In this review, the flow analyses reported up to the present using the unique functions (e.g., spectroscopic characteristics, complex formation, photo-decomposition reaction, etc.) of porphyrin compound, were summarized and discussed. Moreover, the catalytic reaction and the autocatalytic reaction which has “infinite” (in other words, it is “constant”) sensitivity, were theoretically explained from view point of the usefulness in the field of analytical chemistry. Based on these facts, the length-detection flow analytical system and its application to micro-device were especially described as a new flow method.
In this paper, we summarized flow injection analysis systems for determination of urea in the alcohol beverages. A lot of FIA methods based on the color-forming reactions without enzyme and detection of the hydrolysate of urea with urease were reported. Most of these methods were categorized as spectrophotometry (such as absorptiometry, fluorometry, luminometry), calorimetry, potentiometry and amperometry in combination with gas diffusion devices. The systems for determination of urea in serum, urine, and so on were also described.
Advantages of programmable flow for optimization and automation of assay protocols in the lab-on-valve format are summarized and demonstrated in two laboratory experiments designed for a teaching or research laboratory as a tool for dissemination of this powerful analytical technique.
A simple, rapid and sensitive kinetic spectrophotometric method for the determination of trace amounts of iron (II) was developed based on its catalytic effect on the oxidation of variamine blue with hydrogen peroxide in the presence of triethanolamine as activator to form a deep violet blue colored species with an absorption maximum at 560 nm. The reaction was monitored using FIA and batch methods. The calibration graphs were linear in the concentration range 5.4-130 and 3.4-40 ng of iron for the FIA and batch, respectively. The FIA technique showed good average recoveries with lower detection limit compared with the batch technique. The method was highly selective to iron (the tolerance limit for 20 ions was listed) and successfully applied for iron determination in pharmaceutical preparation, polluted air and tap water with average recoveries agreed with the official method.
Flow injection (FI) spectrophotometric method for iron (III) determination using Disodium-1-nitroso-2-naphthol-3,6-disulphonate (nitroso-R salt) is performed. It is based on the measurement of Fe(III)-nitroso-R salt complex at 720 nm formed by the reaction between Fe(III) and nitroso-R salt in an acetate buffer solution pH 5. The FI parameters that affect the signal response have been optimized in order to get the better sensitivity and low standard deviation. The linear range for determination of iron in water samples was over the range of 0.05- 4.0 μg mL-1 with a correlation coefficient (r2) of 0.9997. The limit of detection (3σ) was 0.011 μg mL-1 with sample throughput of 110 samples h-1. The repeatability measured from three standard Fe (III) (0.1, 2.0 and 4.0 μg mL-1) were 1.42, 1.29 and 1.01% (n = 11) respectively. The proposed method was successfully applied to determination of Fe (III) in water samples and found to be in good agreement with those obtained by flame atomic absorption spectrophotometric (FAAS) method.
An automated iodometric assay, a potential analytical tool for general applications in various quality control and analytical laboratories, was extended for the determination of iodine reactive components in pharmaceutical formulations such as benzylpenicillin. The method was developed based on flow injection analysis (FIA) that utilizes a triiodide (I3-)-selective membrane detector. The principle of the system for penicillin determination was based on the standard iodometric assay, where the penicilloic acid that was produced from the enzymatic hydrolysis reaction was merged and reacted with I3- solutions in the flow system. The excess I3- was then detected by a flow-through potentiometric I3- detector. Under the adopted conditions, a sampling frequency of 75 samples per hour was obtained. The response was linear from 0.05 to 1.0 mmol L-1 and the limit of detection was 0.0025 mmol L-1. Good reproducibility (RSD ±3.80 (n = 4)) was obtained for the determination of 0.5 mmol L-1 benzylpenicillin. Good agreement was obtained between the proposed method and the manufacturer’s claim values when applied to the determination of benzylpenicillin in pharmaceutical formulations.