Determination of ultratrace levels of dissolved metals in seawater by reaction cell inductively coupled plasma mass spectrometry after ammonia induced magnesium hydroxide coprecipitation

A method for the determination of ultratrace amounts of Cr, Fe, Mn, Pb and Zn in seawater has been developed. It combined the low-blank magnesium hydroxide coprecipitation procedure with quadrupole inductively coupled plasma mass spectrometry and used the dynamic reaction cell technique to resolve the polyatomic interferences arising from the residual matrix, the solvent and plasma gases. Detection limits (3σ_B, n = 10) for Cr, Fe, Mn, Pb and Zn were 0.02, 0.10, 0.01, 0.002 and 0.19 nM, respectively, using 50 mL of seawater sample. The accuracy of the analytical procedure was verified by the analysis of the seawater reference materials CASS-4, NASS-5, SAFe D2 and SAFe S. The analytical precision ranged from 3% to 16% (n = 6), with a sample throughput of about 6 samples h⁻¹.     

聚乙烯亚胺螯合-超滤分离富集电感耦合等离子体质谱法测定海水中6种痕量金属元素

建立了高分子聚合物螯合-超滤(PCP-UF)分离富集、电感耦合等离子体质谱(ICP-MS)测定海水中痕量金属元素的方法.海水中的Cu(2+),Pb(2+),Cd(2+),Co(2+),Ni(2+)等金属离子与聚乙烯亚胺(PEI)形成高分子螯合物,经超滤截留、酸解离后,实现金属离子从海水中定量分离、富集.ICP-MS采用...     

Determination of 232Th in seawater by ICP-MS after preconcentration and separation using a chelating resin

This article describes an analytical method for the separation, preconcentration and determination of ²³²Th in seawater samples at sub-ng/L levels using a NOBIAS CHELATE PA1 resin and a sector field (SF) inductively coupled plasma mass spectrometer (ICP-MS). The resin showed excellent adsorption of ²³²Th at a low pH of 2.4 ± 0.4 in a relatively small volume (200 mL) of seawater. ²³²Th adsorbed on the resin was easily eluted using 5 mL of 0.8 M HNO₃. An enrichment factor of 40 was achieved for ²³²Th analysis. Ethylenediamine-tetraacetic acid disodium salt dehydrate (EDTA) was used to investigate the effect of ²³²Th-binding organic ligand on the retention of ²³²Th on the chelating resin. Results obtained using acidified samples (pH of 2.4 ± 0.4) showed EDTA had no significant effect on ²³²Th recovery, indicating that at this low pH, ²³²Th was dissociated from the ²³²Th-binding organic ligand and quantitatively retained on the NOBIAS CHELATE PA1 resin. The developed analytical method was characterized by a separation and preconcentration taking approximately 4 h and a low detection limit of 0.0038 ng/L for ²³²Th, and was successfully applied to the determination of ²³²Th in seawater samples collected from coastal areas, Japan.     

Determination of non-ionic and anionic surfactants in environmental water matrices

Solid-phase extraction (SPE) combined with liquid chromatography electrospray mass spectrometry (LC-(ESI)MS) was used to determine 16 non-ionic and anionic surfactants in different environmental water samples at ng L⁻¹ levels. The proposed method is sensitive and simple and has good linear range and detection limits (less than 50 ng L⁻¹) for most compound classes.The effect of ion suppression was studied in aqueous matrices from several treatment plants—including urban and industrial wastewater treatment plants (WWTPs), drinking-water treatment plants (DWTPs) and seawater desalination plants (SWDPs)—and it was considered when quantifying our samples. In addition, conventional treatments and tertiary treatments that use advanced membrane technologies, such as ultrafiltration (UF) and reverse osmosis (RO) were evaluated in order to determine their efficiency in eliminating these compounds.The concentrations of non-ionic surfactants in the raw waters studied ranged from 0.2 to 100 μg L⁻¹. In effluents, the concentrations ranged from 0.1 to 5 μg L⁻¹, which reflects consistent elimination. Anionic surfactants were present in all waters studied at higher levels. Levels up to 3900 μg L⁻¹ of linear alkylbenzene sulfonates (LASs) and 32,000 μg L⁻¹ of alkyl ethoxysulfates (AESs) were detected in urban WWTP influents, while levels up to 25 μg L⁻¹ of LASs and 114 μg L⁻¹ of AESs were found in drinking-water and desalination treatment plants.The results indicate that conventional processes alone are not sufficient to completely remove the studied surfactants from waste streams. Tertiary treatments that use advanced membrane technologies such as UF and RO can further reduce the amount of target compounds in the effluent water.     

海水中溶解态硝酸盐的氮同位素分析的预处理方法

建立了一套适合海水中溶解态硝酸盐的氮同位素分析的预处理方法.以蒸馏为基础,先去除海水样品中的NO-2-N和NH+4-N,然后加入达氏合金将海水样品中的NO-3-N还原为NH+4-N,并通过蒸馏富集,馏出液用沸石吸附后,经过滤等步骤,送入同位素质谱仪检测15N.研究了预处理过程中的蒸馏条件、盐度影响、沸石吸附效率以及大体积水样预处理方法的改进等.结果表明,每300 mL水样中加入0.5 g达氏合金在强碱性条件下蒸馏30 min,氮回收率平均可达(104.9±4.2)%(n=6);当盐度从0%增加至0.5%时,同位素分馏程度迅速减小盐度再增大时(1%～3.5%),同位素分馏变化不明显.沸石对铵氮的平均吸附率较高,约为(95.96±1.08)%(n=6);处理大体积水样时多次蒸馏并改进了馏出液的收集方式,实验效果较好.应用此方法对长江口海域水样进行了分析,结果表明,这一方法可以应用于海水中溶解态硝酸盐的氮同位素分析,为海水中溶解态氮的来源问题及循环机理研究等提供了有效信息.     

Ionic imprinted polymer for nickel recognition by using the bi-functionalized 5-vinyl-8-hydroxyquinoline as a monomer: Application as a new solid phase extraction support

A new ionic imprinted polymer (IIP) for Ni(II) recognition/pre-concentration was prepared via precipitation polymerization using 2-(diethylamino) ethyl methacrylate (DEM) and divinylbenzene (DVB) as a crosslinking agent in the presence of nickel(II) and 5-vynil-8-hydroxyquinoline (5-VHQ) as a bi-functionalized ligand. An important increase on the selectivity of the synthesised IIP for nickel(II) ions was obtained when comparing to the use of 8-hydroxyquinoline (8-HQ) as a ligand. The synthesised IIP was used as a new support for solid phase extraction (SPE) of nickel(II) from seawater before inductively coupled plasma optical emission spectrometry (ICP-OES) detection. Variables affecting the SPE process, such as pH, load and elution flow rates, and concentration and volume of the eluting solution, were fully evaluated. The optimised procedure consists of a sample loading (100 mL of seawater at a pH of 9.0 ± 0.1) through IIP-SPE cartridges containing 300 mg of the synthesised IIP at a flow rate of 3.0 mL min^{− 1}. Elution was performed by passing 2.5 mL of 2.0 M nitric acid at a flow rate of 1.5 mL min^{− 1}, which gave a pre-concentration factor of 40. The limit of detection (LOD) of the method was 0.26 µg L^{− 1}, while the relative standard deviation (RSD) for eleven replicated measurements was 3%. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water) and TM-23.3 (lake water) certified reference materials. In addition to the selectivity of the synthesised material for nickel(II) ions against other transition metal ions and major alkaline and alkaline-earth metals (Na⁺, K⁺, Mg²⁺ and Ca²⁺) in seawater, it can be stated that the salt matrix is efficiently removed by using the proposed IIP-SPE procedure.     

Reverse flow injection analysis of nanomolar soluble reactive phosphorus in seawater with a long path length liquid waveguide capillary cell and spectrophotometric detection

A novel reverse flow injection analysis method coupled with a liquid waveguide capillary cell (LWCC) and spectrophotometric detection for the determination of nanomolar soluble reactive phosphorus in seawater was established. Reagent was injected into the sample stream and detected in a 2-m path length LWCC with detection wavelength set at 710 nm. Experimental parameters, including the reagent concentration, the injection volume, the flow rate and the length of the mixing coil, were optimized based on univariate experimental design. The interference of silicate and arsenate were also investigated. Under optimized conditions, the linearity and the detection limit of the proposed method were found to be 0-165.0 nM and 0.5 nM, which was estimated to be three times the standard deviation of the measurement blanks (n = 9). The relative standard deviations for the determination of 24.7 and 82.5 nM samples were 1.54% and 1.86% (n = 9), respectively. Three seawater samples were analyzed with recoveries ranging from 87.8% to 101.8%. Using the Student's t-test at the 95% confidence level, the results of the proposed method and a segmented flow analyzer reference method for determination of the two samples showed no significant difference. The proposed method had the advantages of being less reagent consuming, more sensitive and with higher throughput (15 h⁻¹).     

Rapid and direct speciation of methyltins in seawater by an on-line coupled high performance liquid chromatography-hydride generation-ICP/MS system

A novel on-line coupled HPLC-hydride generation (HG)-ICP/MS system was developed for rapid, direct and sensitive speciation of methyltins in seawater without any pretreatment step. Methyltin compounds were separated by reversed phase HPLC, and then on-line reacted with potassium borohydride and acetic acid to generate volatile hydride products. The volatile derivatization products were separated in the spray chamber of ICP/MS and then introduced into ICP/MS by argon gas for detection. Monomethyltin (MMT), dimethyltin (DMT) and trimethyltin (TMT) were baseline separated in less than 15 min by reversed phase HPLC. The influence of KBH₄ concentration and type of acid on the system performance was investigated and optimized. Calibration curves, based on peak heights against concentration, were linear in the range of 0.5-50 ng (Sn) mL⁻¹ of methyltins with correlation coefficients of 0.9990, 0.9990 and 0.9996 for MMT, DMT and TMT, respectively. The relative standard deviations measured at 10 ng (Sn) mL⁻¹ for these three methyltins were in the range of 0.6-1.4% (n = 5), and the calculated detection limits (S/N = 3) for MMT, DMT and TMT were 0.266, 0.095 and 0.039 ng (Sn) mL⁻¹, respectively. This method was successfully applied to the speciation of methyltins in seawater with spiked recovery in the range of 95.4-106.9%. MMT and DMT were detected in all the seawater samples with concentrations in the range of 1.0-1.5 and 0.30-0.57 ng (Sn) mL⁻¹ for MMT and DMT, respectively.     

Fluorescence spectroscopy applied to the optimisation of a desalting step by electrodialysis for the characterisation of marine organic matter

The isolation and characterisation of marine dissolved organic matter (DOM) are still not readily achieved today. The study of this chemically complex material is particularly difficult, especially as it is hindered by the high salinity of seawater. It is therefore essential to develop a method in which a sufficient quantity of marine organic matter can be collected for structural analyses. Reverse osmosis (RO) is often used for the concentration of DOM from freshwaters, due to the fact that DOM is not modified during RO and that DOC recoveries are high (about 80%). Unfortunately, RO cannot be used directly to isolate marine DOM, since both salts and organic matter are concentrated during the process. Therefore, marine samples have to be desalted before their concentration by RO.     

基于分光光度法的海水原位硅酸盐微芯片分析传感器的研制

基于酸性条件下硅酸盐与钼酸铵反应生成硅钼黄后被还原成硅钼蓝的原理,借助微流控芯片平台,建立基于连续流动-分光光度法快速测定海水硅酸盐的分析传感器,传感器测定周期约为300 s,采用双光程方式拓展测量范围,线性测量范围可达0～400 μmol·L-1,双光程的检出限分别为45.1 nmol·L-1和1.6 μmol·L-1;当海水盐度大于15时,传感器测量准确度和稳定性基本不受盐度影响,且实际海水加标回收率在98.1%～104.0%之间。2015年11月在胶州湾开展了20个站点海试和同步比对试验,结果显示,该系统具有准确度高、简单、集成度高、水样消耗少、抗干扰能力强等优点,可用于海水原位硅酸盐的分析。