Normal semen is slightly alkaline. Acidic conditions can lead to reduced sperm motility and viability.
Secretions of the different glands of the male reproductive tract contain fluids of different pH. The portion of semen that originates in the seminal vesicles is basic; that of the prostate gland is acidic. If the pH is low (acidic) it could mean that there is an obstruction in the ejaculatory duct below the level of the seminal vesicles or it could signal absence of the vas deferens. A pH value that is less than 7.0 is often associated with low volume since both basic pH and much of the semen volume are products of the seminal vesicles. Measuring pH can thus help a clinician determine the cause of azoospermia (absence of sperm in semen).
The pH of the sample should be measured after liquefaction at a uniform time but at a minimum within one hour. The pH is measured using pH testing strips. A drop of semen is placed on a pH strip and allowed to develop full color. Final color is compared to a standard. For the most accurate results, use test strips with a sensitivity in the basic range, for example from 6.0 to 10.0. The pH should be measured after liquefaction at a uniform time, but within one hour of ejaculation. PH is altered by the loss of CO2 that begins to occur once the semen is produced.
The pH paper should be tested periodically against known controls to validate its accuracy.