A sensitive spectrophotometric method for the determination of arsenic in environmental samples

We developed a cost-effective and sensitive spectrophotometric method for the determination of arsenic at trace level using a new reagent, leuco malachite green. Here we show that, arsenic reacts with potassium iodate in acidic conditions to liberate iodine, and the liberated iodine selectively oxidizes leuco malachite green to malachite green dye. We studied the Beer’s law at 617 nm, which showed linearity over the concentration range 0.09–0.9 μg ml⁻¹ of arsenic. We show that the molar absorptivity, Sandell’s sensitivity and detection limit of the method are 6.1 × 10⁴ l mol⁻¹ cm⁻¹, 0.0012 μg cm⁻² and 0.025 μg ml⁻¹, respectively. We applied the developed method for the determination of arsenic in environmental samples.     

A rapid kinetic technique for quantifying polycarbonate species in coalspoils

A rapid, automated procedure has been used for differentiation and quantitative determination of siderite, calcite and dolomite, based on the different rates of dissolution of the three carbonate species when reacted with excess 5 mol/litre HCl. The method employs manometric measurements of acid-liberated CO₂ with a membrane differential-pressure transducer coupled to a stripchart recorder. Tested on the three carbonate species, singly and in pairs, the technique is discriminatory, sensitive and relatively rapid.Contributions from the Department of Agronomy, University of Kentucky Agricultural Experiment Station in Lexington, and Institute for Mining and Minerals Research of the University of Kentucky. The investigation reported in this paper (No. 83-3-206) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

A nanosilver-based spectrophotometric method for sensitive determination of methyl violet in river water

A method is reported for the determination of methyl violet in the range of 10–120 nmol L^?1. The method is based on the catalytic effect of silver nanoparticles (AgNPs) on the oxidation reaction of methyl violet by potassium bromate in acid medium. The reaction is followed spectrophotometrically by measuring the change in absorbance () at 620 nm using a fixed time method. The reaction variables were optimized in order to achieve highest sensitivity. The 3б criterion detection limit was 5 nmol L^?1, and the relative standard deviation for ten replicate determinations at a concentration of methyl violet of 15 nmol L^?1 was 0.97% (n = 10). The method was successfully applied to the determination of methyl violet in river water samples.     

A radiotracer technique for the determination of male mating success in natural populations

Summary Males of a natural population of Antechinus stuartii (Marsupialia) were injected at the beginning of their short, synchronous breeding period with one of twelve gamma-emitting nuclides which are individually recognizable by their unique spectial properties. This label passed to the females during ejaculation and was identified when the females were captured and counted in a whole-body counter. This technique established mating success of males and provided an estimate of reproductive success.     

电化学方法检测海水中铁的研究进展

海水中的痕量铁作为限制海洋浮游植物初级生产力的关键因素之一,在海洋生物地球化学循环中起着重要的作用.及时分析海水中铁的不同存在形态及其含量,对于进一步认识铁循环机制和有效预防海洋环境污染具有重要意义.电化学方法较其他分析方法在检测海水中痕量铁的含量,尤其是形态分析方面具有独特的优势.本文总结了运用电化学方法检测海水及其他自然水体中铁的分析方法,以期为发展准确、快速测定海水中痕量铁的形态及其含量的分析技术提供基础性参考.     

A new application of the diacetyl monoxime method to the automated determination of dissolved urea in seawater

A new application of the diacetyl monoxime method for the determination of dissolved urea in seawater is presented, based on the Alpkem autoanalyzer (OI, Analytical). This system has several advantages over automated methods previously described in the literature. The urea cartridge can be easily built using nut/ferrule connections, and the external thermostatic bath is not required. The system is set up to operate at low urea concentrations (0–3 µM urea), but it is linear up to 100 µM urea. The sample volume needed for analysis is 0.4 ml, and the rate of analysis is 25 samples h^–1. The precision of analysis (CV) of seawater samples is 2.1% at 0.50 µM urea, and the detection limit is 0.02 µM urea. The interference on the colorimetric measurement due to formation of Brij-35 aggregate in strongly acidic media was eliminated by substituting this wetting agent with hexadecyl–trimethyl–ammonium bromide; thus, this method is suitable for other autoanalyzer technologies that use small-diameter transmission tubes and small-sized spectrophotometric flowcells.Communicated by R. Cattaneo-Vietti, Genova     

纳米金比色法快速检测水中重金属的研究进展

重金属超标可造成环境污染并对人体健康构成潜在威胁.水环境中重金属污染已经十分普遍并呈现出日益加剧的趋势.近年来,一种基于纳米金比色原理的新型水中重金属快速检测技术迅速发展,并因其具有检测特异性强、灵敏度高、无需配套仪器、操作简便等一系列优点,在水体重金属污染事件的现场筛查及应急处置等方面展现出广阔的应用前景.本文对国内外水环境中重金属污染的现状,重金属检测技术的发展以及基于纳米金比色原理的水中重金属快速检测技术的研究进展等方面进行了综述,指出了该技术在实际应用中面临的主要问题,并提出了未来的发展方向.     

Rapid and sensitive headspace gas chromatographic method for cyanide determination in whole blood

We reported a simple and rapid headspace (HS) gas chromatographic (GC) assay for the determination of cyanide in human whole blood obtained from both cadaveric and intoxicated subjects. The poison was extracted from whole blood samples by HS technique after 10 min incubation at 80°C with a HCl (1N) acidic solution supplemented with 30 g L^?1 of sodium chloride and 10 mg L^?1 of isopropanol as internal standard. A SGE WAX capillary column (30 m × 0.32 mm ID × 0.5 µm df) was used. The Flame Ionization Detector (FID) was set at 250°C. The detection and the quantification limits were 0.02 and 0.2 mg L^?1, respectively. In the within-day study, the coefficients of variation for three different whole blood cyanide concentrations varied between 3.2 and 6.5%, whereas those in the day-to-day study varied between 4.8 and 6.3%. The assay was performed in less than 20 min per sample, which appears to be suitable for emergency toxicological tasks involved in diagnosis of cyanide poisoning.     

A recirculating seawater aquarium system for inland laboratories

We have designed and installed a 7,500 l recirculating aquarium system for the purpose of maintaining marine gastropods in an inland laboratory. It is completely nonmetallic and can be adapted for any number of isolated living compartments. Vonvenient and efficient filtration is achieved by the use of disposable cartridge filters. The water temperature is regulated by a direct expansion cooling coil and a hot water heating coil without the intervention of secondary heat transfer fluids. Most of the water is stored in an underground reservoir which contributes to thermal stability, and the water temperature varies <±0.1°C per week. The pH and specific gravity remain at 8.0±0.1 and 1.023+0.002-0.001, respectively, for as long as 4 months. We have no evidence that any animal (Aplysia, Hermissenda, Tritonia) has died due to poor water quality. The system is constructed from readily available components, is moderate in cost, and has performed reliably for over 2 years.     

An empirical test of biases in the rapid visual technique for species-time censuses of reef fish assemblages

For an assemblage of fishes inhabiting a warm temperate, rock reef near San Diego, California (USA), a series of censuses were made based on frequency of occurrence and standard numerical counts. These data were then compared with a parallel study based on the rapid visual technique (RVT) of Jones and Thompson (1978). Because the RVT ranks abundances according to frequency of encounter and disregards variations in the spatial distributions of different species, the method overemphasizes the importance of widespread albeit rare fishes but under-emphasizes patchy although abundant species. The discussion considers the relative merits of the RVT method for characterizing assemblages of fishes on temperate rock reefs and on tropical coral reefs.     

Quantification of trypsin with a radioimmunoassay in herring larvae (Clupea harengus) compared with a highly sensitive fluorescence technique to determine tryptic enzyme activity

Enzymatic activity and quantity of the protease trypsin were measured in individual herring larvae (Clupea harengus L.). The enzymatic activity assay was done using a fluorescence technique, and a radioimmunoassay was used for quantification of trypsin. The results are compared and the differences between the techniques discussed. Both methods gave similar results, as high or low values in trypsin quantity were reflected in high or low values of tryptic activity. Quantity and activity were linearly and positively correlated, but small differences between methods were found at the lowest detection limits. Both techniques reflect high variability between individual larvae.     

巯基化纳米Fe_3O_4在海水痕量汞检测中的应用

利用共沉淀法和巯基化表面修饰制备Fe3O4纳米吸附材料,并将其应用于海水中痕量汞检测的富集和分离前处理过程.所制备的巯基化Fe3O4纳米颗粒的粒径小于100 nm,饱和磁化强度达63.64 emu·g-1,巯基含量为3.11 mg·g-1.当巯基化Fe3O4的用量为0.5 mg·m L-1、吸附溶液p H值为7.5—8.0、吸附时间为20min时,吸附剂对汞的富集率可达95%以上,并且在外磁场作用下可快速分离.在优化的吸附条件下并借助原子荧光光谱法测定了实际海水样品中汞离子的含量,加标回收率在89.8%—107.3%之间,11次空白样品测量的检出限(3σ)为5.3 ng·L-1.该方法利用巯基化Fe3O4纳米材料具有高效富集的特点,可应用于海水中痕量汞的快速富集和分离,以实现对海水中痕量汞的准确测量.     

A rapid determination of histamine and 3-methylhistamine in human plasma by high performance liquid chromatography

Histamine plays an important pathophysiological role in allergy, inflammation, gastric acid secretion, microcirculation and neurotransmission. 3-Methylhistamine is a prominent metabolite of histamine. Different methods for determination of histamine in biological fluids have been developed. In the present study, a simple, simultaneous determination of histamine and 3-methylhistamine by HPLC (precolumn derivatization with fluorescamine) was developed in human plasma using fluorescence detection with 1-methylhistamine as the internal standard. Linear regression analysis of the ratios of the concentrations of histamine and 3-methylhistamine (X) against peak height ratios (Y) yielded the following: y = 0.0073x ? 0.0096 (R ² = 0.990) and y = 0.0077x ? 0.0111 (R ² = 0.989). In conclusion, it was possible to detect histamine and 3-methylhistamine below 5 ng mL^?1 in 1 mL plasma.     

近岸海水中全氟化合物的液相色谱-离子阱质谱法测定

建立了利用高效液相色谱-电喷雾离子阱质谱(HPLC-ESI-IT-MS/MS)测定近岸海水中多种常见全氟化合物(PFCs)的分析方法.采用固相萃取法(SPE)对海水中的PFCs净化富集,用HPLC-ESI-IT-MS/MS多反应离子监测(MRM)模式对各组分(全氟己烷磺酸、全氟辛烷磺酸、全氟辛烷磺酰胺、全氟己酸、全氟庚酸、全氟辛酸、全氟壬酸、全氟癸酸、全氟十一酸、全氟十二酸)进行测定.在最佳实验条件下,采用基质匹配标准曲线法定量,以消除海水基质的影响,8种目标化合物的检出限介于0.50—1.00 ng·L-1,9种PFCs的回收率在71.0%—130.2%之间,能满足近岸海水中多种PFCs检测的要求.青岛沿岸表层海水样品测定结果显示,全部采样站点的海水样品中均检测到≥4种PFCs,说明青岛沿岸海水中已有一定程度的PFCs污染.     

A sensitive method for determining nitrogen-15 isotope in urea

A method is presented in which the ¹⁵N at.% of urea is determined with high precision on liquid samples containing as little as 10 nmol of urea. The method involves removal of interference from NH₄ ⁺ initially present in the sample by cation exchange. Urea in the sample is subsequently hydrolyzed to NH₄ ⁺ by the enzyme urease. Liberated NH₄ ⁺ is separated from the alkaline sample by diffusion as NH₃ through a helium gas phase where it is finally oxidized to N₂ by reaction with hypobromite iodine. The isotopically labeled N₂ thus formed is mixed with the N₂ initially present in the sample, and the ¹⁵N at.% of urea is calculated from the relative amounts of ¹⁴N¹⁵N and ¹⁵N¹⁵N by means of the isotope pairing principle. The presented method for ¹⁵N-urea analysis proved to be precise (SE < 0.4 at.%, n = 5), when applied on both marine and freshwater samples with an ¹⁵N enrichment >1 at.%, and interference was found only from volatile methyl amines. Received: 19 September 1996 / Accepted: 25 October 1996     

Comparison of methods for the analysis of dissolved urea in seawater

A comparison between the diacetyl monoxime and urease methods for measuring dissolved concentrations of urea in seawater was conducted in artificial seawater, phytoplankton-culture filtrate and both natural and ureaspiked field samples from coastal and oceanic enviroments during 1984. The urease technique underestimated urea concentrations in unbuffered photoplankton-culture filtrate as a result of the inhibition of the urease enzyme, causing the incomplete hydrolysis of urea in these samples. Factors responsible for inhibiting urease included pH, seawater ions, and possibly extracellular metabolites produced in unialgal cultures. Seawater type and time of sample collection were important variables affecting urea measurement by the urease method, and recovery of internal standards ranged from 40 to 100%. Increasing the heating time of the urease assay, or the concentration of urease added to the seawater samples increased the amount of urea determined by the urease method. However, measured values were still less than the concentration of the urea internal standards. The diacetyl monoxime method was suitable for urea determinations in all the seawater samples we examined; it was easily automated, and the results were accurate and reproducible. This modified technique is recommended for measuring disolved concentrations of urea in seawater.     

Effects of ambient ammonia levels on blood ammonia, ammonia excretion and heart and scaphognathite rates of Nephrops norvegicus

During commercial handling of Nephropsnorvegicus (L.) there are a number of situations when the prawns may be exposed to very high ambient ammonia levels. These experiments evaluated the effects of increased levels of ambient total ammonia (TA = NH₃ + NH₄ ⁺) on␣blood ammonia, ammonia efflux rates and on the cardio-ventilatory performance of N. norvegicus. When prawns were taken from <1 to 2000 μmol TA l⁻¹ medium, blood TA concentrations increased rapidly for the first 2 h but tended to drop thereafter. Original blood TA levels were restored 6 h after the prawns were transferred back from seawater containing 2000 to <1 μmol TA l⁻¹. Sudden exposure to 500, 1000, 2000 or 4000 μmol TA l⁻¹ medium induced blood TA concentrations to increase respectively to 50, 30, 33 and 36% of external concentrations (normally, internal TA values are much higher than external levels). Immediately after transfer back to seawater with low ammonia concentration ( <1 μmol TA l⁻¹), excretion rates were higher than those of control prawns, and the absolute amounts of TA excreted were considerably higher than those calculated to have accumulated in the haemolymph. Heart rate (HR) and scaphognathite rate (SR) were not altered when prawns were subjected to sudden alterations in ambient ammonia ( <1 to 2000 to <1 μmol TA l⁻¹). When water ammonia concentrations were altered more gradually, both rates increased, but only at 4000 μmol TA l⁻¹. These results show that N. norvegicus is able to remove ammonia from the haemolymph and/or transform ammonia into some other substance when subjected to increased levels of ambient ammonia. Possible mechanisms involved (e.g. active transport across the gills; storage in some other tissue; glutamate synthe sis) are discussed. Received: 20 May 1996 / Accepted: 1 July 1996     

Feasibility of using an automated colorimetric procedure for the determination of seawater nitrate in the 0 to 100 nM range: Examples from field and culture

An automatic colorimetric procedure for measuring nanomolar quantities of nitrate and nitrite in seawater has been improved in sensitivity. Application of this method toin situ investigations in the North Atlantic Ocean in January 1989 and algal culture (Skeletonema costatum) experiments in the laboratory demonstrated that one can record concentrations in the 0 to 100 nM range using classical Technicon AutoAnalyzer equipment. In this working range highest precision obtained was ±2.87 and ±1.24 nM for nitrate and nitrite, respectively.     

Bisphenol A and metabolites released by biodegradation of polycarbonate in seawater

This is the first report of bisphenol A release from polycarbonate during biodegradation by marine microorganisms. Bisphenol A is a monomer in polycarbonate and an endocrine disruptor toxic for marine organisms. Biodegradation of polycarbonate is poorly documented. Here, we have tested the possible release of bisphenol A and metabolites during biodegradation of polycarbonate by marine microorganisms. Polycarbonate degradation was carried out in vitro using a mixed marine microbial consortium isolated from the Bay of Bengal, India, 1 year under controlled laboratory conditions. The degradation was monitored by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography—mass spectrometry (GC–MS). The organic soluble metabolites were analyzed by high-performance liquid chromatography (HPLC). We found that bisphenol A was released. The amount of bisphenol A released during 1 year is higher than the half-maximal effective concentration (EC₅₀) values reported for marine organisms. We also identified the following bisphenol A metabolites: 4-hydroxyacetophenone, 4-hydroxybenzaldehyde, and 4-hydroxybenzoic acid. Polycarbonate biodegradation was evidenced by gravimetric weight loss and Fourier transform infrared spectroscopy. The reduction of methyl and carbonyl indices suggests oxidation and hydrolysis of the polymer, respectively. 2D NMR showed an aromatic C–C cleavage.