Although particle size and its measurement are intuitively familiar to particle technologists, the concept of point of zero charge (pzc) is less widely understood and applied. This is unfortunate since it is at least as fundamentally important as particle size in determining the behavior of particulate materials, especially those with sizes in the colloidal range below a micrometer. pzc is related to the charge on the surface of the particle and strongly depends on the pH of the material; so it influences a wide range of properties of colloidal materials, such as their stability, interaction with electrolytes, suspension rheology, and ion exchange capacity. The pH dependence of surface charges was quantified for four different adsorbent–aqueous solution interfaces. The points of zero charge were determined for activated charcoal, granite sand, lakhra coal, and ground corn cob materials using three methods: (1) the pH drift method, measuring pH where the adsorbent behaves as a neutral specie; (2) potentiometric titration, measuring the adsorption of H + and OH - on surfaces in solutions of varying ionic strengths; (3) direct assessment of the surface charge via nonspecific ion adsorption as a function of pH. The intrinsic acidity constants for acid and base equilibria, [Formula: see text] and [Formula: see text], were also calculated. Lakhra coal was found to have the lowest pzc value among all other adsorbents studied owing to the presence of a large amount of humus material. The results were used to explain general connections among points of zero charges, cation exchange capacity, and base saturation % of adsorbents.

BACKGROUND: The fruit of date palm is consumed as an ideal high-energy food. It is also used for the treatment of colds, fever, liver and abdominal troubles. Its nutritional composition strongly depends upon variety and ripening stage. A number of varieties are available in Pakistan but little is known about their composition and nutritional characteristics. Inherent moisture, volatile matter, ash, fixed carbon, sugar and mineral metals of seven commercial date varieties (Aseel, Basra, Begun, Janshoor, Mazoee, Rabee and Zaidi) were investigated. The physical and chemical compositions with respect to maturation were also monitored for the Aseel variety. RESULTS:The results showed significant varietal differences in moisture, ash and mineral metal composition when analysis of means was conducted at an alpha level of 0.05. The difference between means was insignificant (P > 0.05) for volatile matter, glucose, fructose and total reducing sugars. All varieties were found to be an excellent source of total reducing sugar (78%), potassium (403-632 mg per 100 g) and calcium (27.41-81.47 mg per 100 g). A gradual increase in total reducing sugar and minerals, especially potassium and copper, was observed with maturation. Variety Aseel was grouped on the basis of maturation using principal component analysis. Local date varieties were separated with 48.63% level of similarity from Iranian variety (29.17%) using Cluster analysis.CONCLUSION: This study provides an overview of the physico-chemical properties of date varieties. The sample varieties showed significant differences except for sugar and volatile matter. Multivariate analysis was found to be an important statistical tool for the separation of samples on the basis of geographical origin and maturations.

The nutritional composition of Ficus carica commonly known as fig is of great interest as it is considered a good source of energy and minerals. Seven samples of fig, cultivated in Pakistan were studied for their physico-chemical properties. All samples had little moisture, less amounts of ash and high volatile matters. Low moisture is favorable in preventing the fermentation of the fruit while high volatiles are responsible for its unique taste. The energy content of the samples ranged between 337.60 -364.70 kcal/100g. The samples were found to be a good source of potassium (3.82-6.11 g/kg), magnesium (0.11-0.20 g/kg), calcium (78.72-132.80 mg/kg) and sodium (5.58-17.69 mg/kg). The mineral and trace contents of the indigenous samples were compared with the samples cultivated in the USA, Turkey and Iran. The samples cultivated in Pakistan were found to have good nutritional values especially higher calorific value and iron content compared to the reported data. The Ca/P ratio in the indigenous variety lies as recommended by nutritionists. This feature made the indigenous variety distinct as the patients suffering from stone formation in kidney may also use it safely. The high potassium in fig is beneficial not only to patients of hypertension but also prevents the bones from rapid thinning by neutralizing the increased urinary calcium loss. Significant correlations were found between iron and potassium, copper and potassium and zinc and copper (p<0.05). The positive correlations are either due to higher uptake of metals by the plant or the excess availability of the metals in the soil. Analysis of means (ANOM) was applied to evaluate the compositional variations between the samples. The study provides an overview of the physico-chemical properties of fig samples indigenous to Pakistan. The results offer useful information not only to consumers who want to buy the best quality fruit, but also to producers interested in increasing the competitiveness of fig cultivation.

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A sensitive and selective kinetic-spectrophotometric method is proposed for the determination of µg mL -1 amounts of Cu 2+ based on its catalytic effect on the oxidation of L-ascorbic acid by Methylene Blue in a strongly acidic medium. The reaction is monitored spectrophotometrically by measuring the decrease in color intensity of Methylene Blue at 665 nm. The analysis of Cu 2+ ion is performed by a fixed-time method. At a given time of 2 min at pH 2.20 and 32˚C, the detection limit is 10 ng mL -1 and the relative standard deviation for 0.4 µg mL -1 Cu 2+ is 3.60% (n = 6). The method is free from most of the interferences and the effect of diverse ions on the determination of Cu 2+ is also reported. The proposed method is virtually specific to copper and has been satisfactorily applied to its determination in electric copper wire samples and pharmaceutical products. Results were also verified by the atomic absorption spectrometry technique (AAS).