Elemental analysis of solutions can be achieved by concentrating and immobilizing the metal ions into a commercially available ion exchange polymer membrane followed by laser-induced breakdown spectroscopy. Two methods of sample preparation were investigated: filtering the solution through the ion exchange membrane with suction, and placing the membrane in the solution and allowing the ions to equilibrate with the membrane. The membrane was then ablated with the focused energy of a Nd:YAG laser at 1064 nm. The emitted light was collected by an echelle spectrometer through a fiber-optic cable and detected with an intensified charge-coupled device (CCD). Ten different metals, most covered by the Resource Conservation and Recovery Act (RCRA), were studied. The concentrations of barium, cadmium, chromium, cobalt, copper, silver, lead, mercury, nickel, and zinc can be measured simultaneously with limits of detection ranging from 2 μg/mL to 4 ng/mL. The linear range is 2–6 orders of magnitude depending upon the element and sampling method. The major advantages of the technique are the multielement capability and the ease of sample preparation.

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A spectrophotometric assay for pyruvic acid in onion has been adapted to a microplate reader. Correlations between the spectrophotometer and microplate reader rangedfiom 0.991-0.997 for sodium pyruvate standards and 0.899-0.934 for onion samples. Onion pungency values were slightly higher with the microplate reader for both sample and background compared with the spectrophotometer when both are used in the single wavelength mode. Comparing the spectrophotometer in the single wavelength mode to the microplate reader in the dual wavelength mode resulted in no statistically significant diference between them. Standards for both the microplate reader and spectrophotometer followed a quadratic function.'To whom to direct inquiries: Ph: (912)681-5639. Fax: (912)6814376. (1999) 225-233. All Righls Resewed. eCopyrighr 1999 by Food di Nutrition Press, lnc.. TNmbulI. Connecticut. 22s 226 G.E. BOYHAN et al. Journal of Food Quality 22

Onion pungency is a major quality attribute with many consumers demanding less pungent onions. In recent years, some growers and retailers have attempted to measure pungency of onions produced in different regions to guarantee a desired level of pungency. However, there are few data on the variability among laboratories using standardized protocols to estimate relative levels of pungencies. Onion cultivars were grown in replicated trials at three locations. Random samples of bulbs from each experimental unit were harvested and shipped to at least three cooperating laboratories, each of which measured soluble solids content (SSC) and pungencies using the same techniques. As expected, cultivars and environments showed significant (P < 0.001) differences. For all three trials, laboratories were a highly significant source of variation (P < 0.024 to 0.001) for measurements of SSC and pungency. Therefore, one cannot make recommendations on relative pungencies of the same lots of onions measured by different labs. The onion research community must identify specific procedures to reduce variation among laboratories to develop a more repeatable standardized assay for the measurement of onion pungency.