离子色谱法测定工业循环冷却水中的总磷量

研究用离子色谱法测定工业循环冷却水中总磷量的方法。采用0.074mol/L K2S2O8-0.500mol/L NaOH作为混合氧化剂，确定了最佳实验条件。方法的标准偏差为2.12%。用离子色谱法测定样品的分析结果与光度法进行比对，结果相吻合。方法简便、实用，灵敏度、准确度高。     

活性炭负载TiO2光催化氧化二苯并噻吩的研究

以活性炭负载的TiO2为光催化剂,H2O2为氧化剂,30W紫外灯为光源,对含二苯并噻吩（DBT）的模型硫化物进行光催化氧化脱硫研究。考察了TiO2的煅烧温度、负载量、催化剂用量、H2O2用量和光照时间对DBT去除率的影响。实验结果表明,用溶胶 凝胶法制备的TiO2 /活性炭催化剂对DBT具有很好的光催化效果。最佳反应条件为,催化剂煅烧温度400℃,TiO2的负载量为32％,催化剂用量0.7g/100mL, H2O2最佳用量为10mL,即O/S（摩尔比）为14。在最佳反应条件下,光照时间8h,DBT去除率为90％, 此反应为一级动力学反应。     

高温燃烧法测定水质总氮

通过高温燃烧法测定了水质总氮含量,与K2S2O8氧化-紫外分光光度法进行比较,高温燃烧法的测定结果准确可靠。方法的检出限为0.05 mg/L,测定下限为0.20 mg/L,样品测定的RSD为0.9%~4.6%,加标回收率为97.4%~103%。对于有悬浮物干扰的水样,可以超声粉碎后测定;Fe3+,Cr6+和卤素离子对高温燃烧法测定总氮无干扰。     

利用过二硫酸盐氧化消除2-碘双氢非那雄胺制备非那雄胺

系统考察了不同碱及氧化剂对2-碘二双氢非那雄胺(2a)氧化消除反应的影响,实验结果表明,当以K2S2O8为氧化剂时,反应效果最佳.以K2S2O8为氧化剂,探索了溶剂、K2S2O8用量、温度、时间对反应的影响,获得最佳反应条件为:四氢呋喃(THF)为溶剂,室温反应10 h,K2S2O8与2-碘二双氢非那雄胺(2a)的投料比为2∶1.在该最优化条件下,非那雄胺(3a)收率为96%,纯度为99.6%.同时,该条件也适用于2-碘-3-氧代-4-氮杂-5α-雄甾-17β-甲酸(2b)和2-碘-3-氧代-4-氮杂-5α-雄甾-17β-甲酸甲酯(2c)的氧化消除反应,得到相应目标产物收率和纯度均高.本方法具有反应条件温和、产品收率和纯度均高且对环境友好等优点.     

碘钟反应测定反应级数中的试剂因素分析

分析了(NH4)2S2O8和KI反应级数测定的实验, 认为(NH4)2S2O8和KI的变质会引起反应速率与反应物浓度的非线性关系, 变化过大时无法正确测得反应级数。(1)(NH4)2S2O8或KI部分变质, 非线性变化突出, 数学处理可采用有效浓度法扣除变质部分。一般主要是(NH4)2S2O8的变质, 用Na2SO3或Na2S2O3预先处理(NH4)2S2O8产生的中间氧化性物质, 可测得正确的反应级数, 也可简化数学处理。(2)测速剂Na2S2O3的用量过大或过小, 均会导致反应速率与(NH4)2S2O8浓度的非线性关系。Na2S2O3的用量较大时, 应使用反应进程系数将平均速率校正为初始速率;而Na2S2O3的用量过小时, 则操作的随机性误差将增大;只有Na2S2O3的用量适中时, 平均速率与初始速率的差别较小, 无需校正。该分析有助于理解反应级数的测定原理, 其校正措施可得到较理想的实验结果。     

响应面法优化H2O2/K2S2O8深度处理印染废水

结合常州市新区某纺织印染厂现有工艺,采用H2O2/K2S2O8深度处理印染废水,探讨了Fe2+浓度、H2O2/K2S2O8摩尔比、pH值和反应时间对COD去除率的影响规律.采用Box-Behnken响应面法优化反应条件并拟合出回归模型,预测COD去除率在最佳反应条件(pH=3.1、Fe2+浓度=0.97 mmol·L-...     

活性炭吸附及离子交换富集分离-分光光度法测定水中痕量银

建立了用活性炭对水中痕量银进行预富集的新方法。结果表明,pH=1.0时,活性炭能对水中被抗坏血酸还原后的痕量银进行吸附富集,而Cu(Ⅱ)、Fe(Ⅲ)、Co(Ⅱ)、Ni(Ⅱ)、Pb(Ⅱ)、Zn(Ⅱ)、Mn(Ⅱ)、Al(Ⅲ)、Bi(Ⅲ)和Sb(Ⅲ)等常见阳离子不被吸附,用K2S2O8将吸附在活性炭上的单质银氧化解脱后,用Mg(NO3)2辅助置换洗脱,可用分光光度法测定。该法在8～50μg/L银(Ⅰ)范围内加标回收率为93.2～97.1%。同时还研究了活性炭对银的吸附行为,提出了活性炭表面上被氧化的Ag(Ⅰ)和Mg(Ⅱ)有离子交换作用。应用该法测定自来水中痕量银,结果令人满意。     

NaIO4-H2O2 流动注射化学发光法测定天然水中硒的研究

建立了一种简易、快速检测天然水中痕量硒的流动注射化学发光法。该法基于NaIO4-H2O2(pH 7.0)氧化Se(0)生成Se(Ⅳ)所产生O*的化学发光,发光强度与一定浓度范围内的Se呈线性关系,加入环己烷和Triton-100能增强这一体系的发光强度。该法测定Se的线性范围为1.0×10-7~1.0×10-5mol.L-1,检测限为4.2×10-8mol.L-1,对4.0×10-7mol.L-1的Se进行测定的RSD为3.5%(n=8)。用该法对天然水体中Se进行了测定,结果满意。     

Na_2S_2O_8-Fe~(2+)对田菁胶的氧化降解行为研究

考察了Na2S2O8-Fe2+对田菁胶的氧化降解行为,系统研究了Na2S2O8和Fe2+用量、温度、降解时间和pH值对田菁胶粘度的影响。结果表明,Na2S2O8和Fe2+合适的体积比为3?1。在较低的温度(40℃)和较短的时间(20 min)内Na2S2O8-Fe2+就能使田菁胶粘度下降90%以上。另外,Na2S2O8-Fe2+氧化还原体系在酸性和中性条件下对田菁胶的降解都有良好的降解性能,考虑到在实际生产中的应用,我们认为中性条件下最合适。     

稀土元素异硫氰酸盐水合物,RE(NCS)_3·nH_2O的低温热容和热力学性质的研究——Ⅰ.La(NCS)_3·7H_2O和Ce(NCS)_3·7H_2O

本文用全自动绝热量热计从13到300K测定了两种稀土元素异硫氰酸盐七水合物,La(NCS)_3·7H_2O和Ce(NCS)_3·7H_2O的热容。较详细描述了量热计结构和操作。在实验温区对两种化合物均未观察到明显的热异常现象。根据实验热容数据,用最小二乘拟合方法得到了计算这两种化合物13—300K热容值的多项式方程。13K以下的热容值用Debye和Einstein热容函数进行了估算。计算出了O—300K的标准热力学函数,标准生成Gibbs能也被计算出来。     

总氮测定过程中空白吸光值偏高的原因分析

使用HJ 636-2012测定水质总氮时,空白吸光值往往偏高。为了寻找最佳的实验条件,使用多元线性回归模型定性评价过硫酸钾和氢氧化钠的纯度、实验用水、碱性过硫酸钾溶液的存放时间、消解条件、冷却时间、消解器皿等因素对空白吸光值的重要性。结果表明:过硫酸钾纯度对空白吸光值影响最显著。为了保证总氮空白吸光值小于0.030,测定总氮时应优先使用经过2~3次重结晶的过硫酸钾以及优级纯的氢氧化钠,碱性过硫酸钾溶液应现配现用;建议消解时间30 min,消解温度123℃,自然冷却时间1.5 h;实验应优先使用超纯水或无氨水;使用哈希消解管代替25 mL比色管。     

水质中总氮测定的影响因素分析

采用碱性过硫酸钾消解―紫外分光光度法对水质中总氮含量进行测定,分析影响总氮测定结果的各种因素。实验结果显示,测定水中总氮过程中,实验所用纯净水、过硫酸钾纯度及碱性溶液存放时间对空白吸光度有明显影响,消解时间和冷却放置时间也会影响测定的空白吸光度和相对误差。在实验确定的最佳条件下对样品进行测定,结果准确可靠。     

A semi-automatic alkaline peroxodisulphate method for the routine determination of total dissolved nitrogen in sea water

Nydahl's method for the determination of dissolved organic nitrogen (DON) in distilled water has been modified for the determination of total dissolved nitrogen (TDN) in sea water. Samples (9 cm³) are digested batch-wise with alkaline potassium peroxodisulphate solution. An improved buffering system permits the automatic measurement of the nitrate formed, and allows the analysis of 50–80 samples per day. DON may be determined as the difference between TDN and the sum of inorganic nitrogen species. The standard deviation of TDN determinations is 0.7 μg N dm^-3 at about 15 μg TDN dm^-3. The method is applied to a range of samples including tanker ballast water, oil platform production water, and zooplankton.     

Determination of total phosphorus in waters with amperometric detection by coupling of flow-injection analysis with continuous microwave oven digestion

For the determination of total phosphorus in waters by flow-injection analysis, a continuous microwave oven decomposition with subsequent amperometric detection of orthophosphate is proposed. The percentage digestion was examined for two different decomposition reagents and by varying the pH of the carrier and the length and diameter of the digestion coil. With potassium peroxodisulphate decomposition the recoveries of phosphorus vary from 91 to 100% for organic phosphorus compounds, and with perchloric acid decomposition the recoveries vary from 60 to 70% for inorganic polyphosphates. Calibration graphs are linear for up to 30 mg P l^?1, the determination limit is 0.1 mg P l^?1 and the precision of the method is 3% (relative standard deviation) (n = 5) at 5 mg P l^?1. The sampling rate is 20 h^?1. Good recoveries of phosphorus after addition to domestic waste water sample are obtained.     

Critical comparison of two standard digestion procedures for the determination of total mercury in natural water samples by cold vapour atomic absorption spectrometry

Two pretreatment procedures for total mercury determinations in natural water samples were compared. The first, the Swedish Standard method (DP1), involves digestion of water in the presence of concentrated nitric acid at 120°C and under pressure for 30 min. In the West German Standard method (DP2), small volumes of nitric and sulphuric acids, permanganate and peroxodisulphate are added to the sample, and digestion proceeded at 50°C in an ultrasonic bath. Mercury was determined after both digestion procedures using a modified cold vapour atomic absorption spectrometric method, in which mercury generated on addition of a reducing agent is collected and subsequently atomized in a platinum-lined graphite furnace. The efficacy of the two digestion procedures was tested using various standard organic mercury compounds and it was found that only DP2 provided quantitative recoveries. Purification of the reagents required by DP2 was achieved using a mercury-selective ion-exchange resin, Chelite S, resulting in blank levels below 1.5 ng Hg l^?1. Both methods were applied to the determination of total mercury in an unpolluted marsh water sample, giving 2.0 ng Hg l^?1 (DP1) and 2.7 ng Hg l^?1 (DP2). The West German Standard digestion procedure (DP2) is recommended for the determination of total mercury in natural water samples.     

Determination of total phosphorus and nitrogen in turbid waters by oxidation with alkaline potassium peroxodisulfate and low pressure microwave digestion, autoclave heating or the use of closed vessels in a hot water bath: comparison with Kjeldahl digestion

The evaluation of the use of alkaline peroxodisulfate digestion with low pressure microwave, autoclave or hot water bath heating for the determination of total phosphorus and nitrogen in turbid lake and river waters is described. The efficiency of these digestion procedures were compared to a Kjeldahl digestion procedure with sulphuric acid-potassium sulfate and copper sulfate. The final solution before digestion was 0.045 M in potassium peroxodisulfate and 0.04 M in sodium hydroxide. Procedures were evaluated by the analysis of suspensions of two reference materials, National Institute of Environmental Science, Japan, no. 3 Chlorella and no. 2 pond sediment and natural turbid waters. Best recoveries of phosphorus and nitrogen by microwave heating were obtained when solutions were digested at 95 °C for 40 min. Quantitative recoveries of phosphorus from Chlorella suspensions up to 1000 mg/l were obtained by all three heating procedures, but incomplete recoveries of nitrogen occurred above 20 mg N/l in the digested sample. Good recoveries of phosphorus and nitrogen from suspended sediment suspensions were obtained only from solutions containing <150 mg/l of suspended sediments. Recoveries of phosphorus from phosphorus compounds containing COP and CP bonds added to distilled water were quantitative (94-113%) except for polyphosphates (microwave, 34±8; autoclave, 114±6; water bath, 96±4) and aluminium phosphate (8-23%). Recoveries of nitrogen compounds containing CN bonds added to distilled water were quantitative (94-96%). The analysis of a range of natural turbid water samples by alkaline peroxodisulfate and microwave, autoclave and water bath heating gave similar total phosphorus and nitrogen results. All procedures using alkaline peroxodisulfate underestimate phosphorus concentrations at high suspended sediment concentrations (>150 mg/l) and are only suitable for the analysis of very turbid samples when the turbidity is due to organic matter (algal cells, plant detritus). Underestimation of nitrogen occurs when samples contain more than 20 mg N/l.     

水中总氮测定分析方法的改进

用"碱性过硫酸钾消解紫外分光光度法"测定水中的总氮时, 通过减少氧化剂中氢氧化钠的浓度, 使消解后溶液可以直接在波长210 nm处进行测定. 与原法相比, 简化了分析步骤, 节约了试剂;而且灵敏度提高了约2倍, 保证有很好的精密度和准确度.     

Potential for chlorate interference in ion chromatographic determination of total nitrogen in natural waters following alkaline persulfate digestion.

Determination of total nitrogen in aqueous samples after thermal potassium peroxydisulfate (persulfate) digestion is a commonly used alternative to the tedious Kjeldahl procedure. When ion chromatography is used to quantify the nitrate formed during digestion, there is a potential for interference from a chlorate peak if the digested sample initially contained chloride in concentrations close to or greater than the concentration of nitrogen. It was determined that this interference can be avoided either by using chromatographic conditions which cleanly resolve the nitrate and chlorate peaks (e.g., the Dionex AG9-HG column) or by using digestion reagent concentrations chosen to maintain a high pH throughout the digestion. The second alternative is not a viable option for investigators using a single digestion for both total nitrogen (TN) and total phosphorus (TP) analysis.     

水杨酸钠紫外分光光度法测定烟草中的总氮

建立水杨酸钠紫外分光光度法测定烟草中总氮含量的方法。烟草样品经硫酸铜–硫酸钾–浓硫酸消化,用水杨酸钠–二氯异氰尿酸钠显色后用紫外分光光度计检测,并对波长、显色剂用量和反应时间等实验条件进行了优化。总氮的质量浓度在5~60 mg/L范围内与其吸光度呈良好的线性关系,线性相关系数为0.998 8,方法的检出限为0.14 mg/L。样品分析结果的相对标准偏差为3.22%(n=6),样品加标回收率为99.30%~101.62%。该方法具有较高的精密度和准确度,尤其适用于样品量少时对烟草中总氮的测定。     

Determination of total tin in river water by hydride generation-atomic absorption spectrometry

Summary The total tin in river water was determined by hydride generation-atomic absorption spectrometry in sulphuric acid medium. The water was concentrated with nitric and sulphuric acids. Interference from copper and iron was eliminated by extracting copper with a carbon tetrachloride solution of zinc dibenzyldithiocarbamate and by complexing iron with 1,10-phenanthroline in solution. The acidities of the sample solutions were checked by weighing the residue in the flasks during the acid digestion so that the acidities of the sample solutions became approximately equal to those of the calibration solutions. When a 1,000 mg/l tin(IV) solution was diluted with water, the hydrolysed tin could not be determined entirely as the total tin by acidification with sulphuric acid, but it could be recovered completely by digestion even after 5 days. Thus digestion is essential when determining the total tin in water.