Fiber-Optic pH Sensor

The new enhancement in the determination of pH using optical fiber system is described here. This work uses the membrane made of cellulose acetate membrane for reagent immobilization and congo red (pK_a 3.7) and neutral red (pK_a 7.2) as pH indicators. An effective covalent chemical binding procedure is used to immobilize the indicators. The response time, reversibility, linear range, reproducibility, and long-term stability of fiber optic sensor with congo red as well as neutral red have been determined. The linear range measured for the sensor based on the congo red and neutral red is 4.2-6.3 and 4.1-9.0, respectively. The response time of sensor membrane is measured by varying the substance pH values between 11.0 and 2.0.     

Intracellular pH mapping with SNARF-1 and confocal microscopy. I: A quantitative technique for living tissue and isolated cells

A fluorescent pH indicator in conjunction with confocal microscopy, was used to map intracellular pH in a variety of cells and tissues with high spatial resolution. The new pH-sensitive fluorescent probe SNARF-1 was excited with the 488 nm band of the argon ion laser of a Bio-Rad MRC-500 confocal microscope. Ratio images were created with pixel-by-pixel division, with the intensity of these images representing a function of pH, that is independent of dye concentration, photobleaching or path length. Cell cultures of rat aortic smooth muscle were loaded with 20 μм SNARF-1/AM for 20 min at 37°C. Intracellular pH levels were calibrated in situ by treatment of each cell with nigericin (20 μм) in solutions of known pH. The cytosolic pH of the majority of cells was uniform, however, pH gradients were evident between the cytosol and nuclear regions, indicating the ability of this technique to map intracellular and intraorganelle pH. Rat C6 glioblastoma spheroids were cultured then loaded with SNARF-1/AM at 10°C for 90 min. The pH values were calibrated in vitro, using SNARF-1 acid in buffered solutions of known pH. Ratio images of the bisected spheroids showed a marked gradient in pH from the outer cells compared with central necrotic cells. The degree of involvement of acidification in muscle fatigue was investigated by simultaneously determining force generation and intracellular pH in individual fibres of an intact rat muscle. The investigation was performed during a stimulation protocol which induced significant fatigue in the force response of the muscle. The fatigue protocol induced little change in cytosolic pH in the fibres. We show that the use of SNARF-1, in conjunction with confocal microscopy is a powerful technique for accurately mapping pH within single cells, multicellular tissues and intact organs, as well as for accurately recording dynamic changes in pH.     

pH配位滴定法同时测定铜和锌

本文将多元线性回归法应用于ｐＨ配位滴定法中，提出了金属离子混合液中各组分同时测定的方法原理，并对铜，锌合成样品进行了测定，得到满意的结果。     

pH值对壳聚糖/羧甲基壳聚糖水凝胶溶胀行为的影响

利用壳聚糖与羧甲基壳聚糖制备了一系列新型的水凝胶，研究了pH值对水凝胶溶胀度、微观结构和基团结构的影响．结果表明，壳聚糖与羧甲基壳聚糖水凝胶的溶胀行为和微观结构均表现出pH值敏感性，但随着羧基的引入，水凝胶的最低溶胀度从pH7．O移向pH3．O．红外光谱证明，水凝胶的pH敏感行为是由基团结构的变化引起的．     

Synthesis and properties of chitosan‐based thermo‐ and pH‐responsive nanoparticles and application in drug release

In this research, thermo‐ and pH‐responsive nanoparticles with an average diameter of about 50–200 nm were synthesized via the surfactant‐free emulsion polymerization. The thermal/pH dual responsive properties of these nanoparticles were designed by the addition of a pH sensitive monomer, acrylic acid (AA), to be copolymerized with N‐isopropylacrylamide (NIPAAm) in a chitosan (CS) solution. The molar ratio of CS/AA/NIPAAm in the feed was changed to investigate its effect on structure, morphology, thermal‐ and pH‐responsive properties of the nanoparticles. It was found that CS‐PAA‐PNIPAAm nanoparticles could be well dispersed in the aqueous solution and carried positive charges on the surface. The addition of thermal‐sensitive NIPAAm monomer affected the polymerization mechanism and interactions between CS and AA. The particle size of the nanoparticles was found to be varied with the composition of NIPAAm monomer in the feed. The synthesized nanoparticles exhibited stimuli‐responsive properties, and their mean diameter thus could be manipulated by changing pH value and temperature of the environment. The nanoparticles showed a continuous release of the encapsulated doxycycline hyclate up to 10 days during an in vitro release experiment. The environmentally responsive nanoparticles are expected to be used in many fields such as drug delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2798–2810, 2009     

有机掺杂溶胶-凝胶法制备pH敏感膜及其光谱响应的研究

使用四甲氧基硅烷（TMOS）和二甲基二甲氧基硅烷（DiMe-DMOS)为共先驱体，采用溶胶－凝胶的有机掺杂，制备对pH具有宽程响应的敏感膜。详细考察了包埋溴酚蓝和溴酚绿的敏感膜对pH的响应值、响应时间、泄漏和可逆性等响应性能指标，并进行了溴酚蓝和溴酚绿在水相与膜内吸收光谱的研究。     

pH-dependent intracellular quenching of the indicator carboxy-SNARF-1

Carboxy-SNARF-1 is an emission-changing, pH-sensitive probe for measurements of intracellular pH. However, the protonated and deprotonated forms of the dye interact differently with intracellular constituents, and this imposes new requirements on the calibration of the system. Whole spectra of intracellular and extracellular C.SNARF-1 were analyzed and showed (1) intracellular quenching which was significantly greater for the deprotonated form of the dye than for the protonated state and (2) a detectable change in pK _a. Importantly for avoiding damage to cells, this mathematical analysis allowed reference spectra for fully protonated and fully deprotonated dye to be obtained without a need for spectra measured at extreme values of pH. It is not known what constituent(s) of the intracellular milieu might be responsible for the changes in dye behavior in the cell. To address this question, preliminary experiments with cell-free buffers compared the pattern seen inside the cell with quenching by a protein (bovine serum albumin; BSA) or that due to ethanol. The BSA result was completely unlike the intracellular case in that the protonated form of the dye was quenched. Buffer containing ethanol, on the other hand, was able to mimic the essential features of the intracellular spectra.     

Evaluation of liquid junction potentials and determination of pH values of strong acids at moderate ionic strengths

A new experimental approach is proposed for the evaluation of liquid junction potentials and single ion activities. Neither of these quantities can be experimentally measured without assumption. Furthermore, they are concentration dependent but without clearly defined functional relationships. Thus, a given assumption may be satisfactory to obtain these quantities at a given concentration, but will fail at another concentration. It is the intent of this paper to establish a functional relationship between the ratio of activity coefficients and the ionic strength, through which the liquid junction potentials may be computed, as well as the pH values at moderate ionic strengths (<1.0 m). Experimental results are presented and uncertainties are discussed.     

The effect of sonication on glass electrodes

This communication describes observations made on the disturbing effect of ultrasound on the functioning of glass electrodes. It was observed that the signal of glass electrodes drops significantly, with as much as several pH units, if sonication is applied to the sample solution. The effect was studied for a variety of electrolyte solutions and for several glass electrode makes, and was always found to be reversible and reproducible. The quality and the concentration of the electrolyte, as well as the ultrasonic power applied were seen to strongly influence the magnitude of the effect. These findings suggests that (i) if a glass electrode is being used to follow chemical reactions in sonicated solutions, irradiation should be intermitted for the time of measurements, and (ii) the phenomenon may provide an alternative method for sensing ultrasound or mapping ultrasound energy distribution.