Phenol sensor

J. Yu, S. Liu, and H.X. Ju, Mediator-free phenol sensor based on titania sol-gel encapsulation matrix for immobilization of tyrosinase by a vapor deposition method. Biosens. Bioelectron. 19, 509-514 (2003). 

Recent development in multilayer sensor architecture using sequential electrochemical polymerization of pyrrole and pyrrole derivatives to entrap enzymes was tested on a tyrosinase-based phenol sensor [127]. A phenothia-zine dye, thionine served as redox mediator and was covalently attached to the thin, functionalized first polypyrrole layer on Platinum disk electrodes. Then, a second layer of polypyrrole with entrapped tyrosinase was electrochemically deposited. The phenol sensor constructed in this manner effectively transferred electron from enz3Tne to the electrode surface. As all steps in preparation, including deposition of the enzyme-containing layer are carried out electrochemically, this technique may prove to be applicable for mass production of miniature sensors. 

Spices Rosemary (1000 ppm of extract with 0.92 mmol/g total phenols) Rosemary (200 ppm of extract with 0.92 mmol/g total phenol) Dried chicken meat for soup powder (up to 1000 ppm is acceptable sensorically) Potato flakes for mashed potatoes (up to 200 ppm is acceptable sensorically) Rosemary extract gave better protection than extracts of tea, grape skin or coffee Rosemary extract gave better protection than extracts of green tea, grape skin or coffee Nissen et al., 2000 Nissen et al., 2002... 

Phenolic copolymers containing fluorophores (fluoroscein and calcein) were synthesized by SBP catalysis and used as array-based metal-ion sensor. Selectivity and sensitivity for metal ions could be controlled by changing the polymer components. Combinatorial approach was made for efficient screening of specific sensing of the metals. 

Scorsone E., Christie S., Persaud K.C., Simon P., Kvasnik F., Fibre-optic evanescent sensing of gaseous ammonia with two forms of a new near-infrared dye in comparison to phenol red, Sensor. Actual. B-Chem. 2003 90 37-45. 

Optical pH sensors with linear responses over different pH ranges can be designed by using different groups of indicators. A silica sol-gel glass pH sensor was developed by co-entrapping three indicators (bromocresol green, bromocresol purple, and phenol red)64, which produced a linear response over 3.5 pH units from pH 6.3 to 9.8 with a standard deviation of pH equal to 0.03. 

The first pH sensor was developed at NIH (Bethesda, Maryland) and made use of phenol red as acid-base indicator, covalently bound to polyacrylamide microspheres10 such microspheres are contained inside a cellulose dialysis tubing (internal diameter 0.3 mm) connected to a 250 pm plastic fibre (Figure 2). The probe was inserted into either the tissue or the... 

Phenol red immobilized PVA membrane for an optical pH sensor is developed based on the same approach, since the molecular structure of phenol red is similar to that of phenolphthalein. Phenol red was first reacted with the formaldehyde to produce hydroxymethyl groups, and then it was attached to PVA membrane via the hydroxymethyl groups. The changes of spectra characteristics after immobilization, the ionic strength effects, response time, reproducibility and long-term stability of the sensor membrane are discussed by Z. Liu et al. [170],... 

Epoxy-based membrane of 2-[(4-chloro-phenylimino)-methyl]-phenol reveals a far Nemstian slope of 43 mV per decade for Pb+2 over a wide concentration range CIO 6 to 10 1 mol dm-3). The response time of the electrode is quite low (< 10 sec) and could be used for a period of 2 months with a good reproducibility. The proposed electrode reveals very high selectivity for Pb(II) in the presence of transition metal ions such as Cu2+, Ni2+, Cr and Cd2+at concentrations l.()xl() 3 M and 1.0><10 4 M. Effect of internal solution concentration was also studied. The proposed sensor can be used in the pH range of 2.50 - 9.0. It was used as an indicator electrode in the potentiometric titration of Pb+2 ion against EDTA. 

A photometric flow-through sensor for the determination of carbamate pesticides (carbofuran, propoxur and carbaryl) based on similar principles as regards the detector and sensor used (a diode array spectrophotometer and a flow-cell packed with C,g resin, respectively) was employed to monitor the formation of the products resulting from hydrolysis of the analytes and online coupling of the respective phenols with diazotized sulphanilic acid. This... 

Recently, DeGrandpre [12] developed a probe-type sensor for the determination of PCO2 in sea water by direct immersion of the probe, which, however, has some connotations of flow-through sensor even though a pH indicator such as Phenol Red (piTj = 7.5) or Bromothymol Blue (pAn = 6.8) rather than the sample is circulated over the sensing microzone —the basic forms of these indicators have a high molar extinction coefficient at 560 and... 

Figure 15.5 Changes of the sensor capacitance on exposure to phenylalanine (Phe), glycine (Gly), phenol, and tryptophan (Trp). Reprinted from Panasyuk et al. (1999). Copyright 1999 American Chemical Society.

Microbial biosensors associated with respiration have been described for the following aromatics phenol, benzoate, naphthalene, dibenzofuran, biphenyl, and benzene. Table 10 gives a survey of the characteristic parameters of these microbial sensors along with interfering substances. 

Similar results were obtained with a Pseudomonas putida biosensor [113]. Phenol-induced cells showed little cross reaction to other compounds. This sensor did not react to benzoate. Detection of benzoate is possible only with cells grown on benzoate. 

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