Fig 1.
Representative chromatogram from the hitachi Amino Acid Analyzer method.
A. Taurine elutes at 1.6 min. 2-aminoethyl dihydrogen phosphate elutes at 2.1 min. Dark line is a representative Alzheimer’s patient sample. Grey line shows the absence of 2-aminoethyl dihydrogen phosphate in a control sample which is considered not detectable. Quantification was achieved by measuring the area under the curve in relation to known standard reference concentrations. B. Representative chromatogram from the tandem mass spectrometer method with 2-aminoethyl dihydrogen phosphate eluting at 2.05 min. The dotted line is an Alzheimer’s patient sample with an injection volume of 6 μl. The overlaid solid line represents the same sample spiked with a 2-aminoethyl dihydrogen phosphate standard. The identity of the peak at 2.1 min is unknown, however, this peak does not change as a result of the addition of 2-aminoethyl dihydrogen phosphate standard which confirms the identity of the peak at 2.05 min.
Fig 2.
Scatter plot of patient age versus arcsin ratio of 2-aminoethyl dihydrogen phosphate / taurine).
Squares are healthy controls (n = 25) and circles are Alzheimer’s patients (n = 25). The arcsin ratio does not correlate with age, however, the incidence of Alzheimer’s disease does increase with patient age.
Table 1.
Concentration (μmoles/L) of 2-aminoethyl dihydrogen phosphate and taurine in blood plasma of controls and Alzheimer’s patients calculated using the Amino Acid Analyzer method.
The lower limit of detection (LOD) for 2-aminoethyl dihydrogen phosphate using this method was 0.9 μmol/L. The lower limit of quantification (LOQ) for taurine was 10.2 μmol/L. This represents a detectable peak but one below the ability of the method to accurately quantify. When 2-aminoethyl dihydrogen phosphate was not-detectable (ND), ratios were assigned a 0.0 value.