A new concept for a simple FI assay of Ca(II) employing a replacement reaction of Mg(II)-EDTA by Ca(II) in the present of Eriochrome Black T (EBT) is proposed. The released magnesium reacts with EBT. FI peak due to absorbance change of Mg(II)-EBT is proportional to Ca(II) concentration. Even with such a very simple FI set up, a through-put of 200 injections/h can be achieved. The procedure was applied to assay Ca(II) in mineral supplement samples. The results obtained agreed well with that of the British Pharmacopoeia titration method.
The photometric flow injection technique using the chromatomembrane preconcentration method was developed to determine the trace amounts of formaldehyde in a stream of air. It is based on chromatomembrane absorption of formaldehyde from the air to a microvolume of distilled water followed by the determination of the product formed upon the reaction of formaldehyde with acetylacetone in the carrier stream under the heating at 90°C. The detection limit of formaldehyde decreased proportionally to the time period of absorption and was 10 μg/m3 after 6 minutes at air flow rate 500 ml/min. Temperature dependence of the partition coefficient of formaldehyde in the system of air/water was established and the technique for generating the modeling gas mixtures with the given concentration of the formaldehyde was offered by the passing nitrogen gas through the water solution of formaldehyde.
The novel reagent 3,5-dibromo-4-hydroxyphenylflurone (DBHF) is exploited in order to design a rugged sequential injection procedure for spectrophotometric determination of molybdenum in steels. DBHF interacts with Mo(VI) under acidic conditions yielding a 1:2 reddish complex (λmax = 530 nm). Beer’s law is followed up to 100 mg l-1 Mo (r > 0.998; n = 5). Sensitivity and detection limit were estimated as 0.007 absorbance l mg-1 and 0.05 mg l-1 Mo, respectively, this latter value corresponding to 0.002 % (w/w) in the steel. Measurement frequency is 60 h-1, and reagent consumption is 250 mg DBHF per determination. Results are precise (r.s.d. < 0.5 %) and in agreement with ICP-OES and with certified values of standard reference materials.
This manuscript describes the adaptation of Sequential Injection Analysis (SIA) for the determination of silica in boiler feed water containing phosphates as a routine method being adopted to a Petrochemical industry in Saudi Arabia (Ibn Zahr). The method is based on the reaction of ammonium molybdate with silica to form an intensely yellow complex (ammonium molybdosilicates) which is reduced to blue complex monitored spectrophotometrically at 813 nm. A comparison was made on the effectiveness of triammonium citrate and oxalic acid to eliminate phosphate by rendering it innocuous. Interference study of phosphate on this method was also studied. The sensitivity of the method was enhanced by sandwiching the reagents in the holding coil between two samples of 100 μL volume each and dispensing to the detector at a flow rate of 10 μL/s. The Reagent and samples were stacked into four distinct zones in a 190 cm long holding coil. Another 190 cm long reaction coil was used to ensure more uniform mixing of samples and reagent by radial dispersion. The sensitivity was further enhanced by heating the holding coil at 60 C in a thermostated water bath. To maximize zone penetration while minimizing dilution of the sample the reaction mixture was delayed at the holding coil for 3.53 mins (fixed time kinetic method). The effect of delay time, flow rate, temperature and volume of analyte and reagents on the sensitivity of this method was also studied. The linear working range is 0.5 ppm to 50 ppm. The detection limit is 0.5 ppm with a sample through put of 10 samples/hour. The method was validated by comparison with (APHA) batch spectrophotometric method. The results were found to be in agreement with these methods thus indicating accuracy. The method described has good reproducibility, rapid and suitable for online and in situ determination.
This manuscript describes the adaptation of Sequential Injection Analysis (SIA) for the determination of silica, iron, ammonia, and phosphates, in water as a routine method being used by the quality control unit of a Petrochemical industry in Saudi Arabia (Ibn Zahr). The results obtained from the adopted SIA methods were found to be in agreement with results obtained from batch spectrophotometric APHA Standard methods (American Public Health Association).SIA has the additional advantage of reducing cost by minimizing time, amount of reagent consumed, man power required and improved accuracy of analysis due to computer aided analysis procedure.
A flow injection spectrophotometric method based on furosemide reaction with potassium permanganate is described. A flow system using as carrier a 3.0 x 10-4 mol/l potassium permanganate solution was developed. This system used a 50 cm sample loop and a 100 cm reactor, which was kept at 50°C. The permanganate flow rate was 2.2 ml min-1. The analytical signal was the bleaching of the carrier solution, caused by the reaction between furosemide and potassium permanganate. The detection at 550 nm presented a linear range from 1.0 to 6.0 x 10-4 mol/l, with a calibration equation equals to y = 587.5x + 0.09 (in which r = 0.995, n = 6), the limit of detection (3σ/slope) was 1.1 x 10-5 mol/l. The proposed method was applied to commercial samples from three different brands, as tablets and ampoules. It presented an adequate analytical frequency (40 measurements per hour), with results according to the labeled values.
This review summarizes a highly sensitive potentiometric flow injection method for the determination of various types of oxidative species, where a large transient potential change due to chlorine or bromine, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing chloride or bromide as an intermediate, is utilized. The analysis of trace amount of hydrazine based on the detection of a transient change in potential caused by the reaction of hydrazine with a Ce(IV)–Ce(III) potential buffer is also described.