Simultaneous determination of inorganic mercury,methylmercury, and total mercury concentrations in cryogenic fresh-frozen and freeze-dried biological reference materials

Two speciated isotope dilution (SID) approaches consisting of a single-spike (SS) method and a double-spike (DS) method including a reaction/transformation model for the correction of inadvertent transformations affecting mercury species were compared in terms of accuracy, method performance, and robustness for the simultaneous determination of methylmercury (MeHg), inorganic mercury (iHg), and total mercury (HgT) concentrations in five biological Standard Reference Materials (SRMs). The SRMs consisted of oyster and mussel tissue materials displaying different mercury species concentration levels and different textural/matrix properties including freeze-dried (FD) materials (SRMs 1566b, 2976, and 2977) and cryogenically prepared and stored fresh-frozen (FF) materials (SRMs 1974a, 1974b). Each sample was spiked with (201)iHg (Oak Ridge National Laboratory, ORNL) and Me(202)Hg (Institute for Reference Materials and Measurements. IRMM-670) solutions and analyzed using alkaline microwave digestion, ethylation, and gas chromatography inductively coupled plasma mass spectrometry (GC/ICP-MS). The results obtained by the SS-SID method suggested that FF and FD materials are not always commutable for the simultaneous determination of iHg, MeHg, and HgT, due to potential transformation reactions resulting probably from the methodology and/or from the textural/matrix properties of the materials. These transformations can occasionally significantly affect mercury species concentration results obtained by SS-SID, depending on the species investigated and the materials considered. The results obtained by the DS-SID method indicated that the two classes of materials were commutable. The simultaneous and corrected concentrations of iHg, MeHg, and HgT obtained by this technique were not found to be statistically different form the certified and reference concentration together with their expanded uncertainty budgets for the five SRMs investigated, exemplifying the robustness, the accuracy, and the improved commutability of this method compared to SS-SID measurements.     

用IR和Raman光谱研究酞菁镍中杂质碘的变迁

本文报道用富里叶变换红外光谱及激光拉曼共振光谱研究了真空老炼导致的杂质碘在酞菁镍中存在形态的变迁。结果表明杂质碘的摩尔比小于1时,碘主要以Ⅰ_3~-离子的形态存在,当摩尔比大于1时,多余的碘与Ⅰ_3~-结合形成Ⅰ_5~-离子。在真空老炼过程中,Ⅰ_5~-又分解为Ⅰ_3~-和Ⅰ_2,并有碘逸出样品。     

Inorganic mercury and methylmercury determination in polluted waters by HPLC coupled to cold vapour atomic fluorescence spectroscopy

A systematic study of Hg²⁺ and CH₃Hg⁺ (MeHg⁺) speciation using hyphenated techniques, was performed for high-performance liquid chromatography coupled to on-line UV irradiation and cold-vapour atomic fluorescence spectroscopy (HPLC-UV-CV-AFS). First, a comparative study of the behaviour of three mobile phase compositions (using tetrabutylammonium bromide (TBAB), L-cysteine and ammonium pyrrolidinedithiocarbamate (APDC)) is presented. The separation and detection system was optimised by considering factors that modify fluorescence signal and the separation such as, the addition of different percentages of an organic modifier (methanol (MeOH) and acetonitrile (ACN)) to the mobile phase, the type of reducing agent used (SnCl₂ and NaBH₄) and the potential memory effects of the material of which the injection system is made (stainless steel, PEEK). The mobile phase selected for its sensitivity was a mixture 80?:?20 MeOH?:?0.0015?mol?l^–1 APDC and 0.01?mol?l^–1 NH₄CH₃COO (pH 5.5). The detection and quantification limits were close to 1.5 and 5?µg?l^?1 for both species (as Hg), respectively. Recoveries obtained using fortified water samples of distinct origin (soft mineral, tap, river, seawater, and wastewater), ranged from 90 to 115% for concentrations about 2 and 20 times over quantification limits. Good repeatability was obtained (about 5%) independently of the concentrations, with reproducibility values about 20% at low concentrations and 5–10% at higher concentrations. Our proposed method proved to be straightforward for use by environmental laboratories for routine Hg²⁺ and MeHg⁺ determinations in polluted water samples.     

Simultaneous determination of three surfactants and water in shampoo and liquid soap by ATR-FTIR

It is demonstrated for the first time that the principal constituents of a shampoo as well as of a liquid soap -three surfactants and water- can be determined directly, simultaneously and quickly in undiluted samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy in the middle infrared region, despite the broad absorption bands of the solvent. Two of the surfactants, sodium lauryl ether sulfate (SLES) and cocoamidopropyl betaine (CAPB), are common to both formulations; alkylpolyglucoside (APG) is the third surfactant of the liquid soap and cocodiethanolamide (CDEA), the corresponding ingredient of the shampoo. Absorbance data of the undiluted samples and of the calibration standards was collected in the middle infrared region of the spectrum (800-1600 and 1900-3000 cm⁻¹). Two methods of multivariate quantification were compared: classical least squares (CLS), where absorbance data measured at 200 wavenumbers was processed, and inverse least squares (ILS), where data at 10 selected wavenumbers was analyzed. A spectra normalization procedure, based on a dominating water band, was examined. Twenty-seven standard mixtures were used for each application, consisting of all combinations at three concentration levels of each surfactant, respectively the lower limit, the expected value and the upper limit accepted in quality control. By favoring wavenumbers where absorption bands of the minor components (APG in the liquid soap and CDEA in the shampoo) are more intense, good results were obtained for 18 simulated samples of shampoo and 18 samples of liquid soap, no matter if calculations were made by CLS or ILS. The relative errors for water (major component, 84-88%) and SLES (7-10%) were always below 2%; for CAPB (2-4%), APG (<2%) and CDEA (<2%), they occasionally reached 5% of the component, an uncertainty of less than 0.07% in terms of the sample weight.     

用色谱联用技术分析桂腈和溴代苏合香烯顺反异构体

应用气相色谱／红外光谱（ＧＣ／ＦＴＩＲ）、核磁共振（ＮＭＲ）等技术快速分离、鉴定了桂腈和溴代苏合香烯的顺反异构体,解决了气相色谱／质谱（ＧＣ／ＭＳ）分析时出现的保留行为不同的顺反异构体因为质谱图类似而导致谱库检索鉴别困难的问题。从而,可将保留指数与质谱数据相结合,互补各自在鉴定上的局限性。     

Monitoring the Phosphorylation of Phenol with Diethyl Chlorophosphate in Aqueous Medium in the Presence of Sodium Hydroxide by in Situ Fourier Transform Infrared Spectroscopy

In situ Fourier transform IR spectroscopy has been found to be an appropriate tool for monitoring the title reaction resulting in the formation of diethyl phenylphosphate.     

Evaluation of molecular structure in Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate by IR external reflection spectroscopy

 In situ polarized Fourier transform IR external reflection spectra of Langmuir monolayers of zinc stearate and zinc 12-hydroxystearate on a water surface were recorded for various surface areas, and their molecular structures were estimated. In the zinc stearate monolayer, the wavenumbers and the absorbances of the antisymmetric and symmetric methylene stretching bands did not change during monolayer compression, which means that orientational and conformational changes of the hydrocarbon chain did not occur. However, wavenumber changes of the antisymmetric and symmetric carboxylate stretching bands were observed during surface compression. The change in the binding nature of the zinc cation to the carboxylate group was speculated. Moreover, it was elucidated that the structure of the hydrocarbon chain in the zinc 12-hydroxystearate monolayer was different from that in the zinc stearate monolayer. Received: 21 March 2001 Accepted: 6 July 2001     

Photocatalytic Removal of Soot: Unravelling of the Reaction Mechanism by EPR and in situ FTIR Spectroscopy

Photocatalytic soot oxidation is studied on P25 TiO₂ as an important model reaction for self‐cleaning processes by means of electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Contacting of carbon black with P25 leads on the one hand to a reduction of the local dioxygen concentration in the powder. On the other hand, the weakly adsorbed radicals on the carbon particles are likely to act as alternative traps for the photogenerated conduction‐band electrons. We find furthermore that the presence of dioxygen and oxygen‐related radicals is vital for the photocatalytic soot degradation. The complete oxidation of soot to CO₂ is evidenced by in situ FTIR spectroscopy, no intermediate CO is detected during the photocatalytic process.     

Simultaneous determination of Folpet and Metalaxyl in pesticide formulations by flow injection Fourier transform infrared spectrometry

Fourier transform infrared (FTIR) spectrometric methodology has been developed for the simultaneous determination of Folpet and Metalaxyl in pesticide formulations. The method involves the extraction of both active principles by sonication of the sample with CHCl₃ and direct measurement of the absorbance using peak height values at 1798 cm⁻¹ corrected with a baseline defined at 1810 cm⁻¹ for Folpet, and peak area data established from 1677 to 1667 cm⁻¹ corrected using a baseline from 1692 to 1628 cm⁻¹ for Metalaxyl. Limits of detection (3 s) values of 17 and 16 μg g⁻¹ were found for Folpet and Metalaxyl, respectively, with results comparable with those found by liquid chromatography with UV detection. The new method involves a considerable decrease in solvent consumption. The automation of the procedure by incorporating on-line dissolution and filtration of the samples allows complete mechanisation of the method and improves the safety of operation.     

Simultaneous determination of mercury, lead and cadmium ions in water using near-infrared spectroscopy with preconcentration by thiol-functionalized magnesium phyllosilicate clay

Analysis of metal ions in environment is of great importance for evaluating the risk of heavy metal to public health and ecological safety. A method for simultaneous determination of metal ions in water samples was developed by using adsorption preconcentration and near-infrared diffuse reflectance spectroscopy (NIRDRS). A high capacity adsorbent of thiol-functionalized magnesium phyllosilicate, named Mg-MTMS, was prepared by co-condensation for preconcentration of Hg²⁺, Pb²⁺ and Cd²⁺ in aqueous solutions. After adsorbing the analytes onto the adsorbent, NIRDRS was measured and PLS models were established for fast and simultaneous quantitative prediction. Because the interaction of the ions with the functional group of the adsorbent can be reflected in the spectra, the models built with the samples prepared by river water were proven to be efficient enough for precise prediction. The determination coefficients (R²) of the validation samples for the three ions were found as high as 0.9197, 0.9599 and 0.9861, respectively. Furthermore, because the high adsorption efficiency of Mg-MTMS, the detected concentrations are as low as milligrams per liter for the three ions, and the concentration can be further reduced. Therefore, the feasibility of quantitative analysis metal ions in river water by NIRDRS is proven and this may provide a new way for fast simultaneous determination of trace metals in environmental waters.     

Determination of mercury and methylmercury in seafood by ion chromatography using photo-induced chemical vapor generation atomic fluorescence spectrometric detection

A novel method based on photo-induced chemical vapor generation (CVG) as interface to on-line coupled Hg-cysteine ion chromatograpy (IC) with atomic fluorescence spectrometry (AFS) was developed for rapid determination of methylmercury (MHg) in seafood. Separation of inorganic mercury (Hg²⁺) and methylmercury(CH₃Hg⁺) was accomplished on a Hamilton PRP X-200 polymer-based exchange column with a mobile of 3% acetonitrile, 1% (w/w) L-cysteine and 20 mmol L^{− 1} pyridine and 160 mmol L^{− 1} formic acid, at pH 2.4 within 7 min. Once separated, both species are reduced by formic acid in mobile phase under UV radiation to convert Hg⁰ on-line, which is subsequently swept (by argon carrier gas) into an atomic fluorescence spectrometry (AFS) for measurement. Under the optimized experiment conditions, the detection limits (as Hg), based on three times the standard deviation of a standard solution, were found to be 0.1 ng mL^{− 1} for mercury and 0.08 ng mL^{− 1} for methylmercury, with an injection volume of 100 μL. The developed method was validated by determination of certified reference material DORM-2 and was further applied in determination of seafood samples.     

Two-dimensional correlation spectroscopy and multivariate curve resolution for the study of lipid oxidation in edible oils monitored by FTIR and FT-Raman spectroscopy

Accelerate oxidative degradation of six vegetable oils was monitored using FTIR and FT-Raman spectroscopy. Two-dimensional correlation spectroscopy and multivariate curve resolution alternating least squares (MCR-ALS) were applied to the analysis of the data. The use of hetero-spectral two-dimensional correlation of FTIR and FT-Raman data allowed the use of well established band assignments to interpret less clearly assigned spectral features. With a moving window approach it was possible to obtain simplified two-dimensional correlation maps and to detect compounds evolving with different kinetic. Simultaneous analysis of the oxidation experiments of the six different oils monitored by both spectroscopic techniques was performed using MCR-ALS. Although a complete resolution of the data was not possible, the spectral changes occurring during the oxidative degradation of the oils were described with a five-component model. The two fundamentally different chemometric approaches lead to coincident results.     

应用光谱和分子模拟法研究一种聚酰亚胺聚合物与人免疫球蛋白的相互作用

本文利用荧光猝灭法、红外光谱法及计算机模拟技术研究了一种聚酰亚胺聚合物(2,6-Bis(4-amino-2-trifluoromethyl phenoxy-4’- benzoyl)-pyridine,简称BAFP )与人免疫球蛋白（HIgG）的相互作用。同步荧光的结果定性地说明了BAFP影响水溶液中HIgG二级结构的情况。而判定BAFP影响HIgG二级结构的定量依据来自红外光谱,实验数据表明α螺旋结构的含量相比未加入药物时增加了约2.6～10.2%,,β折叠增大了约13.6～27.7%,,而β转角则减小了约23.8～30.3%。分子模拟的结果显示BAFP与HIgG的键合作用很强,并且有四个氢键在BAFP与HIgG分子的色氨酸Trp 170, 缬氨酸Val 105, 甲硫氨酸Met 139 及天冬酰胺Asn 52之间形成;同时也显示出维持药物与蛋白质的相互作用力主要是疏水作用,这与实验所得到的热力学参数判定作用力的结果相一致（依据范德霍夫公式计算得 与 的值分别为-6.70KJ.mol-1 和 71.93 J.mol-1.K-1）。     

Rapid and simultaneous determination of salvianolic acid A and salvianolic acid B by complex chromatography and study on related mechanism of coordination

Salvianolic acid A (Sal A) and salvianolic acid B (Sal B) are water-soluble phenolic acids in Danshen extract and they have high medicinal value. A rapid and novel complex high-performance liquid chromatography (HPLC) method has been developed and validated for the simultaneous determination of Sal A and Sal B within 10 min. The determination of Sal A and Sal B was carried out on a Waters Symmetry Shield RP18 column (5 μm, 3.9 mm × 150 mm), using methanol-deionized water (55:45, v/v, with 5 mmol L⁻¹ CaCl₂ and 1% acetic acid) as the mobile phase at the flow rate of 0.8 mL min⁻¹ within 10 min. The wavelength was set at 280 nm. It changed the peak sequence of Sal A and Sal B and improved their effect of determination by adding CaCl₂ in the mobile phase because Sal A and Sal B coordinated with Ca²⁺. The mechanism of coordination between Sal A, Sal B and Ca²⁺ has been studied by way of Fourier transform infrared spectroscopy (FTIR), electrospray ionization mass spectrometry (ESI-MS) and computer model. The possible structures of the complex and complex ratio are provided in this article. The experiments have facilitated the study of Sal A-Ca²⁺ complex, Sal B-Ca²⁺ complex and provide a theoretical basis for industrialized extraction of Sal A and Sal B in the future.     

水相衍生-气相色谱-质谱法同时测定水产品中甲基汞和无机砷

建立了同时测定水产品中甲基汞和无机砷的水相衍生-气相色谱-质谱联用分析方法。采用6 mol/L盐酸超声辅助提取水产品中的甲基汞与无机砷,于-10℃冷冻离心后,提取液中的无机砷（As³⁺与As⁵⁺）与2,3-二巯基丙醇（BAL）溶液于35℃水浴中衍生反应30 min,用甲苯萃取衍生物与甲基汞,萃取前加入无水乙醇避免非脂成分进入有机相中,向甲苯萃取液中添加甲基汞的衍生剂四苯硼钠溶液（pH 3.6）。采用选择离子监测（SIM）模式,外标法测定水产品中的甲基汞与无机砷。结果表明,水产品中甲基汞与无机砷在5～2000 μg/L范围内线性关系良好,相关系数（r）均大于0.999;检出限为0.7～3 μg/kg （S/N=3）。在10、100、1000 μg/kg加标水平下,方法加标回收率为80.0%～110.0%,相对标准偏差（n=6）为2.5%～9.4%。该方法操作简便、准确、灵敏度高,已成功应用于水产品中无机砷与甲基汞的食品污染物风险监测中。     

以动力学光度法测定痕量钴的新方法及阳离子表面活性剂增敏效应的机理研究

研究了以钴对鲁米诺桑色素 (LAM)氧化的催化反应作为指示反应的测定痕量钴的新方法及表面活性剂对该催化反应的增敏作用。LAM在碱性条件下被H2 O2 氧化褪色 ,钴对该氧化反应有强烈的催化作用。阳离子表面活性剂 ,如CTMAB对此催化反应有较强的增敏作用 ,可将灵敏度提高 4倍。据此建立了测定痕量钴的催化动力学新方法 ,并测定了该催化反应的动力学参数 ,以探讨表面活性剂增敏的机理。方法的检出限为 7.5ng/mL ,相对标准偏差为 4× 1 0 - 3%。用该法测定了维生素B1 2 中钴的质量分数 ,与原子吸收测定结果十分吻合。     

In situ Fourier transform IR spectroscopy and variable-temperature wide-angle X-ray diffraction studies on the crystalline transformation of melt-crystallized nylon 12 12

 The crystalline transformation in nylon 12 12 was monitored by variable-temperature wide-angle X-ray diffraction during heating, isothermal and cooling processes. It could be found that the α phase of the sample transforms into a γ phase at about 130 °C if the sample is heated from room temperature to a high temperature, which is the so-called Brill transition temperature. In addition, nylon 12 12 was found to crystallize into the γ phase when isothermally crystallized at high temperature from the melt. Upon further cooling from the crystallization temperature to room temperature, the reverse transition from the γ phase to the α phase can be detected. Furthermore, in situ Fourier transform IR spectroscopy was also used to study the Brill transition of nylon 12 12 samples on both heating and cooling. It is interesting that the hydrogen-bond strength in nylons decreases dramatically and that some Brill bands of nylon 12 12 disappear abruptly during the Brill transition on heating. Received: 3 April 2001 Accepted: 28 July 2001     

Simultaneous determination of methylmercury and ethylmercury in rice by capillary gas chromatography coupled on-line with atomic fluorescence spectrometry

A comprehensive method for simultaneous determination of methylmercury (MeHg) and ethylmercury (EtHg) in rice by capillary gas chromatography (GC) coupled on-line with atomic fluorescence spectrometry was developed. The experimental conditions, including the pyrolyzer temperature and flow rates of the make-up gas and sheath gas, were optimized in detail. The absolute detection limits (3sigma) were 0.005 ng as Hg for both MeHg and EtHg. The relative standard deviation values (n=5) for 10 ng Hg/mL of MeHg and EtHg were 2.5 and 1.3%, respectively. The method was evaluated by analyzing 2 certified reference materials (DORM-2 and GBW08508), and the determined values of MeHg and total mercury concentrations were in good agreement with the certified values. In addition, the recoveries of MeHg and EtHg spiked into a rice sample collected from Jiangsu province in China were 86 and 77%, respectively. The proposed method was applied to analysis of MeHg and EtHg in 25 rice samples cultivated in 15 provinces of China. In all samples, MeHg was detectable and no EtHg was found. The MeHg contents in rice samples ranged from 1.9 to 10.5 ng/g, accounting for 7-44% of the total mercury measured.     

FTIR spectroscopic characterization of structural changes in polyamide‐6 fibers during annealing and drawing

First, we report the development of Fourier transform infrared (FTIR) spectroscopic methods to determine the α/γ‐crystalline phase ratio of polyamide‐6 fibers and, in combination with density measurements, the total crystallinity. Using density determinations of the crystallinity of pure α and pure γ samples, we found the absorption coefficient ratio for the 930 (α) and 973 cm⁻¹ (γ) bands to be 4.4, from which we could obtain the α/γ ratio for any polyamide‐6 sample. The application of this FTIR method to the quantitative analysis of phase changes during thermal treatment and the drawing of polyamide‐6 was then made. We confirmed that crystallization during thermal treatments involved increases in both phases and did not involve crystal‐to‐crystal transformation, whereas drawing involved both crystallization of the amorphous phase in the α form and γ→α transformation. Finally, we revisited the band assignments for the amorphous phase of polyamide‐6 and found that the band at 1170 cm⁻¹ was not an amorphous band but, because its absorbance was independent of crystallinity, could be used as an internal reference band. The band at 1124 cm⁻¹ was reliably attributed to the amorphous phase. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 536–547, 2001     

Comparison of three strategies to evaluate uncertainty from in-house validation data. A case study: mercury determination in sediments

In the present paper, three approaches are compared for the evaluation of the combined uncertainty in the determination of mercury in aquatic sediments by an aqua regia extraction procedure. For this, the data obtained in validation studies from five certified reference materials (CRMs), covering a range of concentrations from 0.8 to 130 mg kg⁻¹ of mercury and analysed by three atomic spectroscopic techniques (cold vapour generation atomic fluorescence spectrometry, CV-AFS, cold vapour generation atomic absorption spectroscopy, and inductively coupled plasma mass spectroscopy), were considered. The combined uncertainty was firstly assessed by considering separately the data obtained for each CRM analysed (approach A). Moreover, this assessment was also performed with two other calculation approaches (B and C) based on the pooled data obtained from the validation step. The comparison of the results obtained for the different techniques showed a clear bias effect when using CV-AFS with nitric acid as a diluent. In relation to the strategies tested for the combined uncertainty assessment, approach C proved to be the easiest and friendliest method for uncertainty assessment.