Fadhil Jasim

Measurements of some spectrophotometric parameters of curcumin in 12 polar and nonpolar organic solvents

Abstract Curcumin (Turmeric Yellow) dissolves in various polar and nonpolar organic solvents (Table 1) and gives sensitive and stable yellow to greenish-yellow (depending on the solvent) colors. λmax, molar absorptivity, durability, sensitivity, limit of detection, linearity, precision, and accuracy have been evaluated for each of the 12 curcumin-solvent nonaqueous systems.

A novel method for the spectrophotometric determination of curcumin and its application to curcumin spices

Abstract A specific spectrophotometric method for the determination of (0.01–15) ppm of curcumin in spices using acetone-bicarbonate buffer (pH 11) is described. The effects of various experimental conditions such as pH of solutions, volume ratio of acetone-buffer solution, and interferences have been discussed. The detection limit and molar absorptivity have been found to be 1 ng ml−1 and 46,000 liters mol−1 cm−1, respectively. RSD and relative accuracy percentages have been determined to be 2.67-2.0 and 2.70-2.50% for 1 and 15 ppm curcumin, respectively.

A Novel and Rapid Method for the Spectrofluorometric Determination of Curcumin in Curcumin Spices and Flavors

Abstract A sensitive and rapid spectrofluorometric method for determination of microamounts of curcumin in curcumin spices and related flavors has been developed. It involves dissolving curcumin samples in dry acetone, irradiating the resulting clear solution at λE = 424 nm, and measuring the stable intense green-yellow fluorescence at λF = 504 nm. The fluorescent solution shows no change in λE or λF or in fluorescence intensity for at least 1 month under ambient conditions. Beers law is followed over the range 0.0–500 ppb of curcumin. The sensitivity and detection limit ( S N = 2 ) are 4.7 and 0.34 ppb of curcumin per fluorescence unit, respectively. The RSD and recovery for a series of concentrations (0.01–0.3 ppm) are 1.13–2.03 and 98.96–100%, respectively. Temperature control is needed; pH adjustment and O2 removal from test solution are unnecessary. Under the specified conditions, water is the only quencher for curcumin fluorescence. Direct calibration determination is satisfactory and therefore there is no need to use a rather lengthy standard additions technique.

Electrothermal atomic-absorption spectrophotometric determination of molybdenum

The sensitivity for determining Mo by ETA-AA is dependent on the heating programme employed when the peak-height method is used, but not when the peak area is used for evaluation of the AA signals. The linear range is greater at lower heating rate. Molybdenum can be directly determined in up to 8% NaCl solution without chemical pretreatment or background correction by making use of the high ashing temperature allowed, at which the matrix NaCl can be totally removed. The minimum recovery is 94.5%. Amounts of alkaline earth metals greater than 4000 times the amount of Mo give scatter signals, but these are time-resolved from the Mo signal. Any small effect on the peak height or area can be compensated for by background correction. The interference of tungsten is significant even at low concentrations (2-5 mug/ml) owing to the formation of stable compounds. Mo is determined in brines and acid digests of phosphate rocks after preconcentration and separation with the APDC-MIBK system, by ETA-AA of the organic extracts with or without mineralization.

Effects of nickel(II) oxide on the thermal decomposition of alkali persulfates

Abstract The thermal decomposition of Na 2 S 2 O 8 and K 2 S 2 O 8 has been studied derivatographically in the presence of NiO at various molar mixtures. Experiments have proved that the first decomposition stage (persulfate into pyrosulfate) is independent of the amount of the oxide present. During the second decomposition stage (pyrosulfate into sulfate) which occurs in the melt, NiO plays the role of lowering the melting, the initial and final decomposition temperatures of pyrosulfates. The lowest melting temperatures recorded for Na 2 S 2 O 8 and K 2 S 2 O 8 are 320 and 280°C, respectively. A mechanism has been proposed to describe the catalytic action of NiO on the thermal decomposition of alkali pyrosulfates. The mechanism makes use of the semiconductivity of NiO and the availability of electron-rich centers in the pyrosulfate group to help the formation of an adsorption complex between them. NiO reacts to some extent with alkali pyrosulfates forming the yellow NiSO 4 and alkali sulfates as separate products. NiO and NiSO 4 form eutectic mixtures with alkali sulfates melting at temperatures lower than those of the pure salts.

High temperature reactions of titanium(IV) oxide with some alkali persulfates and their decomposition products

Abstract The solid state reactions between TiO 2 and Na 2 S 2 O 8 or K 2 S 2 O 8 have been investigated using TG, DTG, DTA, IR, and X-ray diffraction studies in the range of 20 to 1000°C. It has been shown that TiO 2 reacts stoichiometrically (1 : 1) with Na 2 S 2 O 8 in the range of 160 and 220°C forming the complex sodium monoperoxodisulfato—titanium(IV) as characterized by IR and X-ray analysis. The new complex then decomposes into the reactants above 190°C. An exothermic reaction has been observed between TiO 2 and molten K 2 S 2 O 7 at mole ratio 1:2 respectively and higher, in the range of 280 and 350°C. The IR and X-ray analyses have shown the formation of a complex namely, potassium tetrasulfato titanium(IV) for which the formula and structure have been proposed. This complex decomposes at higher temperatures into K 2 SO 4 and a mixed sulfate of potassium and titanium. The mixed sulfate melts at 620°C and decomposes into K 2 SO 4 , TiO 2 , and the gaseous SO 3 . On the other hand, Na 2 S 2 O 8 decomposes in a special mode producing a polymeric product of Na 10 S 9 O 32 . Decomposition of this species occurs after melting at 560°C into Na 2 SO 4 and sulfur oxides. The decomposition reaction has been proved to be catalysed by TiO 2 itself.

Electrothermal atomic-absorption determination of vanadium

Factors such as sample nature, matrix and heating programme have been found to influence both the sensitivity and precision of the determination of vanadium by electrothermal AAS. The reciprocal sensitivity, detection limit and precision (RSD) are 55 pg, 86 pg and 4%, respectively for aqueous solutions and 88 pg, 80 pg and 4% for organic solutions. Only tungsten and nitric acid have been found to interfere appreciably. Moderately concentrated sodium chloride solutions (6%) can be analysed for vanadium (0.05 mug/ml) without background correction, as can the acid digests of phosphate rocks and crude petroleum samples.

Thermal and X-Ray investigation of binary cobalto-cobaltic oxide—alkali persulfate systems

Abstract It has been found that cobalt(II, III) oxide, Co 3 O 4 , lowers the thermal decomposition temperature of Na 2 S 2 O 8 and K 2 S 2 O 8 by about 25°C by catalysis, and it therefore acts as a P-type semiconductor at high temperature and atmospheric (air) pressure. Also, this oxide reacts at high temperature with sodium or potassium pyrosulfates to form thermally stable sodium cobalt disulfate, Na 2 Co(SO 4 ) 2 and potassium cobalt trisulfate, K 2 Co 2 (SO 4 ) 3 , respectively. Binary systems, consisting of a 1 : 3 mole ratio (oxide : persulfate), are established as representing the solid state stoichiometric reaction. X-Ray diffractometry is employed to identify intermediate and final reaction products in general. All calculations are based on data obtained from TG, DTG and DTA curves.

Thermal and X-Ray studies of reactions between scandium(III) oxide and sodium or potassium persulfates

Abstract TG, DTG, and DTA experiments were carried out to elucidate the influence of Sc 2 O 3 on the thermal decomposition of Na 2 S 2 O 8 and K 2 S 2 O 8 under a static (air) atmosphere from ambient to 1050°C, using a derivatograph. X-Ray diffractometry has been employed to identify the intermediate and final decomposition products. Different Sc 2 O 3 Na 2 (K 2 )S 2 O 8 molar ratios were investigated and the 1 : 3 ratio found to be the one that gives stoichiometric reactions with either of these salts. Sc 2 O 3 was found to react at 250 and 440°C with the thermally produced Na 2 S 2 O 7 yielding Sc 2 (SO 4 ) 3 . The scandium(III) sulfate was thermally stable up to 840°C. Similarly, the oxide reacts stoichiometrically at 420°C to produce KSc(SO 4 ) 2 , a double salt which began to decompose at 840°. Moreover, three new crystalline phase-transformations were detected for Sc 2 (SO 4 ) 3 at 640, 695, and 735°C.

Thermoanalysis and catalytic study of transition metals acetylacetonates

Abstract The T, TG, DTG, and DTA curves of eight transition metals acetylacetonates, namely, those of Cr(II), Co(II), Cu(II), Fe(III), Mn(II), Ni(II), V(III) and VO(III) have been studied under air static and inert dynamic nitrogen or argon gases. Under the letter, their decomposition temperatures were increased by about 30–50 C. Their roles as promoting catalysts for the thermal decomposition of barium perchlorate trihydrate (BP.3H2O) have been investigated as well as the kinetic parameters, such as n, E, and log Z, of the decomposition of them. Evolved gaseous products (methane, acetylacetone, carbon dioxide and water) have been detected by GC. Solid intermediates and final products have been identified by XRD methods. Eight DIG and eight DTA curves (Figures 1 and 2) have been established to characterise each of the above metals acetylacetonates.