Handling multiple HttpSession across multiple browsers on same system

With below code, trying to handle session. This code is working fine when tried to do transaction with multiple tab that means it is allowing only one tab to do transation. If other tab in same browser is opened then Error.jsp is shown. But this code is not able to allow to do transaction when other instance of browser is opened. Brower maintains cache hence same sessionId is provided.

if(session!=null && url.equalsIgnoreCase("/abc/doMEPayRequest")){
                //check if session is not new and entry request then throw error
                    System.out.println("Session id: "+httpReq.getSession().getId());

                    ((HttpServletResponse) response).sendRedirect("errDuplicateSession.jsp");
            }



if(session == null){
                //if session is new & check if entry request
                if(url.contains("abc")){
                    //create new session
                    session=httpReq.getSession(false); 
                }else{
                    //else throw some session related error
                    System.out.println("session expired error");
                }

            }

What can be done so that transaction can be done if new instance of browser is opened.

Any suggestion will be appreciated