pH Test

CD Formulation provides professional pH testing of medications, usually we test liquid medications, including injections, eye drops, etc. By testing the pH of a drug, we can determine whether it is suitable for use in the human body and avoid pain or poisoning caused by too high or too low pH.

About pH Testing of Drugs

Since the pH value varies in different parts of the organism, for example, the pH value of serum and tear fluid is about 7.4, the pH value of gastric fluid is about 0.9~1.2, the pH value of bile is about 5.4~6.9, and the pH value of plasma is 7.4. However, when the pH value of a drug solution deviates too far from the normal pH value of the body fluid concerned, it tends to cause irritation to the tissues, therefore, when preparing infusions, injections, eye drops and solutions for wounds, attention must be paid to the pH of the drug solution. The pH of injection solution should be in the range of 4~9, otherwise it will cause pain and tissue necrosis; the pH of eye drops should be 6~8. The pH value used should consider the effect of pH on drug stability and drug solubility.

Factors Affecting pH

Usually, the factor that affects pH is temperature.

• When the temperature changes, the internal components of pH and reference electrode tend to thermal equilibrium and the result will be shifted.
• When the pH electrode and temperature probe are placed in a sample with drastic temperature changes, the measurement results will drift.
• Buffer and sample pH will change with temperature.

Determination of pH of Drug Solutions

The determination of pH value of drug solution is generally performed by pH meter with glass electrode as the indicator electrode and a cell composed of glycury electrode as the reference electrode.

Steps of pH determination

• Temperature compensation

The pH value varies with the temperature of the solution in the measuring cell. Therefore, the pH meter is equipped with a temperature compensation knob.

• Positioning

To use the pH meter, the instrument must be pre-calibrated (positioned) with a standard buffer and adjusted with the positioning knob so that the pH indication is the same as the pH value of the standard buffer.

• Measurement

After the temperature compensation adjustment and positioning adjustment, change the solution to be measured for determination, and the pH meter will indicate the pH value of the test solution accurately.

The following points should be noted during the test

• Whether the pH value is accurate or not depends directly on the accuracy of the standard buffer used. The instrument must be calibrated with two standard buffers as required before measuring the sample.
• The temperature has a great influence on the electrode resistance, which should generally be measured at 5~40℃. The fastening screw of the temperature compensation adjustment knob is calibrated and should not be loosened when used, otherwise it should be recalibrated.
• If you use standard buffer to calibrate the instrument and the positioning knob cannot be adjusted to the specified value, you can consider the contamination damage of the glycol electrode or the damage of the glass electrode or the mismatch between the electrode and the instrument, you can replace the new electrode and try it.

If you have a requirement about our services, please contact us by phone or email, our colleagues will reply to you within three working days.