Rapid detection of l-glutamic acid using a series-electrode piezoelectric quartz crystal sensor

Two methods are described for the determination of l-glutamic acid using a series-electrode piezoelectric quartz crystal sensor. The effect of formaldehyde solution on the frequency shift is discussed. For the calibration curve method, in formaldehyde medium, the detection limit is 3.8 · 10 −5 M, the recovery is 100.4%, the relative standard deviation is 3.32% (n = 5) and the frequency shift is linear up to 8 · 10−4 M; in aqueous medium, the above values are 2.0 · 10−5 M, 99.1%, 3.01% (n = 6) and 1.1 · 10−3 M, respectively. The frequencimetric titration method is also described and the lowest titratable concentration of l-glutamic acid is 7.0 · 10 −5 M. The detecting results for tablet samples show good agreement with the values determined by the pharmaceutical method.