Maximum RSD Research Articles

Fe3O4@PS-DVB microspheres modified with urea functional groups for rapid and green extraction of fluorinated aromatic carboxylic acids from tap and formation water

The present study describes the trace analysis of 23 fluorinated aromatic carboxylic acids based on the dispersive magnetic solid phase extraction (m-SPE) technique coupled with the gas chromatography coupled with mass spectrometry (GC–MS) electron ionization (EI) technique. A commercial hydrophilic-lipophilic balanced (HLB) material polystyrene divinyl benzene having urea functional groups was modified with magnetite nanoparticles and employed as a sorbent for dispersive m-SPE of fluorobenzoic acids (FBAs) from the tap and formation water samples. The extraction occurred due to π- π interaction between the aromatic ring of synthesized sorbent and the aromatic ring of FBAs, the hydrogen bond formation between the urea functional group of the sorbent and carbonyl oxygen, fluorine of the FBAs. As a result, the method was precise, rapid, reproducible, and calibrated with the coefficient of variation (R2) greater than 0.98 for all 23 compounds. The instrument detection limit (IDL) and method detection limit (MDL) were found in the range of 2.60 – 8.25 ng/mL and 0.08 – 0.28 ng/mL respectively. Extraction efficiencies were found in the range of 83.80–100 % for tap water samples and 78.41–98.92 % for formation water samples, respectively, with an enrichment factor of 33.33–66.66 and a maximum RSD of 7.07 %. The recyclability and magnetic properties of the synthesized material were also investigated, resulting in the material being reused for six cycles without impacting its performance; hence, the method offers rapid determination and high throughput analysis of FBAs. In addition, simulation studies were performed using the adsorption location tool of Material Studio, confirming the interaction sites of sorbent with FBAs. AGREE evaluated the analytical greenness of the method, and the score was found to be 0.51.

Copper Micro-Flowers for Electrocatalytic Sensing of Nitrate Ions in Water.

The progressive increase in nitrate's (NO3-) presence in surface and groundwater enhances environmental and human health risks. The aim of this work is the fabrication and characterization of sensitive, real-time, low-cost, and portable amperometric sensors for low NO3- concentration detection in water. Copper (Cu) micro-flowers were electrodeposited on top of carbon screen-printed electrodes (SPCEs) via cyclic voltammetry (with voltage ranging from -1.0 V to 0.0 V at a scan rate of 0.1 V s-1). The obtained sensors exhibited a high catalytic activity toward the electro-reduction in NO3-, with a sensitivity of 44.71 μA/mM. They had a limit of detection of 0.87 µM and a good dynamic linear concentration range from 0.05 to 3 mM. The results were compared to spectrophotometric analysis. In addition, the devices exhibited good stability and a maximum standard deviation (RSD) of 5% after ten measurements; reproducibility, with a maximum RSD of 4%; and repeatability after 10 measurements with the RSD at only 5.63%.

Development of an electrochemical sensor for the quantification of ascorbic acid and acetaminophen in pharmaceutical samples

This work presents the modification of glassy carbon electrodes (GCE) by using a dispersion resulting from the non-covalent functionalization of multi-walled carbon nanotubes (MWCNT) with polyarginine (polyArg). MWCNT-polyArg is used for the quantification of ascorbic acid (AA) in the presence of acetaminophen (APAP) and viceversa. Since ascorbic acid and acetaminophen are strongly absorbed on GCE/MWCNT-polyArg, they can be detected in the presence of 4.0×10−5 M acetaminophen (and 3.0×10−5 M ascorbic acid) by using adsorptive stripping with media exchange and differential pulse voltammetry. Using water as the solvent for the MWCNT dispersion, the result was Z-potential of 0.053 ± 0.006 V. The developed sensor showed excellent specificity, sensitivity, stability and reproducibility compared to previously published sensors. The GCE/MWCNT-polyArg sensor shows a fast response time of ∼5 minutes, low limits of detection and quantification for AA (0.95 and 2.9 μM respectively) and APAP (0.27 and 0.82μM, respectively), high sensitivity of 0.0616 μA/M for AA or APAP 0.240μA/M. It was used to test its practicability by determining the concentration of AA or APAP (AA and APAP) in pharmaceutical samples. Finally, the simultaneous measurement of ascorbic acid and acetaminophen in pharmaceuticals showed a good correlation, with a maximum error and RSD of 4.5 and 5.1 %, respectively.

Chronoamperometric Ammonium Ion Detection in Water via Conductive Polymers and Gold Nanoparticles.

Monitoring of ammonium ion levels in water is essential due to its significant impact on environmental and human health. This work aims to fabricate and characterize sensitive, real-time, low-cost, and portable amperometric sensors for low NH4+ concentrations in water. Two strategies were conducted by cyclic voltammetry (CV): electrodeposition of Au nanoparticles on a commercial polyaniline/C electrode (Au/PANI/C), and CV of electropolymerized polyaniline on a commercial carbon electrode (Au/PANIep/C). Au NPs increase the electrical conductivity of PANI and its ability to transfer charges during electrochemical reactions. The electrode performances were tested in a concentration range from 0.35 µM to 7 µM in NH4+ solution. The results show that the Au/PANI/C electrode performs well for high NH4+ concentrations (0.34 µM LoD) and worsens for low NH4+ concentrations (0.01 µM LoD). A reverse performance occurs for the electrode Au/PANIep/C, with a 0.03 µM LoD at low NH4+ concentration and 0.07 µM LoD at high NH4+ concentration. The electrodes exhibit a good reproducibility, with a maximum RSD of 3.68% for Au/PANI/C and 5.94% for Au/PANIep/C. In addition, the results of the repeatability tests show that the electrochemical reaction of sensing is fully reversible, leaving the electrode ready for a new detection event.

Diffusive gradients in thin films (DGT) as a robust and reliable technique to measure bioavailable metals in anaerobic digestates

Applying diffusive gradients in thin films (DGT) to digestates as a standardized method requires addressing unclear precision of the method and the lack of information on compounds in digestates responsible for metal binding. We tested the precision of the method on seven different digestates by measuring Co, Ni, Fe and Mn accumulated in the DGT devices. Next, we tested gels with two different pore sizes in parallel (restricted gel with smaller and open gel with bigger pore size) to identify organic complexes that bind trace metals. Finally, we tried to understand how the feedstock affects DGT concentrations. The precision of the method was acceptable as the RSDs of the DGT technical triplicates for Co were lower than 10% for all seven digestates. For the other metals, slightly higher RSDs were detected in a few samples: Mn RSD varied more than 10% in only one digestate sample (27% RSD), Ni RSD in two samples (19% twice) and Fe RSD in three (with 18% maximum RSD). The measurements of Co, Ni and Fe after diffusion through the restricted gel compared to the open gel showed a significant difference in maximum three out of seven samples. The investigated metals were found in higher concentrations on the DGT resins exposed to digestates originating from manure, energy crops and food waste than in DGT resins exposed to samples originating from wastewater treatment plant digesters. Overall, open DGT appears to be applicable for Co, Ni, Fe and Mn bioavailability measurements in digestates originating from various feedstocks.

A Eu3+doped functional core-shell nanophosphor as fluorescent biosensor for highly selective and sensitive detection of dsDNA

Lanthanide-doped core-shell nanomaterials have illustrated budding potential as luminescent materials, but their biological applications have still been very limited due to their aqueous solubility and biocompatibility. Here, we report a simple and cost-effective approach to construct a water-stable chitosan-functionalized lanthanoid-based core shell (Ca-Eu:Y2O3@SiO2) nanophosphor. The as-synthesized Ca-Eu:Y2O3@SiO2-chitosan (CEY@SiO2-CH) nanophosphor has been characterized for its structural, morphological, and optical properties, by employing different analytical tools. This sensing platform is suitable for dsDNA probing by tracing the “turn on” fluorescence signal generated by CEY@SiO2-CH nanophosphor with the addition of dsDNA. The ratio of fluorescence intensity enhancement is proportional to the concentration of dsDNA in the range 0.1–90 nM, with the limit of detection at ⁓16.1 pM under optimal experimental conditions. The enhancement in fluorescence response of functionalized core-shell phosphor with dsDNA is due to the antenna effect. Additionally, response of probe has been studied for the real samples displaying percent recovery in between 101 and 105, maximum RSD% upto 5.23 (n = 3). This outcome can be applied to the selective sensing of dsDNA through optical response. These findings establish the CEY@SiO2-CH a simple, portable, and potential candidate as a sensor for rapid and analytical detection of dsDNA.

Electrocatalytic Platform Based on Silver-Doped Sugar Apple-like Cupric Oxide Embedded Functionalized Carbon Nanotubes for Nanomolar Detection of Acetaminophen (APAP)

Economical and nanomolar-level determination of the analgesic drug, acetaminophen (APAP), is reported in this work. A novel ternary nanocomposite based on silver-doped sugar apple-like cupric oxide (CuO)-decorated amine-functionalized multi-walled carbon nanotubes (fCNTs) was sonochemically prepared. CuO nanoparticles were synthesized based on the ascorbic acid-mediated low-temperature method, and sidewall functionalization of CNTs was carried out. Important characterizations of the synthesized materials were analyzed using SEM, TEM, HAADF-STEM, elemental mapping, EDX, lattice fringes, SAED pattern, XRD, EIS, UV-Vis, micro-Raman spectroscopy, and FTIR. It was noted the sonochemically prepared nanocomposite diligently fabricated on screen-printed carbon electrode showcased outstanding electrocatalytic performance towards APAP determination. The APAP sensor exhibited ultra-low limit of detection of 4 nM, wide linear concentration ranges of 0.02-3.77 and 3.77-90.02 μM, and high sensitivity of 30.45 μA μM-1 cm-2. Moreover, further evaluation of the sensor's performance based on electrochemical experiments showcased outstanding selectivity, stability, reproducibility, and repeatability. Further, excellent practical feasibility of the proposed APAP sensor was affirmed with excellent recovery larger than 96.86% and a maximum RSD of 3.67%.

Spectroscopic ellipsometry-based aptasensor platform for bisphenol a detection

Endocrine-disrupting chemicals (EDC) are pollutants that alter the function of the endocrine system by interfering with hormone biosynthesis, metabolism, or action. In this study, a spectroscopic ellipsometry platform is proposed using aptamers for the sensitive and selective detection of an EDC, 2,2-Bis(4-hydroxyphenyl)propane (Bisphenol A, BPA). Two different BPA-specific aptamers (Anti-BPA1 and Anti-BPA2) were immobilized to silicon wafer chips by the layer-by-layer self-assembly, a detection limit of 215 pM and 36 pM was obtained using the ellipsometric method for Anti-BPA1 and Anti-BPA2, respectively. Sensor specificity was tested with 2,2-Bis(4-hydroxyphenyl)butane and a maximum RSD of 3.8% was obtained. It has been reported that both aptasensors based on spectroscopic ellipsometry exhibit adequate analytical performance.

HEAVY METALS IN SEA FOOD: METHOD VALIDATION AND EVOLUTION BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY IN ACCORDANCE WITH COMMISSION REGULATION (EC) 333/2007, 582/2016

The goal of this study was to validate the analytical technique for determining the immediate development of lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) in various Indian seafood products. According to Commission Regulation (EC) 333/2007, various marine foods, including crustaceans, cephalopods, and fish species, were employed for the validation of the developed method by ICP-MS. HNO3 and H2O2 were combined to prepare the sample during microwave digestion. Specificity/selectivity, linearity, LOD, LOQ, precision-repeatability and reproducibility, accuracy-recovery, robustness, and fitness studies were used to validate the approach. The maximum RSD value and Horrat value (HorRat) for the within-lab reproducibility for all analytes (Pb, Cd, Hg, and As) in marine food were 5% and 1 respectively. The mean recovery for all analytes examined at three spiking levels (0.5, 1 & 1.5 of the permitted limit) was between 92.67 and 107.33%.Whereas limit of detection (LOD) values for Pb, Cd, Hg and As were 0.018 µg/g, 0.032 µg/g, 0.031 µg/g and 0.034 mg/kg for repeatability 6% and < 1) showed that this analytical method could be used for the routine analysis of these four toxic metals in seafood with acceptable analytical performance in the laboratory

3-D printed electrode integrated sensing chip and a PoC device for enzyme free electrochemical detection of blood urea

Herein we report a novel electrochemical sensing chip and a point-of-care device (PoC) for enzyme-free electrochemical detection of urea in human blood. The electrochemical sensing chip was developed by 3-D printing of conductive Ag ink and subsequent electrodeposition of AuNP-rGO nanocomposite. Material characterization of the sensing chip was conducted to find a plausible mechanism for the electrochemical reaction with urea. Subsequently, the response with varying concentrations of urea in solution and human blood samples was tested. High peak response current (~5 times than that of the highest reported value), low impedance, rapid sensor fabrication procedure, high selectivity towards urea, excellent linear response (R2 = 0.99), high sensitivity of 183 μA mM−1 cm−2, the fast response indicated by high diffusion coefficient, the limit of detection of 0.1 µM, tested shelf life of more than 6 months and recovery rate of >99% ensured the application of the developed sensor chip towards PoC urea detection test kit. A PoC device housing an electronic circuitry following the principles of linear sweep voltammetry and compatible with a sensing chip was developed. A maximum percentage error of 4.86% and maximum RSD of 3.63% confirmed the use of the PoC device for rapid urea measurements in human blood.

Determination of the experimental extinction coefficient of therapeutic proteins using the Edelhoch method

The objective of this study was to determine how the theoretical values of the extinction coefficient (EC) compares to the experimentally determined extinction coefficient for a large set of biotherapeutic proteins measured by the Edelhoch method. We have performed extensive analysis based on over 176 observations covering 19 different types of molecules from different structural classes covering mAbs, bispecific antibodies, fusion proteins and BiTE molecules. Precision was measured by assessing the repeatability of the measurements for each molecule and determining the relative standard deviation (%RSD). The maximum RSD observed for any given molecule was 1.7% with an average RSD of 0.9%. Deviation from the theoretical extinction coefficient was determined by calculating the experimental bias first, which is the difference between the mean experimental extinction coefficient and the theoretical extinction coefficient. The percent bias (%bias) was then calculated as (bias ÷ theoretical EC) × 100. The maximum %bias observed for any given molecule was 5.3% with an average %bias of 2.6%. Our results indicate that the Edelhoch method is highly reliable with significant improvement in execution efficiency with reduction in cost, time and improvements in safety when compared to the commonly used methods such as amino acid analysis (AAA) technique.

Theory and Experimental Study of Corona Initial E-Field Strength of HVDC Large Fittings

The electrode were used to imitate the valve tower shield plate, grading ring, grading ball and grading shield for UHVDC valve hall. Uneven electric field of the irregular conductor can not be calculated theoretically or measured accurately. The variation of typical electrode corona inception electric field strength is analyzed and threshold value of the corona inception electric field of the valve hall fittings is acquired. With the adequate modification, limited electric field magnitude for the valve hall is proposed. With the gray system MGM (1, M) model fitting and predicting technology, the E-field strength single-point high-precision measurement and the the wide-area time interval corona initial E-field fitting and predicting operation can be realized. The experimental results show that the maximum error is 3.25% within the measured concentration range, which increases with applied voltage. The maximum RSD% is less than 2.7%, showing the good stability. This system can provide the novel method for the study of corona detection of large fittings in UHVDC valve hall.

Ultrasensitive detection of cytotoxic food preservative tert-butylhydroquinone using 3D cupric oxide nanoflowers embedded functionalized carbon nanotubes

Accurate detection of cytotoxic food preservative tert-butylhydroquinone (TBHQ) has significant importance in maintaining food quality and safety. TBHQ is a chronic hazard to aquatic life and its use in applications involving direct human exposure and frequent release to environment makes its quantification critical to maintain safety. Hence, we report development of a sensitive electrochemical sensor for TBHQ determination at nanomolar level in commonly used edible oils and water sample. Novel cupric oxide (CuO) decorated amine functionalized carbon nanotubes (NH2-CNTs) were prepared for development of TBHQ sensor. 3D CuO nanoflowers and NH2-CNTs were synthesized using hydrothermal and ultrasound-assisted method respectively. Techniques such as SEM, elemental mapping, XRD, FTIR, micro Raman, XPS, EIS, and UV–Visible spectroscopy were taken to affirm significant characterizations of synthesized materials. We have observed outstanding electrocatalytic activity towards TBHQ detection using the sonochemically prepared nanocomposite modified screen printed carbon electrode (SPCE). The proposed sensor exhibited ultra-low detection limit at 3 nM and exceptional sensitivity at 37.7 μA μM−1 cm−2. Furthermore, TBHQ sensor showcased outstanding anti-interference, stability, reproducibility, and repeatability. The practical feasibility of TBHQ detection was validated using real sample analysis resulting in excellent recovery in the range 95.90–104.87% and a maximum RSD of mere 2.71%.

Quality control of Aloe vera (Aloe barbadensis) and Aloe ferox using band-selective quantitative heteronuclear single quantum correlation spectroscopy (bs-qHSQC)

In the present study, band-selective quantitative heteronuclear single quantum correlation spectroscopy (bs-qHSQC) was applied for the quality control of the two Aloe species present in the European Pharmacopeia. After development and validation of a complete spectral range (csr-) qHSQC assay, a specific pulse program with selective excitation was applied and the measuring time was reduced from 135 to 32 min, while maintaining the same resolution. This bs-qHSQC method (method I) showed slightly higher RSD values compared to the csr-qHSQC method (maximum RSD of 2.80%), but better recovery rates in comparison to the assay of the Pharmacopeia (97.3% for Aloe vera and 96.6% for Aloe ferox). Apart from quantifying the total anthranoid content, the method moreover allows the quantitation of aloin among other aloin derivatives, such as 7-hydroxyaloin, as well as the differentiation of the two investigated species. Additionally, a second bs-qHSQC method (method II) for the fast (4 min) determination of the aloin A/B ratio was developed and compared to 13C qNMR measurements. Showing the same results in much less analysis time, the latter approach contributes to a general problem in natural product chemistry, the co-occurrence of structurally similar compounds and their analysis in complex matrices, e.g. plant extracts.

A simple GC–MS method for the determination of diphenylamine, tolylfluanid propargite and phosalone in liver fractions

In this study, an accurate and robust gas chromatography/mass spectrometry method was developed for quantitative analysis of diphenylamine, tolylfluanid, propargite and phosalone in liver fractions. Different injector parameters were optimized by an experimental design technique (central composite design). An optimal combination of injector temperature (°C), splitless time (min) and overpressure (kPa) values enabled to maximize the chromatographic responses. Sample preparation was based on protein precipitation using trichloroacetic acid followed by liquid-liquid extraction (LLE) of the pesticides with hexane. All compounds and endrin as internal standard were quantified without interference in selected ion monitoring mode. The calibration curves for diphenylamine, tolylfluanid, propargite and phosalone compounds were linear over the concentration range of 0.1 to 25 μM with determination coefficients (R2) higher than 0.999. A lower limit of quantification of 0.1 μM was obtained for all analytes, i.e. 422.5, 868.0, 876.2 and 919.5 μg/kg of liver fraction (hepatocytes) for diphenylamine, tolylfluanid, propargite and phosalone, respectively. All compounds showed extraction recoveries higher than 93%, with a maximum RSD of 3.4%. Intra- and inter-day accuracies varied from 88.4 to 102.9% and, imprecision varied from 1.1 to 6.7%. Stability tests demonstrated that all pesticides were stable in liver extracts during instrumental analysis (20 °C in the autosampler tray for 72 h) following three successive freeze-thaw cycles and, at −20 °C for up to 12 months. This simple and efficient analytical procedure is thus suitable for metabolism studies or for assessing mammals liver contamination.

A validated HPLC-UV method for the analysis of galloylquinic acid derivatives and flavonoids in Copaifera langsdorffii leaves.

Copaifera langsdorffii Desf. (Fabaceae, Caesalpinioideae), popularly known as "copaiba" or "pau d'óleo", is a species of tree that is found throughout Brazil. The leaves of this tree are used in folk medicine to treat kidney stones. Galloylquinic acid derivatives and flavonoids are the main secondary metabolites found in C. langsdorffii leaves and are likely to be responsible for the effectiveness of this treatment. As an attempt to produce a phytotherapic, we have developed a reliable HPLC-UV method for the quality control of C. langsdorffii leaves. Phenolic compounds were extracted from C. langsdorffii leaves using 70% aqueous ethanol as the extraction solvent. HPLC-UV analyses were carried out on a Synergi Polar-RP column (100×3.0mm, 2.5μm), and the mobile phase was made up of formic acid-water (0.1:99.9, solvent A), and isopropanol-methanol-acetonitrile (5:40:60, solvent B). The elution gradient was A:B (90:10 to 85:15) in 8.0min, followed by A:B (85:15 to 64:36) up to 30.0min, using a flow rate of 0.7mL/min, and UV detection at 280nm. This method was used to quantify nine galloylquinic acid derivatives and two flavonoids, which gave a good detection response and linearity in the range of 1.88-110.0μg/mL. Furthermore, the detection and quantification limits ranged from 0.070 to 0.752μg/mL, and 0.211-2.278μg/mL respectively, with a maximum RSD of 4.18%. The method is reliable for the quality control of C. langsdorffii raw material, its hydroethanolic extract, and could potentially be used to quantify these compounds in other Copaifera species.

Ultra-high performance liquid chromatography with ultraviolet and tandem mass spectrometry for simultaneous determination of metabolites in purine pathway of rat plasma.

It has been proved that the purine metabolic pathway has been implicated in various biological disorders including gout, diabetes, coronary heart diseases, and neurodegenerative diseases. The analysis of the purine metabolic pathway in organisms reveals important alterations under different physiological and pathological conditions, which contributes to the pathological study, diagnosis, and therapy of related diseases. In the present study, an ultra-high performance liquid chromatography with ultraviolet and tandem mass spectrometry (UHPLC-UV-MS/MS) method was developed for conducting the comprehensive analysis of the metabolite profiles of the purine pathway in rat plasma through a single analysis. The purine metabolites including adenosine-5'-monophosphate, guanosine-5'-monophosphate, adenosine, inosine, guanosine, inosine-5'-monophosphate, deoxyadenosine, deoxyguanosine, deoxyinosine, xanthine, hypoxanthine, and uric acid, were separated and quantified in the short running time of 10min. After rapid chromatographic separation achieved by an Agilent Zorbax SB-Aq column, high concentration of uric acid and the remaining purine metabolites at lower levels were respectively detected by ultraviolet detector and triple quadruple mass spectrometry within a single analysis. The proposed method was validated by applying charcoal-stripped plasma as a matrix and it was proved to be linear (R2>0.982), accurate (with a relative error for accuracy <±15% and the relative standard deviation for intra- and inter-run precision <11%) and reproducible (with a matrix effect ranging between 86.49% and 111.44% with a maximum RSD of 8.69%). As a result, the method was successfully applied to the quantification of the endogenous purine metabolites in rat plasma. It was found that the concentration levels of the purine metabolites may keep a physiological balance as an integrated system in normal individuals and the concentration level of uric acid in rat plasma was 64μM which was more than 200 times greater than the other purine metabolites. The established method and the measurement of the concentration of these purines in normal rat plasma may help the investigation of the action mechanisms between purine disorders and related diseases.

Differential scanning calorimetric characterization of pharmaceutical powder blend uniformity in a laboratory-scale V-blender

Testing of powder blend uniformity is one of the important steps during formulation development and routine commercial production of pharmaceutical products. Pharmaceutical industries heavily rely on chemical analysis by UV or HPLC for the same. However, the chemical methods are time consuming, need a few grams of powder sample, and they are not green in nature. The objective of this research is to explore the use of DSC as an alternative of UV analysis to assess the powder blend uniformity of a binary mixture of metformin hydrochloride and HPMC (5:95 w/w) at 50% and 60% occupancy of a laboratory-scale V-blender. Samples were withdrawn at 5, 10, 15, and 20min intervals each of the top, middle, and bottom positions of the blender. Samples from all three locations at all time-points were found to have similar concentrations by both methods with the maximum RSD below 26%. Percent of metformin HCl recovery from the powder mixture after 20min was comparable to the DSC method (2.68±0.22% and 2.29±0.14% at 50% and 60% occupancy, respectively) and UV method (2.66±1.10% and 2.60±0.32% at 50% and 60% occupancy levels, respectively). DSC, after a careful evaluation of drug and excipient specific interaction, can be considered as an alternative of pharmacopoeial spectrophotometric or chromatographic methods for powder blend uniformity assessment at various stages of pharmaceutical product development and its commercial production.

Anatomical mercury speciation in bay scallops by thio-bearing chelating resin concentration and GC-electron capture detector determination

The highly toxic methyl-, ethyl- and phenylmercury species that may exist in the three main anatomical parts – the adductor muscle, the mantle and the visceral mass – of bay scallops (Argopecten irradias) were quantitatively released by cupric chloride, zinc acetate, sodium chloride and hydrochloric acid (HCl) under ultrasonic extraction. After centrifugation, the mercury species in the supernatant were concentrated by thio (SH)-bearing chelating resins, eluted with HClO4 and HCl and extracted with toluene. Separation was achieved by capillary GC equipped with programmed temperatures, a constant nitrogen flow and detected by a micro-electron capture detector (μECD). Under optimised conditions, the LODs for methyl-, ethyl- and phenylmercury in bay scallop samples were 1.1, 0.65 and 0.80 ng g−1, respectively. The maximum RSD for three replicate determinations of methyl-, ethyl- and phenylmercury in bay scallop samples were 13.7%, 14.0% and 11.2%, respectively. In the concentration range of 4–200 ng g−1 in bay scallop samples, the calibration graphs were linear with correlation coefficients not less than 0.997. Recoveries for spiked samples were in the range of 92.7–103.5% (methylmercury), 87.5–108.3% (ethylmercury) and 91.6–106.0% (phenylmercury), respectively. The method was verified by the determination of methylmercury in a CRM GBW10029 (Total Mercury and Methyl Mercury in Fish Tissue), with results in good agreement with the certified values. Methylmercury – the only existing species in bay scallops – was successfully determined by the method.

Ultra high performance liquid chromatography with ion‐trap TOF‐MS for the fast characterization of flavonoids in Citrus bergamia juice

We have developed a fast ultra HPLC with ion-trap TOF-MS method for the analysis of flavonoids in Citrus bergamia juice. With respect to the typical methods for the analysis of these matrices based on conventional HPLC techniques, a tenfold faster separation was attained. The use of a core-shell particle column ensured high resolution within the fast analysis time of only 5 min. Unambiguous determination of flavonoid identity was obtained by the employment of a hybrid ion-trap TOF mass spectrometer with high mass accuracy (average error 1.69 ppm). The system showed good retention time and peak area repeatability, with maximum RSD% values of 0.36 and 3.86, respectively, as well as good linearity (R(2) ≥ 0.99). Our results show that ultra HPLC can be a useful tool for ultra fast qualitative/quantitative analysis of flavonoid compounds in citrus fruit juices.