Constantinos A. Georgiou

Rapid Quantitative Determination of Ciprofloxacin in Pharmaceuticals by Use of Solid-State FT-Raman Spectroscopy

FT-Raman spectroscopy based on band intensity or band area measurements was used for the quantitative determination of ciprofloxacin in pharmaceutical solid dosage forms. Univariate calibration was used for quantitative analysis. Bands observed at 1708, 1624, 1548, 1493, 1273, 1253, 1238, 1024, 805, 787, 752, 718, 665, and 638 cm−1 were used. Calibration curves were linear in the concentration range of 3–100% w/w with correlation coefficients of 0.99–0.996 and 0.991–0.9993 for band intensity and band area measurements, respectively. Precision ranged from 0–11 and 0.4–12% relative standard deviation (RSD) (n = 3) for band intensity and band area measurements, respectively, and results were in good agreement with the results obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. Multivariate calibration was also used for quantitative analysis. Multiple linear regression using the intensities of the 1545 and 1272 cm−1 bands gave results in accordance with those obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. As measurement takes just 30 s using the analytical readout from a single band, the proposed method can be used to replace tedious and time-consuming methods.

Construction of a L-lysine biosensor by immobilizing lysine oxidase on a gold-poly(o-phenylenediamine) electrode.

The construction of a l-lysine biosensor on a Si-gold strip electrode (SGSE) is described in this study. The construction comprises (a) the formation of poly(o-phenylenediamine, o-PD) membrane on the electrode surface via electropolymerization and (b) the immobilization of lysine oxidase on the gold/poly(o-PD) electrode with glutaraldehyde. The behavior of the gold/poly(o-PD) electrode against H(2)O(2) and lysine, as well as the repeatability of the electropolymerization and the time stability of the polymer were studied. The study showed that the electropolymerization procedure is repeatable, and that the polymer is quite stable for at least 40 days. The biosensor showed a linear calibration curve in the range 0.01-1x10(-5) M (0.1-10 muM) lysine. The interfering effect of other amino acids on the biosensor performance was also studied and amperometric selectivity coefficients were calculated. The biosensor responded mainly against tyrosine and cysteine, while the response to phenylalanine, arginine, histidine and ornithine was very low. By changing the electropolymerization conditions, the effect of interferents was further reduced.

Selenium affects the expression of GPx4 and catalase in the liver of chicken

A total of 128 chickens (Gallus gallus, broilers) were used to investigate the effect of organic selenium (Se) in expression of catalase (CAT) and phospholipid hydroperoxidase 4 (GPx4) genes. There were 4 replicates of 4 dietary treatments: T1 (basal diet with no added Se), T2 (T1 with 0.15 ppm Se added), T3 (T1 with 0.3 ppm Se) and T4 (T1 with 3.0 ppm Se). At 4th and 6th week, 2 chickens per replicate pen were sacrificed for whole blood and liver sample collections. Samples were analyzed for total Se by ICP-MS and gene expression by RT-PCR. Dietary supplementation with organic Se (Se-yeast) readily elevated its concentration in the tissues. GPx4 mRNA levels, pooled for both ages, of chickens fed T3 and T4 diets were significantly reduced compared to those fed diet T1 by 47% and 77% respectively, while that of T2 did not differ. Liver CAT mRNA levels at 4th week were significantly decreased as Se supplementation increased, while at 6th week, were not significantly affected by Se. The study showed that liver GPx4 mRNA levels could be down-regulated by excess of Se. It is possible that reserves built by excess of Se meet antioxidant requirements and no additional GPx4 transcription is necessary.

Automated flow injection spectrophotometric non-aqueous titrimetric determination of the free fatty acid content of olive oil

An automated flow injection titrimetric method for the determination of olive oil acidity is proposed. A 175 μl olive oil aliquot is injected in a carrier stream (the titrant) of n-propanol containing 7.5 × 10−4 M KOH and 4.0 × 10−5 M phenolphthalein indicator. The sample zone is dispersed in the titrant while flowing at 4.4 ml min−1 through a 1.1 ml Plexiglas mixing chamber and the absorbance of the resulting mixture is continuously monitored at 562 nm, λmax, for the basic form of the indicator. The resulting negative absorbance peaks indicate the transition base (red)-acid (colorless)-base (red) of the indicator. Quantitation is based on peak width measurements. Peak widths of 31.7–97 s were measured with a relative standard deviation (RSD) of < 2.1% (n = 10), and the analytical range was 0.15 – 8.0% (w/w) free fatty acid content calculated as oleic acid. The sampling rate is 30 – 100 h−1 while n-propanol consumption is only 3 – 7 ml per run. Recoveries of oleic acid from commercial olive oils ranged from 97.9 to 101.6% (mean 99.5%). The method was applied for the determination of free fatty acid content of thirty two samples of olive oils. Results obtained by the proposed method compare well (0.3 – 3.6% relative difference, mean 1.5%) with those obtained by the official European Community method that is time consuming and uses gross amounts of organic solvents. Moreover comparison with a Fourier transform infrared (FT-IR) method reveals that by using the proposed method the useful range can be extended to lower concentrations.

Synchronous fluorescence spectroscopy: tool for monitoring thermally stressed edible oils.

Total synchronous fluorescence spectra are proposed for monitoring edible oils during thermal stress. Synchronous fluorescence spectra obtained at an 80 nm wavelength interval combined with principal component analysis are suitable for classification of vegetable oil deterioration. Spectroscopic features in the range of 300-500 nm have been used for extra virgin olive, olive pomace, and sesame oil and the range of 320-520 nm has been used for corn, soybean, sunflower, and a commercial blend of oils. The score in the first two principal components explains 91.1% of the data matrix variance for extra virgin olive, sesame, and olive pomace oil and 89.3% for corn, soybean, sunflower, and the commercial blend of oils. The objective of this study is to develop a rapid method for the prediction of edible oil quality during thermal stress. Spectroscopic changes are indicative of oxidative deterioration as measured through wet chemistry methods: peroxide value, p-anisidine value, totox value, and radical-scavenging capacity.

FLOW-INJECTION STOPPED-FLOW KINETIC SPECTROPHOTOMETRIC DETERMINATION OF DRUGS, BASED ON MICELLAR-CATALYSED REACTION WITH 1-FLUORO-2,4-DINITROBENZENE

A flow-injection stopped-flow kinetic spectrophotometric method for the determination of hydrazines, hydrazides, amines and amino-acids, based on the cetyltrimethylammonium bromide catalysed reaction with 1-fluoro-2,4-dinitrobenzene is described. With the proposed method dihydralazine, isoniazid, levodopa and aspartame can be determined at concentrations of 0.1-6 x 10(-4)M. The calibration ranges can be varied by adjusting the pH and surfactant concentration. The determination of amphetamine, cysteine, s-carboxymethylcysteine, cephalexin, tobramycin and gentamicin is also feasible. The method has been applied to the determination of levodopa, isoniazid and aspartame in commercial pharmaceutical formulations. The determination of isoniazid in formulations containing the highly coloured antibiotic rifamycin, and of aspartame in coloured beverages was also accomplished. The results were in good agreement with those obtained by reference methods and the throughput was 40 measurements per hour with 0.4-3.9% RSD.

Rapid, noninvasive quantitative determination of acyclovir in pharmaceutical solid dosage forms through their poly(vinyl chloride) blister package by solid-state Fourier transform Raman spectroscopy.

Fourier transform (FT) Raman spectroscopy based on band intensity or band area measurements was used for the quantitative determination of acyclovir in pharmaceutical solid dosage forms through their poly(vinyl chloride) blister package. Univariate calibration using the bands observed at 1690, 1630, 1574, 1482, 1181, 578, and 508 cm−1 was found to be sufficient for the analysis. Calibration curves were linear, the correlation coefficients being 0.997–0.9993 and 0.996–0.9991 for band intensity and band area measurements, respectively. Results obtained compare well, as indicated by the t-test, with those obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. Precision ranged from 0.7–4.5 and 0.4–4.0% RSD (n = 3) for band intensity and band area measurements, respectively. The developed nondestructive FT-Raman method is rapid, simple, and can be used for the on-line, real-time monitoring of acyclovir formulation production lines.

Updating a Synchronous Fluorescence Spectroscopic Virgin Olive Oil Adulteration Calibration to a New Geographical Region

Detecting and quantifying extra virgin olive adulteration is of great importance to the olive oil industry. Many spectroscopic methods in conjunction with multivariate analysis have been used to solve these issues. However, successes to date are limited as calibration models are built to a specific set of geographical regions, growing seasons, cultivars, and oil extraction methods (the composite primary condition). Samples from new geographical regions, growing seasons, etc. (secondary conditions) are not always correctly predicted by the primary model due to different olive oil and/or adulterant compositions stemming from secondary conditions not matching the primary conditions. Three Tikhonov regularization (TR) variants are used in this paper to allow adulterant (sunflower oil) concentration predictions in samples from geographical regions not part of the original primary calibration domain. Of the three TR variants, ridge regression with an additional 2-norm penalty provides the smallest validation sample prediction errors. Although the paper reports on using TR for model updating to predict adulterant oil concentration, the methods should also be applicable to updating models distinguishing adulterated samples from pure extra virgin olive oil. Additionally, the approaches are general and can be used with other spectroscopic methods and adulterants as well as with other agriculture products.

Automated flow injection spectrophotometric determination of para- and meta-substituted phenols of pharmaceutical interest based on their oxidative condensation with 1-nitroso-2-naphthol

The reaction of para- and meta-substituted phenols with 1-nitroso-2-naphthol in the presence of either CeIV or PbIV as an oxidant has been used to develop a fast automated flow injection (Fl) method. A stopped-flow kinetic study of the reaction revealed the optimum conditions for the proposed Fl method. Acetaminophen, amoxicillin, cefadroxil, isoxsuprine, nylidrin, propylparaben, tyrosine and metaraminol can be determined in the range 1 x 10(-4)-8 x 10(-4) M, with relative standard deviations of less than 2%, and a measurement throughput of 40 measurements h-1. The method was evaluated by performing interference studies of common excipients and assaying commercial formulations of acetaminophen and isoxsuprine. The results were in good agreement with those obtained by acceptable spectrophotometric or high-performance liquid chromatographic methods (mean difference 2.1%). The high sample throughput of the Fl method was exploited by performing a content uniformity test of isoxsuprine tablets.

Influence of organic selenium supplementation on the accumulation of toxic and essential trace elements involved in the antioxidant system of chicken.

The aim of the study was to investigate the interactions between selenium (Se) and various trace elements, both toxic and essential, involved in the antioxidant system. A total of 128 day-old chicks (Gallus gallus, broilers) were used to investigate the effect of Se yeast supplementation on the accumulation of cadmium (Cd), copper (Cu) iron (Fe) and zinc (Zn). There were four replicates of four dietary treatments: T1 (basal diet with no added Se, analyzed to contain 0.21 mg kg−1), T2 (T1 with 0.15 mg kg−1 Se added), T3 (T1 with 0.3 mg kg−1 Se) and T4 (T1 with 3.0 mg kg−1 Se). At week 4 and 6, two chickens per replicate pen were sacrificed for whole blood, breast muscle and liver sampling. Samples were analyzed by ICP–MS. Supplementation with Se-yeast, not only increased Se concentration but also reduced Cd concentration in the tissues. Selenium was negatively correlated with Cd and positively correlated with Zn, Cu and Fe. Cadmium was negatively correlated with Zn and Cu. Zinc was positively correlated with Cu. Iron was negatively correlated with Cu and uncorrelated with Zn and Cd. The balance between Se, Cu, Fe and Zn is important for proper antioxidant defense since they are an integral part of various antioxidant enzymes.