Nicotine presence can be detected in the blood for a short period only (about 48 hours) . However, its metabolite, cotinine, can be detected up to about three weeks from the last use and the cut-off detection levels is 200 ng/ml.
Q: What is the purpose of toner? Our skin is happiest at a pH of 5.5. Toner balances the pH of your skin. If you are acne prone the skin is too acidic. So finding a slightly alkaline toner can help balance the acidic nature. If the skin is dry, it is too alkaline, so finding a toner that has a lower pH can bring it to a happy balance of 5.5. Toning 1 minute after cleansing allows all the beneficial molecules to absorb into the skin as it is still wet.
Now that we understand the basics of calibration, why should a meter be calibrated at more than one pH value? Most pH meters should be calibrated at a minimum of two points. The most common points are values of pH 7.01 and 4.01 or 7.01 and 10.01 if you are going to be reading alkaline values.The more advanced Hanna meters will let the user calibrate at three, four or five pH values.ne more point needs to be considered. The temperature of a solution when depressed or elevated from 20 C will also contribute an error to the pH reading if the meter does not have a temperature sensor built in to correct for this variation.