Amperometric detection with HPLC

Figure 19.5—Amperometric detection in HPLC and CE. a) Two models of amperometric detection are shown. The working electrode, made of porous graphite with a large surface area, operates under coulometric conditions. The flow of the mobile phase at the working electrode ensures renewal of electroactive species b) expanded diagram of the end of the capillary in CE. Ions exiting the capillary impinge on the working electrode, which is placed on the cathodic side of the instrument. The complete detection cell is not shown.

HPLC method with amperometric detection was applied for detenuination of phenols in sea sediment and some dmg preparation. Peaks of phenol, guaiacol, cresols, hydroquinon and resorcinol were identified on chromatogram of birch tai. The HPLC method with electrochemical detectors was used for detenuination of some drug prepai ation of aminophenol derivate. So p-acetaminophenol (paracetamol) was determined in some drug. 

The quality of this library was examined by monosaccharide compositional analysis. A portion of the trisaccharide library was treated with aqueous trifluroacetic acid at 100°C for 4 h. Analysis of the resulting mixture of monosaccharides on a Dionex HPLC system with a PA1 column and pulsed amperometric detection (PAD) showed that galactose, glucose, and mannose were present in approximately the required ratio. 

Determination of halogenated 2-aminobenzophenones (64a-c), which are metabolites of psychotropic drugs, was performed by HPLC with amperometric detection (GCE vs Ag/AgCl) LOQ 750 ng of metabolite/L of biological fluid (urine or serum), with recovery better than 97%183. 

A study was made of RP-HPLC with constant-potential (1.2 V vs SCE) and pulsed-potential amperometric detection using platinum or gold electrodes, of the derivatives of the common amino acids, obtained from phenyl and methyl isothiocyanates. All the thiohydantoins (98) were oxidized at both electrodes LOD was less than 0.2 pM for lysine and glycine, for 50 pL injection268. 

Because of its advantages (high sensitivity and selectivity, low cost and miniaturization) amperometric detection has been frequently used in flow injection analysis (FIA) and RP-HPLC. However, it has been established that the peak area (detector response) considerably depends on the flow rate. A general approach has been proposed to predict the effect of flow rate on the peak area in FIA and RP-HPLC. The general form of the correlation describing the flow in a parallel plate cell with short rectangular electrodes is... 

Two analytical methods for priority pollutants specified by the USEPA (38) use HPLC separation and fluorescence or electrochemical detection. Method 605, 40 CFR Part 136, determines benzidine and 3,3-dichlorobenzidine by amperometric detection at +0.80 V, versus a silver/silver chloride reference electrode, at a glassy carbon electrode. Separation is achieved with a 1 1 (v/v) mixture of acetonitrile and a pH 4.7 acetate buffer (1 M) under isocratic conditions on an ethyl-bonded reversed-phase column. Lower limits of detection are reported to be 0.05 /xg/L for benzidine and 0.1 /xg/L for 3,3-dichlorobenzidine. Method 610, 40 CFR Part 136, determines 16 PAHs by either GC or HPLC. The HPLC method is required when all 16 PAHs need to be individually determined. The GC method, which uses a packed column, cannot adequately individually resolve all 16 PAHs. The method specifies gradient elution of the PAHs from a reversed-phase analytical column and fluorescence detection with an excitation wavelength of 280 nm and an emission wavelength of 389 nm for all but three PAHs naphthalene, acenaphthylene, and acenaphthene. As a result of weak fluorescence, these three PAHs are detected with greater sensitivity by UV-absorption detection at 254 nm. Thus, the method requires that fluores-... 

HPLC methods were developed for the detection and isolation of the free and Fe(III) complexed forms of the siderophores, pseudobactins, containing a pyrimido[l,2-a]quinoline chromophore (93JPR157 94MI1, 94MI2). A microbial siderophore and its Fe(III) complex were analyzed by means of HPLC with amperometric detection (93MI4). 

Recently, new methods have been developed for very precise quantification of tomatine in tomato plants [13, 48-50]. Thus, Friedman and Levin, used HPLC with a pulse amperometric detection method, for the direct analysis of tomatine in different parts of tomato plants. They found 0.134 % in roots, 0.287 % in stems, 0.567% in calyxes, 0.64% in leaves and 0.745% in flowers [13]. 

Fig. 10 HPLC chromatograms of supercritical fluid extracts of (A) an unfortified wheat sample and (B) a vitamin A-fortified bran-based ready-to-eat breakfast cereal. Column, 5-/rm Altex C8 (octyl) (150 X 4.6-mm ID) mobile phase, acetonitrile/2-propanol/aqueous 25 mM sodium perchlorate (45 45 10), 2.0 ml/min amperometric detection (oxidative mode), glassy carbon electrode, +1.2 V, vs saturated calomel electrode. Peak (1) retinyl palmitate. (Reprinted from Ref. 90, Copyright 1997, with the kind permission of Elsevier Science-NL, Sara Burgerhartstraat 25, 1055 KV Amsterdam, The Netherlands.)...

Linuron,3,4- dichloroaniline Potatoes - Cis HPLC with amperometric detection - [109]... 

The redox chemistry of PQQ has been investigated by a number of research groups. Duine et al. [14,15] performed potentiometric titrations of PQQH2 at several pHs and measured the redox potential of PQQ/PQQH2. Eckert et al. [16,17] compared the redox properties of PQQ with those of o-phenanthroline quinones. Kano et al. [18] performed cyclic voltammetry at acidic pH. Bergethon [19] investigated the amperometric detection of PQQ as a tool for HPLC. From pulse radiolysis experiments, McWhirter and Klapper [20] derived a value of -122 mV (NHE) for Em PQQ/PQQH at pH 7, as compared to the value of - 218 mV calculated from mediator-linked potentiometric titrations [15],... 

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