Dispersive liquid-liquid microextraction followed by gas chromatography–electron capture detection for determination of polychlorinated biphenyls in fish

A new method of dispersive liquid-liquid microextraction (DLLME) combined with GC-electron capture detection (GC-ECD) was proposed for the extraction and determination of four polychlorinated biphenyls (PCBs) congeners in fish samples. Acetone was used as extraction solvent for the extraction of PCBs from fish samples. The target analytes in the acetone solvent were rapidly transferred to chlorobenzene, which was used as extraction solvent in DLLME procedures. Under the optimum conditions, linearity was obtained in the concentration range from 1.25 to 1250 μg/kg for PCB 52, and 0.25 to 250 μg/kg for PCB 101, 138 and 153. Coefficients of correlation (r²) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking fish samples at 10 μg/kg PCBs, and RSD% (n = 8) varied between 2.2 and 8.4%. The LODs were between 0.12 and 0.35 μg/kg. The enrichment factors of PCBs were from 87 to 123. The relative recoveries of the four PCB congeners for the perch, pomfret and yellow-fin tuna at spiking levels of 10, 20 and 50 μg/kg were in the range of 81.20–100.6%, 85.00–102.7% and 87.80–108.4%, respectively. The results demonstrated that DLLME combined with GC-ECD was a simple, rapid, and efficient technique for the extraction and determination of PCBs in fish samples.     

Determination of N-Nitroso Compounds in the Environment of a Metal Factory Using Metalworking Fluids

Abstract

By use of GLC-ECD and HPLC-TEA techniques for N-nitroso compounds, N-nitroso-diethanolamine (NDELA) has been found in concentrations of 1.4–6.0 μg/m³ and 1.3–5.0μg/m³ respectively in all four air samples collected in the environment of a metalworking plant during metallurgical operations. NDELA was quantitated in air samples by GLC-ECD after converting it to its trifluoroacetyl derivative by reaction with the appropriate anhydride. NDELA was analyzed without derivatization in air samples using HPLC-TEA method. N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) were also identified and later determined in two out of four air samples in concentrations of 0.08μg/m³ (for NDMA in both samples) and 0.14–0.16μg/m³ (for NDEA) using GLC-TEA procedure. The described method did not cause artifactual formation of N-nitrosomethyl-N-butylamine (NMBA) when methyl-N-butylamine was used as an internal marker of nitrosation during collection of NDELA in impinger traps.     

The impact of nitrogen fertilizers on degradation and leaching of chlorotoluron in soil

Abstract

This study presents the developed and applied methods for the determination of carbendazim in environmental samples originating from several field studies.

For water samples sample pretreatment consisted of a solid phase extraction (SPE) on cartridges packed with 200 mg SDB-1. In case of solid samples the performance of microwave assisted solvent extraction (MASE) and classical ultrasonic extraction with acetone-ethyl acetate were studied. The latter technique was selected because of the reduced time of manual operations. Instrumental analysis of extracts of water samples was performed on-line with coupled column reversed phase liquid chromatography (LC/LC) and UV detection (280 nm) allowing to assay carbendazim to a level of at least 0.1 μg/l. Improved column life time was obtained by performing the favorable LC separation of carbendazim at high pH on newly developed 5 μm Extend-pH bidentate C18 material.

The combination of a short column packed with 5 μm Inertsil ODS-5 and a mobile phase at low pH material was most adequate as the regards the robust and fast processing of extracts of solid samples and allowed in most cases the screening of carbendazim in soils and sediments to a level of 10μg/kg.

The developed procedures yield overall recoveries for carbendazim of 101, 80 and 71 % in water (levels, 0.1—1.2 μg/l: n=12), soil (levels, 10 and 100 μg/kg; n=22) and sediments (levels, 10 and 100 μg/kg; n=11), respectively, with a repeatability and reproducibility below 7 % for all method/matrix combinations. Soil samples with aged residues (level, 100 μg/kg; n=10) provided an overall recovery of 71% and no significant decrease of carbendazim was observed during nine weeks of storage in the refrigerator.     

Atmospheric Hydrocarbon Concentrations in the Baltic Sea Area

Abstract

During a marine research expedition in 1983 in the Baltic Sea area air samples were collected for the analysis of several organic and inorganic pollutants. The aim of the expedition was to obtain information on the airborne load in the sea as well as to measure the concentrations of the pollutants far away from source areas. In this paper the background concentrations of the primarily traffic originated aromatic hydrocarbons benzene, toluene and xylenes will be presented.

The concentrations of benzene were from 0.2 to 2μg/m³, of toluene between 0.4–3μg/m³, of m-xylene 0.02–0.60μg/m³ while the concentrations of o-xylene were 0.01–0.1 μg/m³. The concentrations did not depend too much on the origin (continental/sea type) of the air masses. A weak minimum in the concentrations of the measured hydrocarbons was noticed in the central Baltic Sea area. When comparing lead concentrations in fine particles (< 2.5 μm) with those of benzene, toluene and m-xylene some coincidence between them could be observed.     

Multiresidue analysis of 36 pesticides in soil using a modified quick,easy, cheap,effective, rugged,and safe method by liquid chromatography with tandem quadruple linear ion trap mass spectrometry

A new method for simultaneous determination of 36 pesticides, including 15 organophosphorus, six carbamate, and some other pesticides in soil was developed by liquid chromatography with tandem quadruple linear ion trap mass spectrometry. The extraction and clean‐up steps were optimized based on the quick, easy, cheap, effective, rugged, and safe method. The data were acquired in multiple reaction monitoring mode combined with enhanced product ion to increase confidence of the analytical results. Validation experiments were performed in soil samples. The average recoveries of pesticides at four spiking levels (1, 5, 50, and 100 μg/kg) ranged from 63 to 126% with relative standard deviation below 20%. The limits of detection of pesticides were 0.04–0.8 μg/kg, and the limits of quantification were 0.1–2.6 μg/kg. The correlation coefficients (r²) were higher than 0.990 in the linearity range of 0.5–200 μg/L for most of the pesticides. The method allowed for the analysis of the target pesticides in the lower μg/kg concentration range. The optimized method was then applied to the test of real soil samples obtained from several areas in China, confirming the feasibility of the method.     

Determination of metoserpate,buquinolate, and diclofenac in pork,eggs, and milk using liquid chromatography–tandem mass spectrometry

In this work, a method was developed for the simultaneous determination of residual metoserpate, buquinolate and diclofenac in pork, milk, and eggs. Samples were extracted with 0.1% formic acid in acetonitrile, defatted with n‐hexane, and filtered prior to analysis using liquid chromatography–tandem mass spectrometry. The analytes were separated on a C₁₈ column using 0.1% acetic acid and methanol as the mobile phase. The matrix‐matched calibration curves showed good linearity over a concentration range of 5–50 ng/g with coefficients of determination (R²) ≥0.991. The intra‐ and inter‐day accuracies (expressed as recovery percentage values) calculated using three spiking levels (5, 10, and 20 μg/kg) were 80–108.65 and 74.06–107.15%, respectively, and the precisions (expressed as relative standard deviation) were 2.86–13.67 and 0.05–11.74%, respectively, for the tested drugs determined in various matrices. The limits of quantification (1 and 2 μg/kg) were below the uniform residual level (0.01 mg/kg) set for compounds that have no specific maximum residue limit (MRL). The developed method was tested using market samples and none of the target analytes was detected in any of the samples. The validated method proved to be practicable for detection of the tested analytes in pork, milk, and eggs.     

Residue analysis of tebufenozide and indoxacarb in chicken muscle,milk, egg and aquatic animal products using liquid chromatography–tandem mass spectrometry

We developed an analytical method using liquid–liquid extraction (LLE) and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) to detect and quantify tebufenozide (TEB) and indoxacarb (IND) residues in animal and aquatic products (chicken muscle, milk, egg, eel, flatfish, and shrimp). The target compounds were extracted using 1% acetic acid (0.1% acetic acid for egg only) in acetonitrile and purified using n‐hexane. The analytes were separated on a Gemini‐NX C₁₈ column using (a) distilled water with 0.1% formic acid and 5 mm ammonium acetate and (b) methanol with 0.1% formic acid as the mobile phase. All six‐point matrix‐matched calibration curves showed good linearity with coefficients of determination (R²) ≥0.9864 over a concentration range of 5–50 μg/kg. Intra‐ and inter‐day accuracy was expressed as the recovery rate at three spiking levels and ranged between 73.22 and 114.93% in all matrices, with a relative standard deviation (RSD, corresponding to precision) ≤13.87%. The limits of quantification (LOQ) of all target analytes ranged from 2 to 20 μg/kg, which were substantially lower than the maximum residue limits (MRLs) specified by the regulatory agencies of different countries. All samples were collected from different markets in Seoul, Republic of Korea, and tested negative for tebufenozide and indoxacarb residues. These results show that the method developed is robust and may be a promising tool to detect trace levels of the target analytes in animal products.     

Determination of Iodine in Cereal Grains and Standard Reference Materials by Neutron Activation Anaylsis

Abstract

Trace amounts of iodine in thirty-eight cereal grain samples cultivated at different locations in Austria were determined for the first time in this study by radiochemical neutron activation analysis. For the dissolution of cereal grain samples and standard reference materials, two different procedures, alkaline and acidic dissolution, were applied in the presence of an iodine carrier. Rapid and simple dissolution procedure with acidic solution was demonstrated in this study. The analytical values in the cereal grain as well as in the standard reference materials obtained by the different dissolution procedures were in good agreement within one standard deviation. The iodine in cereal grains and the standard reference materials ranged from 0.002 to 0.03 μg g^?-1 and 0.0015 to 0.30 μg g^?-1, respectively. The distribution of relative standard deviation (RSD) for iodine concentration below 0.01 μg g^?-1 were 21% and 24% of all data for the range 1–10% RSD and 11–20% RSD, respectively. The RSD for 0.1 μg g^?1 of iodine concentrations were around 10%     

Rapid and sensitive double‐label based immunochromatographic assay for zearalenone detection in cereals

A double‐label immunochromatographic based assay (DL‐ICA) was developed to monitor zearalenone (ZEN) levels in cereals, based on Eu³⁺ nanoparticles (EuNP). The DL‐ICA exhibited excellent sensitivity, reliability and selectivity in real samples. It showed low limits of detection (0.21–0.25 μg/kg) and broad analytical ranges (up to 120 μg/kg). The total analytical time, including sample preparation and DL‐ICA execution, was reduced by 15 min compared with HPLC. The recovery rates ranged from 95.0–118.4%, with relative standard deviations (RSD) <11.6%. Inter‐ and intra‐day validations were assessed, recovery rates of 89.3–106.9% and RSD of 2.3–9.7% were obtained, suggesting considerable stability and reliability for the assay. An excellent correlation was observed between DL‐ICA and a reference HPLC method (R² = 0.9899). Compared to current immunoassays, the current DL‐ICA is inexpensive, highly sensitive, and rapid. Therefore, DL‐ICA constitutes a novel tool for monitoring mycotoxins in food and feed to ensure safety.     

Preparation of Various Bonded Phases for HPLC Using Monochlorosilanes

Abstract

Monochlorosilanes have been prepared with yields of about 80% through a catalytic hydrosilylation of terminal olefins. Subsequently, the silanes are chemically bonded to silica to obtain: (i) n-octyldimethylsilyl bonded phases with reproducible surface coverage ranging from 0.8 to 3.5 μmol/m², (ii) propyldimethylsilyl bonded phases with different functional groups at the γ-position, all showing a nearly equal surface coverage of some 3.3 μmol/m², and (iii) n-alkyldimethylsilyl bonded phases with chainlengths ranging from 1 to 22 carbon atoms and with surface coverages ranging from 3.9 μmol/m² for RP-1 to 3.0 μmol/m² for the RP-22 bonded phase. A simplified model based on the pore structure of silica allows an explanation and estimation of the maximum surface coverage as a function of the chainlength of the bonded phase.     

The determination of free ammonia in ambient air with diffusion/denuder tubes

Ammonia is important in atmospheric chemistry because it neutralises acidic species and increases the pH of cloud droplets. Data on the concentration of free ammonia in the atmosphere are sparse because it is difficult to separate free ammonia from particulate ammonium salt aerosol. A manual method for the determination of free ammonia in air is described based on diffusion/denuder tube separation of ammonia from ammonium salt aerosol. When air is drawn through a tube coated with a selective absorbent (here oxalic acid) separation is achieved because the gaseous species diffuses much more rapidly to the tube wall than the particles. After the sampling period (usually 1–4 h, depending on the free ammonia concentration expected), the sorbed ammonia is washed from the tube and measured potentiometrically with an ammonia probe. The method is tested theoretically and experimentally. The absorption efficiency of the coated tubes is ca. 90%. In samples of room air containing 12–28 μg m^?3, the standard deviation is estimated as 1.0 μg m^?3. In field use, ammonia contents were in the range 0.53–5.0 μg m^?3.     

Determination of volatile organic compounds in urban and industrial air from Tarragona by thermal desorption and gas chromatography-mass spectrometry

This study describes the optimisation of an analytical method to determine 54 volatile organic compounds (VOCs) in air samples by active collection on multisorbent tubes, followed by thermal desorption and gas chromatography-mass spectrometry. Two multisorbent beds, Carbograph 1/Carboxen 1000 and Tenax/Carbograph 1TD, were tested. The latter gave better results, mainly in terms of the peaks that appeared in blank chromatograms. Temperatures, times and flow desorption were optimised. Recoveries were higher than 98.9%, except methylene dichloride, for which the recovery was 74.9%. The method's detection limits were between 0.01 and 1.25 μg m⁻³ for a volume sample of 1200 ml, and the repeatability on analysis of 100 ng of VOCs, expressed as relative standard deviation for n = 3, was lower than 4% for all compounds. Urban and industrial air samples from the Tarragona region were analysed. Benzene, toluene, ethylbenzene and xylenes (BTEX) were found to be the most abundant VOCs in urban air. Total VOCs in urban samples ranged between 18 and 307 μg m⁻³. Methylene chloride, 1,4-dichlorobenzene, chloroform and styrene were the most abundant VOCs in industrial samples, and total VOCs ranged between 19 and 85 μg m⁻³.     

Trace determination of EDTA from water samples using dispersive liquid–liquid microextraction coupled with HPLC-DAD

Dispersive liquid–liquid microextraction (DLLME) in conjunction with high-performance liquid chromatography-diode array detection (HPLC-DAD) has been applied to the extraction and determination of EDTA in sediments and water samples. The effect of extraction, nature and volume of disperser solvent, pH value of sample solution, extraction time and extraction temperature were investigated. Under the optimal conditions the analytical range of EDTA was from 3.0 to 50.0 μg L^?1 with a correlation coefficient of 0.9982 and a detection limit of 1.7 μg L^?1. The relative standard deviation (RSD) was less than 5.4% (n?=?5), and the recovery values were in the range of 89–95%. The simplicity, high enrichment, high recovery and good repeatability are the main advantages of the method presented. The DLLME-HPLC-DAD method was successfully applied to the analysis of EDTA in aqueous samples.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Organic Compounds in High Alpine Snow

Abstract

Snow samples were taken in June 1995 at the Sonnblick Observatory located at the top of Mt. Sonn-blick (3106 m a.s.l.) in the main ridge of the Austrian Alps, as part of the project “Organic Aerosol Scavenging”. The main interest focused on the determination of aliphatic compounds and phenols. First the method for the extraction of the organic compounds was developed using standard samples prepared in the lab. The preconcentration of the samples was performed by liquid-liquid extraction with hexane and hexane/diethylether respectively. To characterize the analytical procedure, the efficiency of the extraction procedure, the reproducibility of the overall method and the detection limits were determined. Values for the recovery of the extraction method range from 57% (fatty acids) to 95% (aliphatic alcohols). Reproducibility was found to be between 3-5%, except for the fatty acids which gave a value of 16%. Detection limits were calculated for the various substances and are between 5μg/l (phenols) and 30μg/l (fatty acids). The analysis of the eight snow samples were performed using a GC-MS-FID system. The following compounds were identified as major compounds in the snow samples: 1-dodecanol, 1-tetradecanol, 1-hexadecanol, 1-octadecanol, 2-isobutyl-4-methoxy-phenol, diisobutylphenol and dibutylphthalate. The aliphatic alcohols are of biogenic origin and are present in a concentration range from 30 to 115 μg/l melted snow. The phenols show concentrations between 5 and 30 μg/l and the phthalates range up to 40 μg/l.     

Accurate and simple determination of oxcarbazepine in human plasma and urine samples using switchable-hydrophilicity solvent in GC–MS

This work presents a sensitive and rapid analytical method for the determination of oxcarbazepine in human plasma and urine samples. A vortex-assisted switchable hydrophilicity solvent-based liquid phase microextraction (VA–SHS–LPME) was used to preconcentrate oxcarbazepine from the samples before the determination by gas chromatography mass spectrometry. The switchable hydrophilicity solvent was synthesized by protonating N,N-dimethylbenzylamine with carbon dioxide to make it totally miscible with an equivalent volume of water. Parameters of the VA–SHS–LPME method including volume of switchable hydrophilicity solvent, concentration/volume of sodium hydroxide and vortex period were systematically optimized. Under the optimum conditions, good linearity ranging from 27.03 to 353.47 μg/kg was obtained for the analyte. Limit of detection and quantitation values were found to be 6.2 and 21 μg/kg (mass base), respectively. The relative standard deviation was calculated as 6.9% for six replicate measurements of the lowest concentration of the calibration plot. Satisfactory recovery results were calculated in the range of 97–100% for human plasma and urine samples spiked at five different concentrations.     

Trace determination of perchlorate using electromembrane extraction and capillary electrophoresis with capacitively coupled contactless conductivity detection

Electromembrane extraction (EME) and CE with capacitively coupled contactless conductivity detection (CE‐C⁴D) was applied to rapid and sensitive determination of perchlorate in drinking water and environmental samples. Porous polypropylene hollow fiber impregnated with 1‐heptanol acted as a supported liquid membrane (SLM) and perchlorate was transported and preconcentrated in the fiber lumen on application of electric field. High selectivity of perchlorate determination and its baseline separation from major inorganic anions was achieved in CE‐C⁴D using background electrolyte solution consisting of 7.5 mM L ‐histidine and 40 mM acetic acid at pH 4.1. The analytical method showed excellent parameters in terms of reproducibility; RSD values for migration times and peak areas at a spiked concentration of 15 μg/L of perchlorate (US EPA recommended limit for drinking water) were below 0.2 and 8.7%, respectively, in all examined water samples. Linear calibration curves were obtained for perchlorate in the concentration range 1–100 μg/L (r²≥0.999) with limits of detection at 1 μg/L for tap water and at 0.25–0.35 μg/L for environmental and bottled potable water samples. Recoveries at 15 μg/L of perchlorate were between 95.9 and 106.7% with minimum and maximum recovery values for snow and bottled potable water samples, respectively.     

Development of a single‐run analytical method for the detection of ten multiclass emerging contaminants in agricultural soil using an acetate‐buffered QuEChERS method coupled with LC–MS/MS

This study was undertaken to develop and validate a single multiresidue method for the monitoring of ten multiclass emerging contaminants, viz. ceftiofur, clopidol, florfenicol, monensin, salinomycin, sulfamethazine, sulfathiazole, sulfamethoxazole, tiamulin, and tylosin in agricultural soil. Samples were extracted using an acetate‐buffered, modified quick, easy, cheap, effective, rugged, and safe method followed by liquid chromatography with tandem mass spectrometric analysis in positive ion mode. Separation on an Eclipse Plus C₁₈ column was conducted in gradient elution mode using a mobile phase of methanol (A) and distilled water (B), each containing 0.1% formic acid and 5 mM ammonium formate. The linearity of the matrix‐matched calibrations, expressed as determination coefficients, was good, with R ² ≥ 0.9908. The limits of quantification were in the range 0.05–10 μg/kg. Blank soil samples spiked with 4 × and 20 × the limit of quantification provided recovery rates of 60.2–120.3% (except sulfamethoxazole spiked at 4 × the limit of quantification, which gave 131.9%) with a relative standard deviation < 13% (except clopidol spiked at 20 × the limit of quantification, which gave 25.2%). This method was successfully applied to the monitoring of 51 field‐incurred agricultural loamy‐sand soil samples collected from 17 provincial areas throughout the Korean Peninsula. The detected and quantified drugs were clopidol (≤ 4.8 μg/kg), sulfathiazole (≤ 7.7 μg/kg), sulfamethazine (≤ 6.6 μg/kg), tiamulin (≤ 10.0 μg/kg), and tylosin (≤ 5.3 μg/kg). The developed method is simple and versatile, and can be used to monitor various classes of veterinary drugs in soil.     

Development of a New Voltammetric Methodology for the Determination of Ciprofloxacin in Beef Samples Using a Carbon Paste Electrode Modified with Nafion and Fullerenes

A sensitive, selective, and low cost electrochemical new methodology was developed for the quantification of ciprofloxacin (Cip) in beef samples by cyclic voltammetry and differential pulse voltammetry, using a CPE electrode modified with Nafion and Fullerenes (N−F/CPE). The optimum parameters for the composition of the N−F/CPE electrode are 0.19 g mineral oil, 0.01 g Nafion, 50 μL fullerene, and graphite powder 0.3 g. The electrochemical characterization was carried out by obtaining maximum anodic peak current associated with the oxidation of ciprofloxacin at 1.1 V, where the electrochemical process resulted to be irreversible and diffusion-controlled. The analytical characterization of the proposed methodology was carried out resulting in a LOD of 1.0 μmol L⁻¹, a LOQ of 3.0 μmol L⁻¹, a sensitivity of 0.37±0.006 μA/μmolL⁻¹, and repeatability of 5.38 %.     

Determination of Trace Methyl Tert‐Butyl Ether in Water Samples Using Dispersive Liquid‐Liquid Microextraction Coupled with GC‐FID

A rapid and sensitive analytical method has been developed for trace analysis of methyl tert‐butyl ether (MTBE) in water samples using dispersive liquid‐liquid microextraction and gas chromatography with flame ionization detection. Factors relevant to the microextraction efficiency, such as the kind of extraction solvent, the disperser solvent and their volumes, the effect of salt, sample solution temperature and the extraction time were investigated and optimized. Under the optimal conditions the linear dynamic range of MTBE was from 0.2 to 25.0 μg L^?1 with a correlation coefficient of 0.9981 and a detection limit of 0.1 μg L^?1. The relative standard deviation (RSD%) was less than 5.1% (n = 3) and the recovery values were in the range of 97.8 ± 0.9%. Finally, the proposed method was successfully applied for the analysis of MTBE in aqueous samples.