To use a mobile phone camera as a spectrophotometer, two steps are usually required. In the first step, the output RGB values of a camera are converted to device-independent color values. Afterward, spectral reflection values are reproduced from those device-independent values. In this paper, the matrix method was used to convert two color spaces to each other in the first step. In the next step, spectral reflection values were reproduced using the principal component analysis (PCA) method. It was shown that the best result is obtained using light source D50/ standard observer in 1964 and light source A/ standard observer in 1931 in a way that the color of the second light source and observer are obtained through a conversion matrix from the color values of the first light source and observer.

In this article, the results of the research related to design and implementation of an experimental prototype of a spectrophotometer, similar to the one which is used routinely in clinical laboratories, are presented. In this research, after the designing, implementation and testing different optical, mechanical and electronic modules of the system and developing operating software for control and signal processing, a complete system capable of selecting the desired wavelength automatically was implemented. A series of experiments on selected samples were carried out using the implemented system with the objective of testing, calibration and compensation for the errors of the system. The results of the experiments have been presented in this paper.  

Mometasone furoate is a synthetic glucocorticoid with anti-inflammatory and anti-allergic effects, used for the treatment of allergic rhinitis, asthma, and dermatoses. In this study, a spectrophotometric method, as a selective and sensitive method, was developed for the determination of mometasone furoate after derivatization. For this purpose, mometasone was first reacted with sodium cyanide to prepare the drug derivatives. After that, the effects of different variables such as reaction solvent, concentration of the reagents, pH, and reaction time were studied. The final results showed that the determination method was linear in the range of 2-18 μg/ml. It seems that after 24 hours, the reaction was complete. The reaction product was characterized by NMR and FT-IR spectroscopy, and the accuracy and precision of the developed method were also studied. At last, the method was checked on Mometasone Ointment (0. 1%), and the results were compared with the results of the HPLC method as a standard method.

Background and Aim: The success rate of composite restorative materials depends very much on their color stability in the oral cavity. The purpose of this study was to investigate the color changes of four different brands of dental composite resin materials by using four staining solutions.Materials and Methods: A total of 128 disk-shaped specintens of 15. 2 mm were prepared out of 4 composite resin materials. Two nanocomposites: Filtek supreme, Tetric Evoceram and two micro hybrid composites: Filtek Z250 and Tetric ceram, were prepared. The specimens were then divided into 4 groups of 8 specimens each and they were immersed in 4 staining solutions (Coffee, Tea, Cola, and Artificial Saliva) for 3 hours daily over a 24 day testing period. The color of specimens was measured with a spectrophotometer using CIELab color space relative to illuminant D65 at baseline and after staining. The color differences (DE) were calculated. The DE =3.3 was used as an acceptable value in subjective visual evaluations. Data was analyzed using ANOVA and Post-hoc test at significance level of 0.05.Results: All tested materials showed unacceptable color change in coffee and tea groups (DE>3.3). The greatest color change was observed in Filtek supreme in coffee. The specimens in cola and artificial saliva didn't cause a notable color change clinically.Conclusion: Coffee and tea can significantly influence the discoloration of dental resin composite materials under investigation. The nanocomposite Filtek supreme color change was significantly more than other composites when exposed to coffee. Therefore, color stability of composite restorative materials depends very much on dietary habits.