The oral nitrate and nitrite intake in The Netherlands: evaluation of the results obtained by HPIC analysis of duplicate 24-hour diet samples collected in 1994

lit spring and autumn of 1994 duplicates of 24-h diets were collected from 123 respondents. One of the goals of this study was to determine the amount of nitrite and nitrate in the duplicates of 24-h diets to establish the or al daily intake of these analytes. For this purpose an HPIC/UV method for t he determination of nitrate and nitrite in duplicate diets was developed an d validated. The sample preparation procedure was derived from the in-house method used for the determination of nitrate and nitrite in human blood pl asma. The sample is diluted with water, deproteinized with Carrez reagent, followed by chromatographic clean-up on an SPE C18-column. Both the nitrate and the nitrite results are quantitative. The recovery for nitrite was on average 104% (n = 21, spiking levels. 0.84-95 mg/kg) and for nitrate on ave rage 103% (N = 21, spiking levels. 1.8-404 mg/kg). Samples of duplicates of 24-h diets were analysed according to rite method developed. The median in take of nitrite calculated from the samples collected in spying 1994 I vas 0.6 mg/person/day (range < 0.1-6.1 mg/person/day). For the samples collecte d in autumn 1994 these figures were <0.2 mg/person/day (range < 0.1-16 mg/p erson/day). The mean intake of nitrate was 73 mg/person/day (range 7-322 mg /person/day) in spring 1994 and 87 mg/person/day (range 4-310 mg/person/day ) in autumn 1994. The overall mean intake of nitrate in 1994 was 80 mg/pers on/day. The daily intake for nitrate was higher than that found in the dupl icate diet study carried out in 1984/1985, when an average daily intake of 52 mg/person was measured. The intake of nitrite was also higher than found in the duplicate diets collected in 1984/1985. The findings of the study a re discussed in the context of the ADI for nitrate and nitrite as well as t he outcome of other recent European intake studies.