1990/8/31 · The acetonitrile HPLC grade (Carlo Erba, Italy) and double-distilled water were filtered through 0.45 jam Millipore membranes. The high-performance liquid chromatograph used (Perkin Elmer, series 4) was equipped with a injector with a 20 ^1 loop (Rheodyne, model 7125), a variable-wavelength detector (Perkin Elmer, LC 75) and a strip chart recorder (Kipp Zonen, model BD 41).