1998-11. Gradient Background Peaks — A Case Study November 1, 1998 When peaks appear in a blank gradient, isolating the problem source can be a challenge LCGC 16(11) 992-996 (1998) Michael D. Nelson and John W. Dolan Tags: blank gradients, case study, dirty glassware, equilibration, ghost peaks, pH meter, phosphate contamination, water source.