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pH and Ions
Published in Enzo Berardesca, Peter Elsner, Klaus-P. Wilhelm, Howard I. Maibach, Bioengineering of the Skin: Methods and Instrumentation, 2020
For the specific requirements of skin pH measurements a planar electrode was developed with one unit containing the active and the reference electrode (Figure 1). Thus, the contact site between the electrode and the skin covers a greater area, and its use is noninvasive. The so-called combined electrode or “single glass rod measuring circuit” is connected to a pH meter which presents the voltage differences as digital pH values within seconds (Figure 2). The pH meter must be calibrated prior to measurements using standard buffer solutions with pH 4 and 7. Before application to the skin the electrode must be dipped into distilled water to moisten the surface. Then the flat electrode top is placed onto the skin with a slight pressure during the measurement.
Ecological and Biomass Assessment of Vegetation Cover of a University Campus
Published in Jayanta Kumar Patra, Gitishree Das, Sanjeet Kumar, Hrudayanath Thatoi, Ethnopharmacology and Biodiversity of Medicinal Plants, 2019
Kakoli Banerjee, Gobinda Bal, Gopal Raj Khemendu, Nihar Ranjan Sahoo, Gopa Mishra, Chitrangada Debsarma, Rakesh Paul
The ambient water samples were collected from the existing water bodies in the study sites in clean tarson bottles, for in-situ analysis of water temperature, pH, transparency and dissolved oxygen. The surface water temperature was noted by collecting samples using sampler bottles. The sampler bottles were opened at the particular water level, and samples were collected and closed immediately. The values were measured using a digital thermometer (MEXTECH multi stem handheld portable LCD digital thermometer with sensor probe −50°C to 300°C or −58 °F to 572 °F). The values for pH were measured using a pH meter (Oakton eco-testr). The transparency and dissolved oxygen of the water bodies were also measured using Multi-parameter water analysis kit (Model No. 1026G).
Underlying chemical concepts
Published in Maxine Lintern, Laboratory Skills for Science and Medicine, 2018
Thus you must always take care when preparing solutions to ensure that they are made up to the appropriate pH. This may involve correcting the pH by adding an acid or alkali to adjust the [H+]. pH of solutions is usually measured using a pH meter, which has an electrode that can measure the electrical potential of a solution and display it in standard pH units. Operating instructions vary from machine to machine, but generally they are calibrated using standard solutions of known pH. You should always make sure the meter is correctly calibrated before you begin to use it, that your solution is being properly stirred when measuring and correcting the pH, but that the electrode (which is very fragile and expensive to replace) is not in danger of being damaged by the stirrer. Correction is usually done with 1 M HCl to make things more acidic or 1 M NaOH to make things more alkali. Sometimes these reagents are not appropriate (for certain buffers), so always check what is required for the solution you are making.
Monitoring of 2,4-dichlorophenoxyacetic acid concentration in Karun River and effluents of water treatment plants
Published in Toxin Reviews, 2022
Naghmeh Orooji, Afshin Takdastan, Reza Jalilzadeh Yengejeh, Sahand Jorfi, Amir Hossein Davami
An HPLC (Knauer, Berlin, Germany) equipped with C-18 column (250 mm × 4.6 mm, with 5 μm particle size) was used for the separation of the 2,4-D pesticide. The HPLC was applied with a k-1001 pump, UV-Vis detector, and a k-2600 degasser. The chromatographic conditions were as follows: a C-18 column was used as the stationary phase, mobile phase consisted of acetonitrile, deionized water, and acetic acid at the ratios of 80:19.5:0.5, respectively. The HPLC was operated under the mobile phase flow rate of 1 mL/min, column temperature of 40 °C, and a maximum pressure of 40 MPa. The appropriate wavelength for the chromatographic peak area response of the analyte was 283 nm. An ultrasonic bath (SonoSwiss SW 6 H, UK) was utilized for the sample preparation. A pH meter device (model 340i, WTW, DE) and a digital scale with a precision of 0.0100 mg (Sartorius, Göttingen, DE) were used for measuring solution pH and weight measurements, respectively. A UV-vis spectrophotometer (model DR5000, HACH, US) was applied for measuring the concentrations of 2,4-D. A magnetic stirrer (model S0200-26, Cleaver, KR) was used for sample preparation. The samples were also filtered using filter paper 0.45 Watson Micron (GF/C, Wattmann Co., DE). A Hamilton HPLC syringe (100 µL, CH) was used for injecting the samples into the HPLC system.
Mometasone furoate-loaded aspasomal gel for topical treatment of psoriasis: formulation, optimization, in vitro and in vivo performance
Published in Journal of Dermatological Treatment, 2022
Gajanan Shinde, Pankhita Desai, Santosh Shelke, Rakesh Patel, Ganesh Bangale, Deepak Kulkarni
Formulated aspasomal gel was evaluated for drug content, pH, viscosity and spreadability. The drug content of the prepared gel was determined for its drug content. Gel equivalent to 10 mg of MMF was weighed and transferred to 100 ml volumetric flask to which 10 ml of methanol was added and the volume was made up to 100 ml with pH 7.4 phosphate buffer. Absorbance of the resulting solution was recorded by UV. Spectrophotometer at the wavelength of 247.5 nm and drug content was calculated. pH of the dispersion was measured using the pH meter. pH meter was calibrated with standard buffer solutions (pH 4 and pH 7) before starting the experiment to ensure the accuracy in results. The aspasome loaded gel was diluted to 10% using distilled water and pH was determined using digital pH meter. The viscosity of the gel was assessed using Brookfield viscometer (DV3T Rheometer, USA). The samples of 10 ml were taken into the beaker and the viscosity of the formulations was determined using spindle S-64 at room temperature (29). Spreadability of the gel was determined using two petri plates. One of the petri plate was kept in the inverted position and 1 g of the prepared gel was placed on it. Second petri plate was placed on the gel and initial diameter of the gel was measured. Finally, 20 g of the weight was placed and the diameter was recorded. The increase in the diameter exhibits the spreadability of the gel (30).
Formulation and evaluation of butenafine loaded PLGA-nanoparticulate laden chitosan nano gel
Published in Drug Delivery, 2021
Sultan Alshehri, Syed Sarim Imam
The pH of BTNPopG was measured by a pH meter (Edge pH). The electrode of the pH meter was incorporated into the sample and allowed to be stable for few minutes. The reading of the test sample was noted from the pH meter in triplicate at room temperature (Ahmed et al., 2020). The viscosity of the prepared optimized formulation was evaluated by using a viscometer (Brook field viscometer, RV-2 T, USA) using spindle number 6 at room temperature. The extrudability of the prepared BT-NPopG was measured to check the extrusion of formulation from the tube after application of constant weight. The tube is filled with BT-NPopG (20 g) and a constant weight is applied from the crimp end. The cap of the tube opened and the extruded weight of gel was measured to find the extrudability (Kaur & Ajitha, 2019). The spreadability study was performed to evaluate the flow of semisolid formulations. BT-NPopG was performed using a glass plate. The glass slide was pre-marked and the test sample (1 g) was placed over the glass and the gel diameter was noted. Then the second glass was placed over the first plate and the weight (500 g) was applied over for 5 min and then the final diameter was noted. The spreadability was measured by the below equation (Gaba et al., 2015).