HPLC-ECD

Figure 7.4 Dose-response effects of MDMA on extracellular levels of endogenous 5-HT (left panel) and DA (right panel) in rat nucleus accumbens. Male rats undergoing in vivo microdialysis received i.v. injections of 1 and 3 mg/kg MDMA at 0 and 60 min, respectively. Dialysate levels of 5-HT and DA were assayed by HPLC-ECD. Data are mean SEM, expressed as pg/5 pi sample, for N = 6 rats/group. Baseline levels of 5-HT and DA were 0.22 0.03 and 1.44 0.24 pg/5 pi, respectively. Significant with respect to pre-injection control (P < 0.05 Duncan s). See Baumann et al.39 for methods.

Depletions of 5-HT in forebrain regions as measured by HPLC-ECD 10-40 mg/kg, 4 days s.c., twice daily, 2 weeks Commins et al.68... 

UVA exposure of cells gives rise to 8-oxodGuo that was detected by HPLC-ECD. Evidence was provided that mostly O2 is involved in the UVA induced formation of 8-oxodGuo as the result of a predominant type II photosensitization mechanism. ... 

HPLC-based electrochemical detection (HPLC-ECD) is very sensitive for those compounds that can be oxidized or reduced at low voltage potentials. Spectrophotometric-based HPLC techniques (UV absorption, fluorescence) measure a physical property of the molecule. Electrochemical detection, however, measures a compound by actually changing it chemically. The electrochemical detector (ECD) is becoming increasingly important for the determination of very small amounts of phenolics, for it provides enhanced sensitivity and selectivity. It has been applied in the detection of phenolic compounds in beer (28-30), wine (31), beverages (32), and olive oils (33). This procedure involves the separation of sample constituents by liquid chromatography prior to their oxidation at a glassy carbon electrode in a thin-layer electrochemical cell. 

Many published articles on HPLC-ECD refer to the use of one of three voltammetric detectors (amperometric, coulometric, or polarographic). More detailed information on principles and techniques of various electrochemical detection modes can be obtained from the recent book, Coulometric Electrode Array Detectors for HPLC (34). There are also two electrode array detectors, the coulometric electrode array system and the CoulArray detector, currently available. Both detectors offer the qualitative data of PDA and the extreme sensitivity of ECD (34). The... 

Tomato, human prostate Lycopene isomers, a/p-carotene Tomato extraction with acetone-hexane Prostate protein precipitation, extraction with acetone-hexane C-30 MeOH-MTBE- ammonium acetate HPLC/ECD 50 fmol for lycopene 34... 

HPLC-UV 2. Large-volume Inj. HPLC-UV 3. HPLC-CAD 4. HPLC-MS 5. IMS 6. HPLC-ECD 7. HPLC-FLD ... 

Because it is obvious that primarily the parent drug and lipophilic metabolites are found in hair, some lA are rather specific for single substances of a drug class, e.g., RIA for cocaine (Table 2) or 6-MAM. In both cases, the substance with the highest cross reactivity to the antibody is identical with the main compound excreted into hair after drug consumption. Quantitative immunological results correlate with GC/MS. In the case of the DPC-Kit for free morphine (Table 3), there are good correlations with sensitivity and results of GC/MS and/or HPLC-ECD confirmation. ... 

HPLC, high performance (or pressure) liquid chromatography, is particularly suited for small water-soluble molecules and proteins. Most used for analysis of DNA fragments is the reverse phase HPLC. Detection with electrochemical detectors are preferred. There are many different brands of ECD detectors and electrodes/cells. In our laboratory we have found that the ESA Coulochem is working excellent for our purposes and provides excellent sensitivity. Similar experience with other detectors can be found. We have found that for HPLC-ECD analysis of urine, separation is critical due to electrochemically active peaks eluting close to that of 8-oxodG. Ways to detect a false peak is given in details elsewhere [3]. 

The reported values of urinary excretion of 8-oxodG in the literature are in agreement. The reported 8-oxodG urinary excretion rates measured with HPLC-ECD or GC-MS [18] vary from about 100 to 600 pmol kg BW 24 h, excluding the measurements with immunologically based estimations that vary between 1600-4800 pmol kg BW-1 24 h most presumably for the reasons about lack of specificity given above. 

Classic pharmaco-kinetic consideration gives a theoretical steady state plasma concentration equal to production (dosing rate) divided by clearance, i.e. between 0.017 and 0.100 nmol/L. The conventional HPLC-ECD and HPLC-MS/MS methods have sensitivity close to that level. Using up-concentrations and a HPLC-ECD system with a non-commercially available carbon column Bogdanov et al. [19] reported plasma values of 0.014 - 0.070 nmol/L (4- 21 pg/ml), i.e. in close agreement with the theoretical values. 

The CFF-mediated conversion of salicylate to 2,5- and 2,3-DHBA and catechol was used as a semi-quantitative assay to determine the levels of redox-active Fe/Cu, as follows in 100 pi reaction mixture, containing 50 pi CFFs and salicylate and ascorbate (1 mM, each) in KH buffer was incubated for Ih at 37 C. To terminate the incubation, ice-cold TCA (3% final concentration) was added, and the suspensions were centrifuged at 12,000g for 1 min. The supernatant was analyzed for 2,5- and 2,3-DHBA and catechol by HPLC coupled to an electrochemical detector (HPLC-ECD), as previously described [10]. 

Hasler, E, D. Bourquin, R. Brenneisen, T. Baer, and E X. Vollenweider. 1997. Determination of psilocin and 4-hydroxyindole-3-acetic acid in plasma hy HPLC-ECD and pharmacokinetic profiles of oral and intravenous psilocybin in man. Pharmaceutica Acta Helvetiae 72 175-84. 

Drinking water and groundwater Separation of mercury species in sample on HPLC column using buffered methanol as eluent HPLC/ECD 1.8 g/L 77-104 Evans and McKee 1988... 

---