Fig. 4From: Optimization and validation of a highly sensitive method for determining glyphosate in human urine by solid-phase extraction and liquid chromatography with tandem mass spectrometry: a methodological studyVariations of repeat injection from one vial containing prepared sample (0.67 μg/L of glyphosate). X-axis is the passage of time after the first analysis started, Y-axes are glyphosate peak area (left) or glyphosate/IS peak area ratio (right)Back to article page