I need to clean up my PCR amplified DNA samples using the Qiagen PCR Purification kit. I am going to analyze the DNA using microarray. According the protocol, "If the purified PCR product is to be used in sensitive microarray applications, it may be beneficial to use Buffer PB without the addition of pH indicator I." That means I cant use the pH indicator and unable to detect any pH change by the color of the PB buffer.

I know the importance of pH of PB buffer to achieve good DNA yield. Kindly suggest me how can I measure the pH without adding the pH indicator I? And what should be the pH?