Four sensitive and rapid methods for the determination of stavudine (STV) in bulk drug and in dosage forms were developed and optimized. In titrimetry, aqueous solution of STV was treated with a ...known excess of bromate-bromide in HCl medium followed by estimation of unreacted bromine by iodometric back titration. Spectrophotometric methods involve the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange, indigocarmine or thymol blue followed by measurement of absorbance at 520 nm (method A), 610 nm (method B) or 550 nm (method C). In all the methods, the amount of bromate reacted corresponds to the amount of STV. Calculations in titrimetry were based on a 1:0.666 (STV:KBrO3) stoichiometry and the method was found to be applicable over 3.5-10 mg range. A linear increase in absorbance with concentration of STV was observed in the spectrophotometric methods, and the Beer's law was obeyed over the concentration ranges 0.125-1.75, 1-10 and 1-9.0 microg mL-1 STV for method A, method B and method C, respectively. The methods when applied to the determination of STV in tablets and capsules were found to give satisfactory results.
One titrimetric and two spectrophotometric methods which are simple, sensitive and rapid are described for the assay of salbutamol sulphate (SBS) in bulk drug and in tablet dosage forms using ...N-bromosuccinimide (NBS) and two dyes, rhodamine-B and methylene blue, as reagents. In titrimetry, aqueous solution of salbutamol sulphate is treated with a measured excess of NBS in acetic acid medium and after the oxidation of SBS is complete, the unreacted oxidant is determined iodometrically. Spectrophotometric methods entail addition of a known excess of NBS in acid medium followed by the determination of residual oxidant by reacting with a fixed amount of either rhodamine B and measuring the absorbance at 555 nm (method A) or methylene blue and measuring the absorbance at 665 nm (method B). In all methods, the amount of NBS reacting corresponds to the amount of SBS content. Titrimetric method is applicable over 1.74 x 10-4 - 8.68 x 10-4 mol L-1 range and the reaction stoichiometry is found to be 1:6 (SBS:NBS). In spectrophotometric methods, the absorbance is found to increase linearly with the concentration of SBS, which is corroborated by the correlation of coefficients of 0.9993 and 0.9988 for method A and method B, respectively. The systems obey Beer's law for 0.25-1.75 μg mL-1 (method A) and 0.5-5.0 μg mL-1 (method B). The calculated apparent molar absorptivity values were found to be 2.10 x 105 and 6.16 x 104 L mol-1 cm-1, for method A and method B, respectively. The limits of detection and quantification are also reported for both spectrophotometric methods. Intraday and inter-day precision and accuracy for the developed methods were evaluated. The methods were successfully applied to the assay of SBS in tablet and capsule formulations and the results were statistically compared with those of a reference method. No interference was observed from common tablet adjuvants. The accuracy and reliability of the methods were further ascertained by recovery experiments via the standard-addition technique.
Two spectrophotometric methods are proposed for the assay of lansoprazole (LPZ) in bulk drug and in dosage forms using ceric ammonium sulphate (CAS) and two dyes, methyl orange and indigo carmine, as ...reagents. The methods involve addition of a known excess of CAS to LPZ in acid medium, followed by determination of residual CAS by reacting with a fixed amount of either methyl orange, measuring the absorbance at 520 nm (method A), or indigo carmine, measuring the absorbance at 610 nm (method B). In both methods, the amount of CAS reacted corresponds to the amount of LPZ and the measured absorbance was found to increase linearly with the concentration of LPZ, which is corroborated by the correlation coefficients of 0.9979 and 0.9954 for methods A and B, respectively. The systems obey Beer's law for 0.5-7.0 μg mL-1 and 0.25-3.0 μg mL-1 for methods A and B, respectively. The apparent molar absorptivities were calculated to be 3.0 x 104 and 4.4 x 104 L mol-1 cm-1 for methods A and B, respectively. The limits of detection (LOD) and quantification (LOQ) were calculated to be 0.08 and 0.25 μg mL-1 for method A, and 0.09 and 0.27 μg mLs-1 for method B, respectively. The intra-day and inter-day precision and accuracy of the methods were evaluated according to the current ICH guidelines. Both methods were of comparable accuracy (er ≤ 2 %). Also, both methods are equally precise as shown by the relative standard deviation values < 1.5%. No interference was observed from common pharmaceutical adjuvants. The accuracy of the methods was further ascertained by performing recovery studies using the standard addition method. The methods were successfully applied to the assay of LPZ in capsule preparations and the results were statistically compared with those of the literature UV-spectrophotometric method by applying Student's t-test and F-test.
Predložene su dvije spektrofotometrijske metode za određivanje lansoprazola (LPZ) kao čiste supstancije i u doziranim ljekovitim pripravcima koristeći cerijev amonijev sulfat (CAS) i dvije boje, metiloranž i indigo karmin. Metode uključuju dodatak suviška CAS-a u otopinu LPZ u kiselom mediju, nakon čega višak reagensa reagira s poznatom količinom metiloranža (metoda A, mjerenje apsorbancije na 520 nm) ili indigo karminom (metoda B, mjerenje apsorbancije na 610 nm). U obje metode, količina CAS-a koja reagira odgovara količini LPZ i izmjerena apsorbancija linearno ovisi o koncentraciji LPZ-a, uz koeficijent korelacije 0,9979 i 0,9954 za metodu A odnosno B. Oba sustava slijede Beerov zakon u koncentracijskom rasponu 0,5-7,0, odnosno 0,25-3,0 μg mL1. Molarni apsorpcijski koeficijent određen metodom A iznosio je 3,0 x 104 a metodom B 4,4 x 104 L mol1 cm-1. Granica detekcije (LOD) i kvantifikacije (LOQ) bile su 0,08 i 0,25 μg mL-1 za metodu A, te 0,09 i 0,27 μg mL-1 za metodu B. Preciznost i ispravnost metoda procijenjena je prema važećim ICH smjernicama. Obje metode su podjednako ispravne (er ≤ 2%) i precizne (RSD < 1,5%). Nije primijećena interferencija s uobičajenim pomoćnim tvarima. Ispravnost je procijenjena i metodom standardne adicije. Rezultati su statistički uspoređeni s referentnom UV-spektrofotometrijskom metodom pomoću Studentovog t-testa i F-testa.
U radu su opisane jedna titrimetrijska i dvije spektrofotometrijske metode za određivanje salbutamol sulfata (SBS) čiste tvari i u tabletama. Opisane metode su jednostavne, osjetljive i brze, a kao ...reagense koriste N-bromsukcinimid (NBS) i dva bojila, rodamin-B i metilensko modrilo. U titrimetrijskoj metodi, vodenoj otopini salbutamol sulfata dodana je otopina NBS-a u octenoj kiselini u suvišku, te je nakon potpune oksidacije SBS-a jodometrijski određena količina neizreagiranog oksidansa. U spektrofotometrijskim metodama dodaje se poznati suvišak NBS-a u kiselom mediju nakon čega se neizreagirani suvišak oksidansa određuje nakon reakcije s rodaminom-B mjereći apsorbanciju na 555 nm (metoda A) ili metilenskim modrilom mjereći apsorbanciju na 665 nm (metoda B). U svim metodama, količina NBS-a koji reagira ekvivalentna je sadržaju SBS-a. Titrimetrijska metoda je primjenjiva u rasponu koncentracija od 1,74 × 10-4 do 8,68 × 10-4 mol L-1. SBS i NBS reagiraju u stehiometrijskom omjeru 1:6. U spektrofotometrijskim metodama apsorbancija linearno raste s koncentracijom SBS-a, što je potvrđeno koeficijentima korelacije od 0,9993 za metodu A te 0,9988 za metodu B. Sustavi slijede Beer-ov zakon unutar koncentracija 0,251,75 g mL-1 (metoda A) i 0,55,0 g mL-1 (metoda B). Izračunate vrijednosti molarnog apsorpcijskog koeficijenta iznose 2,10 × 105 za metodu A i 6,16 × 104 L mol-1 cm-1 za metodu B. Granice detekcije i kvantifikacije, ispravnost i preciznost (ponovljivost i intermedijarska preciznost) procijenjene su za obje spektrofotometrijske metode. Metode su uspješno primijenjene za analizu SBS-a u tabletama i kapsulama, a rezultati su statistički uspoređeni s referentnom metodom. Uobičajene pomoćne tvari u tabletama nisu interferirale tijekom određivanja. Ispravnost metoda potvrđena je i metodom standardne adicije.
Predložene su dvije spektrofotometrijske metode za određivanje lansoprazola (LPZ) kao čiste supstancije i u doziranim ljekovitim pripravcima koristeći cerijev amonijev sulfat (CAS) i dvije boje, ...metiloranž i indigo karmin. Metode uključuju dodatak suviška CAS-a u otopinu LPZ u kiselom mediju, nakon čega višak reagensa reagira s poznatom količinom metiloranža (metoda A, mjerenje apsorbancije na 520 nm) ili indigo karminom (metoda B, mjerenje apsorbancije na 610 nm). U obje metode, količina CAS-a koja reagira odgovara količini LPZ i izmjerena apsorbancija linearno ovisi o koncentraciji LPZ-a, uz koeficijent korelacije 0,9979 i 0,9954 za metodu A, odnosno B. Oba sustava slijede Beerov zakon u koncentracijskom rasponu 0,5–7,0 g mL-1, odnosno 0,25–3,0 mikrog mL-1. Molarni apsorpcijski koeficijent određen metodom A iznosio je 3,0 × 104, a metodom B 4,4 × 104 L mol1 cm-1. Granica detekcije (LOD) i kvantifikacije (LOQ) bile su 0,08 i 0,25 mikrog mL-1 za metodu A, te 0,09 i 0,27 mikrog mL-1 za metodu B. Intermedijarska preciznost i ispravnost metoda procijenjena je prem važećim ICH smjernicama. Obje metode su podjednako ispravne (er ≤ 2%) i precizne (RSD < 1,5%). Nije primjećena interferencija s uobičajenim pomoćnim tvarima. Ispravnost je procijenjena i metodom standardne adicije. Rezultati su statistički uspoređeni s referentnom UV-spektrofotometrijskom metodom pomoću Studentovog t-testa i F-testa.
A series of novel π-electron rich fluoranthene derivatives (P1–P3) adorned with symmetrical and unsymmetrical alkoxy chains were developed using Diels-Alder reaction. The use of peripheral ...triethyleneglycol (TEG) chains on fluoranthene enhances its electron donating ability and furnishes decrease in their energy levels and optical band gap. The intense sky-blue fluorescence exhibiting fluoranthene ensembles have been investigated as potential fluorescent chemosensors for the detection of explosive nitroaromatics (NACs). Fluorescence studies demonstrate that emission intensity of P1–P3 was efficiently decreased upon interaction with picric acid (PA) in a dominant static quenching phenomena which is attributed to photoinduced electron transfer process. The limit of detection (LOD) was found to be in the range of 2–20 ppb. The vapour phase sensing study involving thin films of P1–P3 showed efficient quenching response and sensing process is found to be highly reversible. Surface morphology of thin films significantly varied with the type of alkyl chain present on fluoranthene. The thin films are highly selective towards PA in aqueous medium containing commonly interfering nitro-explosives. Contact mode approach using silica gel substrates allows femto-gram detection of trinitrotoluene (TNT) and PA makes these materials as potential chemosensors for real time applications.
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•High blue fluorescent novel fluoranthene derivatives with varied nature of alkyl chains•Selective detection of 2,4,6-trinitrophenol in aqueous and vapour phase methods•Porous nature thin films enhance the sensitivity and selectivity.•Good reversibility and recycling of thin films•Femto-gram detection of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol by contact method
Magnetic nanoparticles of Co
1–
x
Mg
x
Fe
2
O
4
(
x
= 0, 0.08, 0.16, and 0.24) were prepared using sol–gel technique with auto-combustion. Citric acid was used as a chelating agent. The X-ray ...diffraction (XRD) studies showed that the lattice constant of cobalt ferrite decreases with the rise of magnesium proportion. Field-effect Scanning Electron Microscopy (FESEM) was used for the morphological study of the powdered ferrites. Energy Dispersive Spectroscopy (EDS) gave the compositional analysis of the samples. Two major vibrational frequencies from the Fourier Transform Infrared (FT-IR) Spectroscopy validate the spinel cubic ferrite structure. Raman spectroscopy exposes a doublet-like peak behaviour in A
1
g
and E
g
modes as a result of different ionic radius of ions belonging to Mg/Co and Fe. The magnetic parameters like saturation magnetization, coercivity, and remanent were also thoroughly analysed against the increase in the Mg-density in cobalt ferrite. The DC electrical resistivity is found to increase with Mg concentration. The room temperature, electrical and dielectric properties were investigated in the frequency range between 100 and 5 MHz. The observed results were related to the microstructural characteristic and amount of Mg dopants.
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