Electrochemical Study Of The Organic Acid Drugs

The studies on polarographic catalytic hydrogen wave of ibuprofen and the reduction wave of coumarin in the presence of surfactants are firstly reported. The mechanisms of the waves and the enhancement effects of surfactants are also discussed. Based on this enhanced polarographic waves, a new method, to determine ibuprofen in tablets and coumarin in Angeleica dahurica Benth et Hook, with the help of 2.5th-order derivative polarography are established. In comparison to other polarography, the proposed methods show higher sensitivity and accuracy. In addition, three medicines, furazolidone, orotic acid and folic acid, have been respectively detected by neopolarography. Satisfactory results are obtained in the determination of samples.This paper includes six chapters. Chapter 1Part oneThe achievements on the electrochemical study of vitamins of folic and orotic acid are reviewed with 62 references, to date 2001. Part twoThe achievements on the electrochemical study of coumarin and furazolidone are reviewed with 68 references, to date 1997. Chapter 2A method for the determination of folic acid is proposed by using 2.5th-order derivative polarography, and the mechanism of the electrode process is discussed. In HAc-NaAc (pH 5.6) buffer solution, folic acid yields a reduction wave at the peak potential of-0.70 V (vs. SCE). The peak current of the reduction wave is rectilinear to folic acid concentration in the range of 2.0x10"8 ~ 4.0x10'6 mol/L (r=0.9988, n= 8). The detection limit is 4.0x10"9 mol/L. The relative standard deviation of 2.5th-order derivative peak current is 1.2% by performing 13 parallel measurements for 4.0x10"7 mol/L folic acid. The proposed method is applied to the determination of folic acid in tablets. Chapter 3A 2.5th-order derivative polarographic method for the determination of oroticacid is proposed, and the mechanism of the electrode process is discussed. In 0.8 mol/L HC1 supporting electrolyte, orotic acid yields a sensitive reduction wave at the peak potential of -0.77 V (vs. SCE). The peak current of the reduction wave is rectilinear to orotic acid concentration in the range of 4.0 X 10"8 ~ 4.0 X 10"5 mol/L (r =0.9996, n=9). The limit of detection is 1.0 X10"8 mol/L. The relative standard deviation of 2.5th-order derivative peak current was 1.8% by performing 13 independent measurements for 4.0 X10"7 mol/L orotic acid. The proposed method has been applied to the direct determination of orotic acid in cow's milk. Chapter 4Using 2.5th~order derivative polarography, a new method for the determination of coumarin is proposed, and the mechanisms of electrode process and the enhancements effect of the cationic surfactants are discussed. In KH2PO4-Na2HPO4 (pH 6.81) buffer solution containing 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride, coumarin yields a reduction wave at the peak potential of-1.68 V (vs. SCE). The peak current of the reduction wave is rectilinear to coumarin concentration in the range of 4.0 x 10~7 ~ 6.0xlO"5 mol/L (r=0.9997, n = 10). A relative standard deviation of 1.5% is obtained by performing 13 parallel determinations of 8.0 x 10-6 mol/L coumarin. The proposed method has been applied to the determination of coumarin in Angeleica dahurica Benth et Hook, a traditional Chinese herbal medicine. Chapter 5In Britten-Robinson (pH 6.8) buffer solution, furazolidone yields two reduction waves. The first wave at -0.30 V (vs. SCE) is due to the six-electron reduction of -NOa to -NH2, while the second wave at -1.20 V is due to the four-electron reduction of -CHN2 to -CH2NH2. The first wave, controlled by absorption, gives rise to a well-defined 2.5th-order derivative polarographic reduction peak at dropping mercury electrodes, and its peak current is rectilinear to furazolidone concentration in the range of 2.0xlO'7 ~ 2.0x10-5 mol/L (r=0.9969, n=7). The relative standard deviation of 2.5th-order derivative peak current is 1.5% by performing 13 parallel measurements of 4.0 x 10'6 mol/L furazolidone. The proposed method is applied to the determinati...