Polypropylene oxide , calibrant

Polyethers. Polyethers such as polyethylene oxide (PEO) and polypropylene oxide (PPO) have been used for ESI-MS calibration [10,11,19]. The predominant ions for these calibrants are cation attachments, and sodium attachment is frequently observed, due to traces of sodium in solvents and glassware. The positive-ion ESI mass spectra of PEO and PPO are characterized by abundant [M + nNa]n+ and some [M + ] + species. Macrocyclic polyethers and crown ethers were also used as ESI-MS calibrants [11]. In general, nonderivatized polyethers show the following drawbacks when used as calibrations solutions (1) they are difficult to flush out of the ion source, (2) they generate complex mass spectra resulting from the presence of several different cation sources, and... 

All reagents must be of recognized analytical grade. The water used for dilution should be deionized and filtered. The water should have a resistance of >10 MD/cm and not contain particles >0.20 pm. The bottles that are to contain sample, calibration standards, and reagent solutions should be made of polyethylene or polypropylene. For the anions, borosilicate glass may also be used. Stock standard solutions may be purchased as certified solutions from different manufacturers or NIST (National Institute for Standards and Technology, USA), or else prepared from salts or oxide that are dried, dissolved, and diluted. 

Acetylcholineesterase and choline oxidase Sensors were developed consisting of a Clarke oxygen electrode modified by superposition (over the polypropylene membrane of the electrode) of a dialysis membrane on which AChE and ChO were immobilized. Both formats are based on the conversion of the substrate to choline which is oxidized in the presence of choline oxidase causing a reduction in p02 which is detected by the electrode. Free choline is measured with a similar electrode with only choline oxidase immobilized on the membrane. Calibration graphs were rectilinear upto 90 pM choline and upto 120 pM acetylcholine. Results were presented for the analysis of tissue extracts and pharmaceutical formulations. [115]... 

The relative contents of ethylene oxide and propylene oxide in polyethylene-polypropylene glycols has been determined using combined pyrolysis-gas chromatography calibrated with polyethylene glycol and polypropylene glycol standards [65]. 

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