Selective Determination Of Trace Amounts Research Articles

Selective Fe(ii)-fluorescence sensor with validated two-consecutive working range using N,S,I-GQDs associated with garlic extract as an auxiliary green chelating agent.

The goal of this work was to use the pyrolysis process to synthesize graphene quantum dots doped with garlic extract (as N,S-GQDs) and simultaneously co-doped with iodine (as I-GQDs). XPS, HR-TEM, FE-SEM/EDX, FT-IR, fluorescence, and UV-visible absorption spectroscopy were used to characterize the N,S,I-GQDs and analyze their morphological images. The quantum yield of N,S,I-GQDs was found to be 45%, greater than that of undoped GQDs (31%). When stimulated at 363 nm, the N,S,I-GQDs display a strong fluorescence intensity at a maximum wavelength of 454 nm. Using N,S,I-GQDs as a fluorescence quenching sensor for screening tests with various metal ions, it was discovered that they are extremely selective towards Fe2+ over Fe3+ and other ions. Thus, solution pH, concentration of N,S,I-GQDs, quantity of garlic extract, EDTA and AgNO3 concentration as masking agents, reaction duration under ultrasonic aid, and tolerable limit of Fe3+ presence in the target analyte were all optimized for Fe2+ detection. A highly sensitive detection of Fe2+ was obtained using a linear curve with y = 141.34x + 5.5855, R2 = 0.9961, LOD = 0.11 mg L−1, and LOQ = 0.35 mg L−1. The method precision, given as RSDs, was determined to be satisfactory at 1.04% for intra-day analysis and 3.22% for inter-day analysis, respectively. As a result, the selective determination of trace amounts of Fe2+ in real water samples using such labile multi-element doped GQDs in conjunction with garlic extract as a green chelating agent to maintain its enhanced sensitivity was successfully applied with good recoveries ranging from 89.16 to 121.45%.

Designing and characterization of a highly sensitive and selective biosensing platform for ciprofloxacin detection utilizing lanthanum oxide nanoparticles

The pervasive presence of antibiotics in food has severe health impacts due to the rise in antibiotic-resistant bacteria. Therefore, the fabrication of a reliable, sensitive, rapid, and selective platform for antibiotics detection is the required for healthcare services. Here, we aim to fabricate an electrochemical immunosensor based on lanthanum oxide nanoparticles (nLa2O3 NPs) for sensitive and selective determination of trace amounts of ciprofloxacin (CPX) antibiotic. Briefly, the synthesis of nLa2O3NPs was carried out via wet-chemical co-precipitation process and characterized with various techniques using X-ray diffraction, fourier transform infrared spectroscopy, Raman spectroscopy, contact angle, atomic force microscopy, transmission electron microscopy, and electrochemical methods. These nLa2O3 NPs were used for enhancing the electrochemical response of the immunosensor. Further, nLa2O3 NPs were functionalized by APTES and were deposited electrophoretically on the surface of ITO glass substrate, followed by immobilizing anti-CPX antibodies covalently via EDC-NHS chemistry. Blocking of the non-specific area was done with the help of BSA. The change in electrochemical response studies of the developed immunosensor (BSA/anti-CPX/APTES/nLa2O3/ITO) was monitored to detect CPX. Under optimized conditions, studies showed that the developed biosensor had a wide linear detection range of 0.001–0.5 ng/mL and 1–1000 ng/mL, with the sensitivities of 11.44 μA ng-1 mL cm-2 (R2 = 0.968), and 7.88 μA ng-1 mL cm-2 (R2 = 0.972), respectively and having lower detection limit of 0.001 ng/mL. The developed immunosensor showed good reproducibility, repeatability, sensitivity, and stability that was effectively explored to detect CPX in milk samples.

Sensitive and selective determination of trace amounts of mercury ions using a dimercaprol functionalized graphene quantum dot modified glassy carbon electrode.

A novel nanomaterial is synthesized based on the functionalization of graphene quantum dot with dimercaprol (GQD-DMC). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (TEM) are used to approve the successful synthesis of GQD-DMC. The synthesized nanomaterial is used as an electrode modifier for the sensitive and selective determination of mercury(ii) ions in real water samples. The method of evaluation is based on the pre-concentration of mercury ions on the GQD-DMC modified glassy carbon electrode, reduction of Hg(ii), and anodic stripping voltammetric measurement of these reduced ions in a buffer solution. The pre-concentration of mercury ions is driven by the affinity interaction between the surface containing functional groups of DMC and Hg(ii) ions. The GQD-DMC modified glassy carbon electrode (GQD-DMC/GCE) shows extra sensitivity and selectivity for mercury(ii) detection, which is assumed to be due to the increased surface area as well as the presence of sulfur-containing functional groups on the modified structure.

Synthesis and Optimization of a Molecularly Imprinted Membrane as a Specific Absorbent to Assess the Occupational Exposure to the 5-Fluorouracil Drug

Objectives: Over the last decades, antineoplastic drugs have resulted in concerns about health care and pharmacy because of the increased incidence of neoplasm due to occupational exposure. Therefore, there is a need for accurate and valid methods to detect and evaluate the trace amount of these drugs in occupational assessment programs. In this study, for occupational exposure assessment of 5-fluorouracil (5-FU), molecularly imprinted membranes (MIMs) were synthesized and optimized as appropriate absorbents for selective determination of trace amount of this antineoplastic drug. Methods: To synthesize MIMs as Specific adsorbent for 5-FU, First, 5-FU molecularly imprinted polymers (MIPs) were prepared by the precipitation polymerization method, and then MIPs encapsulated into PET nanofibers, as the matrix polymer, by electrospinning. Finally, MIMs were fabricated from collection nanofibers. Optimization of electrospinning parameters (e.g., MIP amount, tip needle to the collector, electrospinning voltage and flow rate) was performed by the Central Composite Design (CCD) method using the experimental design software. The diameter of the fiber was analyzed using image analysis software. The applicability of the synthesized membranes for absorbing 5-FU drug was evaluated for assessing occupational exposure to the drug of interest. Results: In this study, MIP particles were successfully encapsulated into PET nanofibers. The optimization process showed that the molecularly imprinted nanofibers diameter of 276.38[Formula: see text]nm could be obtained in 57.4%[Formula: see text]w, 13.9[Formula: see text]cm, 25[Formula: see text]KV and 0.55[Formula: see text]ml/h. The extraction efficacy of 5-FU drugs by synthesized membranes was [Formula: see text]. Conclusion: The optimized MIMs presented in this study can be used as a specific absorbent for occupational and environmental monitoring of the 5-FU drug.

Sensitive and Selective Detection of Oxo-Form Organophosphorus Pesticides Based on CdSe/ZnS Quantum Dots.

A rapid, sensitive and enzyme-based optical biosensor was applied for the determination of seven organophosphorus pesticides (OPPs), including the oxo forms (malaoxon, paraoxon, dibrom, and dichlorvos), the thio forms (malathion and parathion) and the mixed form (demeton) in Panax ginseng. The principal of the proposed method is that the fluorescence quenching effect of quantum dots (QDs) can be observed by enzyme-generated H2O2. The active centers of acetylcholinesterase (AChE) could be inhibited in the presence of pesticides, which caused decrease of the generated H2O2. Then, the inhibition efficiency of pesticide to AChE activity could be evaluated by measuring the fluorescence changes. Different from biosensors based on immobilized enzyme or self-assembling technique, the proposed biosensor demonstrated a good selectivity for the detection of oxo forms of OPPs. In the present study, the important experimental conditions of the proposed biosensor were investigated. Under the optimized conditions (incubation temperature, 35 °C; incubation time, 20 min; pH value, 8.0; detection time, 30 min; AChE concentration, 40.9 U/L; and choline oxidase (ChOx) concentration, 637.5 U/L), the limit of detection for the investigated oxo-form OPPs was no more than 0.05 μM, which suggested that the proposed method could be used for sensitive and selective determination of trace amounts of OPPs residues in real samples with complex matrices.

Development and use of the kinetic method for determination of trace amounts of vanadium (V) in water samples from objects of the environment

A new kinetic method has been developed for simple, fast and selective determination of trace amounts of vanadium (V) (0.5–5 μg/cm3) based on its inhibiting effect on the oxidizing reaction of 4-hydroxicumarine by means of KMnO4 in acid media. The proposed kinetic method was used for determination of vanadium (VP) in different samples of water without its preliminary separation.

A New Micellar Mediated Cloud-Point Extraction Procedure for Sensitive and Selective Determination of Trace Amounts of Total Iodine in Milk-Based Nutritional Products by Means of Indirect Spectrophotometry

A new micellar mediated cloud-point extraction procedure (CPE) has been developed for sensitive and selective determination of trace amounts of total iodine by means of indirect spectrophotometry. The method is based on selective charge transfer complex formation of I3, which is produced by the reaction of iodate in presence of 25-fold excess periodate with excess iodide and with acridine orange (AOH+) being a selective fluorescent cationic dye at pH 3.0 phthalate buffer, and then the CPE of charge transfer complex formed from aqueous solution at phthalate buffer using nonionic surfactant, Triton X-114. The calibration graphs were rectilinear in the ranges of 1.5–20 and 20–160 μg L−1 for IO3 −, with r 2 higher than 0.9996 in two linear regions with changing sensitivity. Under optimal conditions obtained, the limits of detection and quantification were 0.4 and 1.5 μg L−1 and the precision (as RSD) for determination of 10, 50, and 100 μg L−1 of iodate was in the range of 2.4–4.7 % (n 5). The method was successfully applied to selective and reliable determination of total iodine in milk-based nutritional products. The accuracy of the method was controlled by analyzing two standard reference materials (SRMs) at suitable matrix to milk samples.

Modified Carbon Paste Electrode for Pb2+ Ion Determination: Response Surface Methodology

 Abstract— A novel carbon paste electrode (CPE) based on 2, 2'- (ethane 1, 2-diylbis (azanylylidene)) bis (ethan-1- yl- 1- ylidene)) diphenol (L) was prepared for selective determination of trace amount of Pb 2+ ion. The effects of individual variables such as amounts of L, sodium tetraphenylborate (NaTPB), graphite powder and Nujol as well as their possible interactions were investigated and optimized using central composite design under response surface methodology. Optimum composition of carbon paste was set as 100 mg Nujol and the mass (mg) ratio of 209/4/6 for graphite powder: NaTPB: carrier, respectively. Such composition was found to be led to significant enhancement in the selectivity and sensitivity of the CPE toward Pb 2+ ions over a wide concentration range of 3.7×10 -7 -1.0×10 -2 mol L -1 with detection limit of 1.5×10 -7 mol L −1 and a Nernstian slope of 30.7 ± 1.56 mV per decade of Pb 2+ concentration. Negligible significant change in response was seen over wide pH range of 4.0-6.0 with response time lower than 14 s. The good selectivity of the CPE for Pb 2+ ion toward other metal ions was confirmed by the potentiometric selectivity coefficients. Finally, to be practical, these electrodes were accurately and repeatably used for the determination of Pb 2+ ions in real water sample.

Turn-On Detection of a Cancer Marker Based on Near-Infrared Luminescence Energy Transfer from NaYF4:Yb,Tm/NaGdF4 Core–Shell Upconverting Nanoparticles to Gold Nanorods

A homogeneous immunoassay for the sensitive and selective determination of trace amounts of α-fetoprotein (AFP, a cancer marker) by detection in the near-infrared (NIR) region based on luminescence energy transfer (LET) from NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles to gold nanorods (GNRs) is presented. The carboxyl-functionalized NaYF4:Yb,Tm/NaGdF4 core-shell upconverting nanoparticles (UCNPs) were excited by a 980 nm continuous wavelength laser, and its emission peak appeared at a near-infrared wavelength (∼804 nm). The carboxyl-functionalized upconverting nanoparticles were conjugated with the anti-AFP (Ab1) and acted as donor. GNRs with a high absorption band around 790 nm, which was overlapped the UCNPs emission, were synthesized and acted as the acceptor. The donor (negatively charged) interacted with the acceptor (positively charged) via electrostatic interactions to bring them into close proximity. LET could occur, producing a quenching phenomenon. When the AFP antigens were added into the system, the binding affinity between AFP and Ab1 was stronger than the electrostatic interactions, which released the energy acceptors from the energy donors, interrupting luminescence energy transfer, and therefore, the luminescence was recovered. On the basis of the restored luminescence, a turn-on optical immunosening system was developed. Under the optimal conditions, the linear range of detection was from 0.18 to 11.44 ng/mL for AFP (R = 0.99), with a detection limit as low as 0.16 ng/mL. The proposed method has also been used to monitor AFP in human serum samples. Therefore, further study based on the NaYF4:Yb,Tm/NaGdF4 core-shell nanoparticles-GNRs construction may open the way for a new class of NIR-LET biosensors with wide applications.

UPLC versus HPLC on Drug Analysis: Advantageous, Applications and Their Validation Parameters

Liquid chromatography (LC) is a separation technique used in many different areas to aid the identification and quantification of substances in various matrices. LC techniques with various detection modes have been widely used for the sensitive and selective determination of trace amounts of pharmaceutical active compounds in biological samples and their dosage forms. A completely new system design with advanced technology has been developed, called ultra high performance liquid chromatography, which has evolved from high performance liquid chromatography. The application of LC methods to drug analysis introduces a powerful tool for therapeutic drug monitoring as well as for clinical research. The advantages of short turnaround time, method reliability, method sensitivity, and drug specificity justify the use of LC techniques for various groups of the drug active compounds. This review describes some of the principles of ultra high performance liquid chromatography and high performance liquid chromatography, validation of these methods, system suitability tests for the methods, and application of methods to pharmaceutical analysis in the last 3 years.

Optimization of a new cloud point extraction procedure for the selective determination of trace amounts of total iron in some environmental samples

A new, simple, and rapid cloud point extraction (CPE) procedure system, combined with flame atomic absorption spectrometry (FAAS), was developed for selective separation, preconcentration, and determination of trace amounts of total iron in some environmental samples. The complexing agent, N,N'-(2,2'-(ethane-1,2-diylbis(oxy)) bis(ethane-2,1-diyl))bis(2-chloroacetamide) (EDBOCA), is selective at pH 5.0 for only Fe(II) and Fe(III) ions in the presence of Cu(II), Pb(II), Cd(II), Mn(II), Co(II), Cr(III), Cr(VI), Ni(II), Zn(II), Al(III), Mo(VI), Pd(II), Pt(IV), Au(III), and V(V) ions. The procedure is based on the complexation of Fe(III) ions with EDBOCA reagent in the presence of Triton X-114 (TX-114) as a non-ionic surfactant. The optimum conditions for the CPE of Fe(III) ions were investigated with respect to several experimental parameters such as pH of the solution, TX-114 and EDBOCA concentrations, incubation time and temperature, and centrifugation rate and time. The detection limit for Fe(III) ions based on the 3 times the standard deviation of the blanks (N:10) was found to be 1.22 \mu g L^{-1}, while the relative standard deviation (RSD) was 4.2%. Environment Canada TM-25.3 and CRM-SA-C Sandy Soil C, as certified reference materials, were used, and spike tests were applied to validate the method. The method was applied to some real environmental samples to evaluate their total iron levels.

Electrochemical analysis of copper ion using a Gly–Gly–His tripeptide modified poly(3-thiopheneacetic acid) biosensor

A novel biosensor harnessing a conducting polymer functionalized with a copper ion specific peptide proved to be highly effective for electrochemical analysis of copper ions. The developed sensor comprised a transducer based on a conducting polymer (poly(3-thiopheneacetic acid)) electrode and a probe (tripeptide, Gly–Gly–His) selectively cognitive of copper ions. For functionalization of the electrode, the carboxylic group of the polymer was covalently coupled with the amine group of the tripeptide, and its structural features were confirmed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection infrared (ATR-IR) spectroscopy. The peptide modified polythiophene biosensor was used for the electrochemical analysis of various trace metal ions by square wave voltammetry. The electrode was found to be highly sensitive and selective to Cu 2+ in the range of 0.02–20 μM with almost no cross binding to other metal ions such as Ni 2+ and Pb 2+. Furthermore, the developed sensor exhibited a high stability and reproducibility despite the repeated use of the sensor electrode and probe. With the advent of more diverse affinity bioprobes specific towards a broad range of analytes, the demonstrated strategy harnessing peptide modified polythiophene biosensor is likely to provide an excellent platform for the selective determination of trace amount of analytes whose detection is otherwise cumbersome.

Optimization of dispersive liquid–liquid microextraction for the selective determination of trace amounts of palladium by flame atomic absorption spectroscopy

A new simple and reliable method for rapid and selective extraction and determination of the trace levels of Pd 2+ ion was developed by dispersive liquid–liquid microextraction preconcentration and flame atomic absorption spectrometry detection. In the proposed approach, thioridazine HCl (TRH) was used as a Pd 2+ ion selective complexing agent. The effective parameters on the extraction recovery were studied and optimized utilizing two decent optimization methods; factorial design and central composite design (CCD). Through factorial design the best efficiency of extraction acquired using ethanol and chloroform as dispersive and extraction solvents respectively. CCD optimization resulted in 1.50 mL of dispersive solvent; 0.15 mL of extraction solvent; 0.45 mg of TRH and 250 mg of potassium chloride salt per 5 mL of sample solution. Under the optimum conditions the calibration graph was linear over the range 100–2000 μg L −1. The average relative standard deviation was 0.7% for five repeated determinations. The limit of detection was 90 μg L −1. The average enrichment factor and recovery reached 45.7% and 74.2% respectively. The method was successfully applied to the determination of trace amounts of palladium in the real water samples.

Nitrite as undesirable substances in animal feed ‐ Scientific Opinion of the Panel on Contaminants in the Food Chain

Nitrite as undesirable substances in animal feed ‐ Scientific Opinion of the Panel on Contaminants in the Food Chain

Micelle-mediated cloud point extraction and spectrophotometric determination of rhodamine B using Triton X-100

A new micelle-mediated cloud point extraction method is described for sensitive and selective determination of trace amounts of rhodamine B by spectrophotometry. The method is based on the cloud point extraction of rhodamine B from aqueous solution using Triton X-100 in acidic media. The extracted surfactant rich phase is diluted with water and its absorbance is measured at 563 nm by a spectophotometer. The effects of different operating parameters such as concentration of surfactant and salt, temperature and pH on the cloud point extraction of rhodamine B were studied in details and a set of optimum conditions were obtained. Under optimum conditions a linear calibration graph in the range of 5–550 ng mL −1 of rhodamine B in the initial solution with r = 0.9991 ( n = 15) was obtained. Detection limit based on three times the standard deviation of the blank (3 S b) was 1.3 ng mL −1 ( n = 10) and the relative standard deviation (R.S.D.) for 50 and 350 ng mL −1 of rhodamine B was 2.40 and 0.87% ( n = 10), respectively. The method was applied for the determination of rhodamine B in soft pastel, hand washing liquid soap, matches tip and textile dyes mixture samples.

Selective determination of trace amounts of silver in complicated matrices by displacement-cloud point extraction coupled with thermospray flame furnace atomic absorption spectrometry

A novel displacement-cloud point extraction approach was developed for the selective determination of trace silver in complicated matrices by thermospray flame furnace atomic absorption spectrometry. This method involves two steps of cloud point extraction, i.e., firstly, copper ion reacts with diethyldithiocarbamate (DDTC) to form Cu-DDTC before it is extracted; secondly, after removing the aqueous phase, a sample or standard solution containing silver ion is added and another cloud point extraction procedure is carried out. Because the stability of Ag-DDTC is larger than that of Cu-DDTC, Ag+ can displace Cu2+ from the pre-extracted Cu-DDTC and thus the preconcentration and separation of Ag+ from complicated sample matrix is achieved. Potential interference from co-existing transition metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu2+ from Cu-DDTC complex. Up to 5000 μg mL−1Ni(II), 2000 μg mL−1 Cd(II), 1000 μg mL−1Fe(III), 2000 μg mL−1Co(II), 5000 μg mL−1Zn(II) and 5000 μg mL−1Mn(II) caused no significant interference with the determination of silver of 5 μg L−1. Compared with conventional cloud point extraction, the tolerance limit for the co-existing transition metal ions was increased by at least two orders of magnitude. Under the optimal chemical and instrumental conditions, the limit of detection was 0.2 μg L−1 for silver with a sample volume of 10 mL, and a sensitivity enhancement factor of 21 was achieved. The proposed method was successfully applied to interference-free determination of trace silver in soil, marine sediment and ore samples with high contents of co-existing heavy metals.

Preconcentration of inorganic antimony(III) in environmental samples by PSTH-Dowex microcolumn and determination by FI-ETAAS

A flow injection on-line sorption preconcentration system has been synchronously coupled to an electrothermal atomic absorption spectrometry (ETAAS) system for the selective determination of trace amounts of Sb(III) in water, soil and plant. The determination was achieved by selective complexation and sorption of Sb(III) with [1,5-bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion-exchange resin (Dowex 1× 8-200)] at a wide range of pH, quantitative elution with 50 μl of 2 M HNO 3 and subsequent ETAAS detection. ETAAS determination of the analyte was performed in parallel with the preconcentration of the next sample. Using a preconcentration time of 60 s and a sample loading flow rate of 2.8 ml min −1, an enhancement factor of 12 was obtained in comparison with direct injection of 50 μl aqueous solution, resulting in a sampling frequency of 31 samples h −1. The detection limit (3 s) was 2 μg l −1 and the precision was 3.1% (R.S.D.) for 11 replicate determinations at 10 μg l −1. The accuracy of the proposed method was demonstrated by analyzing one certified sample and different spiked samples.

Molecularly Imprinted Polymers Based on Iodinated Monomers for Selective Room-Temperature Phosphorescence Optosensing of Fluoranthene in Water

Aiming at enhancing the advantages of traditional molecularly imprinted polymers (MIPs) for chemical sensing, a new MIP design approach introducing an internal heavy atom in their polymeric structure is described. Based on the heavy-atom effect, the novel polymer allows one to perform room-temperature phosphorescence (RTP) transduction of the analyte. The synergic combination of a tailor-made MIP recognition with a selective RTP detection is a novel concept for optosensing devices which is assessed here for simple and highly selective determination of trace amounts of fluoranthene in water. The noncovalent MIP was synthesized using the laboratory-synthesized tetraiodobisphenol A as one of the polymeric precursors and fluoranthene as template. In the presence of an oxygen scavenger, the iodide included in the polymeric structure induced efficient RTP emission from the analyte, once recognized by the MIP. The developed optosensing system has demonstrated a high specificity for fluoranthene against other polycyclic aromatic hydrocarbons. Detection limit for the target molecule was 35 ng/L (5-mL sample injections), and the linear range extended above 100 microg/L of the analyte. The polymer can be easily regenerated for subsequent sample injections (at least up to 450 cycles) with acetonitrile. The synthesized sensing material showed good stability for at least 6 months after preparation. The feasibility of monitoring fluoranthene in real samples was successfully evaluated through the analysis of five spiked river water samples.

Ultrasensitive and selective determination of trace amounts of nitrite ion with a novel fluorescence probe mono[6- N(2-carboxy-phenyl)]-β-cyclodextrin

A novel fluorescence probe, mono[6- N(2-carboxy-phenyl)]-β-cyclodextrin (OACCD), has been developed for the determination of trace nitrite, In dilute HCl medium, the fluorescence intensity of the newly synthesized fluorescence probe OACCD was quenched in presence of trace nitrite at room temperature. Based on this, a simple, sensitive, and selective method for rapid determination of nitrite was described. Furthermore, common ions do not interfere the determination of trace amounts of nitrite. The fluorescence quenching intensity was linear over a nitrite concentration of 0.02–1.7 μmol l −1 with a detection limit of 0.2 nmol l −1 (S/N = 3). The method was applied to the determination of nitrite in different water samples, soil samples, and food samples with satisfactory results.

Investigation of the Property Constants of Both Al and Cu Complexes with Picramine Ca and Using Competition Coordination for the Selective Determination of Trace Amounts of Cu

The reactions between Cu(II) and picramine CA (PCA) and Al(III) and PCA were both sensitive at pH 7. The competition coordination between Cu and the Al–PCA complex was applied to the selective determination of Cu (CCSD) by the spectral correction technique. Results have shown that the complexes formed at pH 7 are Al2(PCA) and Cu(PCA)3, their cumulative stability constants are 4.43 × 105 and 2.08 × 1015, respectively, and their real molar absorptivities are 5.78 × 103 at 650 nm and 3.19 × 104at 530 nm. At the analysis of the samples, the relative standard deviation (RSD) was 5.0% and the recovery rate of Cu was between 94 and 108%.