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A very simple, automatic, fast method for the photometric determination of bromhexine hydrochloride based on the application of kinetic methodology and the stopped-flow mixing technique to the coupling reaction between the diazotized bromhexine derivative and N-(1-naphthyl)ethylenediamine is proposed. The high initial rate of this reaction allows analytical measurements to be made within only 0.5–1 s, which makes the method applicable to automatic routine analyses. The calibration graph is linear over the range 1.5–65.0 g mL-1 and the precision (as %RSD) is less than 2%. The presence of antibiotics such as penicillins and cephalosporins in a 100-fold excess has no effect on the analyte determination. The proposed method was satisfactorily used for direct analysis of pharmaceutical formulations containing these antibiotics.

Kinetic methodology was for the first time used to develop a simple photometric method for the determination for ephedrine and phenylephrine using the stopped-flow mixing technique. The method involves oxidation of these compounds and kinetic monitoring of the reactions of the aldehydes formed with 2-methylbenzothiazoline-2-one hydrazone in the presence of iron (III) chloride to give the corresponding coloured formazans. Ephedrine and phenylephrine can be determined simultaneously by applying the proportional-equation method to the reaction rate and absorbance amplitude of the kinetic curves obtained for each analyte. The calibration graph was linear over the range 0.7–70.0 µg mL-1 ephedrine and 1.2–70.0 µg mL-1 phenylephrine. The proposed method was applied to the determination of ephedrine in pharmaceutical samples with a mean recovery of 103.2%. Synthetic mixtures of ephedrine and phenylephrine in ratios between 3:1 and 1:5 were satisfactorily resolved.

A fast and simple fluorimetric method is described for the simultaneous determination of ampicillin and tetracycline in milk by combining the stopped-flow mixing technique with a T-format spectrofluorimeter. Ampicillin determination is based on its hydrolysis with penicillinase and reaction with mercuric chloride, while the intramolecular energy transfer from tetracycline to europium ions in the presence of thenoyltrifluoracetone is used for tetracycline determination. The similar excitation wavelengths of both systems and the separation between the corresponding emission wavelengths allow the direct determination of both analytes by measuring simultaneously the initial rate of the ampicillin system and the equilibrium signal of the tetracycline system. The relative standard deviations were lower than 2%. The proposed method was applied to the determination of these antibiotics in different milk samples with a recovery of 95.0–103.3% for ampicillin and 93.3–103.3% for tetracycline.

Abstract: We describe the MRI findings in two patients with giant hypothalamic hamartomas with cystic areas. Cystic change within hypothalamic hamartomas is rarely reported in the literature.