Tandem measurements of iron and creatinine by cross injection analysis with application to urine from thalassemic patients.

This work presents development of a method for the dual determination of Fe(III) and creatinine using cross injection analysis (CIA). Two CIA platforms connected in series accommodated sample and reagents plugs aspirated via y-direction channels while water was pumped through the x-direction channel toward a flow-through cell of a diode array UV-vis. detector. Iron was detected from the colorimetric reaction between Fe(II) and 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-(3-sulfopropyl)amino) aniline (5-Br-PSAA), with prior reduction of Fe(III) to Fe(II) by ascorbic acid. The Jaffe's reaction was employed for the detection of creatinine. Under the optimal conditions, good linearity ranges were achieved for iron in the range 0.5 to 7 mg L(-1) and creatinine in the range 50 to 800 mg L(-1). The CIA system was applied to spot urine samples from thalassemic patients undergoing iron chelation therapy, and was successfully validated with ICP-OES and batchwise Jaffe's method. Normalization of urinary iron excretion with creatinine is useful for correcting the iron concentration between urine samples due to variation of the collected urine volume.

A membraneless gas diffusion unit: design and its application to determination of ethanol in liquors by spectrophotometric flow injection.

This work presents new design of a gas diffusion unit, called 'membraneless gas diffusion (MGD) unit', which, unlike a conventional gas diffusion (GD) unit, allows selective detection of volatile compounds to be made without the need of a hydrophobic membrane. A flow injection method was developed employing the MGD unit to determine ethanol in alcoholic drinks based on the reduction of dichromate by ethanol vapor. Results clearly demonstrated that the MGD unit was suitable for determination of ethanol in beer, wine and distilled liquors. Detection limit (3S/N) of MGD unit was lower than the GD unit (GD: 0.68%, v/v; MGD: 0.27%, v/v). The MGD design makes the system more sensitive as mass transfer is more efficient than that of GD and thus, MGD can perfectly replace membrane-based designs.

Determination of iodide by detection of iodine using gas-diffusion flow injection and chemiluminescence.

This work describes development of a flow injection (FI) system for determination of iodide, based on the chemiluminescence (CL) reaction between iodine and luminol. Iodide in the sample zone is oxidized to iodine. Employment of a gas-diffusion (GD) unit allows for selective detection of the generated CL (425nm). Preliminary results showed for concentrations of less than 2mgL(-1), that signals were irreproducible and that the calibration was not linear. In order to solve these problems, a method of 'membrane conditioning' was investigated, in which iodide stream was continuously merged with oxidant to generate I(2) that conditioned the GD membrane and tubing. This minimized surface interaction between the active surface and the I(2) generated from the samples, thus improving both precision and sensitivity. By employing membrane conditioning, it has been possible to reliably detect concentrations down to 0.1mgL(-1). At the optimized condition, an excellent linear calibration (r(2) = 0.999) was obtained from 0.1 to 1.0mgL(-1). The method was successfully applied to determine iodide in some pharmaceutical products such as potassium iodide tablets and a liquid patent medicine. However, for vitamin tablets, ascorbic acid was found to interfere seriously by causing a negative signal.

Simple flow injection system for colorimetric determination of iodate in iodized salt.

This work presents a flow injection (FI) system that was developed for determination of iodate. The system utilizes the oxidation of iodide by the analyte to iodine, which subsequently forms tri-iodide. In the presence of starch, the blue I(3)(-)-starch complex is developed within the sample zone and can be colorimetrically detected at 590 nm. Optimization was carried out to make the system suitable for quantitating iodate added to table salts. To prevent accumulation of the blue complex residue on walls of tubing and the flow cell, a port was placed in the system for injection of 10(-3) M thiosulfate plug (100 mul). An injection of this cleaning solution after each sample injection is recommended to avoid positive baseline shift. By means of the paired t-test, the amounts of iodine (mg I kg(-1)) were statistically compared with the results determined by titration and by iodide ion selective electrode. No significant disagreement at 95% confidence was observed. The proposed system is very simple, uses common chemicals and provides rapid analysis (65 injections per h) with high precision (R.S.D.=0.66%, n=10). A detection limit of 2 mg I kg(-1) salt can be achieved.