Relative hydrogen index as a fast method for the simultaneous determination of physicochemical properties of petroleum fractions

Fuel ◽  
2017 ◽  
Vol 210 ◽  
pp. 41-48 ◽  
Author(s):  
Lúcio L. Barbosa ◽  
Luciana F. Montes ◽  
Flávio V.C. Kock ◽  
Vinícius G. Morgan ◽  
Andre Souza ◽  
...  
Talanta ◽  
2018 ◽  
Vol 176 ◽  
pp. 102-107 ◽  
Author(s):  
María Jiménez-Moreno ◽  
Miguel Ángel Lominchar ◽  
María José Sierra ◽  
Rocío Millán ◽  
Rosa Carmen Rodríguez Martín-Doimeadios

2003 ◽  
Vol 86 (2) ◽  
pp. 241-245 ◽  
Author(s):  
M Inés Toral ◽  
Andrés Tassara ◽  
César Soto ◽  
Pablo Richter

Abstract A simple and fast method was developed for the simultaneous determination of dapsone and pyrimethamine by first-order digital derivative spectrophotometry. Acetonitrile was used as a solvent to extract the drugs from the pharmaceutical formulations, and the samples were subsequently evaluated directly by digital derivative spectrophotometry. The simultaneous determination of both drugs was performed by the zero-crossing method at 249.4 and 231.4 nm for dapsone and pyrimethamine, respectively. The best signal-to-noise ratio was obtained when the first derivative of the spectrum was used. The linear range of determination for the drugs was from 6.6 × 10−7 to 2.0 × 10−4 and from 2.5 × 10−6 to 2.0 × 10−4 mol/L for dapsone and pyrimethamine, respectively. The excipients of commercial pharmaceutical formulations did not interfere in the analysis. Chemical and spectral variables were optimized for determination of both analytes. A good level of repeatability, 0.6 and 1.7% for dapsone and pyrimethamine, respectively, was observed. The proposed method was applied for the simultaneous determination of both drugs in pharmaceutical formulations.


2002 ◽  
Vol 85 (4) ◽  
pp. 883-888 ◽  
Author(s):  
M Inés Toral ◽  
César Soto ◽  
Pablo Richter ◽  
Ana E Tapai

Abstract This paper reports a simple and fast method for the simultaneous determination of estradiol (ED) and medroxyprogesterone acetate (MP) in pharmaceutical formulations by second-derivative spectrophotometry. Methanol was used to extract the drugs from formulations, and subsequently the extracts were evaluated directly by derivative spectrophotometry. The drugs were determined simultaneously by using the graphic method at 297.4 nm for ED and the zero-crossing method at 273.4 nm for MP. If both compounds are present together in a sample, it is possible to quantitate one in the presence of the other. The best signal-to-noise ratio was found when the second derivative of the spectrum was used. The linear ranges for determination of the drugs were 4.7 × 10−6 to 1.6 × 10−4 and 7.2 × 10−6 to 2.0 × 10−4 mol/L for ED and MP, respectively. The ingredients commonly found in commercial pharmaceutical formulations do not interfere with the determination. Chemical and spectral variables were optimized for the determination of both analytes. Good levels of repeatability (relative standard deviation), 1.4 and 1.9%, were obtained for ED and MP, respectively. The proposed method was applied to the determination of these drugs in pharmaceutical formulations.


2018 ◽  
Vol 15 (29) ◽  
pp. 96-105
Author(s):  
D. PUTRI ◽  
Y. ARISTIAWAN ◽  
N. ARYANA ◽  
D. STYARINI

Classified as food additives, the use of benzoic acid and acesulfame K to preserve foods is finite due to health and environmentreason.In this study, anefficient and fast method for simultaneous determination of benzoic acid and acesulfame-K in soft drinks was validated using high performance liquid chromatography with diode array detector (HPLC-DAD) on a C18 column. The method showed results satisfaction as the coefficient determination for benzoic acid and acesulfame-K were 0.9998 and 0.9991 respectively. The LOD for both compounds found at 0.02 mg/kg and the LOQ were found at 0.07 and 0.06 mg/kg for benzoic acid and acesulfame-K respectively. The recovery studies proved that the method has a good recovery ranging from 96103% for both benzoic acid and acesulfame-K with %RSD varies from 1.6 - 4.6% at different concentrations. The validated method then applied to the inter-laboratory comparison sample conducted by the National Quality Control Laboratory for Drug and Food (NQCLDF), Indonesia, using traceable standard reference materials. Uncertainty evaluation using bottom-up approach showed that the method has reasonable uncertainty value with uncertainty budget derived from weighing process, recovery studies, method precision, calibration curve and standard solution. The uncertainty value (k=2, in confidence level 95%) for benzoic acid was found to be 4% at reported concentration of 343 mg/kg and for acesulfame-K was found to be 6.5% at reported concentration of 195 mg/kg. In conclusion, the validated method offered a simple and fast method, as well as economical reagents consumption indicating its possible application as an alternative method for a routine analysis.


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