A Polypyrrole-Based Sorptive Microextraction Coating for Preconcentration of Malathion from Aquatic Media

A new micro-solid phase extraction method was developed by combining solid-phase extraction and stir bar sorptive extraction to benefit from the advantages of both techniques. A polypyrrole coating was electrochemically synthesized on the surface of an already used graphite furnace, employed in electro-thermal atomic absorption spectroscopy. The cylindrical geometry of the graphite tube provided a rather huge surface area, suitable for sorptive extraction. The novel sorbent coating was examined as an extracting medium to isolate malathion. Effects of different parameters such as extraction time, salt concentration, sample volume, desorption solvent and time were investigated and optimized. Under the optimized conditions, the limit of detection and limit of quantification of the developed method were 5 and 20?ng?L^?1, respectively. The calibration curve showed linearity in the range of 0.1?C100???g?L^?1 (R ²?=?0.9968). The precision was evaluated at 0.1 and 1???g?L^?1 concentration levels and relative standard deviations (n?=?3) were found to be 10 and 7%, respectively. The developed method was successfully applied to the extraction of malathion from real river water and tap water samples, and relative recoveries at the spiked level of 0.1???g?L^?1 were 94 and 97%, respectively.     

Validation of the HS-GC-FID method for the determination of ethanol residue in tablets

This paper describes the validation of a HS-GC-FID method (based on the Pharmacopeia’s method) for the determination of ethanol content in tablets. A general view of the procedure development/optimization process is presented. The main point of this study is the calculation of validation parameters. Selectivity of the method was determined. Linearity (r > 0.997) was observed in the range from 9.0 to 3,040 μg of ethanol per sample (because the mass of the tablets used was around 200 mg, this corresponds to 45–15,200 μg g⁻¹). The method showed good recoveries (average 99.0%), and a relative standard deviation for repeatability and intermediate precision of 4.5% and 5.5% respectively. The limit of detection was calculated to be 3.0 μg of ethanol per sample (15 μg g⁻¹). The uncertainty budget was done according to the "Guide to the Expression of Uncertainty in Measurement" (GUM)[1], and a relative expanded uncertainty was estimated as 4.8%.     

Solid phase extraction based on modified multi-walled carbon nanotubes packed column for enrichment of copper and lead on-line incorporated with flame atomic absorption spectrometry

A simple and rapid solid phase extraction?Cflow injection procedure is developed for on-line trace determination of Cu(II) and Pb(II) by flame atomic absorption spectrometry (FAAS). Multi-walled carbon nanotubes modified with a new Schiff??s base, 2,2??-(1E, 1E??)-(4-Methyl-1, 2-phenylene) bis (azen-1-yl-1-ylidine) bis (Methane-1-yl-1-ylidene) diphenol was used as a novel adsorbent material. Quantitative simultaneous extraction was obtained at pH 7.0. The retained metal ions were then eluted efficiently with 1.0?M HNO₃ into the nebulizer of FAAS for on-line determination. Different variables affecting the preconcentration efficiency, including pH, eluent concentration, sample and eluent flow rates and sample loading time, were optimized. Using 3?min preconcentration of sample solution at flow rate of 5?mL?min^?1 provided the enrichment factors of 20 and 21.5 for Cu(II) and Pb(II), respectively, at a sampling frequency of 17?h^?1. The detection limits (3??) were found to be 0.80 and 1.80???g?L^?1 for Cu(II) and Pb(II), respectively; and the relative standard deviations at 0.05???g?mL^?1 of these metal ions were 1.7 and 1.8% (n?=?8), respectively. The accuracy was assessed by analysis of a certified reference material NKK-916 and the obtained results are in good agreement with certified amounts of Cu(II) and Pb(II). The proposed method was successfully applied to the determination of target analytes in different real samples.     

Chiral Determination of Salbutamol, Salmeterol and Atenolol by Two-Dimensional LC–LC: Application to Urine Samples

A heart-cut two-dimensional high-performance liquid chromatography method for enantiomeric determination of salbutamol, salmeterol and atenolol in urine is presented. It involves the use of two separations in a liquid chromatography?Cliquid chromatography achiral?Cchiral coupling. Target compounds were previously separated in a primary column (Kinetex? HILIC, 2.6???m, 150?×?2.1?mm I.D.) with a mixture of MeOH:ACN:ammonium acetate buffer (5?mM, pH 6) 90:5:5 (v/v/v) as mobile phase at a flow rate of 0.40?mL?min^?1. Enantiomeric separation was carried out by transferring peak of each compound through a switching valve to a vancomycin chiral column (Chirobiotic? V, 2.6???m, 150?×?2.1?mm I.D.) using MeOH:ammonium acetate buffer (2?mM, pH 4) 97:3 (v/v) as mobile phase at a flow rate of 0.50?mL?min^?1. Ultraviolet detection was done at 227?nm. The method was applied to determine target analytes in urine samples after enzymatic hydrolysis with ??-glucuronidase from Helix pomatia, followed by a solid-phase extraction procedure using Isolute^? HCX mixed-mode cartridges. Extraction recoveries ranged from 82 to 90?% in urine samples. Detection limits were 0.091?C0.095???g for each enantiomer of atenolol and between 0.058 and 0.076 and 0.18?C0.14???g for enantiomers of salbutamol and salmeterol, respectively (3?mL of urine). Linearity ranges were between 0.5 and 10???g?mL^?1. Intraday and interday reproducibilities of enantiomeric ratio and enantiomeric fraction, expressed as relative standard deviation, were between 1.9 and 9.0?%. The optimized method was successfully applied to the analysis of urine samples obtained from excretion studies in volunteers and in freeze-dried urine samples, containing urinary components with MW?<?10,000 and components with MW?>?10,000, spiked with different amounts of studied drugs.     

Improved Bioethanol Production Using Fusants of Saccharomyces cerevisiae and Xylose-Fermenting Yeasts

The present research deals with the development of a hybrid yeast strain with the aim of converting pentose and hexose sugar components of lignocellulosic substrate to bioethanol by fermentation. Different fusant strains were obtained by fusing protoplasts of Saccharomyces cerevisiae and xylose-fermenting yeasts such as Pachysolen tannophilus, Candida shehatae and Pichia stipitis. The fusants were sorted by fluorescent-activated cell sorter and further confirmed by molecular characterization. The fusants were evaluated by fermentation of glucose?Cxylose mixture and the highest ethanol producing fusant was used for further study to ferment hydrolysates produced by acid pretreatment and enzymatic hydrolysis of cotton gin waste. Among the various fusant and parental strains used under present study, RPR39 was found to be stable and most efficient strain giving maximum ethanol concentration (76.8?±?0.31?g L^?1), ethanol productivity (1.06?g L^?1 h^?1) and ethanol yield (0.458?g g^?1) by fermentation of glucose?Cxylose mixture under test conditions. The fusant has also shown encouraging result in fermenting hydrolysates of cotton gin waste with ethanol concentration of 7.08?±?0.142?g L^?1, ethanol yield of 0.44?g g^?1, productivity of 0.45?g L^?1?h^?1 and biomass yield of 0.40?g g^?1.     

Determination of Toluene and Ethanol in Urine by Headspace and Cryotrapping Gas Chromatography–Mass Spectrometry

Toluene is the major volatile organic compound found in glue and is often used as a hallucinogenic for abusers. Use with alcohol increases the risk of adverse effects from toluene exposure. In this study, a headspace and cryotrapping gas chromatography–mass spectrometry method was developed and validated for the determination of toluene and ethanol in urine. Experimental and instrumental variables were investigated to optimize the method for sensitivity. Excess sodium sulfate was used as the salting-out reagent before the headspace protocol. Linear least squares regression with a 1/x weighting factor was used to construct calibration curves from 0.002 to 0.4?µg?mL^?1 for toluene and 10 to 2000?µg?mL^?1 for ethanol. The correlation coefficients exceeded 0.9993. The limits of detection were 0.0005?µg?mL^?1 for toluene and 0.21?µg?mL^?1 for ethanol. Intraday and interday precisions were within 5.4 and 11.5%, while intraday and interday accuracies were between ?11.3 to ?4.0% and ?11.0 to 1.2%, respectively. The method validation results for selectivity and stability were satisfactory. The validation results were used to estimate the expanded uncertainty and the contribution of individual steps in the method for the quantification of toluene and ethanol. The relative expanded uncertainties were 14.1% for toluene and 4.6% for ethanol.     

Supramolecular�Cbased dispersive liquid�Cliquid microextraction: A novel sample preparation technique for determination of inorganic species

A new simple and sensitive method has been developed for the determination of trace levels of inorganic species in environmental water samples. It is based on the use of supramolecular?Cbased dispersive liquid?Cliquid microextraction (SM?CDLLME) prior to microsample introduction into FAAS. The ions are micro?Cextracted with coacervates composed of reverse micelles made from decanoic acid and dispersed in tetrahydrofuran?Cwater mixtures. Cobalt ion was used as a model ion, and 1?C (2?Cpyridylazo)?C2?Cnaphthol as the complexing agent. SM?CDLLME results from a combination of DLLME with coacervation?Cbased microextraction. It combines the advantages of DLLME with those of preconcentration based on coacervation and reverse micelles. Factors affecting the extraction efficiency of Co and its subsequent determination by FAAS were optimized. Under the optimized conditions and using 5.00?mL sample only, the enhancement factor is 58, the limit of detection is 4.2???g L^?C1, and the relative standard deviations for 100???g L^?C1 and 30???g L^?C1 of Co are 2.1% and 3.8%, respectively (n?=?6). The accuracy of the method was confirmed by parallel analyses using the ASTM reference method.

Assessment of the occurrence and distribution of pharmaceuticals in a Mediterranean wetland (L'Albufera, Valencia, Spain) by LC-MS/MS

The distribution of 17 pharmaceuticals between water and the solid phase (sediments and soils) was studied by utilizing solid-phase extraction (SPE) and liquid chromatography?Ctandem mass spectrometry (LC-MS/MS). Two extraction procedures for soils and sediments, prior to the SPE, one based on pressurized liquid extraction (PLE) with hot water and the other on methanol/water ultrasonic extraction, were compared. Absolute recoveries were 71.2?C99.3% [relative standard deviation (RSD) <21.4%)] for water, and the method detection limits (MDLs) ranged from 0.3 to 10?ng?L^?1. Recoveries were 35.4?C105.3% (RSDs <19.1%) and 42.1?C97.8% (RSDs <14%) for soil and sediment samples, respectively, using PLE and 20.2?C86.5% (RSDs <25.1%) and 30.3?C97.4% (RSDs <19.1%) using ultrasonic extraction. Fifteen of the 17 pharmaceuticals were present in the L??Albufera water at concentrations up to 17???g?L^?1. Oxytetracycline and tetracycline were not detected. In sediments, only tetracycline, norfloxacin and diclofenac were not found. The other studied pharmaceuticals were present in the range from less than the method quantification limit (MQL) to 35.83?ng?g^?1. Among the 17 target compounds, ofloxacin, ciprofloxacin, norfloxacin, trimethoprim, clofibric acid and diclofenac were not detected in soil samples. The average concentrations ranged from less than the MQL for ibuprofen to 34.91?ng?g^?1 for tetracycline. These results indicate that pharmaceuticals could survive the wastewater treatment processes, which could lead to their dissemination in water environments.     

Application of the molecularly imprinted solid-phase extraction to the organophosphate residues determination in strawberries

This study describe an analytical method employing gas chromatography (GC) using flame photometric detection that has been developed for the simultaneous determination of organophosphate pesticides (diazinon, disulfoton, parathion, chlorpyrifos and malathion) in strawberry samples. For this purpose, molecularly imprinted solid-phase extraction was applied as a sample preparation technique. The method was linear in the ranges from 0.10 to 1.00?μg?g^?1, for diazinon, disulfoton, parathion and chlorpyrifos, and 0.10 to 2.00?μg?g^?1 for malathion with r?>?0.99. The detection limits (LD) ranged from 0.02 to 0.05?μg?g^?1. Recovery studies yielded average recoveries in the range of 65.25 to 87.70?%. These results showed the potential of this technique for organophosphate residue monitoring in strawberry samples.     

Elemental Analysis of Tarhana by Microwave Induced Plasma Atomic Emission Spectrometry

Elemental analysis of tarhana, a traditional Turkish cereal soup, has been conducted. A new method was developed for the determination of calcium, iron, magnesium, manganese, potassium, and sodium, in tarhana by microwave induced plasma atomic emission spectrometry. A sample of 0.1?g were mineralized by microwave digestion in 10?mL of 65% HNO₃. A wheat flour standard reference material (GBW 08503) was used for validation. Linear calibration using standards prepared in acid was conducted for all determinations. The limits of detection were 1.21?µg?g^?1 for Ca at 393.366?nm, 0.43?µg?g^?1 for Fe at 259.940?nm, 11.5?µg?g^?1 for K at 766.491?nm, 0.12?µg?g^?1 for Mg at 285.213?nm, 0.04?µg?g^?1 for Mn at 403.076?nm, and 0.04?µg?g^?1 for Na at 588.995?nm. Ca, K, Fe, Mg, Mn, and Na were determined in tarhana with values from 0.73 to 1.61, 0.016 to 0.061, 2.02 to 4.09, 0.473 to 1.414, 0.019 to 0.043, and 0.26 to 1.83?mg?g^?1, respectively.     

Simultaneous determination of levodopa and carbidopa by a novel nanostructure modified carbon paste electrode

The electrochemical behavior of levodopa (LD) was investigated on the surface of a carbon paste electrode modified with TiO₂ nanoparticles and 2,2??-(1,2 butanediylbis(nitriloethylidyne))-bis-hydroquinone (BNH). The prepared modified electrode showed an efficient catalytic role in the electrochemical oxidation of LD, leading to a remarkable decrease in oxidation overpotential and enhancement of the kinetics of the electrode reaction. The mechanism of the electrocatalytic process on the surface of the modified electrode was analyzed by obtaining the cyclic voltammograms in various potential sweep rates. This modified electrode exhibited well-separated oxidation peaks for LD and carbidopa (CD). The differential pulse voltammetry was applied as a very sensitive analytical method for the determination of LD and CD. A linear dynamic range of 2.0?C600.0 and 20.0?C400.0???M with a detection limit of 0.2???M (with sensitivity of 0.199 ??A ??M^?1) and 10???M (with sensitivity of 0.024???A???M^?1) was obtained for LD and CD, respectively. The modified electrode was prepared quite easily and renewed on the surface by simple polishing.     

An inorganic nano-sorbent based on nickel–aluminum–zirconium ternary-layered double hydroxide for solid-phase extraction of chloride ions

A well crystalline nickel?Caluminum?Czirconium ternary-layered double hydroxide was firstly synthesized and applied as a solid-phase extraction sorbent for the separation of trace levels of chloride ions from aqueous solutions. An indirect method was used for monitoring of the extracted chloride ions. For this purpose, the extracted chloride ions were passed through a reaction column containing silver chloranilate powder and the analyte was precipitated as silver chloride. The concentration of chloranilate ions released from the reaction column, which corresponds to the chloride ions concentration, was then determined spectrophotometrically at 530?nm. The effect of several parameters, such as pH, sample loading flow rate, elution conditions, amount of nano-sorbent, sample volume and effect of potential interfering ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3?s) and enrichment factor were 0.12 and 40???g?mL^?1, respectively. The calibration graph using the pre-concentration system was linear in the range of 0.25?C3.00???g?mL^?1 with a correlation coefficient of 0.997. The validation of the presented method was checked by the analysis of two certified reference materials. The optimized method was successfully applied to the determination of chloride ions in waters, food and biological samples.     

Simultaneous determination of ofloxacin and flavoxate hydrochloride by first-and ratio first-derivative UV spectrophotometry

Two simple, precise, accurate and sensitive UV spectrophotometric methods were developed and validated for the simultaneous determination of ofloxacin (OFX) and flavoxate HCl (FLX) in bulk and pharmaceutical formulations. In one method, first-derivative absorption at 303.6?nm (for OFX at its zero crossing) and 329.8?nm, (for FLX at its zero crossing) was used for the determination of the drugs and the linearity range was found to be 0.5?C70???g?ml^?1 for FLX and 0.5?C30???g?ml^?1 for OFX. In the second method, the ratio derivative spectrophotometry method was developed making use of amplitude in the first derivative of the corresponding ratio spectra at 290?nm (maxima) and 254?nm (minima) to estimate OFX and FLX, respectively. Further, the linearity range was found to be 0.5?C25???g?ml^?1 for OFX and 0.5?C30???g?ml^?1 for FLX. In both the methods, correlation coefficient was found to be more than 0.999. Both methods were validated according to ICH guidelines by assessing the linearity, accuracy, precision, limit of quantification, limit of detection and selectivity. The results demonstrate that both methods are accurate, precise and reproducible (relative standard deviation <2), while being simple, cheap and less time-consuming, and hence can be suitably applied for the simultaneous estimation of OFX and FLX in pharmaceutical formulation and for dissolution studies.     

Validation of a highly sensitive method for the determination of neonicotinoid insecticides residues in honeybees by liquid chromatography with electrospray tandem mass spectrometry

The validation of a multi-residue method for the determination of five neonicotinoid insecticides (imidacloprid, clothianidin, acetamiprid, thiacloprid and thiamethoxam) in honeybees is described. The method involves the extraction of pesticides using acetonitrile and liquid partitioning with n-hexane. One clean-up is then performed on a florisil cartridge (1?g, 6?mL) and the extract is analysed by liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS). The recovery data were obtained by spiking honeybees samples free of pesticides at two concentration levels of the various neonicotinoids. The recoveries were in the range between 93.3 and 104.0% with relative standard deviation (RSD) less than 20%. The limit of quantification (LOQ) was 0.5?ng?g^?1 (corresponding to 0.05?ng?bee^?1) for all pesticides except for acetamiprid which was 1?ng?g^?1 (corresponding to 0.1?ng?bee^?1).     

Synthesis and characterization of an ion-imprinted polymer for selective solid phase extraction of thorium(IV)

A new surface ion-imprinted composite polymer containing 3-methyl-1-phenyl ?4-(cis-acylbutenoic acid)-2-pyrazolin-5-one as the functional reagent is presented that is capable of extracting and preconcentrating traces of Th(IV) ion prior to its photometric determination. Parameters affecting the recovery of Th(IV) such as acidity, shaking time, initial concentration of Th(IV), elution condition, sample flow rate, and influence of potentially interfering ions were investigated. The maximum uptake capacity of this material and that of the non-imprinted polymer at pH 4.5 are 56.8 and 26.3?mg?g^?1, respectively. Recovery exceeds 95% and is complete within 5?min. A Langmuir isotherm fits the experimental data. The relative selectivity factor for Th(IV)/U(VI), Th(IV)/La(III), and Th(IV)/Ce(III) are 50.8, 78.3, and 82.6, respectively. The relative standard deviation is <2.5%, the detection limit is 0.54???g?L^?1 (3??). The imprinted polymer was coupled to spectrophotometry to separate and determine trace levels of Th(IV) in a soil standard material with satisfactory results.

Method validation and measurement uncertainty evaluation for measurement of mass concentration of organic acids in fermentation broths by using ion chromatography

In the present paper, a methodology for method validation and measurement uncertainty evaluation for the measurement of mass concentration of organic acids in fermentation broths was developed. Acetic acid was selected as a representative of organic acids. A detailed procedure for in-house method validation based on simple experimental design and consistent statistics is presented. In addition, a step-by-step illustration of ??Bottom-Up?? approach for measurement uncertainty evaluation of acetic acid in fermentation broths is also provided. The major sources of uncertainty of the result of measurement were identified and the combined uncertainty was calculated. Our analytical protocol allowed us to quantify acetic acid in fermentation broths in mass concentrations up to 75?g?L^?1 with satisfactory recovery (102.3%) and repeatability lower than 2%. We also estimated within-laboratory reproducibility over 3-month period, which was 2.3%. We proved that the method was selective for the measurement of mass concentration of acetic acid in fermentation broths. Measurement uncertainty of results was evaluated to be 6.2% with 95% confidence level. After validation and measurement uncertainty evaluation steps, results obtained showed that the method can be applied to efficiently monitor fermentation processes.     

Uncertainty Analysis of Chlormequat Residue in Fruits by LC�CMS�CMS

A method for determination of chlormequat (CCC) residue in fruits by liquid chromatography?Ctandem mass spectrometry (LC?CMS?CMS) was developed. Residue of CCC was extracted from samples with methanol?Cwater (v/v, 1:1) containing 1.0% acetic acid, cleaned up by strong cationic exchange (SCX) cartridge, and then determined by LC?CMS?CMS. The method showed good linearity over the concentration range 0.002?C5.0 mg kg^?1 with correlation coefficient above 0.997. The limit of detection (LOD) and limit of quantitation (LOQ) for CCC were 5 × 10^?4 mg kg^?1 (S/N = 3) and 0.002 mg kg^?1 (S/N = 10), respectively. Recoveries for CCC at three spiked levels (0.025, 0.050, and 0.20 mg kg^?1) were in the range 80?C102%. Estimation of measurement uncertainty was calculated for CCC at the level of 0.025 mg kg^?1 in fruits. The results demonstrated that the uncertainty of recovery was the main contribution to the combined standard uncertainty. The relative combined standard uncertainties associated with the method ranged from 11 to 13%, depending on the sample matrices.     

Effect of plastic deformation on the character of micro-brownian motions in glassy poly(methyl methacrylate)

Glassy PMMA samples are plastically deformed at room temperature in the uniaxial compression regime to residual strains of e _res = 25%. Dielectric spectra of the initial and deformed samples are recorded via the method of broadband dielectric spectroscopy in the frequency range f = (5 × 10^?4) ? 10⁷ Hz. The results are compared with the dynamic mechanical spectra of samples deformed under the same conditions. Dielectric and mechanical spectra are noticeably distorted by deformation. As a result, dielectric permittivity ??? increases, shear modulus G?? decreases, and the intensity of dielectric ?? losses slightly increases, while dielectric and mechanical ?? losses increase appreciably. In addition, the ??anomaly?? of total dielectric ???_tot and total mechanical ??G _tot dispersions (???_tot = ?₀ ? ?_?? ?? ???_?? + ???_?? and ??G _tot = G ₀ ? G _?? ?? ??G _?? + ??G _??) occurs, that is, the polymer is transformed from the state with ???_?? ? ???_?? and ??G _?? < ??G _?? into the state with ???_?? > ???_?? and ??G _?? > ??G _??. The described phenomenon is related to a strong gain in ?? dielectric and mechanical losses in the deformed material. It is found that ?? losses increase owing to an anelastic deformation component arising during glass loading. This component is responsible for an increase in the internal energy of the glass during its anelastic deformation. Possible causes of the observed effects are discussed.     

A biopolymer-based carbon nanotube interface integrated with a redox shuttle and a D-sorbitol dehydrogenase for robust monitoring of D-sorbitol

We describe the preparation and characterization of a glassy carbon electrode modified with a bionanocomposite consisting of a hyaluronic acid, dispersed carbon nanotubes, and electrostatically bound toluidine blue. The electrode was used to detect NADH in the batch and flow-injection mode of operation. The electrode was further modified by immobilizing sorbitol dehydrogenase to result in biosensor for D-sorbitol that displays good operational stability, a sensitivity of 10.6???A?mM^?1?cm^?2, a response time of 16?s, and detection limit in the low micromolar range. The biosensor was successfully applied to off-line monitoring of D-sorbitol during its bioconversion into L-sorbose (a precursor in the synthesis of vitamin C) by Gluconobacter oxydans. The sample assay precision is 2.5% (an average RSD) and the throughput is 65?h^?1 if operated in the flow-injection mode. The validation of this biosensor against a reference HPLC method resulted in a slope of correlation of 1.021?±?0.001 (R ²?=?0.99997).

Determination of mercury(II) in water samples using dispersive liquid-liquid microextraction and back extraction along with capillary zone electrophoresis

We have developed a method for the determination of mercury in water samples that combines dispersive liquid-liquid microextraction (DLLME) with back-extraction (BE) and detection by capillary zone electrophoresis. DLLME is found to be a simple, cost-effective and rapid method for extraction and preconcentration. The BE procedure is based on the fact that the stability constant of the hydrophilic chelate of Hg(II) with L-cysteine is much larger than that of the respective complex with 1-(2-pyridylazo)-2-naphthol. Factors affecting complex formation and extraction efficiency (such as pH value, concentration of the chelating agent, time of ultrasonication and extraction, and type and quantity of disperser solvent) were optimized. Under the optimal conditions, the enrichment factor is 625, and the limit of detection is 0.62???g?L^?1. The calibration plot is linear in the range between 1 and 1,000???g?L^?1 (R ²?=?0.9991), and the relative standard deviation (RSD, for n?=?6) is 4.1%. Recoveries were determined with tap water and seawater spiked at levels of 10 and 100???g?L^?1, respectively, and ranged from 86.6% to 95.1%, with corresponding RSDs of 3.95?C5.90%.