Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.     

Determination of methylmercury in fish using focused microwave digestion following by Cu2+ addition, sodium tetrapropylborate derivatization, n-heptane extraction, and gas chromatography-mass spectrometry

The analytical procedure for analysis of methylmercury in fish was developed. It involves microwave-assisted digestion with alkaline solution (tetramethylammonium hydroxide), addition of Cu2+, aqueous-phase derivatization of methylmercury with sodium tetrapropylborate, and subsequent extraction with n-heptane. The methylmercury derivative was desorbed in the splitless injection port of a gas chromatograph and subsequently analyzed by electron impact mass spectrometry. Optimum conditions allowed sample throughout to be controlled by the instrumental analysis time (near 7 min per sample) but not by the sample preparation step. At the power of 15-30, 45, and 60-75 W, sample preparation time is only 3.5, 2.5, and 1.5 min, respectively. The proposed method was finally validated by the analysis of three biological certified reference materials, BCR CRM 464 tuna fish, NRC DORM-2 dogfish muscle, and NRC DOLT-2 dogfish liver. The detection limit of the overall procedure was found to be 40 ng/g of biological tissue for methylmercury. The recovery of methylmercury was 91.2-95.3% for tuna, 89.3-94.7% for marlin, and 91.7-94.8% for shark, respectively. The detected and certified values of methylmercury of three biological certified reference materials were as follows: 5.34 +/- 0.30 microg/g (mean +/- S.D.) and 5.50 +/- 0.17 microg/g for CRM 464 tuna fish, 4.34 +/- 0.24 and 4.47 +/- 0.32 microg/g for NRC DORM-2 dogfish muscle, and 0.652 +/- 0.053 and 0.693 +/- 0.055 microg/g for NRC DOLT-2 dogfish liver, respectively. It indicated that the method was well available to quantify the methylmercury in fish.     

Improved Method for the Determination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) in Sanitary Napkins

Abstract

An improved method was developed for determining highly toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans (PCDD/Fs) in sanitary napkins. Samples were extracted by Soxhlet (50% dichloromethane/hexane) and sonication (hexane), and a multi-layer silica column was used for clean-up after acetone precipitation to separate the superabsorbent polymers. Improved separation efficiency of PCDD/Fs from sanitary napkins with a high level of superabsorbent polymers was achieved using the acetone precipitation method. Hexane was then applied as an alternative solvent to remove residual interfering substances including sticky components contained on sanitary napkins via alumina column chromatography in the second clean-up step. Recoveries approached 100% with an average relative standard deviation of less than 15%, and recoveries of internal standards were from 70.5 to 114.8% and 0.6 to 13.6% for the two extraction methods. The mean method detection limit was 0.075–0.968?pg/g for Soxhlet extraction and 0.0032–0.091?pg/g for sonication extraction. The established method meets the quality criteria for the screening of dioxins stated in EU Regulations 589/2014 and 709/2014, and therefore provides a suitable alternative for the determination of dioxins in sanitary napkins containing superabsorbent polymers.     

Comparison of extraction procedures for methylmercury determination by a SPME-GC-AFS system

In this study the comparison of three different alkaline extraction techniques carried out with methanolic NaOH followed by phenylation derivatization for the determination of methylmercury in marine fish was performed. The investigated three methods differed in the technique how the extraction assisting energy was introduced to the sample. Namely, closed vessel ultrasonic bath, an open vessel technique using an ultrasonic probe and the microwave assisted extraction procedures were characterized and optimized. Optimum values of 3 h at 75 °C for the ultrasonic bath, 25 min for the ultrasonic probe and 6 min at 60 W for the microwave method were obtained. All three methods were validated using the BCR-464 tuna fish certified reference material.     

同位素稀释的气相色谱/高分辨质谱联用测定食品中二噁英和共平面多氯联苯

采用HRGC/HRMS和同位素稀释定量技术对样品中17种4~8个氯原子取代的二噁英和呋喃(PCDDs/Fs)与12种共平面多氯联苯(PCBs)定量分析。样品经索式抽提、FMSPowerPrep系统净化、浓缩,利用高分辨气相色谱/高分辨质谱联用仪的多离子检测方式,同位素稀释技术对样品中的目标化合物进行定性和定量。该方法的检出限为pg/g水平。13C同位素内标回收率范围为47%~100%。对3个CRM鱼样中17个PCDDs/Fs和4个PCBs的检测值均在标准定值允许误差范围内。对5个不同的实际样品鱼进行测定表明,样品的回收率在48%~100%之间,回收率的相对标准偏差小于20%;对同一样品进行定量检测的精密度测试结果表明,17种PCDDs/Fs浓度的RSD低于16%,12种PCBs浓度的RSD低于11%。本方法定量分析重现性良好。     

Validation of the CALUX bioassay for the screening of PCDD/Fs and dioxin-like PCBs in retail fish

The chemical-activated luciferase expression (CALUX) assay is a reporter gene assay that detects dioxin-like compounds based on their ability to activate the aryl hydrocarbon receptor (AhR) and thus expression of the reporter gene. In this paper, the CALUX assay was examined for its application in the screening of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in retail fish. The sample extracts were cleaned up on a sulfuric acid-silica gel column followed by an activated carbon column, and the AhR activity of the separated PCDD/F and dioxin-like PCB fractions was determined using the assay. The quantitative limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was 0.98 pg ml(-1) (0.19 pg assay(-1) in the standard curve, corresponding to 0.16 pg g(-1) of CALUX-based toxic equivalency (2,3,7,8-TCDD equivalents) in the tested sample. Recovery tests in which dioxins were added to fish samples resulted in acceptable recoveries (77-117%). The CALUX assay performed well in the analysis of dioxins in fish samples and a comparative study revealed a strong correlation between the CALUX assay and high-resolution gas chromatography-high-resolution mass spectrometry analysis for the determination of PCDD/Fs (r = 0.89) and dioxin-like PCBs (r = 0.91) in retail fish (n = 22). These data revealed that the CALUX assay would be a useful screening method for PCDD/Fs and dioxin-like PCBs in retail fish.     

Determination of total mercury in environmental and biological samples by flow injection cold vapour atomic absorption spectrometry

A simple and accurate method has been developed for the determination of total mercury in environmental and biological samples. The method utilises an off-line microwave digestion stage followed by analysis using a flow injection system with detection by cold vapour atomic absorption spectrometry.

The method has been validated using two certified reference materials (DORM-1 dogfish and MESS-2 estuarine sediment) and the results agreed well with the certified values. A detection limit of 0.2 ng g⁻¹ Hg was obtained and no significant interference was observed. The method was finally applied to the determination of mercury in river sediments and canned tuna fish, and gave results in the range 0.1–3.0 mg kg⁻¹.     

Chlorobiphenyls in sewage sludge; comparison of extraction methods

Six extraction methods for the analysis of PCBs (CB-28, CB-52, CB-101, CB-118, CB-138, CB-153 and CB-180) in sewage sludge were tested. A certified reference material (CRM 392) was used for the evaluation of the performance of the methods. Soxhlet-Dean-Starch with toluene as solvent, Soxhlet with hexane:acetone (2:3), cold digestion/saponification with 2 mol/L KOH in methanol followed by partition with hexane, and sonicated liquid-solid extraction with hexane:acetone (1:1) produced accurate results (97%, 93%, 104%, and 88%, respectively) with acceptable precisions (6.2%, 6.8%, 15% and 12%, respectively). Results in close agreement with the certified value for all congeners were obtained by treatment with BF₃-methanol prior to partition with dichloromethane. However, this is a tedious procedure and involves the use of hazardous compounds. Cyclic steam distillation produced results with an accuracy of around 80% and a good precision (5.2%). The very low consumption of solvents and other expensive chemicals by this technique and the possibility of analyzing the extract directly without clean-up make it an interesting alternative to the more sophisticated methods. Column elution with dichloromethane was found to be less efficient (61%), but it is a rapid, direct method with a low consumption of solvents and it may therefore serve as screening method. Received: 29 April 1997 / Revised: 30 July 1997 / Accepted: 6 August 1997     

Chlorobiphenyls in sewage sludge; comparison of extraction methods

Six extraction methods for the analysis of PCBs (CB-28, CB-52, CB-101, CB-118, CB-138, CB-153 and CB-180) in sewage sludge were tested. A certified reference material (CRM 392) was used for the evaluation of the performance of the methods. Soxhlet-Dean-Starch with toluene as solvent, Soxhlet with hexane:acetone (2:3), cold digestion/saponification with 2 mol/L KOH in methanol followed by partition with hexane, and sonicated liquid-solid extraction with hexane:acetone (1:1) produced accurate results (97%, 93%, 104%, and 88%, respectively) with acceptable precisions (6.2%, 6.8%, 15% and 12%, respectively). Results in close agreement with the certified value for all congeners were obtained by treatment with BF₃-methanol prior to partition with dichloromethane. However, this is a tedious procedure and involves the use of hazardous compounds. Cyclic steam distillation produced results with an accuracy of around 80% and a good precision (5.2%). The very low consumption of solvents and other expensive chemicals by this technique and the possibility of analyzing the extract directly without clean-up make it an interesting alternative to the more sophisticated methods. Column elution with dichloromethane was found to be less efficient (61%), but it is a rapid, direct method with a low consumption of solvents and it may therefore serve as screening method. Received: 29 April 1997 / Revised: 30 July 1997 / Accepted: 6 August 1997     

Potential artifact formation of dioxins in ball clay during supercritical fluid extraction

Earlier surveys indicate that meat, fish and dairy products are the principal source of polychlorinated dibenzo-p-dioxin (PCDD) exposure in the diet. A recent finding by others of PCDDs in chickens that consumed a feed containing PCDD led to the finding of ball clay, an anti-caking agent, as the source. Supercritical fluid extraction (SFE) was studied as a means to isolate PCDDs from commercial ball clays using GC-electron capture detection (muECD) as a means to screen for these contaminants. The finding of ng/g amounts and recoveries >100% in several samples of ball clay containing octachlorodibenzo-p-dioxin (OCDD) suggested that PCDD may form artifactually as a result of analysis. Studies on pentachlorophenol (PCP) fortified ball clay were carried out by SFE and soxhlet extraction and the results compared. The values obtained by SFE were considered more problematic. The results obtained from ball clay suggest that precautions need to be exercised when using SFE to analyze for dioxins in solid samples containing chlorophenols.     

Simple method for monomethylmercury determination in estuarine sediments

Several analytical methods have been proposed for determining monomethylmercury concentrations in sediments. We give an overview of the methods frequently used in the last few years, including matrix digestion, solvent extraction and preconcentration steps prior to quantification of MMHg by instrumental analysis. We propose a simple method to determine MMHg in estuarine sediments, involving alkaline digestion (KOH/methanol), toluene extraction and preconcentration of MMHg in dithizone. We performed separation as well as quantification by gas chromatography electron capture detection. Obtained and certified MMHg concentrations for international certified reference materials (AIEA-405 and CRM-580) showed no statistically differences (α=0.05). Low limits of detection, good repeatability and recoveries made this method a useful tool for rapid analyses of estuarine sediments. We applied this method to a sediment core collected in the Tagus Estuary, Portugal, giving a rapid vertical distribution of MMHg concentrations.     

Gas chromatographic determination of chlorobenzenes and other chlorinated hydrocarbons in environmental samples using fused silica capillary columns

Summary In order to assess the pathways of chlorinated benzenes and toluenes, hexachlorobutadiene and polychlorinated biphenyls in the environment capillary gas chromatographic methods have been developed for analysis of water, sediments and biological samples. Compound recoveries are reported from water, using liquid-liquid extraction with hexane, and from sediments and fish, using soxhlet extraction with hexane/acetone. After suitable cleanup, hexane extracts are chromatographed on a duel fused silica column arrangement (OV1 and SE54 with electron capture detectors for quantitation. The application of these procedures to environmental analysis is discussed.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Determination of bisphenol A and 4-nonylphenol in human milk using alkaline digestion and cleanup by solid-phase extraction.

A highly sensitive and selective method based on alkaline digestion for the simultaneous determination of bisphenol A (BPA) and 4-nonylphenol (NP) was developed. The method consists of digestion of the matrix with ethanolic KOH, extraction with diethyl ether under a mild alkaline condition, cleaning with successive aminopropyl (NH2) cartridges and derivatization followed by a GC-MS analysis. The assay accuracies, expressed as recoveries, were 82 - 113% for BPA and 89 - 97% for NP. The limits of detection of BPA and NP were 0.09 ng/g and 0.50 ng/g, respectively. The procedure will be reliable for the trace analysis of BPA and NP in human milk, since alkaline digestion can diminish their documented association with protein.     

Comparison of methods with respect to efficiencies, recoveries, and quantitation of mercury species interconversions in food demonstrated using tuna fish

Eight different analytical extraction procedures commonly used to extract mercury species from biological samples were evaluated by analyzing Tuna Fish Tissue Certified Reference Material (ERM-CE464) certified for the content of total mercury and methylmercury. Speciated isotope dilution mass spectrometry (SIDMS; US Environmental Protection Agency’s method 6800) was utilized to evaluate and effectively compensate for potential errors during measurement and accurately quantify mercury species using all the extraction methods. SIDMS was used to accurately evaluate species transformations during sample pretreatment, preparation and analysis protocols. The extraction methods tested in this paper were based on alkaline extraction with KOH or tetramethylammonium hydroxide; acid leaching with HCl, HNO₃ or CH₃COOH; extraction with l-cysteine hydrochloride; and enzymatic digestion with protease XIV. Detection of total mercury and mercury species from all extraction methods was carried out by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography–ICP-MS, respectively. Microwave-assisted extraction and ultrasound-assisted extraction were found to be the most efficient alkaline digestion protocols that caused the lowest levels of transformation of mercury species (6% or less). Extraction with 5 M HCl or enzymatic digestion with protease resulted in the second-highest extraction efficiency, with relatively lower transformation of methylmercury to inorganic mercury (3 and 1.4%, respectively). Despite frequent use of acid leaching for the extraction of mercury species from tuna fish samples, the lowest extraction efficiencies and the highest mercury species transformation were obtained when microwave-assisted extraction with 4 M HNO₃ or CH₃COOH was used. Transformations as high as 30% were found using some literature protocols; however, all the extractions tested produced accurate quantitation when corrected in accordance with the SIDMS method standardized in the US Environmental Protection Agency’s method 6800. Figure Determinative CRM Tuna Fish Tissue Methylmercury Calibration vs. Determinative Calculation.     

Analysis of polycyclic aromatic hydrocarbons in contaminated soil by Curie point pyrolysis coupled to gas chromatography-mass spectrometry, an alternative to conventional methods

Curie point pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) has been compared with classical extraction procedures (Soxhlet, sonication, KOH digestion, microwave-assisted) followed by GC-MS analysis for the determination of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil. In each case, the efficiency of the technique was examined for 16 PAHs included in the US Environmental Protection Agency Priority Pollutant List. The results indicate that the recovery of PAHs is dependent on the extraction technique. The highest recoveries of PAHs were obtained with Curie point pyrolysis and KOH digestion. Py-GC-MS appeared to be interesting alternative method for the determination of PAHs in contaminated soil. The results were validated by certified soil (CRM 104) analysis.     

Optimization of a method for determining dioxin in whole blood samples based on solvent extraction and simplified cleanup

Dioxins, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), such as mono-ortho-PCBs and non-ortho-PCBs, are environmental pollutants that have deleterious effects on human health. Although screening of blood samples for dioxins is necessary, the current methods are time-, reagent- and labor-intensive. To optimize the extraction and cleanup of dioxins, we have designed a column chromatography method, coupled with a water washing step. We used a tandem simplified multilayer silica gel-activated carbon dispersed silica gel column (TS-ML-AC) rather than the conventional two columns. We compared three liquid-liquid extraction (LLE) methods and two pressurized liquid extraction (PLE) methods, when used with this column. For each of these extraction methods, we compared the quantity of lipid obtained when the water washing step was omitted and when it was performed by shaking 30 times by hand or 30 min by a machine. We found that TS-ML-AC was superior to the conventional pair of columns in that only about one third of the solvent and only one quarter of the time was necessary. Of the five extraction methods, the acetone/hexane PLE (AcP) method was superior, since it reduced the amount of organic solvent to half or less of the amount required for the LLE methods. The cleanup step using water was best accomplished by the hand-shaking method. Our results indicate that, for the analysis of dioxin in whole blood samples, the use of AcP together with TS-ML-AC and water washing by hand shaking should be used.     

Feasibility study for the preparation of a tuna fish candidate reference material for total As determination

This work describes the evaluation of several parameters for the preparation of a tuna fish candidate as a reference material (RM) in order to measure the total As mass fraction by slurry sampling graphite furnace atomic absorption spectrometry (SLS-GF AAS) and slurry sampling hydride generation atomic absorption spectrometry (SLS-HG AAS). The main parameters investigated were the homogeneity, analyte segregation and composition during material production. For candidate RM preparation, tuna fish was collected at a local market, cleaned, freeze-dried and treated using different procedures as follows: (1) ground in a cutting mill and separated in different particle sizes (2) ground in cryogenic mill. The mass fraction of As in the cryogenically ground sample was (4.77?±?0.19)?μg?g^?? for SLS-GF AAS and (4.61?±?0.34)?μg?g^?? for SLS-HG AAS. The accuracy of the procedures was checked with tuna fish certified reference material (BCR 627) with recoveries of 102 and 94% for SLS-GF AAS and SLS-HG AAS, respectively. The homogeneity factor was calculated for different pretreatment procedures and for particle sizes in the range of 500??50?μg, indicating good homogeneity, except for raw fish. There was no observed analyte segregation and no losses, no contamination and no changes in the microdistribution of material during preparation.     

Extractability of dioxins from soil: I. Extractability of dioxins from airborne particulates and humic acid fraction in soil

The extractability of dioxins (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls) from airborne particulates (APs) and humic acid (HA) in soil was evaluated. APs collected from ambient atmosphere and dioxins-associated precipitated HA fraction (PHA) were extracted by pressurized liquid extraction with either toluene or acetone. Native dioxins were equivalently extracted from APs with both solvents, whereas only acetone could satisfactorily recover the ¹³C-labelled compounds from metal-free PHA. The recovery rates of dioxins by toluene extraction from metal-free PHA varied with the organic carbon content of the PHA. However, even with acetone, the recovery of dioxins from metal-bound HA was poor (11–40%). These results suggest that PHA prevented the solvents from accessing sequestered dioxins. This characteristic of solid HA may influence the extractability of dioxins from humus-rich soil.     

Simultaneous determination of monomethylmercury, monobutyltin, dibutyltin and tributyltin in environmental samples by multi-elemental-species-specific isotope dilution analysis using electron ionisation GC-MS

In this work, the simultaneous determination of four organometallic species (monomethylmercury, monobutyltin, dibutyltin and tributyltin) in environmental samples by using a GC-MS system with electron ionisation has been established. The measurement of isotope ratios in each species was accomplished by selecting the most adequate molecular cluster, and simple mathematical equations were applied to correct the contributions of 13C from the organic groups attached to the tin and mercury atoms. The influence of different parameters such as dwell time on the precision and accuracy of the measured isotope ratios in each target species has also been studied. The determination and the sample preparation procedures presented in this work were first individually validated by analysing several certified reference materials for butyltin compounds (mussel tissue CRM-477 and marine sediment SOPH-1) and for monomethylmercury (tuna fish CRM-464) using an innovative focused microwave technology for the extraction of the species from the solid samples. Additionally, the simultaneous determination of the four species was successfully validated by obtaining quantitative recoveries in spiked natural waters and by analysing the certified reference material BCR-710 (certified in tributyltin and monomethylmercury). The values obtained in such certified tissue were fully in agreement not only with the certified mass fractions but also with the proposed indicative values for mono- and dibutyltin.     

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.