Ochratoxin A

Ochratoxin A (Figure 3) is a metabolite of some Aspergillus and Penicillium species. It is found as a contaminant of barley, corn, wheat, oats and coffee. It has also been found in meat, human blood and human milk. Ochratoxin A causes porcine neph-ropathy, notably in some Scandinavian countries when contaminated barley is fed to swine. Och-ratoxin A is extracted from samples with chloroform in the presence of phosphoric acid and cleaned up using partition into sodium bicarbonate and C18 solid-phase extraction. In a similar manner to the TLC of aflatoxin discussed above, ochratoxin A is spotted on a plate pre-coated with a 0.25 mm layer of silica gel 60 (E. Merck, Darmstadt) and developed with benzene-methanol-acetic acid (18 : 1 : 1 v/v) or toluene-ethyl acetate-formic acid (5:4:1 v/v). After drying, the plate is examined under long and short wave ultraviolet light (365 and 254 nm). Ochratoxin A (Rf = 0.65) fluoresces brightest under long wave ultraviolet light and is usually accompanied by the less toxic ochratoxin B (RF = 0.5) which fluoresces brightest under short wave ultraviolet light. The fluorescence of the ochratoxins can be enhanced by spraying the plate with alcoholic sodium bicarbonate solution which changes them to their more fluorescent salt forms. The ochratoxins can be confirmed by ester formation using boron trifluoride in ethanol and re-chromatographing using the same conditions as above. The ethyl esters appear at lower RF values than the parent compounds under long and short wave ultraviolet light.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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