Capillary enzyme immunoassay with electrochemical detection for determining indole-3-acetic acid in tomato embryos

An amperometric immunoassay for indole-3-acetic acid (IAA) in tomato embryos was developed. The antibody against IAA was covalently bound to the chemically modified inner surface of a 22 μL silica capillary. The competitive binding of methylated IAA and an IAA alkaline phosphatase conjugate for a limited amount of antibody was accomplished in the silica capillary in 20 min. The enzymatic product p-aminophenol, produced from p-aminophenyl phosphate, was determined by flow injection analysis with amperometric detection. A detection limit for IAA of 3 pg/μL was obtained. The average concentration of IAA in mature embryos measured by this method is 0.37 ± 0.03 μg/g. Although isotope dilution GC-SIM-MS can achieve the same detection limit, the sample analysis is not feasible in such a complicated matrix and further purification and separation are required.     

Immunoassay detection in a perfluorocarbon emulsion oxygen therapeutic

The effect of a perfluorocarbon emulsion oxygen therapeutic (PEOT) on detecting theophylline was explored using a commercial EMIT® (enzyme multiplied immunoassay technique) immunoassay. The EMIT technique is based on a colorimetric reaction, the product of which can be measured spectrophotometrically. The intent was to determine whether the presence of PEOT interferes with this detection. We found that the immunoassay yields excellent quantitative data in the therapeutic range (10–20 ppm theophylline) in 2–10% PEOT, but as the amount of PEOT in the sample increases, the accuracy of the detection method decreases.     

The DH Accident and Emergency Department model: a national generic model used locally

The Department of Health (DH) Accident and Emergency (A&E) simulation model was developed by Operational Research analysts within DH to inform the national policy team of significant barriers to the national target, for England, that 98% of all A&E attendances are to be completed (discharged, transferred or admitted) within 4?hours of arrival by December 2004. This paper discusses why the model was developed, the structure of the model, and the impact when used to inform national policy development. The model was then used as a consultancy tool to aid struggling hospital trusts to improve their A&E departments. The paper discusses these experiences with particular reference to the challenges of using a ‘generic’ national model for ‘specific’ local use.     

Resonance Raman spectroscopy of carbon nanotubes: pressure effects on G-mode

We use 488 and 568 nm laser Raman spectroscopy under high pressure to selectively follow evolution of Raman G-mode signals of single-walled carbon nanotubes (SWCNTs) of selected diameters and chiralities ((6, 5) and (6, 4)). The G-mode pressure coefficients of tubes from our previous work are consistent with the thick-wall tube model. Here we report the observation of well-resolved G-minus peaks in the Raman spectrum of SWCNTs in a diamond-anvil cell. The pressure coefficients of these identified tubes in water, however, are unexpected, having the high value of over 9 cm^?1 GPa^?1 for the G-plus and the G-minus, and surprisingly the shift rates of the same tubes in hexane have clearly lower values. We also report an abrupt increase of G-minus peak width at about 4 GPa superposed on a continuous peak broadening with pressure.     

Determination of serum alkaline phosphatase activity by electrochemical detection with flow injection analysis

Summary In this enzyme assay for kinetic measurement of alkaline phosphatase (EC 3.1.3.1) activity in human serum by flow injection analysis with electrochemical detection (FIA-EC), the substrate phenyl phosphate is enzymatically hydrolyzed and the phenol produced is quantified by FIA-EC. The standard curve is linear over the range 40 to 500 U/l, and the predicted linearity is up to 1000 U/l. The CV is 5% over the range of the assay. Correlation with the Sclavo Diagnostics nitrophenyl phosphate spectrophotometric technique gave an r of 0.98. This new technique requires as little as 1 l of serum. The FIA-EC method is not subject to interference by hemolysis, icteria, or lipemia or by electroactive substances such as urate, ascorbate, or acetaminophen. Sensitive measurements free from spectrophotometric interferences are thus possible.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday