Modifications of the curcumin method enabling precise and accurate measurement of seawater boron concentration

To achieve greater precision and accuracy in the measurement of seawater boron concentrations, we propose a series of modifications to an established (curcumin) method based on the reaction of boric acid with curcumin. The modifications were derived from a series of experiments evaluating the stability of the curcumin–acetic acid reagent, the dependence of the reaction on temperature and duration, the effect of evaporation during the dehydration process, the interference of water, and the effect of sea salts. Application of the modified method to analysis of seawater samples collected from the Pacific Ocean indicated that it yielded considerably better precision and accuracy for boron concentration measurements than both the conventional curcumin method and other analytical techniques.     

热水解-催化分光光度法测定海相碳酸盐岩中的溴

目前衡量古海洋生产力的指标都存在一定的局限性,本文提出将溴元素作为研究古海洋生产力的新指标,建立了海相碳酸盐岩的分解方法以及其中溴元素的测定方法,即热水解-分光光度法。采用热水解方法对海相碳酸盐岩样品进行分解,吸收液充分吸收其释放出的溴,分光光度法检测样品中溴元素的含量。试验确定了热水解的最佳条件和分光光度检测的最佳波长,实际样品加标回收率为97.5%～101.6%,相对标准偏差为1.2%～3.6%(n=10)。本方法的样品分解时间较短,能很好地实现溴与基体组分分离,且所需仪器均为比较常见的仪器,操作简单,成本低廉,适合于海相碳酸盐岩样品的批量分解和元素测定。     

微乳液介质—DBH-PF光度法测定食品中微量锗的研究

以阳离子型 O/ W CTMAB/ n- C5H11OH/ n- C7H16/ H2 O微乳液为介质 ,进行 Ge( IV) - DBH- PF的分光光度法测定 ,ε510 nm=2 .18× 10 5L· mol-1.cm-1,建立了高灵敏测定食品中微量锗的新方法 ,锗量在每 2 5m L 0～ 7.0μg范围内符合比尔定律 ,方法选择性好 ,试样无需萃取分离 ,可快速测定     

分光光度法同时测定岩盐中微量Fe2+和Fe3+的研究

研究了在酸性条件下,邻-菲啉分光光度法测定岩盐中微量Fe2+、Fe3+。实验结果表明,铁的质量浓度在0~5μg/mL范围内测得吸光度值与质量浓度之间的关系遵守朗伯—比耳定律,摩尔吸光系数ε=1.1×104L.moL-1.cm-1。Fe2+、Fe3+平均回收率分别为102.47%、100.93%,相对标准偏差分别为2.82%、2.68%(RSD,N=6)。该方法操作简单、灵敏度高、稳定性好、选择性好,用于岩盐中微量Fe2+、Fe3+的测定,结果令人满意。     

吸光光度法测定卤水、油田水中微量碘的研究

研究了利用亚硝酸钠为氧化剂,在酸性条件下将碘离子氧化为游离的碘,游离的碘遇淀粉形成蓝色化合物,采用分光光度法测定微量碘。试验结果表明:碘含量在4~18μg/mL范围符合朗伯比耳定律,标准偏差S=0.068%,平均回收率可达90%。利用该法对卤水、油田水中微量碘的测定结果满意。该方法简便、快速、准确。     

邻菲啰啉光度法测定高岭土中可溶铁和非可溶铁

高岭土中铁的赋存状态和含量影响其白度和增白效果,因此快速准确地测定高岭土中不同种类的铁含量具有实际应用意义。高岭土中自由铁和结构铁定量分析困难,为此本文将高岭土中的铁分为可溶铁和非可溶铁两类。高岭土经盐酸酸溶处理后溶液中的铁含量为可溶铁含量,经氢氧化钠碱熔处理后溶液中的铁含量为总铁含量,非可溶铁含量由总铁含量减去可溶铁含量计算得出。采用邻菲啰啉光度法测定溶液中的铁含量,该方法的相对标准偏差小于5%,加样回收率范围在95%～105%,最低检测含量为1.06μg/g。高岭土中的其他元素对铁的测定均没有干扰。所测得的可溶铁为大部分自由铁和少数结构铁。通过对高岭土中的可溶铁进行定量分析,可得知漂白工艺中可除去的最大铁含量。     

Ordinary chondrite-like colors in small Koronis family members

A survey of small (<5-10 km diameter) members of the Koronis family shows some objects with visible-wavelength broadband colors consistent with membership in the Q-class (Tholen, D.J. [1984]. Asteroid taxonomy from cluster analysis of photometry. Ph.D. Dissertation, University of Arizona, Tucson, AZ; Bus, S.J., Binzel, R.P. [2002]. Icarus 158, 146-177). This agrees with an ordinary chondritic composition for this family and suggests the timescale for changing Q-class to S-class spectra in the main belt is roughly comparable to the regolith refresh time in the 2-5 km size range.     

Optical measurements of the Moon as a tool to study its surface

This survey is a general overview of modern optical studies of the Moon and their diagnostic meaning. It includes three united parts: phase photometry, spectrophotometry, and polarimetry. The first one is devoted to the progress in the photometry of the Moon, which includes absolute albedo determination to refine the albedo scale (e.g., to connect lunar observations and the data of lunar sample measurements) and mapping the parameters of a lunar photometric function (e.g., the phase-angle ratios method) with the aim of making qualitative estimates of regolith structure variations. This part also includes observations of the lunar opposition effect as well as photogrammetry and photoclinometry techniques. In particular, available data show that because of the low albedo of the lunar surface, the coherent backscattering enhancement hardly influences the lunar opposition spike, with the exception of the brightest lunar areas measured in the NIR. The second part is devoted to chemical/mineral mapping of the Moon's surface using spectrophotometric measurements. This section also includes analyses related to the detection of water ice or hydroxyl, prognoses of maturity, and helium-3 abundance mapping. In particular, we examine the relationship between superficial OH/H₂O compounds spectrally detected recently and bulk “water ice” found earlier by the Lunar Prospector GRS and LRO LEND, assuming that the compounds are delivered to cold traps (permanently shadowed regions) with electrostatically levitated dust saturated by solar wind hydrogen. Significant problems arise with the determination of TiO₂ content, as the correlation between this parameter and the color ratio C(750/415 nm) is very non-linear and not universal for different composition types of the lunar surface; a promising way to resolve this problem is to use color ratios in the UV spectral range. The third part is devoted to mapping of polarization parameters of the lunar surface, which enable estimates of the average size of regolith particles and their optical inhomogeneity. This includes considerations of the Umov effect and results of spectropolarimetry, negative polarization imagery, and measurements of other polarimetric parameters, including the third Stokes parameter. Although these three research divisions have not been developed equally and the numbers of proper references are very different, we try to keep a balance between them, depicting a uniform picture. It should be emphasized that many results presented in this review can be applied to other atmosphereless celestial bodies as well.     

Testing the Hapke photometric model: Improved inversion and the porosity correction

In conjunction with a companion paper (Shepard, M.K., Helfenstein, P. [2011]. Icarus, submitted for publication), we derive, test, and apply a detailed approach for visualizing the phase angle dependence of light scattering in particulate soils from both whole-disk and disk-resolved observations. To reduce the number of model parameters and provide stronger constraints on model fits, we combine Hapke’s (Hapke, B. [2008]. Icarus 195, 918-926) recent correction for effects of porosity with his (Hapke, B. [1986]. Icarus 67, 264-280) model of the shadow hiding opposition effect. We further develop our method as a tool for least-squares fitting of Hapke’s model to photometric data. Finally, we present an improved method for estimating uncertainties in retrieved values of Hapke model parameters. We perform a preliminary test of the model on spectrogoniometric measurements from three selected laboratory samples from Shepard and Helfenstein (Shepard, M.K., Helfenstein, P. [2007]. J. Geophys. Res. 112 (E03001), 17). Our preliminary suite of test samples is too small and selective to permit the drawing of general conclusions. However, our results suggest that Hapke’s porosity correction improves the fidelity of fits to samples composed of low- and moderate-albedo particles and may allow for more reliable retrieval of porosity estimates in these materials. However, we find preliminary evidence that in high-albedo surfaces, the effects of porosity may be difficult to detect.     

Reduced sulfur and iron species in anoxic water column of meromictic crater Lake Pavin (Massif Central, France)

The vertical distribution of reduced sulfur species (RSS including H₂S/HS⁻, S⁰, electroactive FeS) and dissolved Fe(II) was studied in the anoxic water column of meromictic Lake Pavin. Sulfide concentrations were determined by two different analytical techniques, i.e. spectophotometry (methylene blue technique) and voltammetry (HMDE electrode). Total sulfide concentrations determined with methylene blue method (∑H₂S_MBRS) were in the range from 0.6 µM to 16.7 µM and were substantially higher than total reduced sulfur species (RSS_V) concentrations determined by voltammetry, which ranged from 0.1 to 5.6 μM. The observed difference in the sulfide concentrations between the two methods can be assigned to the presence of FeS colloidal species.Dissolved Fe was high (> 1000 µM), whereas dissolved Mn was only 25 µM, in the anoxic water column. This indicates that Fe is the dominant metal involved in sulfur redox cycling and precipitation. Consequently, in the anoxic deep layer of Lake Pavin, “free” sulfide, H₂S/HS⁻, was low; and about 80% of total sulfide detected was in the electroactive FeS colloidal form. IAP calculations showed that the Lake Pavin water column is saturated with respect to FeS_am phase. The upper part of monimolimnion layer is characterized by higher concentrations of S(0) (up to 3.4 µM) in comparison to the bottom of the lake. This behavior is probably influenced by sulfide oxidation with Fe(III) oxyhydroxide species.