected in a column-switching high-performance liquid chromatography fluorescence detection system. The limit of quantification was 0.2 pmol L(-1) (0.05 ng L(-1)) and the limit of detection was estimated at 0.07 pmol L(-1) (0.02 ng L(-1)). Linearity was established for 3-OHBaP concentrations ranging from 0.4 to 74.5 pmol L(-1) (0.1 to 20 ng L(-1)). Relative within-day standard deviation was less than 3% and relative between-day standard deviation was less than 4%. In non-occupationally exposed subjects, median concentrations for smokers compared with non-smokers were 3.5 times higher for 1-OHP (p<0.001) and 2 times higher for 3-OHBaP (p<0.05). The two urinary biomarkers were correlated in smokers (ρ=0.636; p<0.05; n=10) but not in non-smokers (ρ=0.09; p>0.05; n=21).     

Measurements using gas chromatography with coelution and dual-isotope atomic emission detection.

Dual-isotope measurements by gas chromatography (GC)-atomic emission detection (AED) may enhance results for quantitative analyses. Adding a known amount of an isotopically labelled form of target analytes in each sample can compensate for irreproducibilities or uncertainties associated with sample pretreatments and sample loading. Similarly, fluctuations in AED temperatures, flows and interferants can be compensated via the added labelled forms if each target analyte and its isotopically labelled form coelute. Under these conditions they are subject to identical excitation environments and are measured from the same viewed volumes. Consequently, improved quantitative results may be attained by coelution in GC-AED methods which mimic isotope dilution.     

Determination of methacrylonitrile in serum using gas chromatography and flame ionization detection.

A gas chromatographic method is described for the quantitation of methacrylonitrile in serum. Methacrylonitrile was extracted from rat serum with diethyl ether and then quantified using a gas chromatograph equipped with a flame ionization detector and a 60-m megabore column coated with polyethylene glycol polymer. The recoveries obtained following a one-step extraction with diethyl ether varied from 60% at 3.2 micrograms/ml to 70% at 80 micrograms/ml. The coefficient of variation for the analysis ranged from 2.5% at 400 micrograms/ml to 15.0% at 3.2 micrograms/ml.     

Isolation, identification and quantitation of urinary organic acids

An application of the HISLIB program for the comparison of gas chromatographic-mass spectrometric profiles of urinary organic acids isolated by extraction and ion-exchange methods is described. Ion-exchange methods are clearly superior to solvent extraction in terms of the variety of compounds isolated. However, the former method has practical difficulties which make solvent extraction more attractive for rapid analyses. For the compounds isolated by both methods, the precision of analysis is similar, with standard deviations of relative concentration in the range 10--30% for most compounds.     

Determination of urinary beta-phenylethylamine as its N-benzenesulphonamide derivative by gas chromatography with flame photometric detection.

A selective and sensitive method for the determination of urinary beta-phenylethylamine (PEA) by gas chromatography (GC) has been developed. After extraction of the urine sample with n-pentane, PEA was converted into its N-benzenesulphonamide derivative and then determined by GC with flame photometric detection using a DB-1301 capillary column. By using this method, nanogram amounts of PEA in urine could be accurately and precisely determined without any influence from coexisting substances. Analytical results for the determination of PEA in urine samples from normal subjects are presented.     

Element-selective detection using capillary gas chromatography with atomic emission detection

Capillary GC coupled to an atomic emission detector (AED) provides a powerful new hyphenated technique for the separation and characterization of complex mixtures and compounds. The AED provides simultaneous and truly specific multi-element detection. The specificity of detection reduces the need for the complex sample pretreatment procedures which are necessary to reduce the interference from co-eluted substances which is experienced with detectors such as the FID and the ECD. A range of environmentally significant problems has been studied, including PCB analysis, the characterization of the reaction products of a novel waste treatment process, and the profiling of sulfur-containing species formed by the pyrolysis of various types of coal.     

Separation and screening of short-chain chlorinated paraffins in environmental samples using comprehensive two-dimensional gas chromatography with micro electron capture detection

Short-chain chlorinated paraffins (SCCPs) are highly complex technical mixtures with thousands of isomers and numerous homologs. They are classified as priority candidate persistent organic pollutants under the Stockholm Convention for their persistence, bioaccumulation, and toxicity. Analyzing SCCPs is challenging because of the complexity of the mixtures. Chromatograms of SCCPs acquired using one-dimensional (1D) gas chromatography (GC) contain a large characteristic “peak” with a broad and unresolved profile. Comprehensive two-dimensional GC (GC×GC) shows excellent potential for separating complex mixtures. In this study, GC×GC coupled with micro electron capture detection (μECD) was used to separate and screen SCCPs. The chromatographic parameters, including the GC column types, oven temperature program, and modulation period, were systematically optimized. The SCCP congeners were separated into groups using a DM-1 column connected to a BPX-50 column. The SCCP congeners in technical mixtures were separated according to the number of chlorine substituents for a given carbon chain length and according to the number of carbon atoms plus chlorine atoms for different carbon chain lengths. A fish tissue sample was analyzed to illustrate the feasibility of the GC×GC–μECD method in analyzing biological samples. Over 1,500 compounds were identified in the fish extract, significantly more than were identified using 1D GC. The detection limits for five selected SCCP congeners were between 1 and 5 pg/L using the GC×GC method, and these were significantly lower than those achieved using 1D GC. This method is a good choice for analysis of SCCPs in environmental samples, exhibiting good separation and good sensitivity. Graphical Abstract

Chromatograms of a technical C10–C13 SCCP mixture with a 55 % (w/w) chlorine content obtained using a gas chromatography–electron capture detection (ECD) and b GC×GC–μECD     

Screening of urinary coproporphyrin using cloud point extraction and chemiluminescence detection

A simple screening test was developed for the sensitive and selective measurement of urinary coproporphyrin. In this screening test, efficient and selective extraction/pre-concentration of coproporphyrin from the aqueous medium(urine) into a much smaller volume phase containing a common non-ionic surfactant (Triton X-100) and ethyl acetate was accomplished by the addition of a relatively large amount of a cloud point depressing electrolyte (K(3)PO(4)) into the sample solution to effect cloud point separation. Sensitive and selective detection of coproporphyrin in the mixed Triton X-100 and ethyl acetate phase was performed via chemical excitation using the peroxyoxalate chemiluminescence reaction. The effects of surfactant and cations (from the cloud point depressing electrolyte) on the chemiluminescence intensity of coproporphyrin were briefly investigated. Furthermore, the spectrum of urinary coproporphyrin obtained using the present chemiluminescence method was briefly compared with that obtained from fluorescence method.