is it too late to renegotiate pay rate?

[Bella2016]

back ground: currently employed as a per diem RN at an outpatient surgery center in Souther California (Inland empire) where GI procedures are performed and other surgical procedures. 

Recently applied for another RN per diem position at a medical facility.  I was recently contacted to do a phone interview. During my phone interview she mentioned what they perform "GI procedures" and asked about my experience. A few days later,  I was offered a rate of 45.00/hr as a per diem nurse.  The nursing supervisor who interviewed me sent this from HR regarding my pay rate  "You can offer 45.00/hr to Nurse B. for the RN, Surgery Center Per Diem position. I accepted.

After I accepted, I went to visit the facility to meet the staff and had a in person  interview with the same nursing supervisor. During this time the GI nursing supervisor mentioned there was an outpatient surgery center across the street. I didn't think much of it, I was just so excited to be given the opportunity to work for this center as a PREOP/PACU nurse and possibly be trained to be in the GI room and do conscious sedation for these procedures.

Now that I look back and after listening to a recent voice message by HR; There were 2 job openings that were listed and now I am unsure which I applied for originally and which position HR is basing my pay rate from. The 2 positions were 1. RN, Surgery Center (PACU/Pre-Op) and 2. RN, Pre-Op/ PACU/GI. 

I met with the GI lab nursing director. And when we spoke over the phone I knew this position was for GI procedures.

My confusion now comes from not knowing if I was being offered a rate for the RN surgery center across the street from the medical center. Did HR make a mistake and based the pay rate based on what a surgery center nurses gets paid? Was there some type of misunderstanding and HR thinks I'm accepting a posting fromt the outpatient surgery center as opposed to the GI lab PREOP/PACU position where the RN would be performing conscious sedation instead of the anesthesiologist? 

Im so confused because I received a voice mail by HR asking that I schedule a time to fill out paperwork for the RN surgery center position that I recently accepted. Would the pay rate differ within these 2 jobs that I listed? IF so, how should I bring this up to their attention. I would imagine since there are no anesthesiologist when performing these GI procedures and the RNs do the conscious sedation, the pay rate would be a little more than that of an outpatient surgery center? 

 

Is it too late to renegotiate pay rate? I still haven't gone in to sign paperwork. thanks everyone!