μL Sample Volume Research Articles

3D Printing the Way to Truly Remote, Autonomous, Solar Powered Sensor Networks for Environmental Monitoring of Trace Heavy Metals By Calibration-Less Anodic Stripping Coulometry of µl Sized Samples

The agency for toxic substances and disease registry has consistently listed As, Pb Hg, and Cd as the pollutants of most concern at Superfund sites (recently #1, 2, 3, 7, respectively, amongst hundreds of prioritized hazardous substances). Also of concern is the prevalence of arsenic in groundwater at hundreds of thousands of wells used for drinking by millions of people worldwide. Heavy metal monitoring in natural waters is currently performed in a snapshot fashion where analysis is occasionally possible by sophisticated instruments after sample collection and transportation to centralized laboratories or, less frequently, by technicians wielding portable instruments. Such a snapshot approach to analysis requires a sustained and coordinated effort to monitor many thousands of decentralized sites as frequently as possible, and a preferable approach is the deployment of remote sensor networks. Our group has therefore been interested in the development of truly remote sensor platforms that sufficiently deliver a trifecta of important attributes for heavy metals monitoring – practical, sensitive, and selective measurements– to direct the efforts of central laboratories and mobile operators to where they are most needed. The primary challenges of truly remote sensors revolve around the dual challenges of signal calibration and sample pretreatment, which are typically performed by the operator. We will demonstrate a sensor platform that is capable of low ppb level measurements of heavy metals such as copper and arsenite from 2 µL sample volumes – without any calibration. This calibration-less aspect is achieved by using anodic stripping coulometry after exhaustive deposition of dissolved metals from a finite volume within a stopped flow thin layer cell in about a minute. The use of coulometry in this configuration of electrochemical cell offers rapid analysis, independence from ambient conditions such as temperature, and also tolerates partial electrode fouling which is likely to occur during extended field operation. We will also demonstrate simple approaches for automated sample pretreatment including on-site acidification and dissolved oxygen removal. The use of a coulometric electrochemical method offers the advantage of inexpensive and simple to automate instrumentation with minimal energy requirements. The heart of the sensor is a microfabricated thin-film Au microelectrode array housed within a microfluidic chamber which offers practical advantages including mass-producible, redundant, inexpensive sensors, with a minimal need for on-site reagents. Additionally, we will overview how existing technologies such as miniature electronics and the prevalent communications networks for real-time data acquisition further support the feasibility of our approach. For instance, replacing the screen of even the most primitive smart phone with a solar panel already provides a platform which incorporates a micro-processor, communications ability, and a battery. The microprocessor and battery can be used to drive a miniature potentiostat and a host of commercially available, inexpensive micro-pumps to handle on-site sampling and mixing as required. Despite the commercial availability of many individual components and the promise of the methods we have developed, the remote use of the sensor in real world applications has been limited by the challenge of bridging the gap between a bulk volume of water and a microfluidic chamber where the measurements are made. Essentially, the ideal platform should consist of a fluidic inlet port which is compatible with the macro sized sample, and an outlet to discharge the analyzed sample. The focus of this presentation will therefore be a greatly simplified 3D printed version of platform which contains internal components such as channels and valves to direct and control the sample during operation. We also intend to explore how several modules which perform different pretreatment or measurement functions can be connected to a central 3D printed hub which contains a shared set of the most expensive components (i.e., pumps, valves, etc.). Such a design architecture would seem to offer benefits in terms of operational flexibility and simplicity and also offers the potential for the use of redundant sensors to lengthen intervals between manual maintenance. Lastly, we aim to demonstrate the stability of the platform under conditions as close to real world analysis as possible.

Analysis of the contents of isorhynchophylline in different medicinal parts of Ramulus Uncariae Cum Uncis

Objective To explore the content of isorhynchophylline in different medicinal parts of Ramulus Uncariae Cum Uncis. Methods HPLC was adopted to determine 8 batches of different Ramulus Uncariae Cum Uncis of different origin and different medicinal parts. The Waters Symmetry C18 color （4.6 mm×250 mm, 5 μm）was used with mobile phase of methanol -0.01 mol/L ammonium acetate buffer （pH 8.0）（60∶40）, column temperature of 25 ℃, 20 μl sample volume, velocity of 1.0 ml/min, and detection wavelength of 246 nm. Results Isorhynchophylline can be detected in all 8 batchs of Ramulus Uncariae Cum Uncis in different regions, and different content were found among different origins. The content of isorhynchophylline in different parts of the same origin showed a decreasing sequence of the rhabd, stem with hook, stem without hook, and twig without hook and leaves. Conclusion Most of medicinal part of Ramulus Uncariae Cum Uncis contains isorhynchophylline, which provide a lab basis for exploring medicinal parts of this herbal medicine. Key words: Ramulus Uncariae Cum Uncis; Medicinal parts; Content analysis; Isorhynchophylline

Highly efficient capture and harvest of circulating tumor cells on a microfluidic chip integrated with herringbone and micropost arrays.

Circulating tumor cells (CTCs), which are derived from primary tumor site and transported to distant organs, are considered as the major cause of metastasis. So far, various techniques have been applied for CTC isolation and enumeration. However, there exists great demand to improve the sensitivity of CTC capture, and it remains challenging to elute the cells efficiently from device for further biomolecular and cellular analyses. In this study, we fabricate a dual functional chip integrated with herringbone structure and micropost array to achieve CTC capture and elution through EpCAM-based immunoreaction. Hep3B tumor cell line is selected as the model of CTCs for processing using this device. The results demonstrate that the capture limit of Hep3B cells can reach up to 10 cells (per mL of sample volume) with capture efficiency of 80% on average. Moreover, the elution rate of the captured Hep3B cells can reach up to 69.4% on average for cell number ranging from 1 to 100. These results demonstrate that this device exhibits dual functions with considerably high capture rate and elution rate, indicating its promising capability for cancer diagnosis and therapeutics.

Detection and Direct Readout of Drugs in Human Urine Using Dynamic Surface-Enhanced Raman Spectroscopy and Support Vector Machines

A new, novel, rapid method to detect and direct readout of drugs in human urine has been developed using dynamic surface-enhanced Raman spectroscopy (D-SERS) with portable Raman spectrometer on gold nanorods (GNRs) and a classification algorithm called support vector machines (SVM). The high-performance GNRs can generate gigantic enhancement and the SERS signals obtained using D-SERS on it have high reproducibility. On the basis of this feature of D-SERS, we have obtained SERS spectra of urine and urine containing methamphetamine (MAMP). SVM model was built using these data for fast identified and visual results. This general method was successfully applied to the detection of 3, 4-methylenedioxy methamphetamine (MDMA) in human urine. To verify the accuracy of the model, drug addicts' urine containing MAMP were detected and identified correctly and rapidly with accuracy more than 90%. The detection results were displayed directly without analysis of their SERS spectra manually. Compared with the conventional method in lab, the method only needs a 2 μL sample volume and takes no more than 2 min on the portable Raman spectrometer. It is anticipated that this method will enable rapid, convenient detection of drugs on site for the police.

Microchip immunoaffinity electrophoresis of antibody-thymidine kinase 1 complex.

Thymidine kinase 1 (TK1) is an important cancer biomarker whose serum levels are elevated in early cancer development. We developed a microchip electrophoresis immunoaffinity assay to measure recombinant purified TK1 (pTK1) using an antibody (Ab) that binds to human TK1. We fabricated PMMA microfluidic devices to test the feasibility of detecting Ab-pTK1 immune complexes as a step toward TK1 analysis in clinical serum samples. We were able to separate immune complexes from unbound Abs using 0.5× PBS (pH 7.4) containing 0.01% Tween-20, with 1% w/v methylcellulose that acts as a dynamic surface coating and sieving matrix. Separation of the Ab and Ab-pTK1 complex was observed within a 5 mm effective separation length. This method of detecting pTK1 is easy to perform, requires only a 10 μL sample volume, and takes just 1 min for separation.

A generic sample preparation approach for LC–MS/MS bioanalysis of therapeutic monoclonal antibodies in serum applied to Infliximab

In this study, we developed a generic bioanalytical workflow providing sensitive, specific, and accurate absolute quantification of therapeutic monoclonal antibodies in serum. The workflow involves magnetic beads coated with protein A to pull-down therapeutic monoclonal antibodies with affinity for protein A from the biological matrix, followed by tryptic digestion and LC-MS/ MS quantification of a unique signature peptide, considering of course the matrix of interest and other present mAbs, if applicable. The feasibility of this approach was demonstrated for Inflix imab (trade name Remicade) in rat serum. The assigned signature peptide was monitored in the selected reaction monitoring (SRM) mode. Assay variability was determined to be below 20%, except at the QC low level, which was provided through optimization of the sample preparation and monitoring of the LC-MS/MS using a stable isotope labeled signature peptide as internal standard. The 100 ng/ml lower limit of quantification using only 25 µl sample volume, is generally considered as sufficient for pharmaceutical development purposes for monoclonal antibodies.

New Headspace-Mass Spectrometry Method for the Discrimination of Commercial Gasoline Samples with Different Research Octane Numbers

A method for the discrimination of different gasoline samples according to their RON has been developed using an HS-MS system. The working conditions for the HS-MS analytical procedure were optimized by experimental design. The variables optimized were incubation temperature, incubation time, and sample volume. The optimal conditions were as follows: 145 °C incubation temperature, 10 min incubation time, and 80 μL sample volume. The optimized method was applied to a set of 30 gasoline samples with different RON values (95# and 98#). An hierarchical cluster analysis was applied in which the m/z (45–200 m/z) values were used as a variable to form groups. A perfect classification (100%) of the gasoline samples according to their RON was achieved. A linear discriminant analysis was carried out and the resulting linear discriminant function enabled a perfect classification of the gasoline samples according to the RON using only the m/z values of 88, 95, and 112. These results demonstrate the capacity of the new technique for the discrimination of gasoline samples according to their RON and the applicability of this method in this field. For the first time, HS-MS was used for this purpose. The main advantage of HS-MS vs previous methodologies is that no chromatographic separation and no sample manipulation are required. HS-MS is therefore faster than the current techniques used in these kinds of studies; it is also cheaper, ecofriendly, and easy to use for routine analysis.

Determination of loperamide in human plasma and saliva by liquid chromatography-tandem mass spectrometry.

A simple and sensitive liquid chromatography-tandem mass spectrometric method for quantification of loperamide in human plasma and saliva was developed and validated, and then successfully applied in pharmacokinetic clinical study to investigate and correlate bioavailability of Imodium(®) 2mg quartet tablet dose in both human plasma and saliva. Loperamide with labeled internal standard was extracted from its biological matrix by methanol as protein direct precipitant in single extraction step. Adequate chromatographic separation for analytes from plasma and saliva matrices was achieved using ACE C18 (50mm×2.1mm, 5μm) column, eluted by water/methanol/formic acid (30:70:0.1%, v/v), delivered isocratically at constant flow rate of 0.75ml/min. The method validation intends to investigate specificity, sensitivity, linearity, precision, accuracy, recovery, matrix effect and stability according to European guideline, and partial validation was applied on saliva, specificity, matrix effect, recovery, sensitivity, within and between day precision and accuracy. The calibration curve was linear through the range of 20-3000pg/ml in both plasma and saliva using a 50μl sample volume. The partial validation sections outcome in saliva was so close to those in plasma. The within- and between-day precisions were all below 8.7% for plasma and below 11.4% for saliva. Accuracies ranged from 94 to 105% for both matrices. In this study, 26 healthy volunteers participated in the clinical study, and 6 of gave their saliva samples in addition to plasma at the same time schedule. The pharmacokinetic parameters of Cmax, AUC0-t and AUC0-∞, Tmax and T1/2 in both plasma and saliva were calculated and correlated.

A candidate reference method for quantification of low concentrations of plasmid DNA by exhaustive counting of single DNA molecules in a flow stream

This work demonstrates accurate measurement of the amount of substance concentration of low concentration plasmid DNA by counting individual DNA molecules using a high-sensitivity flow cytometric setup. Plasmid DNA is a widely used form of DNA, and its quantity often needs to be accurately determined. This work establishes a reference analytical method for direct quantification of low concentration plasmid DNA prepared as reference standards for polymerase chain reaction-based DNA quantification. The model plasmid DNA pBR322 (4361 bp) was stained with a fluorescent dye and was detected in a flow stream in a micro-fluidic channel with laser-induced fluorescence detection, for which the DNA flow was electro-hydrodynamically focused at the centre of the channel. 200 to 8000 DNA molecules in a ∼1 µL sample volume were counted within 2 min in an ‘exhaustive counting’ manner, which facilitated quantitation without calibration. The sample volume was measured and validated from the close agreement of the results of two independent measurement methods, gravimetric determination of water filling the capillary and graphical estimation of actual cross sectional area of the capillary tubing with the image of calibrated scanning electron microscopy. Within the given concentration range, an excellent measurement linearity (R2 = 0.999) was achieved with appropriate data processing for the correction of the events of double molecules (detection of double molecules opposed to single molecule detection assumed, which occurs due to their coincidental passing of the detection zone). The validity of the proposed method was confirmed from the close agreement with the results of quantitation of enzymatically released nucleotides using capillary electrophoresis.

A Broadband Sensor Interface IC for Miniaturized Dielectric Spectroscopy From MHz to GHz

This paper describes a broadband sensor interface IC as part of a miniaturized measurement platform for MHz-to-GHz dielectric spectroscopy. Developed in 0.35 μm 2P/4M RF CMOS, the IC measures frequency-dependent S 21 magnitude and phase of a microfluidic dielectric sensor fabricated in a thick gold-on-glass microfabrication process and loaded with a material-under-test (MUT). The IC architecture implements a broadband frequency response analysis (bFRA) method by first down-converting the sensor response signal from the RF excitation frequency to an intermediate frequency (IF) of 1 MHz using a low-noise amplifier (LNA) and active mixer, followed by down-converting the IF signal to dc using a coherent detector employing IF amplification stages with programmable gain, a passive mixer driven by in-phase (I) and quadrature-phase (Q) signals and an active-RC low-pass filter (LPF). The sensor interfaced with the IC is fully capable of differentiating among deionized (DI) water, phosphate buffered saline (PBS), ethanol and methanol in tests conducted at four different excitation frequencies of 50 MHz, 500 MHz, 1 GHz and 3 GHz. Further, dielectric readings of ethanol from the sensor interfaced with the IC at five excitation frequencies in the range of 50 MHz to 2 GHz are in excellent agreement (error <;1%) with those from using a vector network analyzer (VNA) as the sensor readout. A bulk-solution reference measurement by an Agilent 85070E dielectric probe kit interfaced with a VNA is also performed to verify proof-of-concept feasibility in conducting MHz-to-GHz dielectric spectroscopy with a miniaturized measurement platform using μL-sample volumes.

An assessment of the potential of laser-induced breakdown spectroscopy (LIBS) for the analysis of cesium in liquid samples of biological origin.

The present study describes the development of an analytical method for the determination of cesium in biological fluid samples (human urine and blood samples) by laser-induced breakdown spectroscopy (LIBS). The developed method is based on sample presentation by liquid-to-solid conversion, enhancing the emission signal by drying the liquid into small "pockets" created in a metal support (zinc plate), and allows the analysis to be carried out on as little as 1 μL of sample volume, in a closed sample cell. Absolute detection limits on the Cs I 852.1 nm spectral line were calculated by the IUPAC 3σ method to be 6 ng in the urine sample and 27 ng in the blood serum sample. It is estimated that LIBS may be used to detect highly elevated concentration levels of Cs in fluid samples taken from people potentially exposed to surges of Cs from non-natural sources.

교반막대 추출법과 GC-MS/MS를 이용한 수중의 합성 향물질류 분석

A highly sensitive analytical method based on stir bar sorptive extraction (SBSE) technique and gas chromatography/ tandem mass spectrometry (GC-MS/MS) has been developed, allowing the simultaneous multi-analyte determination of 11 synthetic fragrances (SFs) in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 40 mL of water sample at pH 3 and stirred at 1,100 rpm for 120 min. Other SBSE parameters (salt effect and presence of organic solvent) were optimised. The method shows good linearity (coefficients > 0.990) and reproducibility (RSD < 10.9%). The extraction efficiencies were above 83% for all the compounds. The limits of detections (LOD) and limits of quantification (LOQ) were 2.1~4.1 ng/L and 6.6~12.9 ng/L, respectively. The developed method offers the ability to detect 11 SFs at ultra-low concentration levels with only 40 mL of sample volume. Matrix effects in tap water, river water, wastewater treatment plant (WWTP) final effluent water and seawater were investigated and it was shown that the method is suitable for the analysis of trace level of 11 SFs. The method developed in the present study has the advantage of being rapid, simple, high-sensitive and both user and environmentally friendly.

교반막대 추출법과 GC/MS-MS를 이용한 수중의 자외선 차단제 분석

A highly sensitive analytical method based on stir bar sorptive extraction (SBSE) technique and gas chromatography/tandem mass spectrometry (GC/MS-MS) has been developed, allowing the simultaneous multi-analyte determination of seven UV filters in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 40 mL of water sample at pH 3 and stirred at 1,100 rpm for 120 min. Other SBSE parameters (salt effect and presence of organic solvent) were optimised. The method shows good linearity (coefficients > 0.990) and reproducibility (RSD < 12.9%). The extraction efficiencies were above 84% for all the compounds. The limits of detections (LOD) and limits of quantification (LOQ) were 2.1∼8.6 ng/L and 6.8∼27.5 ng/L, respectively. The developed method offers the ability to detect 8 UV filters at ultra-low concentration levels with only 40 mL of sample volume. Matrix effects in tap water, river water, wastewater treatment plant (WWTP) final effluent water and seawater were investigated and it was shown that the method is suitable for the analysis of trace level of 7 UV filters except of benzophenone (BP). The method developed in the present study has the advantage of being rapid, simple, high-sensitive and both user and environmentally friendly.

Enhanced charge transfer by gold nanoparticle at DNA modified electrode and its application to label-free DNA detection.

Rational utilization of nanomaterials to construct electrochemical nucleic acid sensors has attracted large attention in recent years. In this work, we systematically interrogate the interaction between gold nanoparticles (GNPs) and single-strand DNA (ssDNA) immobilized on an electrode surface and then take advantage of the ultrahigh charge-transfer efficiency of GNPs to develop a novel DNA sensing method. Specifically, ssDNA modified gold electrode can adsorb GNPs because of the interaction between gold and nitrogen-containing bases; thus, the negative electrochemical species [Fe(CN)6](3-/4-) may transfer electrons to electrode through adsorbed GNPs. In the presence of target DNA, the formed double-strand DNA (dsDNA) cannot capture GNPs onto the electrode surface and the dsDNA may result in a large charge-transfer resistance owing to the negatively charged phosphate backbones of DNA. So a simple but sensitive method for the detection of target DNA can be developed by using GNPs without any requirement of modification. Experimental results demonstrate that the electrochemical method we have proposed in this work can detect as low as 1 pM breast cancer gene BRCA1 in a 10 μL sample volume without any signal amplification process or the involvement of other synthesized complex, which may provide an alternative for cancer DNA detection. This method may also be generalized for detecting a spectrum of targets using functional DNA (aptamer, metal-specific oligonucleotide, or DNAzyme) in the future.

RNF 4 interacts with both SUMO and nucleosomes to promote the DNA damage response

The post-translational modification of DNA repair and checkpoint proteins by ubiquitin and small ubiquitin-like modifier (SUMO) critically orchestrates the DNA damage response (DDR). The ubiquitin ligase RNF4 integrates signaling by SUMO and ubiquitin, through its selective recognition and ubiquitination of SUMO-modified proteins. Here, we define a key new determinant for target discrimination by RNF4, in addition to interaction with SUMO. We identify a nucleosome-targeting motif within the RNF4 RING domain that can bind DNA and thereby enables RNF4 to selectively ubiquitinate nucleosomal histones. Furthermore, RNF4 nucleosome-targeting is crucially required for the repair of TRF2-depleted dysfunctional telomeres by 53BP1-mediated non-homologous end joining.

Ultra trace determination of fluorobenzoic acids in reservoir and ground water using isotope dilution gas chromatography mass spectrometry

The accurate ultra-trace analysis of six fluorobenzoic acids (FBAs) via isotope dilution gas chromatography mass spectrometry through their deuterated analogues is described. North Sea reservoir and ground water samples were spiked with six deuterated FBAs (dFBAs), enriched using solid-phase extraction (SPE) and analysed using GC/MS after derivatisation with BF 3· MeOH. All FBAs were enriched and determined simultaneously. SPE allowed a 250-fold enrichment of the acids if 100 mL of sample volume was used. The method enables the determination of FBAs down to the range of 8–37 ng L −1 with recoveries between 66 % and 85 %. It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes.

Optimization of parameters for the alcoholic-assisted dispersive liquid–liquid microextraction of estrogens in water

Extraction and determination of estrogens in water samples were performed using alcoholic-assisted dispersive liquid–liquid microextraction (AA-DLLME) and high-performance liquid chromatography (UV/Vis detection). A Plackett–Burman design and a central composite design were applied to evaluate the AA-DLLME procedure. The effect of six parameters on extraction efficiency was investigated. The factors studied were volume of extraction and dispersive solvents, extraction time, pH, amount of salt and agitation rate. According to Plackett–Burman design results, the effective parameters were volume of extraction solvent and pH. Next, a central composite design was applied to obtain optimal condition. The optimized conditions were obtained at 220 μL 1-octanol as extraction solvent, 700 μL ethanol as dispersive solvent, pH 6 and 200 μL sample volume. Linearity was observed in the range of 1–500 μg L−1 for E2 and 0.1–100 μg L−1 for E1. Limits of detection were 0.1 μg L−1 for E2 and 0.01 μg L−1 for E1. The enrichment factors and extraction recoveries were 42.2, 46.4 and 80.4, 86.7, respectively. The relative standard deviations for determination of estrogens in water were in the range of 3.9–7.2 % (n = 3). The developed method was successfully applied for the determination of estrogens in environmental water samples.

Microfluidic channel‐assisted screening of hematopoietic malignancies

A simple microfluidic fluorescence in situ hybridization (FISH) device allowing accurate analysis of interphase nuclei in 1 hr in narrow channels is presented. Photolithography and fluorosilicic acid etching were used to fabricate microfluidic channels (referred to as FISHing lines) that allowed analysis of 10 samples on a glass microscope slide 0.2 µl of sample volume was used to fill a micro-channel, which resembled a 250-fold reduction compared to conventional FISH. FISH signals were comparable to conventional FISH, with 50-fold less probe consumption and 10-fold less time. Cells were immobilized in single file in channels just exceeding the diameter of the cells, and were used for minimal residual disease (MRD) analysis. To test the micro-channels for application in FISH, MRD was simulated by mixing K562 cells (an established chronic myeloid leukemia cell line) carrying the BCR/ABL fusion gene across 1:1 to 1:1,000 Jurkat cells (an established acute lymphoblastic leukemia cell line). The limit of detection was seen to be 1:100 cells and 1:1,000 cells for FISHing lines and conventional FISH, respectively; however, the conventional method seemed to over-score the presence of K562 cells. This may in part be attributed to FISHing lines practically eliminating the chance of duplicate screening of cells and hastened the time of screening, enhancing scoring of all cells within the channels. This was compared to 1 in 500 cells on the slide being analyzed with the conventional FISH.

Separation and pre-concentration of palladium(II) from environmental and industrial samples by formation of a derivative of 1,2,4-triazole complex on Amberlite XAD–2010 resin

A simple separation/pre-concentration method was developed for extraction of Pd(II) in various environmental samples, based on its adsorption of 4–phenyl–5–{[(4–phenyl–5–pyridin–4–yl–4H–1,2,4–triazole–3–yl)thio]methyl}–4H–1,2,4–triazole–3–thyol (PPTTMET) complex on Amberlite XAD–2010 resin in a mini column. The ligand has high affinity for Pd(II) among many other metals that are taken into consideration. The flame atomic absorption spectrometry is employed to determine the concentration of Pd(II). The optimum working conditions which were determined are as follows: 0.05 mol L−1 HNO3 as working medium, 1.0 mol L−1 HCI in acetone as elution solvent, 0.75 mg of PPTTMET amount and 750 mL of sample volume. The system was independent from the flow rates between 3.1 and 23.1 mL min−1. The Pd(II) adsorption capacity of Amberlite XAD–2010 resin was found to be 12.8 mg g−1 and the enrichment factor was calculated as 375. The method was successfully applied for the determination of Pd(II) in motorway dust samples, anodic sludge, gold ore, industrial electronic waste materials and various water samples.

Silver modified magnetic carbon nanotubes composite as a selective solid phase extractor for preconcentration and determination of trace mercury ions in water solution

A magnetic composite of silver/iron oxides/carbon nanotubes (Ag/Fe3O4/CNTs) was synthesized and used as an adsorbent for the preconcentration of mercury ions in water solutions at room temperature (25°C) in this study. The silver nanoparticles were supported on the magnetic CNTs. The modification enabled the composite had not only a high adsorption capacity for mercury ions (Hg2+) but also the magnetic isolation properties. A fast, sensitive, and simple method was successfully developed for the preconcentration and determination of trace amount of Hg2+ in water using the synthesized nanocomposite as adsorbent. The mercury concentration was determined by an atomic fluorescence spectrometer (AFS). The experimental conditions such as pH value, extraction temperature, extraction time, sample volume, eluent composition and concentration, sorbent amount, and coexisting ions were investigated for the optimization. A 500 mL of sample volume resulted in a preconcentration factor of 125. When a 200 mL of sample was employed, the limit of detection for Hg2+ was as low as 0.03 ng mL−1with relative standard deviation of 4.4% at 0.1 ng mL−1 (n = 7). The ease of synthesis and separation, the good adsorption capacity, and the satisfactory recovery will possibly make the composite an attractive adsorbent for the preconcentration of ultratrace Hg2+ in waters.