Lycopene that imparts red color to the tomato fruit is the most potent antioxidant among carotenes, an important nutrient and also used as a color ingredient in many food formulations. Since cooked and processed foods derived from tomatoes were shown to provide optimal lycopene boost, products such as paste, puree, juice, etc. are nowadays gaining popularity as dietary sources. The analysis of lycopene in tomato paste ͑partially dehydrated product prepared by vacuum concentrating tomato juice͒ is carried out using either high pressure liquid chromatography ͑HPLC͒, spectrophotometry, or by evaluating the color. The instability of lycopene during processes of extraction, etc., handling, and disposal of organic solvents makes the preparation of a sample for the analysis a delicate task. Despite a recognized need for accurate and rapid assessment of lycopene in tomato products no such method is available at present. The study described here focuses on a direct determination of a total lycopene content in different tomato pastes by means of the laser optothermal window ͑LOW͒ method at 502 nm. The concentration of lycopene in tomato paste ranged between 25 and 150 mg per 100 g product; the results are in excellent agreement with those obtained by spectrophotometry. The time needed to complete LOW analysis is very short, so that decomposition of pigment and the formation of artifacts are minimized. Preliminary results indicate a good degree of reproducibility making the LOW method suitable for routine assays of lycopene content in tomato paste.

An acidic homogenate method, which includes simple homogenization pre-treatment of tissue material and direct nebulization flame atomic absorption spectrometry (FAAS), is successfully applied to the simultaneous determination of copper, manganese and zinc in rat liver. The proposed method involves only a few steps for sample pre-treatment at room temperature, making the risk of systematic errors very small. Because recoveries of 101% for copper, 98% for manganese and 100% for zinc could be achieved using aqueous standards, matrix-matched standards were redundant. Favourable results obtained in biological media, including limits of detection of 0.04, 0.03 and 0.04 mg l-1 for Cu, Mn and Zn, respectively, together with accuracies of 0-3%, and relative standard deviations ranging from 2 to 10% are further evidence of the suitability of the method.

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A new photothermal method suitable for direct, accurate and highly reproducible quantitative measurements of lycopene in tomato products has been introduced. The intrinsic precision of the method is typically better than 0.2%; the repeatability of determination is comparable to that of high-performance liquid chromatography, with 0.86% least overall error.