Semiquantitative and Quantitative Determination of Trace Amount of Phosphate Ion in Water Using Polyurethane Foam Thin -Layer Colorimetry

Abstract

A simple, sensitive and fast method for the colorimetric determination of phosphate ion in water is described.

The method is based on spectrophotometric measurement of the blue molybdoantimony phosphoric acid species sorbed in a polyurethane foam thin-layer for quantitative determination of phosphate ion, or the visual color comparison technique for rapid semiquantitative determination.

The detection limit for the quantitative procedure is 5 μg/1 and for semiquantitative procedure 20 μg/1 for sample volumes of 100 ml and 25 ml, respectively.     

香兰素－亚硝酸钠比色法对辣椒素的测定

本试验改进了辣椒素的亚硝酸钠比色测定法，以１９０μｇ／ｍＬ香兰素液取代１００μｇ／ｍＬ标准辣椒素液，在４２０ｎｍ波长下比色测定。以乙酸乙酯萃取辣椒素２４ｈ，萃取液通过氧化铝吸附层析，经热风挥发有机溶剂后，显色３０ｍｉｎ测定，不产生混浊，测定结果准确，重现性好。     

TMB目视比色法检测水中余氯的改进

为解决GB/T 5750.11-2006生活饮用水标准检验方法中的3,3',5,5'-四甲基联苯胺(TMB)目视比色法检测余氯时出现的评价方法准确性欠佳、TMB显色剂发黄、显色体系偏绿等问题,对TMB目视比色法的评价方法、TMB显色剂的配制条件和水样的检测条件进行了研究。结果表明,次氯酸钠不宜作为余氯标准物质来评价TMB目视比色法的改进效果,而通过检测显色体系的A450和目视比色值相结合的方法来判断方法改进效果更为准确。采用优级纯浓盐酸和无氯纯水室温搅拌溶解,可使显色剂无色透明,从而解决TMB显色剂发黄的问题,符合国标要求。将显色剂配制用酸(盐酸)的浓度由国标中0.1mol/L变更为0.6 mol/L,可解决余氯显色体系偏绿的问题。显色体系pH变化后,显色时间、显色温度、显色剂用量可仍按照国标方法的要求进行操作。通过以上改进措施,进一步提高了余氯检测结果的准确度。     

数码成像比色法测定水样中的总磷

在酸性介质中,磷酸二氢钾与钼酸铵、酒石酸锑钾及抗坏血酸作用,生成蓝色的络合物。随着磷酸二氢钾浓度的增加,溶液颜色加深,其数码成像的RGB值亦随着磷酸二氢钾浓度的增加而增加,由此建立数码成像比色法(DIC)测定水样中总磷的新方法。考察了DIC法的影响因素和最佳反应条件。与钼酸铵分光光度法对照,该方法简单,快速。用于实际水样的测定,相对标准偏差为1.8%~3.4%,回收率为99.7%~102.5%,结果与分光度法一致。     

光波导共振技术结合比色法检测葡萄糖溶液的浓度

利用比色法结合双面金属包覆波导构建了一种高灵敏度的光波导振荡场传感器. 将葡萄糖溶液与氧化酶试剂混合, 使葡萄糖溶液显色并注入波导结构, 采用波长为650 nm的激光入射于波导表面, 经角度扫描产生衰减全反射(ATR)吸收峰, 通过ATR吸收峰的极小值来检测葡萄糖溶液的浓度变化. 实验结果表明, 该技术对葡萄糖溶液浓度的分辨率达到111 nmol/mL, 其灵敏度高于分光光度计.     

离子交换固相比色法测定氰化物浸液中的微量金

本文采用Ｄ２９０大孔强碱性阴离子交换树脂首先预富集王水介质中的微量金，然后在ｐＨ３．２条件下用硫代米酮（ＴＭＫ）显色，从而建立了固相比色法测定微量金的方法，应用于金矿石氰化物浸液中微量金的测定，结果令人满意。     

Miniaturized Optical System for Detection of Ammonia Nitrogen in Water Based on Gas-Phase Colorimetry

A small-size gas-tight optical measuring system for detection of ammonia nitrogen in water was prepared based on gas-phase ammonia induced color change of the sensing element that was made by loading bromothymol blue (BTB) in a transparent porous glass fiber membrane. The gas-tight optical measuring system consists of a gas-testing and a liquid-sample chamber connected with each other by means of tubes and a mini-pump that cycles the gas between the two chambers. A 625-nm light emitting diode (LED), a photodetector and a sensing element were mounted in the gas-testing chamber for optical response to ammonia gas released from the water in the liquid-sample chamber. Release of ammonia gas was realized by alkalinizing the water sample with NaOH. Owing to the amount accumulation of ammonia gas in the sealing system, the ammonia nitrogen detection limit of the device can be very low. A small concentration of ammonia nitrogen, as low as 0.05 mg/L, was detected. The two linear-response ranges from 0.05 mg/L to 0.26 mg/L and from 0.26 mg/L to 2.62 mg/L were obtained. A relative standard deviation of ≤1% was determined by multiple measurements of the same sample.     

3,5-二硝基水杨酸比色法在烷基多苷体系中的应用研究

将3,5-二硝基水杨酸比色定糖法(DNS法)引入烷基多苷体系中,研究了丁苷化过程中葡萄糖含量随时间的变化,表征了丁苷化反应产率,测定了烷基多苷产品中残留的葡萄糖含量,并将测定结果与传统方法进行了比较,结果表明该法是一种简便快速、准确度高的方法。     

Glucose Biosensor With Extended Linearity

Abstract

In this paper we report results of experiments designed to obtain a glucose probe with extended linearity. the general strategy was to interpose a membrane between the sample and the glucose sensor to limit the diffusion of the glucose toward the sensor without affecting the oxygen diffusion.     

Determination of Total Tannin of White and Red Rind Pomegranate (Punica Granatum L.) by Colorimetry Method Using Reagent 1, 10 Phenantroline

Determination of the total tannin of white and red rind pomegranate (Punica granatum L.) has been carried out by colorimetry method using reagent 1,10 phenantroline. This method is based on reduction of iron (III) into iron (II) by tannin at temperature 80⁰C for 20 min. Then the formed of iron (II) was reacted with 1,10 phenantroline to form orange red colour complex that could be measured by spectrophotometer visible at maximum absorption wavelength of 508 nm. The limit of detection (LOD) and the limit of quantitation (LOQ) obtained were 0.34 μg/mL and 1.14 μg/mL, respectively. This result was found to be linier with R value of 0.9984; accuracy as percent recovery was 84.69 ± 0.85% and coefficient of variant (KV) was 1.003% for white rind pomegranate while red rind pomegranate percent recovery was 84.38 ± 0,45% and coefficient of variant (KV) was 0.53%. The total tannin of white rind pomegranate was 18.28 ± 0.072%b/b and red rind pomegranate was 17.33 ± 0.081%b/b     

Identification and Quantification of Chloramphenicol in Medicines by Multisensory Digital Colorimetry

An effective, affordable, and rapid method for the analysis of drugs based on chloramphenicol is developed using multisensory digital colorimetry. The use of a two-dimensional code for the identification and quantification of chloramphenicol with the minimum level of informational noise is proposed. The principal component analysis is used to increase the reliability of the results of the determination of the medicinal substance. The adequacy of the developed approach is confirmed by the analysis of chloramphenicol preparations in the form of two dosage forms: tablets and eye drops. The accuracy of the results is confirmed by the standard addition method. The results prove that the preparations do not have statistically significant differences from the values declared by the manufacturer.     

Extended connectivity in chemical graphs

The true nature of the extended connectivity, used in Morgan algorithm for the canonical numerotation of points in chemical graphs, is discussed. An alternative method for its calculation based on the number of walks is described and shown to yield results identical to Morgan's method.     

双功能碳点用于葡萄糖的比色/比率荧光测定

以生物质(合果芋叶片)、 十二水合硫酸铁铵和脲为原料, 采用水热法制备了铁、 氮共掺杂碳点(Fe,N-CDs), 采用透射电子显微镜和X射线光电子能谱对其形貌与元素组成进行了表征. 该Fe,N-CDs既具有类过氧化物酶活性, 也能在450 nm处产生强荧光发射. 以Fe,N-CDs和邻苯二胺(OPD)为探针, 建立了一种比色/比率荧光测定双氧水（H₂O₂）的双信号方法. 在H₂O₂存在下, Fe,N-CDs催化OPD氧化成黄色的2,3-二氨基吩嗪(DAP), DAP在420 nm处有1个特征吸收峰. 在360 nm波长光的激发下, DAP在550 nm处有强荧光发射; 由于荧光内滤效应, DAP又可猝灭Fe,N-CDs在450 nm处的荧光. 基于此, DAP在420 nm处的吸光度(A₄₂₀)及DAP与Fe,N-CDs的荧光强度比(I₅₅₀/I₄₅₀)均可用于H₂O₂的定量分析. 考虑到葡萄糖氧化酶能催化葡萄糖氧化生成H₂O₂, 进一步发展了一种比色/比率荧光双信号葡萄糖测定方法. 在pH=5.4, 温度40 ℃, 1.75 mmol/L OPD及反应时间25 min的条件下, 当葡萄糖浓度在1.0~100 μmol/L范围内时, A₄₂₀及I₅₅₀/I₄₅₀值与浓度呈良好的线性关系, 方法的检出限分别为0.8(比色)和0.6 μmol/L(比率荧光). 将该方法成功应用于人体血清中葡萄糖的测定.     

Determination of Low Level Sulfides in Environmental Waters by Automated Gas Dialysis/Methylene Blue Colorimetry

Abstract

A sensitive and rapid automated method has been developed for the selective analysis of acid extractable sulfide in environmental samples by combining gas dialysis separation techniques with methylene blue detection procedures. Acid extractable sulfide is separated from the sample matrix by the gas dialysis membrane and subsequently trapped in a dilute sodium hydroxide receiving stream. This stream is reacted with N, N-dimethyl-p-phenylenediamine and ferric chloride to produce methylene blue which is then quantitated colorimetrically at 660 nm. For standards and nonturbid environmental samples, there is good agreement between the results obtained by this procedure and the standard methylene blue method. The effect of interferences on the accurate determination of sulfide by both methods was also examined and it was found that cupric ions significantly interfered with sulfide estimation. To obtain adequate sulfide recoveries in tap water and environmental samples ascorbic acid must be added as an antioxidant. A detection limit of 2 μg/L of sulfide has been obtained using this procedure.     

Portable Colorimetric Hydrogel Test Kits and On-Mobile Digital Image Colorimetry for On-Site Determination of Nutrients in Water

Portable colorimetric hydrogel test kits are newly developed for the on-site detection of nitrite, nitrate, and phosphate in water. Griess-doped hydrogel was prepared at the bottom of a 1.5 mL plastic tube for nitrite detection, a nitrate reduction film based on zinc powder was placed on the inner lid of a second 1.5 mL plastic tube for use in conjunction with the Griess-doped hydrogel for nitrate detection, and a molybdenum blue-based reagent was entrapped within a poly(vinyl alcohol) hydrogel matrix placed at the bottom of a third 1.5 mL plastic tube to detect phosphate. These test kits are usable with on-mobile digital image colorimetry (DIC) for the on-site determination of nutrients with good analytical performance. The detection limits were 0.02, 0.04, and 0.14 mg L⁻¹ for nitrite, nitrate, and phosphate, respectively, with good accuracy (<4.8% relative error) and precision (<1.85% relative standard deviation). These test kits and on-mobile DIC were used for the on-site determination of nutrients in the Pak Bang and Bang Yai canals, the main canals in Phuket, Thailand. The concentrations of nitrite, nitrate, and phosphate were undetectable to 0.60 mg L⁻¹, undetectable to 2.98 mg L⁻¹, and undetectable to 0.52 mg L⁻¹, respectively.     

分散液液微萃取-数码比色法测定环境及生物样品中亚硝酸根

研究了分散液液微萃取(DLLME)-数码比色(DC)法测定水样中的亚硝酸根.在酸性介质中,亚硝酸根和对硝基苯胺及二苯胺作用,生成红色偶氮化合物.用乙醇作分散剂,以四氯化碳为萃取剂进行分散液液微萃取,萃取液点样在薄层硅胶板上用数码相机进行数码成像.成像斑点的灰度值和亚硝酸根的浓度成正比,据此建立了测定水样中痕量亚硝酸根的新方法.对影响萃取富集效率和数码成像效果的因素进行了优化.亚硝酸根浓度在2.0～80 μg/L范围内有良好的线性关系(r=0.9997);检出限为0.22 μg/L.方法已应用于实际水样及人体体液分析,加标回收率在97.6%～103.4%之间,相对标准偏差在1.7%～3.4%之间;方法具有仪器成本低、方便快速、灵敏度高、环境友好等特点,可满足野外现场的检测要求.