Ratio subtraction and isosbestic point methods are two innovative spectrophotometric methods for determining the concentrations of metronidazole (I) and diloxanide furoate (II) in a mixture. Metronidazole was determined by direct spectrophotometric method at k max 314.0 nm in the presence of diloxanide furoate in the range of 4-24 lg ml À1 with a mean recovery percentage of 99.83 ± 1.41. Two spectrophotometric methods were developed for the spectral resolution of diloxanide furoate when present in mixture with metronidazole without preliminary separation. The first method depends on measuring the absorbance at the isosbestic point at 277.2 nm in the range of 5-30 lg ml À1 with a mean recovery percentage of 99.96 ± 1.47 for diloxanide furoate. The second method is the ratio subtraction spectroscopic method for spectral isolation of diloxanide furoate present in the mixture which can be measured at 251.2 nm in the range of 5-30 lg ml À1 with a mean recovery percentage of 99.73 ± 1.33 for diloxanide furoate determination. The suggested procedures were validated using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical preparations. The methods retained their accuracy and precision when the standard addition technique was applied. The results obtained by applying the proposed methods were statistically analyzed and compared with those obtained by the reported method.

Cross-linking of superabsorbent hydrogels based on poly(acrylamideco-sodium alginate) is carried out using 60 Co γ-radiation. Hydrogels of PAM/NaAlg with 1.5:0.5 and 1.0:1.0 w/v concentrations showed good gel contents of 87 and 66 (%) and swelling degrees in water of 3.7 and 5 (g/g) after 40 min, respectively. The chemical structure of the hydrogel is confirmed by FTIR, XRD, and ESR. The morphology of the hydrogel is observed using scanning electron microscopy. Intramolecular H-bonding in the hydrogel network is confirmed by TGA and DSC. The pH-responsive swelling behavior of (PAMco-NaAlg) hydrogels is tested in different pH ranges showing higher swelling capacities in basic than in acidic media. This property proposes the use of (PAMco-NaAlg) hydrogel as internal curing agent for concrete.The hydrogel is examined with cement weight ratios of (0.1-0.5) wt%. The study shows that cement with (PAMco-NaAlg) hydrogel improves the compressive strength of cement at 0.1 and 0.2 wt%. K E Y W O R D Sγ-radiation, cement, hydrogel, internal curing, smart polymer, sodium alginate How to cite this article: Ghobashy MM, Bassioni G. pH stimuli-responsive poly(acrylamideco-sodium alginate) hydrogels prepared by γ-radiation for improved compressive strength of concrete. Adv Polym

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Gamma radiation can be used for enhancing the physical properties of polyurethane (PU). Radiation was used to crosslink a polyurethane at room temperature; four samples of the PU solid film are irradiated at variable four radiation doses 0, 50, 100, and 150 kGy under vacuum conditions. Crosslinking radiation is more common than oxidative degradation and crosslinking is believed to be more efficient in the soft segment of PU. The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR), Thermogravimetric Analysis (TGA-DTG), and X-ray Diffraction (XRD) which have been used to investigate the effect of gamma radiation on the polyurethane (PU). The results showed that the radiation crosslinking of polyurethanes improved the thermal stability and the crystallinity. The microstructure modifications of polyurethane samples have also been studied as a function of the dose using the scanning electron microscope (SEM). The effects of gamma irradiation on the color changes of polyurethane were observed. The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence.

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The pattern surface structure of a thin blend polymer film of Poly methyl methacrylate (PMMA) – Poly ethylene glycol (PEG) induced by Ar+ ion etching (5 keV) has been investigated by scanning electron microscopy. Blend polymer films have been obtained consisting of a hydrophilic PEG and a hydrophobic PMMA distributed in co-continuous phases. Four different compositions of the two polymers are dissolved in chloroform and irradiated with gamma rays (60Co) at 20 kGy to produce transparent films of blend polymer PMMA-PEG after casting. Self-assembled of PMMA-PEG film is obtained because of the high contrast between the two polymers. Ion-polymer interaction with a hydrophilic polymer (Ar+ +PEG) rather than the high etch resistance of hydrophobic polymer (Ar+ −PMMA) was observed. The results are discussed in terms of significant destruction of bonds in the blend polymer films as a result of which one polymer undergoes rapid dissociation rather than the other one. This means that etching with Ar+ ions of the PMMA domains are stable and PEG can be selective. The ATR-FTIR spectrum shows the absence of hydrogen bonds and XRD/DSC curves show the crystanility of PMMA depending on the PEG contents and gamma radiation effect, irradiated blend polymer PMMA/PEG has shown more resistant at thermal degradation than irradiated PMMA. This indicates that the PEG contents have an effect on the thermal stability of PMMA/PEG as detected by TGA. Finally, the pattern surface of irradiated blend polymer (PMMA-2%PEG) was plated with two coaxial layers subsequently of copper (Cu) and silver (Ag) using sputter technique.

In this work two well known oral hypoglycemic drugs that are administered in combination for patients with type-II diabetes were simultaneously determined. Several spectrophotometric methods were developed and validated for the determination of metformin hydrochloride (MET), pioglitazone hydrochloride (PIO) and pioglitazone acid degradate (PIO Deg). Derivative, ratio derivative, isosbestic and chemometric-assisted spectrophotometric methods were developed. The first derivative (D(1)) method was used for the determination of MET in the range of 5-30 microg x mL(-1) and PIO in the range of 10-90 microg x mL(-1) by measuring the peak amplitude at 247 nm and 280 nm, respectively. The concentration of PIO was calculated directly at 268 nm. The first derivative of ratio spectra (DD(1)) method used the peak amplitudes at 238 nm and 248.6 nm for the determination of MET in the range of 5-30 microg x mL(-1). In the isosbestic point method (ISO), the total mixture concentration was calculated by measuring the absorbance at 254.6 nm. Classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS-2) were used for the quantitative determination of MET, PIO and PIO Deg. The methods developed have the advantage of simultaneous determination of the cited components without any pre-treatment. Resolution and quantitative determination of PIO degradate with a minimum concentration of 3 microg x mL(-1) in drug samples was done. The proposed methods were successfully used to determine each drug and the acid degradate in a laboratory-prepared mixture and pharmaceutical preparations. The results were statistically compared using one-way analysis of variance (ANOVA). The methods developed were satisfactorily applied to the analysis of the two drugs in pharmaceutical formulations.

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