Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

Determination of Methyl Parathion in Water and Its Removal on Zirconia Using Optical Enzyme Assay

A simple, miniaturized microplate chemiluminescence assay for determination of methyl parathion (MP) was developed in 384-microwell plates. Zirconia (ZrO₂) was added in microwell for adsorption of acetylcholinesterase (AChE). The developed assay is based on inhibition of AChE by MP. A good dynamic range 0.008–1,000 ng/mL was obtained for MP with limit of detection 0.008 ng/mL. Intrabatch and interbatch reproducibility for miniaturized assay was obtained with % RSD up to 3.07 and 5.66, respectively. In 384 well plate formats, 70 samples were simultaneously analyzed within 20 min with assay volume of 41.5 μL. The application of developed assay was extended for MP remediation. Column containing ZrO₂ was utilized for remediation where MP was selectively adsorbed. Under optimized condition, adsorption of MP on ZrO₂ was found to be 98–99% with 2-h contact time in real water samples. Adsorption of MP on ZrO₂ column followed by quantification using developed bioassay provides a novel approach to monitor remediation. The applicability of assay was successfully extended for determination of MP in water samples after removal through ZrO₂.     

Determination of Dimethyl Phthalate in Environment Water Samples by a Highly Sensitive Indirect Competitive ELISA

Recent controversy over the discovery of clouding agents containing the banned chemical di(2-ethylhexyl) phthalate in beverages in 2011 in Taiwan has caused public concerns. For the detection of dimethyl phthalate (DMP) in environment water samples, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed in this paper. Dimethyl 4-aminophthalate (4-DMAP) was covalently attached to bovine serum albumin as immunogen by a diazotization method. The conjugation of DMAP and ovalbumin as coating antigen was obtained in the same way. Polyclonal antibody was obtained from New Zealand white rabbits. Under the optimized conditions, DMP was detected in the concentration range of 0.02–419 ng/mL with a detection limit of 0.01 ng/mL. The proposed method has been applied to the analysis of river water, lake water, and rain water samples. Satisfactory recoveries were obtained ranging from 90.6% to 105.5%. The cross-reactivities of the anti-DMP antibody to seven structurally related phthalate esters were below 10%. The data demonstrated that the ic-ELISA method described in our study is a simple, sensitive, and specific method and showed that this assay is a reliable tool to detect DMP in water samples.     

Quantification of femtomolar concentrations of the CYP3A substrate midazolam and its main metabolite 1'-hydroxymidazolam in human plasma using ultra performance liquid chromatography coupled to tandem mass spectrometry

The benzodiazepine midazolam is a probe drug used to phenotype cytochrome P450 3A activity. In this situation, effective sedative concentrations are neither needed nor desired, and in fact the use of very low doses is advantageous. We therefore developed and validated an assay for the femtomolar quantification of midazolam and 1′-hydroxymidazolam in human plasma. Plasma (0.25 mL) and 96-well-based solid-phase extraction were used for sample preparation. Extraction recoveries ranged between 75 and 92% for both analytes. Extracts were chromatographed within 2 min on a Waters BEH C18 1.7 μm UPLC? column with a fast gradient consisting of formic acid, ammonia, and acetonitrile. Midazolam and 1′-hydroxymidazolam were quantified using deuterium- and ¹³C-labeled internal standards and positive electrospray tandem mass spectrometry in the multiple reaction monitoring mode, which yielded lower limits of quantification of 50 fg/mL (154 fmol/L) and 250 fg/mL (733 fmol/L) and a corresponding precision of <20%. The calibrated concentration ranges were linear for midazolam (0.05–250 pg/mL) and 1′-hydroxymidazolam (0.25–125 pg/mL), with correlation coefficients of >0.99. Within-batch and batch-to-batch precision in the calibrated ranges for both analytes were <14% and <12%. No ion suppression was detectable, and plasma matrix effects were minimized to <15% (<25%) for midazolam (1′-hydroxymidazolam). The assay was successfully applied to assess the kinetics of midazolam in two human volunteers after the administration of single oral microgram doses (1–100 μg). This ultrasensitive assay allowed us to quantify the kinetics of midazolam and 1′-hydroxymidazolam for at least 10 h, even after the administration of only 1 μg of midazolam.     

Nanocarbon Materials Modified with the Zinc Complex of Protoporphyrin IX,Recognized Antibiotics in Water Samples

The complex between protoporphyrin IX and zinc was immobilized on nanocarbon paste and on nanodiamond paste to design two stochastic microsensors. The microsensors were used for the recognition and analysis of antibiotics: amoxicillin, ampicillin, and biotin in water samples. Stochastic sensors provided different signatures for the three antibiotics making possible their simultaneous recognition and assay in water samples. Low limits of determination 0.3 pg/mL for amoxicillin and ampicillin, and 0.21 pg/mL for biotin were obtained when nanocarbon paste was used, and 0.03 pg/mL for amoxicillin, 0.30 pg/mL for ampicillin, and 2.14 fg/mL for biotin were obtained when nanodiamond paste was used. Recoveries higher than 99.32 % with RSD lower than 1.00 % were obtained for the assay of the antibiotics in water samples.     

Optimization of multiwalled carbon nanotubes reinforced hollow‐fiber solid–liquid‐phase microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples using experimental design

A novel design of hollow‐fiber liquid‐phase microextraction containing multiwalled carbon nanotubes as a solid sorbent, which is immobilized in the pore and lumen of hollow fiber by the sol–gel technique, was developed for the pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples. The proposed method utilized both solid‐ and liquid‐phase microextraction media. Parameters that affect the extraction of polycyclic aromatic hydrocarbons were optimized in two successive steps as follows. Firstly, a methodology based on a quarter factorial design was used to choose the significant variables. Then, these significant factors were optimized utilizing central composite design. Under the optimized condition (extraction time = 25 min, amount of multiwalled carbon nanotubes = 78 mg, sample volume = 8 mL, and desorption time = 5 min), the calibration curves showed high linearity (R ² = 0.99) in the range of 0.01–500 ng/mL and the limits of detection were in the range of 0.007–1.47 ng/mL. The obtained extraction recoveries for 10 ng/mL of polycyclic aromatic hydrocarbons standard solution were in the range of 85–92%. Replicating the experiment under these conditions five times gave relative standard deviations lower than 6%. Finally, the method was successfully applied for pre‐concentration and determination of polycyclic aromatic hydrocarbons in environmental water samples.     

A combination of dispersive liquid–liquid microextraction and surface plasmon resonance sensing of gold nanoparticles for the determination of ziram pesticide

We have developed a reliable, fast, and highly sensitive analytical method utilizing dispersive liquid–liquid microextraction and gold nanoparticles probes for ziram (zinc bis(dimethyldithiocarbamate)) determination. The method is based on the in situ formation of gold nanoparticles in carbon tetrachloride as an organic phase. It was found that the trace levels of ziram influenced the formation of gold nanoparticles, leading to absorbance change of a sedimented phase. The results of the colorimetric ziram determination were in the concentration range of 0.12–2.52 ng/mL with a limit of detection of 0.06 ng/mL. The formation of the stable and dispersed gold nanoparticles in the organic phase provides a good precision for dispersive liquid–liquid microextraction method, resulting in the relative standard deviation of 3.8 and 1.2% for 0.56 and 1.58 ng/mL of ziram, respectively. This method has been successfully used for the ziram determination in samples of well and river water, soil, potato, carrot, wheat, and paddy soil.     

Development of Magnetic Particle-based Chemiluminescence Enzyme Immunoassay for the Detection of 17β-estradiol in Environmental Water

In the present work, a simple, fast, and highly sensitive chemiluminescence enzyme immunoassay for 17β-estradiol (E2) in environmental water samples was developed, using magnetic particles (MPs) labeled with secondary antibody as both the immobilization matrix and the separation tools. The specific anti-E2 polyclonal antibody (PcAb) was produced against a conjugate of estradiol–bovine serum albumin. The specificity of the anti-E2 antibody was studied. The results showed that the antibody did not cross-react with the structurally related endocrine-disrupting compounds, including estrone, ethinyl E2, estriol, E2-17-glucuronide, E2-3-sulfate-17-glucuronide, androstenedione, and dihydrotestosterone. The water samples were pretreated with solid-phase extraction using C₁₈ cartridges for the removal of matrix effects. Several physicochemical parameters including the dilution ratios of E2-6–horseradish peroxidase conjugate and anti-E2 PcAb, immunoreaction time, volume of chemiluminescent substrate and MPs, chemiluminescence reaction time, and pH of assay solution were studied and optimized. At optimal experimental conditions, it was found that the proposed method exhibited high performance with detection limit of 2.0 pg/mL, linear range of 20–1,200 pg/mL, and total assay time of 45 min. Both inter- and intra-assay coefficient of variation were less than 10%. The average recoveries of three different spiked concentration samples ranged from 86.3% to 108%. The method was successfully applied to the determination of E2 in river, waste, and tap water, and showed a good correlation with the commercially available radioimmunoassay kit.     

Chitosan Based Diamond Paste Stochastic Microsensors Modified with Gold Nanoparticles Detect Hepatitis C Virus Core Antigen

Three types of chitosan (chitosan I (n=371–744), chitosan II (n=682–930), and chitosan III (n=868–1365)) as well as gold nanoparticles (10 nm diameter) were used to modify diamond paste for the design of new stochastic microsensors. Hepatitis C virus core antigen was used as model analyte to prove the stochastic behavior of the proposed microsensors. The microsensors cover a linear range of concentration between 40 fg/mL and 4 ng/mL. The highest sensitivity (1.38×10⁵ s^?1/mg/mL) and the lower limit of determination (40 fg/mL) were obtained for chitosan III based microsensor. The hepatitis C virus core antigen was assayed from whole blood samples with recoveries higher than 98.00 %.     

Quantitation of native and forced degraded collagens by capillary zone electrophoresis: Method development and validation

A new capillary zone electrophoresis method for collagen quantitation was developed and validated according to the International Council for Harmonization guideline Q2 (R1). The Sircol collagen assay and ultraviolet spectrometry were employed as reference methods. Capillary zone electrophoresis enables specific, simple, and fast determination within 9 min. It is less user-dependent and more automated than the Sircol collagen assay. With a limit of detection of 18.0 μg/mL, the new method is less sensitive than the Sircol collagen assay, which has a limit of detection of 6.5 μg/mL. Nonetheless, capillary zone electrophoresis covers a wider linearity range (50-400 μg/mL) compared to the Sircol collagen assay (5-80 μg/mL), with similar precision. Additional advantages of capillary zone electrophoresis are the ability to gain information on collagen integrity and to simultaneously determine native and denatured collagens. This approach represents a modern and legitimate alternative to the Sircol collagen assay. The developed method has been successfully applied to the study of three collagen products and samples from forced degradation.     

Development of multi‐response optimization and quadratic calibration curve for determination of ten pesticides in complex sample matrices using QuEChERS dispersive liquid–liquid microextraction followed by gas chromatography

In this study, QuEChERS combined with dispersive liquid‐liquid microextraction is developed for extraction of ten pesticides in complex sample matrices of water and milk. In this regard, effective factors of proposed extraction technique combined with gas chromatography with flame ionization detector were designed, modeled, and optimized using central composite design, multiple linear regression, and Nelder–Mead simplex optimization. Later, univariate calibration model for ten pesticides was developed in concentration range of 0.5–100 ng/mL. Surprisingly, quadratic calibration behavior was observed for some of the pesticides. In this regard, Mandel's test was used for evaluating linearity and types of calibration equation. Finally, four pesticides followed linear calibration curve with sensitivity (0.23–0.66 mL/ng), analytical sensitivity (0.20–0.32), regression coefficient (0.988–0.995), limit of detection (0.39–1.83 ng/mL), and limit of quantitation (1.30–6.10 ng/mL) and six of them followed quadratic calibration curve with sensitivity (0.18–0.93 mL/ng), analytical sensitivity (0.25–0.86), regression coefficient (0.944–0.999), limit of detection (0.59–1.92 ng/mL), and limit of quantitation (1.96–6.40 ng/mL). The calculated limits of detection were below the maximum residue limits according to European Union pesticides database of European Commission. Finally, the proposed analytical method was used for determination of ten pesticides in water and milk samples.     

Field‐amplified sample injection combined with capillary electrophoresis for the simultaneous determination of five chlorophenols in water samples

A sensitive method of CZE‐ultraviolet (UV) detection based on the on‐line preconcentration strategy of field‐amplified sample injection (FASI) was developed for the simultaneous determination of five kinds of chlorophenols (CPs) namely 4‐chlorophenol (4‐CP), 2‐chlorophenol (2‐CP), 2,4‐dichlorophenol (2,4‐DCP), 2,4,6‐trichlorophenol (2,4,6‐TCP), and 2,6‐dichlorophenol (2,6‐DCP) in water samples. Several parameters affecting CZE and FASI conditions were systematically investigated. Under the optimal conditions, sensitivity enhancement factors for 4‐CP, 2‐CP, 2,4‐DCP, 2,4,6‐TCP, and 2,6‐DCP were 9, 27, 35, 43, and 43 folds, respectively, compared with the direct CZE, and the baseline separation was achieved within 5 min. Then, the developed FASI‐CZE‐UV method was applied to tap and lake water samples for the five CPs determination. The LODs (S/N = 3) were 0.0018–0.019 µg/mL and 0.0089–0.029 µg/mL in tap water and lake water, respectively. The values of LOQs in tap water (0.006–0.0074 µg/mL) were much lower than the maximum permissible concentrations of 2,4,6‐TCP, 2,4‐DCP, and 2‐CP in drinking water stipulated by World Health Organization (WHO) namely 0.3, 0.04, and 0.01 µg/mL, respectively, and thereby the method was suitable to detect the CPs according to WHO guidelines. Furthermore, the method attained high recoveries in the range of 83.0–119.0% at three spiking levels of five CPs in the two types of water samples, with relative standard deviations of 0.37–8.58%. The developed method was proved to be a simple, sensitive, highly automated, and efficient alternative to CPs determination in real water samples.     

Cetylpyridinium chloride functionalized silica‐coated magnetite microspheres for the solid‐phase extraction and pre‐concentration of ochratoxin A from environmental water samples with high‐performance liquid chromatographic analysis

A new method based on cetylpyridinium chloride coated ferroferric oxide/silica magnetic microspheres as an efficient solid‐phase adsorbent was developed for the extraction and enrichment of ochratoxin A. The determination of ochratoxin A was obtained by high‐performance liquid chromatography with fluorescence detection. In the presence of cetylpyridinium chloride, the adsorption capacity of ferroferric oxide/silica microspheres was 5.95 mg/g for ochratoxin A. The experimental parameters were optimized, including the amounts of ferroferric oxide/silica microspheres (20 mg) and cetylpyridinium chloride (0.18 mL, 0.5 mg/mL), pH value of media (9), ultrasonic time (5 min), elution solvent and volume [2(1 + 1) mL (washed twice, 1 mL each time) 1% acetic acid acetonitrile]. Under optimal experiment conditions, ochratoxin A had good linearity in the range of 2.5–250.0 ng/L in water samples with correlation coefficient of the calibration curve 0.9995. The limit of detection for ochratoxin A was 0.83 ng/L, and the recoveries were 89.8–96.8% with the relative standard deviation of 1.5–3.5% in environmental water samples. Furthermore, ferroferric oxide/silica microspheres show excellent reusability during extraction procedures for no less than six times.     

Hyphenation of field‐amplified sample injection and transient isotachophoresis in CE for the determination of sotalol and metoprolol in human urine samples

A sensitive approach of capillary electrophoresis coupled with field‐amplified sample injection and transient isotachophoresis was developed for the simultaneous determination of two β‐blockers: sotalol and metoprolol. In this dual focusing technique, the samples were prepared via only dissolution in ultrapure water and then injected electrokinetically. Phosphate acted as both the background electrolyte and the leading electrolyte. Its optimized concentration was 80 mM. A total of 25 mM of glycine was used as the terminating electrolyte. Under optimum conditions, good separation of sotalol and metoprolol was achieved within 10 min. In comparison with the conventional method, the sensitivity enhancement factors were up to 1031 and 919 for sotalol and metoprolol, respectively. The proposed method was employed in the determination of sotalol and metoprolol in spiked human urine samples. The limits of detection and limits of quantitation obtained via ultraviolet detection were 5 and 12 ng/mL, respectively, for sotalol, and 10 and 25 ng/mL, respectively, for metoprolol. The intraday repeatability values were lower than 2.7 and 1.7% for peak area and migration time, respectively. The assay is a simple and efficient strategy with potential for application in clinical and biochemical laboratories for monitoring sotalol and metoprolol.     

Solid phase immunoradiometric assay for CA125 antigen levels in blood using monoclonal antibodies

We have developed a simple one step ‘sandwich’ immunoradiometric assay for CA125 using monoclonal antibodies directed against two different epitopes of the antigen. The detection antibody was radiolabeled with I-125 and the selected capture antibody was chemically coupled to magnetizable cellulose to form immobilized solid support. In the developed inclusive assay procedure, 200 μL of standard or sample was incubated with 100 μL of radiolabeled and capture antibody suspension for 18 h at room temperature with shaking. At the end of the incubation, the sandwich complex attached to solid phase is separated and counted for associated radioactivity. The analytical sensitivity for the developed assay procedure was observed to be 3.0 U/mL with an assay range up to 500 U/mL of CA125. The developed assay displayed acceptable precision; expressed in terms of percentage Coefficient of Variation (CV) estimated by repeated analyses of the quality control samples. Intra-assay CV was observed to be less than 5% whereas inter-assay CV was also less than 6%. The analytical recovery of the developed assay observed to be in the range of 88–107%. The clinical samples analyzed by the developed procedure showed a good correlation with that of a commercial kit (r = 0.99; y = 1.0052x − 38.942).     

Real-time immuno-PCR assay for detecting PCBs in soil samples

A fast and robust assay, based on immuno-polymerase chain reaction (IPCR) techniques, was developed for the detection of polychlorinated biphenyls (PCBs) in soil samples. Real-time IPCR (rt-IPCR) is a powerful technique that combines enzyme-linked immunosorbent assay (ELISA) with the specificity and sensitivity of PCR. In our assay, indirect ELISAs based on immobilization of PCB37 hapten–ovalbumin conjugates was used for evaluation of the immune response. The effect of optimal reagent concentrations to reduce background fluorescence was also investigated. Using the optimized assay, the linear sensitivity range of the assay covered more than six orders of magnitude, and the minimum detection limits reached 5 fg ml^–1 antigen. Rt-IPCR was tested for its cross-reactivity profiles using four selected congeners and four Aroclor products. The assays were highly specific for congeners but less specific for Aroclor1242. We took four soil samples to validate the method, and the results were confirmed by gas chromatography/mass spectrometry (GC/MS). The rt-IPCR results for soil samples correlated well with the concentrations of PCBs obtained by GC/MS (r = 0.99, n = 6). These data indicate that this highly specific, sensitive, and robust assay can be modified for detecting PCB compounds in the environment.     

Hydrophobic deep eutectic solvent as a green extractant for high‐performance liquid chromatographic determination of tetracyclines in water samples

A green extractant, hydrophobic deep eutectic solvent was first introduced for extraction of tetracycline, oxytetracycline, and chlortetracycline from environmental water samples prior to high‐performance liquid chromatography determination. Deep eutectic solvents consist of methyltrioctylammonium chloride and various medium‐chain alcohols/acids, and are easy in preparation, low cost and toxicity, desirably biodegradable, and biocompatible. The overall time required for sample preparation was 6 min and the volume of organic solvent used for extraction was only 400 µL. Under the optimized extraction condition, the present method yielded low limit of detection (0.5–2.0 ng/mL), acceptable precision (relative standard deviations < 9.7%), good linearity from 2.0 to 500 ng/mL (r² ≥ 0.9991). This optimized procedure was applied for determination of tetracyclines in different water samples with desirable spiked recovery ranged from 77.5 to 87.6%. There is, therefore, a great potential to further expand application of the method for investigation of other ultra‐trace analyte(s) in environmental matrixes.     

Magnetic solid‐phase extraction or dispersive liquid–liquid microextraction for pyrethroid determination in environmental samples

The determination of 15 pyrethroids in soil and water samples was carried out by gas chromatography with mass spectrometry. Compounds were extracted from the soil samples (4 g) using solid–liquid extraction and then salting‐out assisted liquid–liquid extraction. The acetonitrile phase obtained (0.8 mL) was used as a dispersant solvent, to which 75 μL of chloroform was added as an extractant solvent, submitting the mixture to dispersive liquid–liquid microextraction. For the analysis of water samples (40 mL), magnetic solid‐phase extraction was performed using nanocomposites of magnetic nanoparticles and multiwalled carbon nanotubes as sorbent material (10 mg). The mixture was shaken for 45 min at room temperature before separation with a magnet and desorption with 3 mL of acetone using ultrasounds for 5 min. The solvent was evaporated and reconstituted with 100 μL acetonitrile before injection. Matrix‐matched calibration is recommended for quantification of soil samples, while water samples can be quantified by standards calibration. The limits of detection were in the range of 0.03–0.5 ng/g (soil) and 0.09–0.24 ng/mL (water), depending on the analyte. The analyzed environmental samples did not contain the studied pyrethroids, at least above the corresponding limits of detection.     

Detection of PCB77 by Antibody-Coated Competitive Fluorescent Quantitative Immuno-PCR Using Molecular Beacon

Abstract

A rapid and quantitative technique is urgently needed in detecting toxicological and carcinogenic polychlorinated biphenyls (PCBs) in the environment. In this study, a high sensitive real time fluorescent quantitative immuno-PCR (FQ-IPCR) approach using molecular beacon (MB) was developed to detect PCB77, which was classified as a human carcinogen. MB-based FQ-IPCR was then performed on serial dilutions of known PCB77 concentrations equivalent to 10-fold dilutions of 10–10⁵ fg/mL. A correlation coefficient of 0.997 was identified, and a linear relationship between 10 fg/mL and 100 pg/mL, with y = 0.543x + 21.779, was obtained. Three soil samples were determined by MB-based FQ-IPCR to proof the validity of the method, and the results of which were further confirmed by conventional enzyme-linked immuno sorbent assay (ELISA). Based on sensitivity and reproduction, the MB-based real time FQ-IPCR technique will become a promising monitoring tool for environmental endocrine disruptors.     

Computer‐assisted design and synthesis of molecularly imprinted polymers for the simultaneous determination of six carbamate pesticides from environmental water

The computer‐assisted design and synthesis of molecularly imprinted polymers for the simultaneous capture of six carbamate pesticides from environmental water are reported in this work. The quantum mechanical computational approach was employed to design the molecularly imprinted polymers with carbofuran as template. The interaction energies between the template molecule and different functional monomers in various solvents were calculated to assist in the selection of the functional monomer and porogen. The optimised molecularly imprinted polymer was subsequently used as a class‐selective sorbent in solid‐phase extraction for pre‐concentration and determination of carbamates from environmental water. The parameters influencing the extraction efficiency of the molecularly imprinted solid‐phase extraction procedure were systematically investigated to facilitate the class‐selective extraction. For the proposed method, linearity was observed over the range of 2–500 ng/mL with the correlation coefficient ranging from 0.9760 to 1.000. The limits of detection ranged from 0.2 to 1.2 ng/mL, and the limit of quantification was 4 ng/mL. These results confirm that computer‐assisted design is an effective evaluation tool for molecularly imprinted polymers synthesis, and that molecularly imprinted solid‐phase extraction can be applied to the simultaneous analysis of carbamates in environmental water.