[Turbidimetric determination of tenoxicam using molybdophosphoric acid]. / Determinarea turbididimetrica a tenoxicamului folosind ca reactiv solutia de acid fosfomolibdenic.

UNLABELLED: A turbidimetric method was developed for tenoxicam quantification using the complexing reaction with molybdophosphoric acid in hydrochloric acid medium; the complex has a maximum of absorbance at 369 nm. MATERIALS AND METHOD: The practical working conditions were established. In the 2.5 division by 15.0 microg/mL concentration range of tenoxicam in 1N hydrochloric acid, were added 1 mL of 1% molybdophosphoric acid solution and 1 mL of 0.1% sodium lauryl sulphate. The stability of product was evaluated over 60 minutes. The developed method was validated. RESULTS: The method showed a good linearity in the range of 2.5 division by 15.0 microg/mL (the correlation coefficient r = 0.9996). The detection limit (LD) was 0.44 microg/mL and the quantification limit (LQ) was 1.47 microg/mL. There were established the precision (RSD = 1.82%) and the accuracy (mean recovery is 100.79% in 97.55 division by BY 04.41% the range). CONCLUSIONS: The experimental results demonstrated a good sensibility. The specific absorptivity for this method is A(1cm,369nm)(1%) higher than tenoxicam in hydrochloric acid medium A(1cm,354nm)(1%).

[Construction and characterization of a selective membrane electrode for tenoxicam determination]. / Constructia si caracterizarea electrodului membrana selectiv pentru determinarea tenoxicamului.

UNLABELLED: This paper describes the construction and characterization of a selective membrane electrode which can be used for determination of tenoxicam. MATERIAL AND METHOD: The electroactive compound is a precipitate obtained in 2 N hydrocloric acid solution containing tenoxicam in which a solution of iodine is added. The membrane is made by mixing the electroactive compound with polyethylene using tetrahydrofurane as solvent. The solution is evaporated in order to obtain a thick membrane, which is attached at one end of a PVC tube and is fixed with the same polymeric solution. In this tube an internal Ag/AgCl reference electrode is inserted. The assembly is filled with an internal solution containing tenoxicam. The electrode was characterized (electrode slope, selectivity, optimal pH range, response time, life time). The developed method was validated. RESULTS: The method showed a good liniarity in the range of 10(-6)-10(-1) M (the correlation coefficient r = 0.9999). The detection limit (LD) was 7.347 x 10(-7) M and the quantification limit (LQ) was 1.017 x 10(-6) M. There were established the precision (RSD = 1.79%) and the accuracy (mean recovery is 100.17%) CONCLUSIONS: The experimental results demonstrated a good sensibility.

[Construction and characterisation of a selective membrane electrode for the assay of lisinopril]. / Constructia si caracterizarea unui electrod membrana selectiv pentru determinarea lisinoprilului.

UNLABELLED: In order to analyze lisinopril using a selective membrane electrode, the electro-active compound was obtained and included in the selective membrane. The new analysis method was developed and validated. MATERIAL AND METHOD: The electro-active compound was obtained through the precipitation of lisinopril in acidic media using silicowolframic acid solution. The membrane was obtained by mixing the electro-active compound with polyvinylchloride using tetrahydrofurane as solvent. The solution was evaporated in order to obtain a thick membrane, which was then attached at one end of a polyvinylchloride tube. The internal Ag/AgCl reference electrode was inserted in that tube. The assembly was filled with a lisinopril internal solution. The electrode was characterized by establishing the following characteristics: electrode slope, selectivity, optimal pH range, response time and life-time period. The developed method was validated. RESULTS: The method showed a good linearity in the range of 10(-7) and 10(-2)M (the correlation coefficient r = 0.9991). The detection limit (LD) was 8,66 x 10(-8)M and the quantification limit (LQ) was 7,8 x 10(-7)M. There were established the precision (RSD = 1.73%) and the accuracy (mean recovery was 99.92%) CONCLUSIONS: The experimental results demonstrated a good sensibility.

[Spectrophotometric determination of piroxicam using ferric ferricyanide as reagent]. / Determinarea spectrofotometrica în vizibil a piroxicamului folosind ca reactiv fericianura ferica.

UNLABELLED: For the piroxicam determination (nonsteroidal antiinflammatory drug-NSAID) it was developed a spectrophotometric method, based on the reduction of ferric ferricyanide into ferro-ferricyanide (Prussian Blue), with maximum of absorbance at 760 nm. MATERIAL AND METHOD: The practical working conditions were established. In the 0.2 divided by 2.0 microg/mL range of piroxicam concentration, were used the 2 mL of ferric ferricyanide 1 mL of 2N hydrocloric acid. To delay the flocculation of Prussian Blue it was to add a 1 mL solution of sodium lauryl sulfate 1%. After 15 minutes read the absorbance at 760 nm. The developed method was validated. RESULTS: The method showed a good linearity in the range of 0.2 divided by 2.0 microg/mL (the correlation coefficient r = 0.9995). The detection limit (LD) was 0.056 microg/mL and the quantification limit (LQ) was 0.18 microg/mL. There were established the system precision (RSD = 0.25%), the precison (RSD = 1.91%) and the accuracy-recovery in the range 98.21 divided by 104.92% with a mean recovery of 100.91%. CONCLUSION: The experimental results demonstrated a good sensibility. The specific absorptivity for this method is A(1 cm, 760 nm)(1%) = 4374 much higher than piroxicam in UV (A(1 cm, 330 nm)(1%) = 296)

[Ultraviolet spectrophotometric determination of tenoxicam using iodine solution as reagent]. / Determinarea spectrofotometrica in ultraviolet a tenoxicamului folosind ca reactiv solutia de iod.

UNLABELLED: For the tenoxicam determination (Nonsteroidal Antiinflammatory Drug - NSAID) it was developed a spectrophotometric method, after the coupling reaction of tenoxicam with iodine, in methanolic medium, with maximum of absorbance at 289 nm. MATERIALS AND METHOD: The practical working conditions were established. In the 0.5 divided by 5.0 microg/mL range of tenoxicam concentration, were used 5 x 10(-3) M iodine solution and 0.5 N hydrocloric acid. The stability of product were evaluated for 30 minutes. The developed method was validated. RESULTS: The method showed a good linearity in the range of 0.5 divided 5.0 microg/mL (the correlation coefficient r = 0.9995). The detection limit (LD) was 0.14 microg/mL and the quantification limit (LQ) was 0.49 microg/mL. There were established the precison (RSD = 1.90%) and the accuracy-recovery in the range 97.27 divided by 102.56% with a mean recovery of 99.49%. CONCLUSIONS: The experimental results demonstrated a good sensibility. The specific absorptivity for this method is A1%(1 cm,289 nm) = 1770 much higher than tenoxicam in methanol (A1%(1 cm,360 nm) = 323).

[Nimesulide spectrophotometric determination in the visible region]. / Determinarea spectrofotometrica in vizibil a nimesulidului.

UNLABELLED: Nimesulide is a nonsteroidal antiinflammatory (NSAID) drug whose mechanism of action is characterized by selective inhibition of cyclooxygenase-2. Nimesulide have analgesic and antipyretic properties. MATERIALS AND METHOD: For nimesulide analysis we developed a spectrophotometric method based on reduction of the nitro group of nimesulide by zinc and hydrochloric acid followed by diazotization and coupling with thymol (5-methyl-2-(1-methylethyl) phenol) in ammonia medium to form a stable chromophore which absorbs at 476 nm. There were established the practical working conditions. The developed method was validated. RESULTS: The method showed a good linearity in the range of 5 - 40 microg / sample (the correlation coefficient r = 0.9990). The detection limit (LD) was 0.99 microg/sample and the quantification limit (LQ) was 3.32 microg/sample. There were established the system precision (RSD = 1.70%), the precision (RSD < 2.2%) and the accuracy (recovery in the range 97.66 - 102.69% with a mean recovery of 99.81%) of the method. CONCLUSIONS: A new method for nimesulide spectrophotometric quantification in visible has been developed.