Cheng-Fa Lee

On-line microdialysis–nano-Au/TiO2–high-performance liquid chromatography system for the simultaneous determination of cobalt and nickel in water

An on-line configuration of microdialysis (MD), Au/TiO2 nanoparticle preconcentration, and high-performance liquid chromatography-ultraviolet (HPLC-UV) detection method was developed for the simultaneous measurement of cobalt (Co) and nickel (Ni) concentrations in water. The sample matrix was first cleaned with an MD system using a MD probe. A continuously flowing dialysate stream was introduced into tubing coated with Au/TiO2 nanoparticles to adsorb metals, followed by elution by an acidic eluent. The enriched samples were derivatized on-line using 8-hydroxyquinoline. The separation of Co and Ni were achieved by using a LC-C18 column. The three aforementioned system components were connected on-line using a valve control. The UV detection was performed at 319nm. Validation experiments demonstrate good linearity, precision, accuracy, and recovery. The proposed method offers a simple and reliable procedure to determine the levels of Co and Ni in environmental water samples. Moreover, the methodology described in this study adheres to the concept of green chemistry, including the absence of organic solvents in the MD sampling and extraction processes. To the best of our knowledge, the proposed method is the first reported on-line connection of MD, Au/TiO2 nanoparticle tubing, and HPLC devices for the measurement of Co and Ni concentrations in water.

Selective and eco-friendly method for determination of mercury(II) ions in aqueous samples using an on-line AuNPs–PDMS composite microfluidic device/ICP-MS system

In this study we developed an on-line, eco-friendly, and highly selective method using a gold nanoparticle (AuNP)-coated polydimethylsiloxane (PDMS) composite microfluidic (MF) chip coupled to inductively coupled plasma mass spectrometry (ICP-MS) to separate trace Hg(2+) ions from aqueous samples. Because Hg(2+) ions interact with AuNPs to form Hg-Au complexes, we were able to separate Hg(2+) ions from aqueous samples. We prepared the AuNPs-PDMS composite through in situ synthesis using a PDMS cross-linking agent to both reduce and embed AuNPs onto PDMS microchannels so that no additional reductants were required for either AuNP synthesis or the PDMS surface modification (2% HAuCl4, room temperature, 48 h). To optimize the proposed on-line system, we investigated several factors that influenced the separation of Hg(2+) ions in the AuNPs-PDMS/MF, including adsorption pH, adsorption and elution flow rates, microchannel length, and interferences from coexisting ions. Under optimized conditions (pH 6.0; adsorption/elution flow rates: 0.05/0.5 mL min(-1); channel length: 840 mm), we evaluated the accuracy of the system using a standard addition method; the measured values had agreements of ≥ 93.0% with certified values obtained for Hg(2+) ions. The relative standard deviations of the proposed method ranged from 2.24% to 6.21%. The limit of detection for Hg(2+) for the proposed on-line AuNPs-PDMS/MF/ICP-MS analytical method was as low as 0.07 µg L(-1).

On-line microdialysis sampling coupled with flame atomic absorption spectrometry for continuous in vivo monitoring of diffusible magnesium in the blood of living animals.

A novel on-line microdialysis sampling coupled with flame atomic absorption spectrometry (FAAS) with an attractive application is reported. Microdialysates perfused through implanted microdialysis probes were directly introduced into the flame atomizer of a FAAS system using 0.2% HNO(3) as carrier solution at a nebulizer uptake flow rate of 6mlmin(-1). The interval for each determination was 90s (60s sampling time, 10s read time and 20s washing time). The analytical characteristics of the on-line microdialysis-FAAS system were validated as follows: linearity range, 0-300mgl(-1); detection limit (3sigma, n=7), 0.53mgl(-1); precision (R.S.D., n=50), 4.1%. By comparing Mg levels in the blood of living rabbits with the results obtained from in vivo no net flux (NNF) method, the accuracy of the proposed on-line method was found to be good. The present method can be successfully applied to the in vivo monitoring of diffusible Mg in the blood of living rabbits after magnesium sulfate (MgSO(4)) administration with a temporal resolution of 1.5min.

Combining Microdialysis Sampling and Inductively Coupled Plasma Mass Spectrometry for Dynamic Monitoring of Trace Metal Ions during Bacterial Growth Periods

Monitoring the dynamic variations of trace metal ions allows us to understand their roles in basic cellular functions and also in microbial-mediated detoxification of metal pollutants. The objective of this study was to develop an easily operated, simultaneous, and continuous method for dynamic monitoring of trace metal ions during bacterial growth periods. Here, we used a microdialysis (MD) sampling technique combined with detection through inductively coupled plasma mass spectrometry (ICP-MS) to determine and quantify trace metal ions. After optimization, we used a retrodialysis technique and a no-net-flux method to assess the probe recovery and analytical performance of the proposed system. The mean probe recoveries of cobalt, copper, strontium, cadmium, and lead were 64.4, 92.6, 40.8, 84.2, and 54.7%, respectively, with typical precision values of 0.5–6.2, 1.1–7.7, 2.0–6.3, 2.3–7.8, and 1.5–7.8%, respectively. To further evaluate the practical applicability of using our proposed MD/ICP-MS method, we monitored, continuously for 24 h, the dynamic variations of the concentrations of each metal ion in four standardized bacterial species (ATCC 35218, 25922, 25923, 29213). Our analytical results revealed that MD sampling combined with ICP-MS detection had the ability to accurately and continuously monitor the levels of trace metal ions in microbial inoculated culture broths, potentially benefiting research into the bioavailability and detoxification processes of trace metal ions in microbial samples.

Real-time dynamic monitoring of nonprotein-bound copper in the blood

To obtain real-time dynamic changes of non-protein-bound copper in the blood, we have developed an online microdialysis sampling system coupled with a flow-injection graphite furnace-atomic absorption spectrometer (FI-GFAAS). The analytical performances of the online system such as linearity, limit of detection, precision, and spiked recoveries were validated. Before the in vivo experiments, the in vivo recovery was conducted. The levels of non-protein-bound Cu in the blood of living rabbits were evaluated before and after administering them with 5 mg/kg body weight of CuSO4 by the online microdialysis-FI-GFAAS system. The results showed that the avarage basal concentration of non-protein-bound Cu in the blood of living rabbits was 16.2 μg/L (n=3). Furthermore, the levels of non-protein-bound Cu in the blood of living rabbits were observed after a long delay following intravenous injection of CuSO4. The non-protein-bound Cu reached the maximum value at 125 min after injection. Our present study might provide the in vivo, direct observation that different metals have their own binding characteristics with proteins when transported into the blood of living organisms.

Ultrasound-assisted hollow fiber/ionic liquid-based liquid phase microextraction using an ionic liquid solvent for preconcentration of cobalt and nickel ions in urine samples prior to FAAS determination

Ultrasound-assisted (UA) hollow fiber (HF) liquid-phase microextraction (LPME) coupled with flame atomic absorption spectrometry (FAAS) has been developed to preconcentrate and determine ultra-trace amounts of cobalt (Co) and nickel (Ni) ions in human urine. To the best of our knowledge, no previous reports have described the coupling of UA-ionic liquid (IL)-HF-LPME with an FAAS system to analyze metal ions in biological samples. In this study, the ILs 1-hexyl-3-methylimidazolium hexafluorophosphate, sodium hexafluorophosphate, and 1-(2-pyridylazo)-2-naphthol were used as extraction, ion-pairing, and chelating agents, respectively. With the assistance of an ultrasonic probe, the analyte exchange between the phases increased, and the extraction efficiency of Co and Ni ions improved significantly. The collected extraction phase was subsequently analyzed directly through FAAS. Under optimized conditions, the detection limits of Co and Ni ions were 0.09 and 0.03 μg L−1, respectively. The precision of the analysis of Co and Ni ions was within a relative standard deviation of 10% under normal operating conditions. The ultrasonic assistance provided enrichment factors of 66 and 82 for Co and Ni ions, respectively. The recoveries of Co and Ni ions spiked in urine samples ranged from 93.8 to 104.3%. The practicality of the proposed method was demonstrated through satisfactory analyses of samples of a standard reference material and real human urine.