Flow-injection determination of thyroxine using immobilized enzyme with tris(2,2'-bipyridyl)ruthenium(III) chemiluminescence detection

A flow-injection method is reported for the determination of thyroxine based on its enhancement effect on the tris(2,2'-bipyridyl)ruthenium(III) chemiluminescence reaction in the presence of NADH using immobilized alcohol dehydrogenase purified from baker yeast. The limit of detection (3 sigma blank) was 5.0 x 10(-8) M with a sample throughput of 80 h(-1). The calibration graph was linear over the range 0.5 - 10 x 10(-7) M (r2= 0.9988) with the relative standard deviation in the range 1.4 - 3.5% (n = 4). The effect of common excipients used in pharmaceutical preparations, some organic compounds and metal ions was studied. The method was applied to pharmaceutical thyroxine tablets, and the obtained results were not significantly different from the amount quoted.

Flow-injection determination of carbaryl and carbofuran based on KMnO4–Na2SO3 chemiluminescence detection

A flow-injection method is described for the determination of carbaryl and carbofuran. It was found that a strong chemiluminescence (CL) signal was generated when these pesticides were mixed with Na(2)SO(3) and KMnO(4) in acidic medium. Under the optimum experimental conditions, the enhanced CL intensity was linear, with the concentrations in the range 0.1-2.0 microg/mL (r(2) = 0.9996 and 0.9993, n = 6) with relative standard deviation (n = 4) in the range 1.0-2.3%. The limits of detection (3sigma blank) were 10 and 50 ng/mL, respectively, with a sample throughput of 180/h. The proposed method was applied to determine carbaryl and carbofuran in freshwaters with satisfactory results. Most metal and non-metal ions and some pesticides, such as carbophenothion and aldicarb, do not interfere with the determination. Dinoseb, diazinon and malathion calibration graphs (in the range 0.2-2.0 microg/mL, r(2) = 0.9966-0.9988, n = 6) were also established with relative standard deviations (n = 4) in the range 1.2-2.0% with limits of detection (3sigma blank) in the range 100-300 ng/mL.

Determination of thyroxine in pharmaceuticals using flow injection with luminol chemiluminescence inhibition detection

A simple flow injection method is reported for the determination of thyroxine, based on its inhibition effect on luminol-iron(II) chemiluminescence in alkaline medium in the presence of molecular oxygen. The detection limits (2s) for d- and l-thyroxine are 0.08 and 0.1 mg/L, respectively, with a sample throughput of 100/h. The calibration data for d- and l-thyroxine over the range 0.2-1.0 mg/L gives correlation coefficients (r(2)) of 0.9915 and 0.984 with relative standard deviations (RSD; n = 4) in the range 1.2-2.8%. The effects of some organic compounds was studied on luminol-iron(II) CL system for thyroxine determination. The method was applied to pharmaceutical thyroxine tablets and the results obtained (in the range 50.5 +/- 2.0-51.6 +/- 1.2 microg l-thyroxine/tablet) were in reasonable agreement with the value quoted.

Determination of iodide using flow injection with acidic potassium permanganate chemiluminescence detection

A simple and rapid flow-injection method is described for the determination of iodide, based on potassium permanganate chemiluminescence detection via oxidation of formaldehyde in aqueous hydrochloric acid. The calibration graph was linear over the range 1.0-12 x 10(-6) mol/L (r2 = 0.9955) with relative standard deviations (n = 4) in the range 1.0-3.5%. The detection limit (3sigma) was 1.0 x 10(-7) mol/L, with sample throughput of 120/h. The effect of interfering cations [Ca(II), Mg(II), Ni(II), Fe(II), Fe(III) and Pb(II)] and anions (Cl-, SO4(2-), PO4(3-), NO3-, NO2-, F- and SO3(2-)) were studied. The method was applied to iodized salt samples and the results obtained in the range 0.03 +/- 0.005 - 0.10 +/- 0.006 mg I/g were in reasonable agreement with the amount labelled. The method was statistically compared with the results obtained by titration; no significant disagreement at 95% confidence was observed.

Flow injection chemiluminescent assays for glycerol and triglycerides using a co-immobilized enzyme reactor

A flow injection method for the determination of glycerol using a co-immobilized enzyme reactor containing glycerokinase and glycerol-3-phosphate oxidase is described. The hydrogen peroxide produced is monitored by using a luminol chemiluminescence reaction in the presence of catalyst such as Co(II). The detection limit (2.5 x blank noise) for glycerol is 7 x 10(-3) mmol/L with a sample throughput of 40/h. The calibration graph is linear over the range studied (0.2-1.0 mmol/L) with relative standard deviation 1.2-2.4%. The method is applied to the determination of glycerol in blood serum produced off-line from triglycerides using lipase isolated from bovine pancreas.