Lobster Hepatopancreas Research Articles

A Comparison of ETV and LA for the Determination of Trace Elements in Solid Samples by MIP OES

AbstractThe performance of electrothermal vaporization (ETV) and laser ablation (LA) of dry aerosols as sample introduction systems for microwave induced plasma optical emission spectrometry (MIP OES) are compared and evaluated in terms of detection limits, precision and accuracy for the determination of trace elements (Ca, Cd, Cu, Fe, Mg, Mn, Sr, Zn) in the same solid micro samples. In MIP OES both radiation sources can be independently adjusted to optimize the sampling process and then its subsequent excitation. A univariate approach and simplex optimization procedure were used to obtain the best signal/noise (S/N) ratio and derive analytical figures of merit. A comparison using a Student’st-test between the results obtained by both ETV/LA-MIP OES methods for trace elements, and concentrations in standard reference material (SRM) and certified reference materials (CRMs) showed that there was no significant differences on a 95 % confidence level. The detection limits of the tested elements in solid samples by ETV/LA-MIP OES were in the range of 0.1 to 11 µg g−1for all elements determined, while the corresponding absolute values in the range of ng. The precision of the results for ETV-MIP OES and LA-MIP OES varied between 2 and 4 % and 3 and 7 %, respectively. The linear dynamic ranges in the ETV/LA-MIP OES are extend over three decades of concentration. The methods were validated by the analysis of NIST SRM 2711Montana Soil, NRCC CRM PACS-2 Marine Sediment and NRCC CRM TORT-2 Lobster Hepatopancreas of different matrix composition and by the standard addition technique.

Paralytic shellfish toxins in Australian Southern Rock Lobster (Jasus edwardsii): Acute human exposure from consumption of hepatopancreas

ABSTRACTParalytic shellfish toxins (PST) were identified in the hepatopancreas of Southern Rock Lobster (Jasus edwardsii) during Alexandrium tamarense blooms in Tasmania, Australia. Human health risk from PST in lobsters was unknown – this study assesses exposure to PST from hepatopancreas consumption. Lobster hepatopancreas samples collected during blooms (n = 181) were mostly positive for PST (>88%), the highest concentration was 4032 μg STX-2HCl eq/kg. Consumer exposure to PST was estimated using a 2-D Monte Carlo model. Mean PST intake (pi) from hepatopancreas consumption (raw and cooked) was below the lowest-observed-adverse-effect-level (LOAEL) for PST (<2.0 μg/kg bw), however the 97.5th percentile pi for raw meals (2.64 μg/kg bw) exceeded the LOAEL. A total of 4.1% of raw hepatopancreas meals were estimated to exceed the LOAEL. Lobster hepatopancreas consumption during A. tamarense blooms may be concerning for a small proportion of consumers, particularly those that eat large meals at the bloom peak. However, when the model was re-run with PST concentration capped at the bivalve regulatory limit (800 μg STX-2HCl eq/kg) pi decreased, with the 97.5th percentile values below the LOAEL. Thus, issuing public health warnings and harvesting restrictions for lobsters when levels exceed 800 μg STX-2HCl eq/kg would reduce the probability of illness occurring.

Speciation analysis of arsenic in seafood and seaweed: Part II-single laboratory validation of method.

Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76-106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90-105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80-92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6-16ng g-1 arsenic.

Doehlert design in the optimization of ultrasound assisted dissolution of fish fillet samples with tetramethyl ammonium hydroxide for metals determination using FAAS

Doehlert design and desirability function were used in the optimization of an ultrasound assisted dissolution method of fish fillet samples with tetramethyl ammonium hydroxide (TMAH) for the determination of Ca, Fe, Zn and Mg by flame atomic absorption spectrometry. The variables values after optimization were 620 μL (volume of TMAH), 25 min (sonication time) and 46 °C (bath temperature). The quantification limits for Ca, Mg, Fe and Zn were 56, 107, 23 and 2.9 μg g−1, respectively. Accuracy was evaluated by comparing the results generated from the analysis of the samples treated by the proposed method and by wet digestion. Additionally, accuracy for Fe and Zn was assessed by the analysis of certified reference materials Tort-3 (Lobster hepatopancreas), ERM-CE 278 (mussel tissue) and Dolt-4 (Fish liver). There were no significant differences between the results obtained at a 95% confidence level when results were evaluated by t-test application.

Fate of Paralytic Shellfish Toxins in Southern Rock Lobster (Jasus edwardsii) during Cooking: Concentration, Composition, and Distribution

Paralytic shellfish toxin (PST) producing microalgal blooms have a significant economic impact on the Southern Rock Lobster ( Jasus edwardsii) fishery in Tasmania, Australia. The regulatory level of 0.8 mg of saxitoxin (STX) eq/kg in place for bivalve shellfish fisheries is applied to lobster hepatopancreas during blooms of toxic algae, resulting in harvest closures and ongoing risk management implications for the fishery. This cooking study was undertaken to inform a human health risk assessment, in conjunction with studies on the uptake and elimination of PST in J. edwardsii. Live lobsters in tanks were contaminated through consumption of PST-containing mussels harvested during an Alexandrium tamarense Group 1 bloom event. This resulted in a mean lobster hepatopancreas level of 2.83 ± 0.84 mg of STX·2HCl eq/kg. Other edible tissues contained negligible concentrations of toxin. PST concentrations in all tissues did not significantly change after boiling or steaming, although the amount of hepatopancreas available for consumption did decrease significantly with both cooking methods, because the tissue became more dispersed, resulting in an overall reduction in the toxin exposure per hepatopancreas consumed. The toxin profile was dominated by STX; gonyautoxin 2, 3; N-sulfocarbamoyl-gonyautoxin 2, 3 (C1,2); and gonyautoxin 5. No significant changes to the toxin profile were observed after either of the cooking methods. Pâté, bisque, and soufflé prepared from the hepatopancreas of toxic lobsters contained negligible levels of PST in each serving; on average, a serving of pâté contained 0.01 mg of STX·2HCl eq, whereas a serving of bisque or soufflé contained <0.01 mg of STX·2HCl eq. The findings of this study will inform a risk assessment of PST in J. edwardsii to determine risk management options for this fishery in Australia.

Rock lobster hepatopancreas consumption data for dietary exposure assessment among recreational harvesters in Tasmania and South Australia

ABSTRACTIn 2012 and 2015, blooms of Alexandrium tamarense occurred in Tasmania, Australia, and paralytic shellfish toxins (PST) were identified in the hepatopancreas of Southern Rock Lobsters. The human health risk was unclear, because consumption data were not available for lobster hepatopancreas. Thus, the aim of this study was to investigate the types of lobster tissues consumed, hepatopancreas portion size, and consumption format (boiled, steamed, raw, etc.), for Tasmanian and South Australian recreational harvesters.A significant proportion of harvesters (15%) eat lobster hepatopancreas, with the majority consuming it as a dipping sauce for cooked (boiled or steamed) lobster meat. Two different methods were used to estimate portion size, a recollection-based food consumption questionnaire (FCQ) and a prospective Food Diary – mean portion size estimates showed good agreement: 3.4 g and 4.8 g, respectively. These results are critical for assessing the exposure of recreational harvesters to acute contaminants, such as PST, in lobster hepatopancreas. Results from the FCQ showed that lobster hepatopancreas is not consumed as often as white meat, suggesting that exposure to contaminants in hepatopancreas may be less frequent than white meat. This should be considered when evaluating human health risk from repeated or long term (chronic) exposure to contaminants in lobsters.

Experimental uptake and depuration of paralytic shellfish toxins in Southern Rock Lobster, Jasus edwardsii

In October 2012, paralytic shellfish toxins (PST) were detected in the hepatopancreas of Southern Rock Lobsters (Jasus edwardsii) collected from the east coast of Tasmania, Australia. This resulted in the first commercial closure in Australia for this species. Questions were raised on how the toxins were transferred to the lobsters, how long the toxins would persist, whether PST-contaminated hepatopancreas posed a risk to human health, and what management strategies could be applied. The aim of this study was to investigate whether PST-contaminated mussels are a potential vector enabling toxin accumulation in J. edwardsii and to collect information on toxin uptake, distribution and depuration rates and toxin profiles under controlled experimental settings. Lobsters were fed mussels naturally contaminated with PST for a period of 28 days in an experimental setting; following this, lobsters were allocated to either fed or starved treatment groups. PST were not detected in the tail tissue of lobsters at any stage of the experiment. Lobster hepatopancreas contained mean levels of 2.4 mg STX.2HCl eq/kg after 28 days of uptake, although substantial variability in total toxicity was observed. The PST profile of the hepatopancreas was similar to that of the contaminated mussels used as feed. Significant differences were noted in the PST depuration rates between fed and starved treatment groups. The daily depuration rate for total PST was estimated to be 0.019 and 0.013 mg STX.2HCl eq/kg for the fed and starved treatment groups respectively using a constant-rate decay model. After 42 days of depuration, total PST (STX equivalents) levels in the hepatopancreas of all lobsters were below 0.8 mg STX.2HCl eq/kg, which represents the regulatory level applied to bivalves. This result indicates that long-term holding to depurate PST may potentially be used as a risk management tool.

Sensitive Determination of Cd in Small-Volume Samples by Miniaturized Liquid Drop Anode Atmospheric Pressure Glow Discharge Optical Emission Spectrometry.

A novel liquid drop anode (LDA) direct current atmospheric pressure glow discharge (dc-APGD) system was applied for direct determination of Cd in liquid microsamples (50 μL) by optical emission spectrometry (OES). The microdischarge was generated in open-to-air atmosphere between a solid pin type tungsten cathode and a liquid drop placed on a graphite disk anode. The arrangement of the graphite disk placed on a PTFE chip platform as well as the solid pin type cathode was simple and robust. The limit of detection (LOD) of Cd for the developed LDA-APGD-OES method was 0.20-0.40 μg L-1, while precision (as the relative standard deviation for the repeated measurements) was within 2-5%. By using the liquid drop of 50 μL, the linearity range of 1-1000 μg L-1 was achieved. The effect of addition of the low-molecular weight (LMW) organic compounds, easily ionized elements (EIEs), i.e., Ca, K, Mg, and Na, as well as the foreign ions (Al, Cu, Fe, Mn, Zn) to the solution on the in situ atomization and excitation processes occurred during operation of the LDA-APGD system, and the response of Cd was studied. Validation of the proposed method was demonstrated by analysis of Lobster hepatopancreas (TORT-2), pig kidney (ERM-BB186), and groundwater (ERM-CA615) certified reference materials (CRMs) and recoveries of Cd from water samples spiked with 25 μg L-1 of Cd. Very good agreement between the found and certified values of Cd in the CRMs (the recoveries were within the range of 96.3-99.6%) indicated trueness of the method and its reliability for determination of traces of Cd. In the case of the spiked water samples, the recoveries obtained were in the range from 95.2 to 99.5%.

Functional characterization of a novel disaccharide transporter in lobster hepatopancreas.

In animals, the accepted model of carbohydrate digestion and absorption involves reduction of disaccharides into the monosaccharides glucose, fructose, and galactose followed by their individual transmembrane transport into cells. In 2011, a gene for a distinct disaccharide sucrose transporter (SCRT) was found in Drosophila melanogaster and characterized in a yeast expression system. The purpose of the present investigation was to functionally identify and characterize a putative disaccharide transporter analog in the hepatopancreas of the American lobster, Homarus americanus. Purified hepatopancreatic brush-border membrane vesicles (BBMV) were used in transport experiments using 14C-sucrose and a Millipore filter isolation technique. In the absence of sodium, an external pH of 4 significantly stimulated the uptake of 14C-sucrose compared to that occurring at pH 5, 6, or 7. At pH 7, increasing external concentrations of sodium increased 14C-sucrose uptake by BBMV in a hyperbolic fashion and this stimulation was significantly reduced when the pH was changed to 4, suggesting that both protons and sodium ions were each capable of driving the uptake of the sugar. In experiments with a variety of monosaccharides, disaccharides, and trisaccharides, used as potential inhibitors of 14C-sucrose uptake, only maltose and trehalose inhibited carrier-mediated 14C-sucrose transport. An additional experiment showed that 20mM maltose was a competitive inhibitor of 14C-sucrose uptake. The use of a putative lobster SCRT by both maltose and trehalose is nutritionally appropriate for lobsters as they commonly digest glycogen and chitin, polymers of maltose and trehalose, respectively. These findings suggest there is a brush-border proton- or sodium-dependent, hepatopancreatic carrier process, shared by sucrose, maltose, and trehalose, that may function to absorb disaccharides that are produced from digestion of naturally occurring dietary constituents.

Pump- and Valve-Free Flow Injection Capillary Liquid Electrode Discharge Optical Emission Spectrometry Coupled to a Droplet Array Platform.

A miniature (2.5 cm length × 2.0 cm width × 1.0 cm height), low power (<10 W), and capillary liquid electrode microplasma optical emission spectrometer was developed for rapid determination of metallic species in aqueous solutions. The sample solution can be automatically introduced into the source without a pump owing to the inherent capillary attraction and the force arising from the solution vaporization induced by microplasma. A droplet array was used as a sampling platform to realize flow injection without using any valve and pump, significantly increasing throughput to 90 samples h-1. Sample volume is controlled through the sampling time and reduced to the nanoliter level. With a sampling time of 10 s (equal to 600 nL), detection limits of 30 μg L-1 (18 pg) and 75 μg L-1 (45 pg) were obtained for Cd and Hg, respectively, comparable to those reported for liquid electrode microplasma optical emission spectrometry. However, sample consumption is reduced more than 100-fold, making the proposed technique more suitable for the analysis of elements such as Cd, Hg, Li, Na, and K when sample volumes may be limited. The utility of this system was demonstrated by the determination of Cd and Hg in blood, real water samples, and Certified Reference Materials (rice powder, GBW07601a, and lobster hepatopancreas, TORT-3).

A critical assessment of ultrasound-assisted extraction as sample pre-treatment for fast determination of multielements in seafood using inductively coupled plasma mass spectrometry

In this work, the suitability of extracts obtained from seafood samples after ultrasound-assisted extraction for determining Cd, Cu, Mn, Ni, Pb and Zn by Inductively Coupled Plasma-Mass Spectrometry was evaluated. For this purpose, different strategies were studied: (i) dilution of extracts; (ii) clean-up of extracts with C18 cartridges; (iii) use of a flow injection system for introducing extracts in the instrument. Potential interferences from acid extractant, major elements and organic matter were assessed. Internal standard, measurement mode and signal drift were also studied. Validation was carried out with the certified reference material TORT-2 (lobster hepatopancreas). Recoveries were between 92 and 106%. Precision, expressed as relative standard deviation, ranged from 2 to 6%. By using diluted extracts, limits of detection were similar as compared to those obtained after microwave-assisted digestion, or even better if a clean-up of extracts is applied. Following this approach, seafood samples of common consumption (mussel and shrimp) were rapidly analyzed.

Flowing Liquid Anode Atmospheric Pressure Glow Discharge as an Excitation Source for Optical Emission Spectrometry with the Improved Detectability of Ag, Cd, Hg, Pb, Tl, and Zn.

A novel atmospheric pressure glow discharge generated in contact with a flowing liquid anode (FLA-APGD) was developed as the efficient excitation source for the optical emission spectrometry (OES) detection. Differences in the appearance and the electrical characteristic of the FLA-APGD and a conventional system operated with a flowing liquid cathode (FLC-APGD) were studied in detail and discussed. Under the optimal operating conditions for the FLA-APGD, the emission from the analytes (Ag, Cd, Hg, Pb, Tl, and Zn) was from 20 to 120 times higher as compared to the FLC-APGD. Limits of detections (LODs) established with a novel FLA-APGD system were on average 20 times better than those obtained for the FLC-APGD. A further improvement of the LODs was achieved by reducing the background shift interferences and, as a result, the LODs for Ag, Cd, Hg, Pb, Tl, and Zn were 0.004, 0.040, 0.70, 1.7, 0.035, and 0.45 μg L(-1), respectively. The precision of the FLA-APGD-OES method was evaluated to be within 2-5% (as the relative standard deviation of the repeated measurements). The method found its application in the determination of the content of Ag, Cd, Hg, Pb, Tl, and Zn in a certified reference material (CRM) of Lobster hepatopancreas (TORT-2), four brass samples as well as mineral water and tea leaves samples spiked with the analytes. In the case of brass samples, a reference method, i.e., inductively coupled plasma optical emission spectrometry (ICP-OES) was used. A good agreement between the results obtained with FLA-APGD-OES and the certified values for the CRM TORT-2 as well as the reference values obtained with ICP-OES for the brass samples was revealed, indicating the good accuracy of the proposed method. The recoveries obtained for the spiked samples of mineral water and tea leaves were within the range of 97.5-102%.

Heavy metals in tissues of scorpionfish (Scorpaena porcus) caught from Black Sea (Turkey) and potential risks to human health.

Scorpionfish (Scorpaena porcus) is a demersal fish species commercially important for its of which meat is tough and delicious. The aim of this study was to determine heavy metal (Al, Cu, Ni, As, Cd, Hg, Pb, U) concentrations in this fish species which is traditionally consumed in the Black Sea Area and, to compare the concentrations of various toxic elements in different organs of the fish specimens (muscle, liver, gill, and skin). Within this scope, the mineralization was performed using microwave digestion system. Thirty-two scorpionfish caught from Sinop Inland Port during 2010 were analyzed. The heavy metal concentrations were determined with the method of inductively coupled plasma mass spectroscopy (ICP-MS). Verification of the method was demonstrated by analysis of standard reference material (NRCC-TORT-2 lobster hepatopancreas). After evaluation of the results, it was determined that the highest heavy metal accumulation was generally found in the liver. The maximum aluminum level and the minimum uranium level were found in the analyzed tissues. In terms of heavy metals, Al, Cu, Cd, and Hg showed a statistically significant difference between tissues (p<0.05). It was determined that heavy metal concentrations obtained from the muscle tissues did not exceed the national and international recommended limits; and also it was found that daily intake amounts did not exceed tolerable daily intake amounts. Furthermore, in THQ based risk evaluation, the value 1 which is crucial for children and adults was not surpassed. In terms of public health, it was found out that there was not any risk in consumption of scorpionfish in the study area.

Measurement of selenomethionine and selenocysteine in fish tissues using HPLC-ICP-MS

The extraction and measurement of selenomethionine (SeMet) and selenocysteine (SeCys) in fish muscle and liver tissues were evaluated. Preliminary experiments were undertaken with marine certified reference materials. NRCC TORT 1/2 Lobster hepatopancreas, NRCC DOLT 2/3; Dogfish liver and NIST 1566 a/b Oyster tissue were extracted using aqueous leaching, enzymatic hydrolysis and acid hydrolysis with ultrasound, microwave assisted heating and conventional heating using a hybridisation oven. High Se recoveries were obtained with the use of methanesulfonic acid as an extractant (89–92%); however, the low pH required for extraction is not compatible with most HPLC columns and dilution is required to analyse extracts that precluded the measurement of Se in samples from relatively uncontaminated environments. As well, Se species (SeMet and SeCys) degrade with the use of highly acidic extractants. Enzymatic hydrolysis with protease type XIV gave good recoveries (63–67%), but only SeMet was stable in the extract. As SeCys was not stable, a derivatisation step using iodoacetamide to form a stable carboxymethylated complex was used prior to enzymatic hydrolysis. Conventional heating at 37°C for 20h and microwave assisted heating at 45°C for 45min gave similar recoveries for CRMs but conventional heating gave slightly better recoveries for fish tissues.Two separate complementary methods were developed for the measurement of SeMet and SeCys in marine fish tissues; SeMet was measured after protease XIV hydrolysis and analysis using anion or cation exchange chromatography-ICPMS, while for the measurement of SeCys a carbamidomethylation derivatisation procedure prior to the protease hydrolysis was used and the separation of the species was carried out using size exclusion chromatography, followed by C8 ion-pair reversed-phase chromatography with ICPMS. Recoveries of SeMet and SeCys added to CRMs and fish tissues were 97±9% and 84±9% respectively.

Solid Phase Extraction to On-Line Preconcentrate Trace Cadmium Using Chemically Modified Nano-Carbon Black with 3-Mercaptopropyltrimethoxysilane

Carbon black (CB) grafted with 3-mercaptopropyltrimethoxysilane (3-MPTMS) was used as solid phase extractor for Cd2+ in a flow injection system coupled to flame atomic absorption spectrometry (FAAS). The influence of pH, buffer concentration, preconcentration flow rate and eluent concentration on preconcentration of Cd2+ were investigated by means of chemometric tools. The characterization of the adsorbent chemically modified was performed by Fourier transform infrared, scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, Raman spectroscopy and textural analysis. To perform the on-line preconcentration, 20.0 mL of a pH 7.0 Cd2+ solution at a flow rate of 4.0 mL min−1 was loaded through 30.0 mg of modified CB and then eluted with 1.0 mol L−1 HCl toward the FAAS instrument. The limits of detection and quantification were found to be 0.20 and 0.66 µg L−1, respectively. Addition and recovery tests carried out in real samples (mineral, tap and saline waters, and cigarette sample) and the analysis of certified reference material (TORT-2, lobster hepatopancreas reference) attested the applicability of proposed method.

Comparative tissue expression of American lobster (Homarus americanus) immune genes during bacterial and scuticociliate challenge.

The American lobster (Homarus americanus) fishery is the most economically significant fishery in Canada; although comparatively little is known about the lobsters' response to pathogenic challenge. This is the first study to investigate the expression of immune genes in tissues outside of the lobster hepatopancreas in response to challenges by the Gram-positive bacteria, Aerococcus viridans var. homari or the scuticociliate parasite, Anophryoides haemophila. The hepatopancreas has been regarded as the major humoral immune organ in crustaceans, but the contribution of other organs and tissues to the molecular immune response has largely been overlooked. This study used RT-qPCR to monitor the gene expression of several immune genes including three anti-lipopolysaccharide isoforms (ALF) Homame ALF-B1, Homame ALF-C1 and ALFHa-1, acute phase serum amyloid protein A (SAA), as well as thioredoxin and hexokinase, in antennal gland and gill tissues. Our findings indicate that the gene expression of the SAA and all ALF isoforms in the antennal gland and gill tissues increased in response to pathogenic challenge. However, there was differential expression of individual ALF isoforms that were dependent on both the tissue, and the pathogen used in the challenge. The gene expression changes of several immune genes were found to be higher in the antennal gland than have been previously reported for the hepatopancreas. This study demonstrates that increased immune gene expression from the gill and antennal gland over the course of pathogen induced disease contributes to the immune response of H. americanus.

Solid Phase Extraction of Trace Elements in Waterand Tissue Samples on a Mini Column with Diphenylcarbazone Impregnated Nano-TiO2 and Their Determination by Inductively Coupled Plasma Optical Emission Spectrometry.

This study presents a simple, robust and environmentally friendly solid phase preconcentration procedure for multielement determination by inductively coupled plasma optical emission spectrometry (ICP-OES) using diphenylcarbazone (DPC) impregnated TiO2 nanopowder (n-TiO2). DPC was successfully impregnated onto n-TiO2 in colloidal solution. A number of elements, including Co(II), Cr(III), Cu(II), Fe(III), Mn(II) and Zn(II) were quantitatively preconcentrated from aqueous solutions between pH 8 and 8.5 at a flow rate of 2 mL min-1, and then eluted with 2 mL of 5% (v/v) HNO3. A mini-column packed with 0.12 g DPC impregnated n-TiO2 retained all elements quantitatively from up to 250 mL multielement solution (2.5 μg per analyte) affording an enrichment factor of 125. The limits of detection (LOD) for preconcentration of 50 mL blank solutions (n = 12) were 0.28, 0.15, 0.25, 0.22, 0.12, and 0.10 μg L-1 for Co, Cr, Cu, Fe, Mn, and Zn, respectively. The relative standard deviation (RSD) for five replicate determinations was 0.8, 3.4, 2.6, 2.2, 1.2 and 3.3% for Co, Cr, Cu, Fe, Mn and Zn, respectively, at 5 μg L-1 level. The method was validated with analysis of Freshwater (SRM 1643e) and Lobster hepatopancreas (TORT-2) certified reference materials, and then applied to the determination of the elements from tap water and lake water samples by ICP-OES.

Determination and speciation of trace and ultratrace selenium ions by energy-dispersive X-ray fluorescence spectrometry using graphene as solid adsorbent in dispersive micro-solid phase extraction

A dispersive micro-solid phase extraction (DMSPE) with graphene as a solid adsorbent and ammonium pyrrolidinedithiocarbamate (APDC) as a chelating agent was proposed for speciation and detemination of inorganic selenium by the energy-dispersive X-ray fluorescence spectrometry (EDXRF). In developed DMSPE, graphene particles are dispersed throughout the analyzed solution, therefore reaction between Se(IV)–APDC complexes and graphene nanoparticles occurs immediately. The concentration of Se(VI) is calculated as the difference between the concentration of selenite after and before prereduction of selenate. A central composite face-centered design with 3 center points was performed in order to optimize conditions and to study the effect of four variables (pH of the sample, concentration of APDC, concentration of Triton-X-100, and sample volume). The best results were obtained when suspension consisting of 200µg of graphene nanosheets, 1.2mg of APDC and 0.06mg of Triton-X-100 was rapidly injected to the 50mL of the analyzed solution. Under optimized conditions Se ions can be determined with a very good recovery (97.7±5.0% and 99.2±6.6% for Se(IV) and Se(VI), respectively) and precision (RSD=5.1–6.6%). Proposed DMSPE/EDXRF procedure allowed to obtain low detection limits (0.032ngmL−1) and high enrichment factor (1013±15). The proposed methodology was successfully applied for the determination of Se in mineral, tap, lake and sea water samples as well as in biological materials (Lobster Hepatopancreas and Pig Kidney).

Rapid QuEChERS Approach Using Novel Solid Phase Extraction for Insecticides in Lobster and Shellfish Tissue with Gas Chromatography–Tandem Mass Spectrometry

Novel, rapid, inexpensive, and simple QuEChERS extraction followed by phospholipid solid phase extraction was successfully developed and validated for the determination of methoprene, resmethrin, bifenthrin, cyhalothrin, and permethrin in lobster and shellfish tissues by gas chromatography–tandem mass spectrometry. This method is equivalent in final sample purity to the traditional gel permeation and open column chromatography sample preparation techniques, but has clear advantages due to reductions in time, labor, solvent use, and can be performed with minimal staff training. The proposed methodology was effectively applied to the analysis of North Atlantic lobster (hepatopancreas and muscle) and shellfish tissue. The linearity of the calibration curves for all analytes were R2 > 0.9991. The surrogate recoveries were 98.2 ± 18.0%, while the target compound recoveries, for fortified samples, were in the range of 62.0%–128.8% with RSD values <17.2% for all compounds. The detection limits for the analytes ranged from 0.0056 µg/g to 0.76 µg/g with 84.4–119.5% accuracy and relative standard deviations less than 3.77%.

Bioaccumulation of heavy metals in tissues of the gibel carp Carassius gibelio: Example of Marmara Lake, Turkey

Within the scope of this study, heavy metals presence (Al, Cr, Ni, Cu, As, Cd, Hg, Pb) in water samples and liver, gills and muscle tissue of gibel carp Carassius gibelio caught in Marmara Lake was analyzed seasonally. It was determined that there was not any difference seasonally with regard to heavy metals studied in lake waters (p > 0.05). Mineralization of fish tissues was made by microwave-wet decomposition. To evaluate heavy metal concentrations in water and tissue samples, method of inductively coupled plasma—mass spectroscopy (ICP-MS) was applied. TORT 2 lobster hepatopancreas was used as certified reference matter in this study. According to obtained results, bioaccumulation rates for gills were found as Cu > Cd > Ni > Pb > Cr > Al > As > Hg, for liver and muscle tissues they were found as Cu > Cd > Ni > Cr > Pb > Al > As > Hg. It was proved that the most bioaccumulated heavy metal was Cu and the least bioaccumulated was Hg for all of the studied tissues.