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Anovel economic procedure for stereospecific separation and analysis of ( R )-and ( S )-bupivacaine has been developed and validated. Use of different thin-layer chromatographic plates and different cyclodextrins at different temperatures was investigated. The spots were detected with either iodine vapor, or by use of a UV lamp followed by densitometric measurements at 262 nm. A comparative study was performed using different cyclodextrins — hydroxylpropyl-β-cyclodextrin (HP-β-CD), methyl-β-cyclodextrin (M-β-CD), and dimethyl-β-cyclodextrin (DM-β-CD) — as chiral selectors. The mobile phase enabling successful resolution of ( RS )-bupivacaine was acetonitrile-methanol-water 15:2.5:2.5 ( v/v ) containing 1 mM HP-β-CD; analysis was performed at ambient temperature (25 ± 2°C). The effect on resolution of the concentration of different chiral selectors, temperature, and pH was studied. Calibration plots for analysis of the R and S enantiomers were linear in the range 1.25–35.00 μg per spot ( r ≥ 0.9995, n = 6) with acceptable precision (RSD < 2.0%) and accuracy (RE = −1.5–2.8%). The limits of detection and quantification were 0.66 and 2.22 μg per spot, respectively, for ( R )-bupivacaine, and 0.88 and 2.94 μg per spot for ( S )-bupivacaine. The method is simple, selective, and robust, and can be used for identification and quantification of the enantiomers of bupivacaine in the drug substance and in pharmaceutical dosage forms.
A simple, rapid and precise thin-layer chromatographic (TLC) method for analysis of escitalopram oxalate (ESC-OX) (S-enantiomer) in presence of “in-process impurities” using β-cyclodextrin (β-CD) and urea as two different selectors was developed and validated as per ICH guidelines. Chromatography was performed on silica gel 60 F254 plates with acetonitrile-0.1% acetic acid-methanol-water (5:0.5:3:1 ν/ν) as a mobile phase containing 3 mg β-CD per 100 cm2 of silica-coated plates as a chiral additive. Using urea 3 mg per 100 cm2 of silica-coated plates as a chiral additive also achieves a good enantiomeric separation with acetonitrile-1% acetic acid-ethyl acetate-methanol-water (5:0.5:1:2:1.5 ν/ν) as a mobile phase. Successful resolution was observed for the (S-enantiomer) ESC-OX, escitalopram cyanodiol, the R-enantiomer and escitalopram N-oxide impurities with significant R F values of 0.75 ± 0.02; 0.40 ± 0.02; 0.31 ± 0.02 and 0.23 ± 0.02, respectively. Densitometric measurement of (S-enantiomer) ESC-OX was carried out at 240 nm. The linear regression analysis data for the calibration plots showed a good correlation coefficient(r = 0.9991) at concentration range of 0.25–10 mg per 10 mL with percentage accuracy 99.74 ± 0.42 for ESC-OX. The limits of detection and quantitation were 0.133 and 0.44 mg per 10 mL, respectively. The proposed TLC method was applied to investigate the enantiomeric purity of (S-enantiomer) ESC-OX in drug substance and drug product. Uniformity of dosage units was demonstrated according to USP guidelines.
Six, sensitive, precise and accurate methods have been developed for the determination of cefditoren pivoxil (CP). The first two methods were based on the formation of charge transfer colored complex between CP and p-chloranilic acid (p-CA) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in the concentration range of 50.00–225.00 μg mL−1 and 75.00–250.00 μg mL−1, respectively. The influence of different parameters on color formation was studied to determine optimum conditions for the visible spectrophotometric methods. The other four methods were adopted for determination of the studied drug in the presence of its acid degradation products including two spectrophotometric methods, namely, first derivative (D1) and first derivative of ratio spectra (DD1), and two chromatographic methods, namely, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), as stabilityindicating techniques. The degradation products were identified by infrared and mass spectroscopy. All the proposed methods were validated and successfully applied for determination of CP in pure form and in pharmaceutical preparations with good recovery ranges between 99.19 and 100.62. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the manufacturer method, and no significant difference was found.
A selective densitometric analysis has been adopted for the determination of pantoprazole sodium sesquihydrate, metronidazole, and clarithromycin as they play an important rule as co-administrated drugs in the treatment of helicobacter infection. The aim of this work was to find greener thin-layer chromatographic (TLC) solvents to follow the environmental safety measurements. The three drugs are vastly different in chemical structure, so it was very challenging to carry out the simultaneous separation and quantitation by TLC technique at R F values 0.49 ± 0.01, 0.72 ± 0.01, and 0.83 ± 0.01, respectively. In the developed method, chromatography was performed on TLC plates with pre-coated silica gel 60 F254 using ethyl acetate and absolute ethanol (3:1)‒heptane‒ammonia 33% (14:5:1, v/v) as the developing system with calculated polarity (3.535). Densitometric measurements were carried out using CAMAG Linomat 5 TLC scanner at 280 nm. Regression line data were evaluated by the least square method within the concentration range of pantoprazole sodium sesquihydrate, metronidazole, and clarithromycin 0.8–8, 4–40, and 5–50 μg band−1, and the detection limits of the drugs were 0.15, 0.76, and 0.88 μg band−1, respectively. The suitability of this TLC method for the quantity determination of three compounds in drug substances and drug products was proved by validation in accordance with the International Conference on Harmonization (ICH) guidelines (Q2R1). Statistical analysis was performed using Student’s t and F test, revealing no significant difference between the TLC method and the official ones concerning accuracy and precision.
A simple and robust thin-layer chromatography (TLC) method has been developed and validated for the simultaneous quantitative analysis of formoterol fumarate (FOF) and budesonide (BUD) in pressurized metered-dose inhaler (pMDI). Separation was carried out by using silica gel 60 F254 TLC plates. The R f values were 0.50 ± 0.01 for FOF and 0.74 ± 0.01 for BUD when isopropanol—ammonia (8:2, v/v) was used as the mobile phase. The plates were scanned using a CAMAG spectrodensitometer at 214 nm. The regression plots revealed good linear relationships of concentration ranges 0.2–4 μg band−1 for FOF (r = 0.9999) and 7–140 μg band−1 for BUD (r = 0.9998). Method validation was performed in accordance with the International Conference on Harmonization (ICH) guidelines. Accuracy was checked by conductive recovery studies; mean percentage recovery was 99.69% ± 0.97 for FOF and 100.03% ± 1.41 for BUD. The limit of detection was 0.05 and 0.17 μg band−1, while the limit of quantification was 0.16 and 0.53 μg band−1 of FOF and BUD, respectively. Other aspects of the analytical validation such as accuracy, precision, specificity, and robustness were also evaluated. The proposed method was successfully applied to the analysis of the two drugs in combination in pressurized metered-dose inhaler. Therefore, the proposed method is suitable for the routine quality control of FOF and BUD in drug substance and drug product.
Abstract
The determination of neptunium-237 (237Np) traditionally has been performed by alpha spectrometry or neutron activation analysis. These methods are labor intensive and require several days for completion. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is a possible alternative for237Np determinations. This paper describes the analytical method developed for samples that have significant levels of uranium present. The lower reporting limits achievable by ICP-MS are competitive with the counting methods, but the real advantage for this laboratory lies in the lower cost and faster turnaround time provided by ICP-MS.
Abstract
Radon (222Rn) and thoron (220Rn) fluxes were measured in locations in Tasmania and Victoria. Emphasis was on an evaluation of seasonal variability of the fluxes. The work is the first part of a program of mapping radon and thoron fluxes in the island of Tasmania on a scale commensurate with requirements of modelling the behaviour of environmentally important trace gases in a limited area around the Baseline Air Pollution Station at Cape Grim, Tasmania.
Abstract
A six month survey of radon, radon progeny and condensation nuclei (CN) has been conducted in an Australian tourist cave. The measurements have been made continuously at two sites within the cave: one a small chamber with a high air exchange rate close to one entrance and connected to several other entrances by complex passages; the other a large chamber with a low air exchange rate 1 km from the nearest entrance. The measurements form a basis for evaluation of the accuracy with which dose due to radon can be determined for different monitoring strategies. It is shown that the estimate of dose based on the measurement of radon concentration and recommendations in ICPR-65, is low by a factor of 1.3 at the well ventilated site and 1.5 at the site with a low air exchange rate and low CN. At each site the weekly average equilibrium factor and unattached fraction were steady, leading to the possibility of establishing a cave system average of these factors. However, given the technical diffuculties involved, it may not be practicable to make enough unattached fraction measurements to fully represent the cave system. Therefore it may be necessary to use a conservative approach to the dosimetry and add 50% to values determined by the ICRP-65 conversion convention.
Abstract
Aluminum is a pathogenic factor in some diseases, like Alzheimer and aluminum toxicity in dialysis patients. This subject signifies Al measurement in biological samples. Different methods have been proposed for Al determination. One of the known methods for the analysis of this element is instrumental neutron activation analysis (INAA). 31P, 28Si, 32Cl and 24Na interfere the determination of Al in this method. In this study, the effects of high amounts of 38Cl and 24Na on the measurement of 28Al are discussed. The data gathered by the detector is filtered by an equation named digital low pass filter equation with the help of a computer. The net-areas of filtered and non-filtered peaks of 28Al are compared. Finally these areas are compared with the net-area of 28Al peak in the standard reference material, NIST-SRM-1547.
