The effects of Cu and Mn on the microstructure, mechanical, corrosion properties and biocompatibility of Zn–4Ag alloy

Zinc (Zn) alloys have been paid increasing attention in the field of biodegradable implantable materials due to their moderate degradation rate compared to magnesium (Mg) and iron (Fe) alloys. In this study, Zn–4Ag, Zn–4Ag–Cu and Zn–4Ag–Mn were prepared to investigate the effects of Cu and Mn elements on the microstructure and properties of Zn–4Ag alloys, and the addition of Cu and Mn improved the mechanical properties and degradation rate of Zn–4Ag alloys. The tensile strength of Zn–Ag after rolling was increased from 141.9 MPa to 168.4 MPa and 206.3 MPa after the addition of Cu and Mn. The degradation rate of Zn–4Ag increased from 0.17 mm/year to 0.22 mm/year and 0.39 mm/year in the first 5 days after the addition of Cu and Mn. The cytotoxicity testing showed good biocompatibility for human umbilical vein endothelial cells (HUVEC) in as-rolled Zn–4Ag–Mn diluted 4 times, and its cytotoxicity showed grade 0 or 1 toxicity with the cell survival rate of 83.7%. The antibacterial experiment showed the highest antibacterial rate for methicillin-resistant Staphylococcus aureus (MRSA) in as-rolled Zn–4Ag–Cu with the antibacterial rate of 90.3%

Spectrophotometric flow injection determination of dissolved titanium in seawater exploiting in-line nitrilotriacetic acid resin preconcentration and a long path length liquid waveguide capillary cell

A sensitive spectrophotometric method for the determination of dissolved titanium (Ti) in seawater is developed. It involves in-line preconcentration and a long path length liquid waveguide capillary cell (LWCC). Nitrilotriacetic acid (NTA) resin is used to preconcentrate Ti from ∼25 mL seawater sample at pH 1.7, and elution is accomplished with 0.8 mol L−1 hydrochloride acid. The eluted Ti solution is buffered to pH 6.0 with 1.0 mol L−1 ammonium acetate and mixed with 1.5 mmol L−1 Tiron solution. The mixture is then injected into LWCC and measured by spectrophotometry at 420 nm. Before the preconcentration step, the sample is treated with 7 mmol L−1 ascorbic acid to reduce Fe(III) to Fe(II), in order to eliminate the Fe interference. The method is not interfered by Fe(III) and Cu(II) present in seawater samples at concentrations 50-fold higher in relation to Ti, and by Cd(II), Pb(II), Cr(VI), Mn(II), Al(III), Zn(II), and Ni(II) at concentrations 100-fold higher in relation to Ti. It is time efficient (7.5 minutes per sample), sensitive (0.10 nmol L−1 detection limit), precise (1.40% measurement RSD at 1.00 nmol L−1 Ti) and is characterized by a linear range of 0.50–5.00 nmol L−1 Ti. The method was applied to analysis of natural water samples collected from the Jiulongjiang Estuary, Fujian, China. [Display omitted] •Sensitive spectrophotometric detection of dissolved Ti in seawater is developed.•NTA resin is used to preconcentrate dissolved Ti in seawater at pH 1.7.•Fe(III) is reduced to Fe(II) before resin to avoid Fe retention and interference.•In-line preconcentration and detection is realized with flow analysis and LWCC.•Estuarine dissolved Ti is analyzed and reported

A modified method for on-line determination of trace ammonium in seawater with a long-path liquid waveguide capillary cell and spectrophotometric detection

Science Fund for Creative Research Groups of the National Natural Science Foundation of China [41121091]An automated calorimetric method for the on-line determination of trace ammonium in seawater was established using a flow injection technique coupled with a 2.5-m liquid waveguide capillary cell. Using low ammonium seawater as a carrier, a sample was injected into the carrier and mixed with reagents to form indophenol blue dye, which was monitored at a wavelength of 690 nm. Different strategies of reagent injection were investigated to obtain a lower reagent blank and a higher detection sensitivity. Experimental parameters were optimized using a univariate experimental design, and the matrix effect of seawater was preliminarily investigated. The proposed method had high sensitivity with a detection limit of 3.6 nmol.L-1. The linearity was 10 to 500 nmol.L-1 and the upper limit could be extended to 30 mu mol.L-1 by choosing a less sensitive detection wavelength or lower reaction temperature. The recoveries were between 95.0 and 104.3% and the relative standard deviation was 4.4% (n = 7) for an aged seawater sample spiked with 50 nmol.L-1 ammonium. The sample throughput was 22 h(-1). The analytical results obtained with the proposed method showed good agreement with those using reference fluorescence methods. Compared with the normal indophenol blue (off-line) method, the proposed method was superior due to its lower reagent consumption, greater convenience, higher sample throughput, wider linear range (10 nmol.L-1 to 30 mu mol.L-1), as well as higher sensitivity. The method was applied in-field in Wuyuan Bay for 24 h on-line monitoring of ammonium concentrations in the surface seawater. In addition, it was also used to analyze surface seawater samples collected from the South China Sea for the study of ammonium distribution. (C) 2014 Elsevier B.V. All rights reserved

Automated Spectrophotometric Determination of Carbonate Ion Concentration in Seawater Using a Portable Syringe Pump Based Analyzer

Observations of seawater carbonate ion concentrations are critical to assess the ecological effects of ocean acidification. Nevertheless, currently available methods are labor intensive or too complex for field applications. Here, we report the design and performance of the first fully automated portable carbonate ion analyzer. Measurements are based on reaction of carbonate and chloride ions with Pb(II) followed by quantitative UV spectrophotometric detection of the PbCO30 complex. The core hardware is a syringe pump equipped with a multi-position valve that is controlled by software written in LabVIEW. Measurement precision is 1.1% (n = 13) with a measurement frequency of 12 h−1. The analyzer was used to continuously monitor carbonate ion concentration variations in a 2500 L coral reef tank for five days (test 1), and used for shipboard underway and vertical profile analysis during a 13-day cruise (test 2). The analyzer attained a combined standard uncertainty of 3.0%, which meets the Global Ocean Acidification Observing Network\u27s “weather level” goal. Through use of a syringe pump mechanism for mixing seawater and reagent solution, the analyzer is robust, functionally flexible, and quite suitable for continuous environmental monitoring under harsh conditions

Development of an Integrated Syringe-Pump-Based Environmental-Water Analyzer (<i>i</i>SEA) and Application of It for Fully Automated Real-Time Determination of Ammonium in Fresh Water

The development of a multipurpose integrated syringe-pump-based environmental-water analyzer (<i>i</i>SEA) and its application for spectrophotometric determination of ammonium is presented. The <i>i</i>SEA consists of a mini-syringe pump equipped with a selection valve and laboratory-programmed software written by LabVIEW. The chemistry is based on a modified indophenol method using <i>o</i>-phenylphenol. The effect of reagent concentrations and sample temperatures was evaluated. This fully automated analyzer had a detection limit of 0.12 μM with sample throughput of 12 h^–1. Relative standard deviations at different concentrations (0–20 μM) were 0.23–3.36% (<i>n</i> = 3–11) and 1.0% (<i>n</i> = 144, in 24 h of continuous measurement, ∼5 μM). Calibration curves were linear (<i>R</i>² = 0.9998) over the range of 0–20 and 0–70 μM for the detection at 700 and 600 nm, respectively. The <i>i</i>SEA was applied in continuous real-time monitoring of ammonium variations in a river for 24 h and 14 days. A total of 1802 samples were measured, and only 0.4% was outlier data (≥3 sigma residuals). Measurements of reference materials and different aqueous samples (<i>n</i> = 26) showed no significant difference between results obtained by reference and present methods. The system is compact (18 cm × 22 cm × 24 cm), portable (4.8 kg), and robust (high-resolution real-time monitoring in harsh environments) and consumes a small amount of chemicals (20–30 μL/run) and sample/standards (2.9 mL/run)