Mortality of eggs and third instar larvae of Anastrepha ludens and A. obliqua with insecticidal controlled atmospheres at high temperatures     

Elhadi M. Yahia  Dora Ortega-Zaleta 《Postharvest Biology and Technology》2000,20(3):295-302

The in vitro mortality of eggs and third instar larvae of Anastrepha ludens and A. obliqua was determined after exposure to 21 treatments of air or controlled atmospheres (CA) at high temperatures and 50% RH. Air at 44°C for 160 min caused very low mortality, which increased significantly by CA. Higher temperatures caused a more rapid kill. One hundred percent mortality was achieved for third instar larvae of both species in air or CA at 48°C for 220 min. A 100% mortality of eggs of A. ludens was achieved in air at 51°C for 240 min or in CA at 52°C for 240 min, and 100% mortality of eggs of A. obliqua was achieved in air or in CA at 55°C for 240 min. A. obliqua was slightly more tolerant than A. ludens, and eggs were more tolerant than third instar larvae in both species. CA had a synergistic effect at <50°C, but was slightly less effective than air at higher temperatures. Low O₂ concentrations were more effective than high CO₂ levels. The mean estimated temperatures for 50, 99 and 99.9968% mortality (LT₅₀s, LT₉₉s, LT_99.9968s) of eggs of A. obliqua (the most tolerant) exposed to 0 kPa O₂+50 kPa CO₂ for 240 min were 49.4, 54.8 and 60.9°C, respectively. We conclude that dry hot air at ≥44°C and 50% RH in CA (0 kPa O₂+50 kPa CO₂), for 160 min or longer, is effective in increasing mortality of eggs and third instar larvae of A. ludens and A. obliqua.  相似文献   

Postcolumn Fluorimetric HPLC Procedure for Determination of Niacin Content of Cereals     

Padmanaban G. Krishnan  Iftekher Mahmud  Duane P. Matthees 《Cereal Chemistry》1999,76(4):512-518

Analytical procedures for determining niacin or vitamin B3 content of foods are tedious, require large quantities of toxic chemicals, and are timeconsuming. In addition, food matrices are difficult as samples because of their complex nature. A selective, sensitive HPLC technique was developed with postcolumn derivatization as well as fluorescence and spectroscopic detection systems. Niacin was separated and retained for 6.5 min on a polymeric column with an aqueous mobile phase containing sodium acetate buffer. A postcolumn system consisting of a stainless-steel pump and reaction coil allowed detection and quantitation of niacin. An acid-enzyme sample-extraction method was most compatible with HPLC and postcolumn derivatization with 5% each of acidified p-aminophenol and cyanogen bromide. Lower detection limit and mean recovery were 3.6 ng and 99.43%, respectively. Fluorescence response for nicotinamide was half that of nicotinic acid. A lower response for nicotinamide was also noted with conventional spectroscopy. However, the new method yielded comparable values for six of eight ready-to-eat commercial cereal samples. No significant difference was observed between the AACC reference and HPLC fluorimetric methods. Chemical derivatization was done within a reaction coil with reagents at half strength, limiting exposure to hazards and minimizing waste-disposal problems.  相似文献