Hi,

I'm having some trouble with calibration curves for some of the anions (especially bromides). There are 6 calibration levels for fluorides, chlorides, nitrates, sulfates and phosphates: 0.1 mg/l, 1 mg/l, 2.5 mg/l, 5 mg/l, 7.5 mg/l and mg/l. Nitrites and bromides have one more: 0.05 mg/l. Fluorides always seem to have the best linearity (>0.999) while bromides always seem to be problematic. Namely, their linearity meets the criteria (>0.995) but concentractions below 5 mg/l are below the curve and when I spike at those concentrations recoveries are too small (around 70%, requirements are 80-110%), also two highest concentrations are above the curve. So I'm not sure what exactly is the problem, are lower levels too low or higher levels too high. I tried splitting the calibration in two (for lower and higher levels) it kinda worked for lower one but there is still issue with the higher one so I suppose it's 7.5 mg/l and 10 mg/l that are too big. I thought maybe there is cross-contamination but blanks afterwards are fine. If anyone has an idea how to improve this I would be very grateful.