Development of a voltammetric assay, using screen-printed electrodes, for clonazepam and its application to beverage and serum samples. Talanta, 147. pp. 510-515. ISSN 0039-9140 Available from: http://eprints.uwe.ac.uk/27297We recommend you cite the published version. The publisher's URL is: http://dx.doi.org/10.1016/j.talanta.2015.10.032Refereed: Yes (no note) Disclaimer UWE has obtained warranties from all depositors as to their title in the material deposited and as to their right to deposit such material. UWE makes no representation or warranties of commercial utility, title, or fitness for a particular purpose or any other warranty, express or implied in respect of any material deposited. UWE makes no representation that the use of the materials will not infringe any patent, copyright, trademark or other property or proprietary rights. UWE accepts no liability for any infringement of intellectual property rights in any material deposited but will remove such material from public view pending investigation in the event of an allegation of any such infringement. AbstractThis paper describes the development of an electrochemical assay based on screen-printed carbon sensors for the determination of clonazepam in serum and in wine. The cyclic voltammetric behaviour of the drug was investigated and the effects of pH and scan rate on the peak current and peak potential determined. Two reduction peaks were recorded on the initial negative going scan, which were considered to result from the 2e -, 2H + reduction of the 4,5-azomethine and from the 4e -, 4H + reduction of the 7-NO 2 to a hydroxylamine. On the return positive going scan an oxidation peak was seen, which was considered to result from the 2e -, 2H + oxidation (O1) of the hydroxylamine to the corresponding nitroso species.At pH 11 the solution of clonazepam was found to turn from clear to yellow in colour and the voltammetric signal of the O1 oxidation process was found to be adsorptive in nature, this was exploited in the development of an adsorptive stripping voltammetric assay.Experimental conditions were then optimised for the differential pulse adsorptive voltammetric measurement of clonazepam in wine and serum samples. It was shown that these analyses could be performed on only 100 µL of sample which was deposited on the sensor surface. Mean recoveries of 79.53 % (%CV = 9.88 %) and 88.22 % (%CV = 14.1 %) 2 were calculated for wine fortified with 3.16 µg/mL and serum fortified with 12.6 µg/mL respectively.

Two-site or sandwich immunoradiometric assays (IRMAs) offer theoretical advantages over competitive immunoassay systems for sensitivity, precision, and rapid incubation. The practical realization of these advantages has been limited by the phenomenon of the "high-dose hook effect," such that high concentrations of an analyte give similar responses to those of much lower concentrations. We have developed a kinetic rate monitoring IRMA system for use with the Kineti-Count 48TM, an automated kinetic radioassay analyzer, which eliminates "hook-effect" interference, thereby permitting optimal assay design for increasing sensitivity and reducing incubation time. Practical illustration of these concepts is demonstrated by a 10-min, automated, quantitative assay we developed for human choriogonadotropin. The assay can detect as little as 1.2 int. units/L and kinetically screens for the hook effect. Kinetic rate analysis of the two-site IRMA and potentially of nonisotopic counterparts permits improvements in the speed and reliability of these immunoassays.