Search

We present a detailed study of the performance parameters for Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF with Ag, we get stable (CaF) currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate Ca from the isobar K at the detector, but the interference is reduced by using (CaF) ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, K, to estimate this interference (K-correction). After this correction, we reach a Ca/Ca background level between 5 × 10 and 8 × 10, making possible measurements of Ca/Ca ratios higher than 4 × 10. Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation.

We present a detailed study of the performance parameters for 41Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF2 with Ag, we get stable (40CaF3)− currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate 41Ca from the isobar 41K at the detector, but the interference is reduced by using (41CaF3)− ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, 39K, to estimate this interference (K-correction). After this correction, we reach a 41Ca/40Ca background level between 5 × 10−12 and 8 × 10−12, making possible measurements of 41Ca/40Ca ratios higher than 4 × 10−11. Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation.

We present a detailed study of the performance parameters for 41Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF2 with Ag, we get stable (40CaF3)− currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate 41Ca from the isobar 41K at the detector, but the interference is reduced by using (41CaF3)− ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, 39K, to estimate this interference (K-correction). After this correction, we reach a 41Ca/40Ca background level between 5 × 10−12 and 8 × 10−12, making possible measurements of 41Ca/40Ca ratios higher than 4 × 10−11. Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation.

We present a detailed study of the performance parameters for Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF with Ag, we get stable (CaF) currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate Ca from the isobar K at the detector, but the interference is reduced by using (CaF) ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, K, to estimate this interference (K-correction). After this correction, we reach a Ca/Ca background level between 5 × 10 and 8 × 10, making possible measurements of Ca/Ca ratios higher than 4 × 10. Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation.

Infant formula based on pea (Pisum sativum)-protein isolate has been suggested as an alternative to soyabean formula in countries where soyabean is not a native crop, or when soyabean protein cannot be used due to allergic reactions or intolerances. In the present study, Fe absorption from experimental infant formulas based on pea-protein isolate was measured in healthy non-anaemic young women. The influence of phytic acid and ascorbic acid on Fe absorption was evaluated, using a stable-isotope technique based on incorporation of Fe stable-isotope labels into erythrocytes 14 d after administration. Geometric mean Fe absorption increased from 20·7 (+1SD 41·6, -1sd 10·3) % to 33·1 (+1sd 58·6, -1sd 18·7) %; (P<0·0001; n 10) after enzymic degradation of virtually all phytic acid. Doubling the molar ratio Fe : ascorbic acid from 1 : 2·1 to 1 : 4·2 in the infant formula with native phytic acid content also increased Fe absorption significantly (P<0·0001; n 10); geometric mean Fe absorption increased from 14·8 (+1sd 32·1, -1sd 6·8) % to 22·1 (+1sd 47·2, -1sd 10·4) %. These results confirm the inhibitory and enhancing effects of phytic acid and ascorbic acid respectively on Fe absorption, but also indicate relatively high fractional Fe absorption from the pea-protein-based formulas. After adjusting for differences in Fe status, our data indicate that Fe absorption from dephytinised pea protein might be less inhibitory than dephytinised soyabean protein as measured in a previous study ()

We have evaluated urinary monitoring and erythrocyte analysis to determine Mg absorption in human subjects as alternatives to the conventional technique of faecal monitoring by stable-isotope techniques. Ten healthy adults received 2·2 mmol 25Mg in water, together with wheat bread, followed 15 min later by intravenous injection of 0·6 mmol 26Mg (day 1). Brilliant blue and Yb (given on day 0 and day 1 respectively) served as qualitative and quantitative faecal markers. Urine was collected for 6 d after test meal intake. Complete collections of faeces were made until excretion of the second brilliant blue marker (given on day 7). Mg isotope ratios were determined by thermal ionisation-MS in urine and faeces and by inductively coupled plasma-MS in erythrocytes. Absorption was determined based on: (1) 6 d urine pools; (2) 24 h urine pools (collected 22-46 h after test meal intake); (3) erythrocytes from a blood sample drawn on day 14; (4) complete 6 d faecal pools; (5) faecal pools based on the first three consecutive stools after excretion of the first brilliant blue marker. Differences in mean Mg absorption (42 44 %) were statistically insignificant between techniques, except when based on 6 d urine pools for which the value was significantly lower (33 (sd 7) %, P=0·0003, ANOVA). The results indicate that Mg absorption can be determined from 24 h urine pools or erythrocytes obtained 14 d after test meal intake, an alternative method to the more time-consuming and labour-intense faecal monitoring. The choice of technique depends on practical and financial considerations

The aim of the present study was to evaluate Mg absorption from a test meal served with an oxalate-rich vegetable, spinach, as compared with a test meal served with a vegetable with a low oxalate content, kale. Mg absorption was measured by a stable-isotope technique based on extrinsic labelling of the test meals and faecal monitoring of the excreted isotope labels. Nine healthy adults participated in the study. The test meals were based on 100g phytate-free white bread, served with 300g spinach (6·6mmol oxalate; 0·7mmol 25Mg label added, 5·0mmol total Mg) or 300g kale (0·1mmol oxalate; 1·2mmol 26Mg label added, 4·8mmol total Mg). The test meals were served on days 1 and 3, at breakfast and lunch, using a cross-over design. The results from the present study demonstrated that apparent Mg absorption was significantly lower from the meal served with spinach (26·7 (sd 10·4) %) than the meal served with kale (36·5 (sd 11·8) %) (P=0·01). However, the lower fractional apparent Mg absorption from the test meal served with spinach can be assumed to be, at least partly, counterbalanced by the higher native Mg content of spinach as compared with kale. Although based on indirect evidence, i.e. not based on an evaluation of added (or removed) oxalic acid, the difference in Mg absorption observed in the present study is attributed to the difference in oxalic acid content between the two vegetables

Ascorbic acid and Na2EDTA enhance Fe absorption from the water-soluble Fe compound FeSO4 but their effect on poorly water-soluble Fe compounds such as ferrous fumarate is less well established. In the present study, the effects of ascorbic acid and Na2EDTA on Fe absorption from ferrous fumarate were evaluated in adult women (ten women/study) from the erythrocyte incorporation of Fe stable isotopes (57Fe or 58Fe) 14 d after administration. Two separate studies were made with test meals of Fe-fortified infant cereal (5 mg Fe/meal). Data were evaluated by paired t tests and the results are presented as geometric means. In study 1a, the comparison between Fe absorption from ferrous fumarate- and FeSO4-fortified cereal showed that adult women absorb Fe as well from ferrous fumarate as from FeSO4 (3·0 and 3·1 % respectively, P=0·85). After addition of Na2EDTA (Na2EDTA:fortification Fe molar ratio of 1:1), Fe absorption from FeSO4 was significantly higher than from ferrous fumarate (5·3 v. 3·3 % respectively, P<0·01; study 1b). In study 2, Fe absorption was compared from ferrous fumarate-fortified meals with and without ascorbic acid added at a 4:1 molar ratio (relative to fortification Fe) and the results showed that ascorbic acid increased Fe absorption from ferrous fumarate significantly (6·3 v. 10·4 %, P=0·02). The results of the present studies show that Fe absorption from ferrous fumarate is enhanced by ascorbic acid but not by Na2EDTA, thus emphasising that not all findings from Fe absorption studies made with FeSO4 can be extrapolated to Fe compounds with different solubility properties

We present a detailed study of the performance parameters for 41Ca measurements at the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Seville. Mixing CaF2 with Ag, we get stable (40CaF3)− currents between 50 and 100 nA. Transmission of the 2+ state in the He stripper is 41%, while optical transmission in the HE sector is typically higher than 95%. At low energies we cannot separate 41Ca from the isobar 41K at the detector, but the interference is reduced by using (41CaF3)− ions. The remaining contribution is corrected by measurement of the other stable isotope of potassium, 39K, to estimate this interference (K-correction). After this correction, we reach a 41Ca/40Ca background level between 5 × 10−12 and 8 × 10−12, making possible measurements of 41Ca/40Ca ratios higher than 4 × 10−11. Intercomparisons with the 0.6 MV AMS system at ETH Zurich show a quite good correlation.

1.Introduction. 2.41Ca measurements at low energy. 3.Performance of the 1 MV AMS system for 41Ca. 4.Measurements from biomedical samples; intercomparison with ETH Zürich 0.6 MV system. 5.Conclusions and prospects.

The biennial review of atomic-weight determinations and other cognate data has resulted in changes for the standard atomic weights of five elements. The atomic weight of bromine has changed from 79.904(1) to the interval [79.901, 79.907], germanium from 72.63(1) to 72.630(8), indium from 114.818(3) to 114.818(1), magnesium from 24.3050(6) to the interval [24.304, 24.307], and mercury from 200.59(2) to 200.592(3). For bromine and magnesium, assignment of intervals for the new standard atomic weights reflects the common occurrence of variations in the atomic weights of those elements in normal terrestrial materials.

Retinyl palmitate added to Fe-fortified maize bread has been reported to enhance Fe absorption in adult Venezuelan subjects but not in Western Europeans. It is not known to what extent these results were influenced by differences in vitamin A status of the study subjects. The objective of the present study was to evaluate the influence of retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe in children with vitamin A deficiency, before and after vitamin A supplementation. Erythrocyte incorporation of Fe-stable isotopes was measured 14 d after intake of maize porridge (2·0 mg Fe added as ferrous sulfate) with and without added retinyl palmitate (3·5 μmol; 3300 IU). The study was repeated 3 weeks after vitamin A supplementation (intake of a single dose of 210 μmol retinyl palmitate; ‘vitamin A capsule'). Vitamin A status was evaluated by the modified relative dose-response (MRDR) technique. Retinyl palmitate added to the test meal reduced the geometric mean erythrocyte incorporation of Fe at baseline from 4·0 to 2·6 % (P=0·008, n 13; paired t test). At 3 weeks after vitamin A supplementation, geometric mean erythrocyte incorporation was 1·9 and 2·3 % respectively from the test meal with and without added retinyl palmitate (P=0·283). Mean dehydroretinol:retinol molar ratios were 0·156 and 0·125 before and after intake of the single dose of 210 μmol retinyl palmitate; ‘vitamin A capsule' (P=0·15). In conclusion, retinyl palmitate added to the labelled test meals significantly decreased erythrocyte incorporation of Fe in children with vitamin A deficiency at baseline but had no statistically significant effect 3 weeks after vitamin A supplementation. The difference in response to retinyl palmitate added to Fe-fortified maize porridge on erythrocyte incorporation of Fe before and after intake of the vitamin A capsule indicates, indirectly, changes in vitamin A status not measurable by the MRDR technique. The lack of conclusive data on

Ferric pyrophosphate is a water-insoluble Fe compound used to fortify infant cereals and chocolate-drink powders as it causes no organoleptic changes to the food vehicle. However, it is only of low absorption in man. Recently, an innovative ferric pyrophosphate has been developed (Sunactive Fe™) based on small-particle-size ferric pyrophosphate (average size 0·3 μm) mixed with emulsifiers, so that it remains in suspension in liquid products. The aim of the present studies was to compare Fe absorption of micronised, dispersible ferric pyrophosphate (Sunactive Fe™) with that of ferrous sulfate in an infant cereal and a yoghurt drink. Two separate Fe absorption studies were made in adult women (ten women/study). Fe absorption was based on the erythrocyte incorporation of stable isotopes (57Fe and 58Fe) 14 d after the intake of labelled test meals of infant cereal (study 1) or yoghurt drink (study 2). Each test meal was fortified with 5 mg Fe as ferrous sulfate or micronised, dispersible ferric pyrophosphate. Results are presented as geometric means. There was no statistically significant difference between Fe absorption from micronised, dispersible ferric pyrophosphate- and ferrous sulfate-fortified infant cereal (3·4 and 4·1 % respectively; P=0·24) and yoghurt drink (3·9 and 4·2 % respectively; P=0·72). The results of the present studies show that micronised, dispersible ferric pyrophosphate is as well absorbed as ferrous sulfate in adults. The high relative Fe bioavailability of micronised, dispersible ferric pyrophosphate indicates the potential usefulness of this compound for food fortification

Infant formula based on pea (Pisum sativum)-protein isolate has been suggested as an alternative to soyabean formula in countries where soyabean is not a native crop, or when soyabean protein cannot be used due to allergic reactions or intolerances. In the present study, Fe absorption from experimental infant formulas based on pea-protein isolate was measured in healthy non-anaemic young women. The influence of phytic acid and ascorbic acid on Fe absorption was evaluated, using a stable-isotope technique based on incorporation of Fe stable-isotope labels into erythrocytes 14 d after administration. Geometric mean Fe absorption increased from 20·7 (+1SD 41·6, -1sd 10·3) % to 33·1 (+1sd 58·6, -1sd 18·7) %; (P<0·0001; n 10) after enzymic degradation of virtually all phytic acid. Doubling the molar ratio Fe : ascorbic acid from 1 : 2·1 to 1 : 4·2 in the infant formula with native phytic acid content also increased Fe absorption significantly (P<0·0001; n 10); geometric mean Fe absorption increased from 14·8 (+1sd 32·1, -1sd 6·8) % to 22·1 (+1sd 47·2, -1sd 10·4) %. These results confirm the inhibitory and enhancing effects of phytic acid and ascorbic acid respectively on Fe absorption, but also indicate relatively high fractional Fe absorption from the pea-protein-based formulas. After adjusting for differences in Fe status, our data indicate that Fe absorption from dephytinised pea protein might be less inhibitory than dephytinised soyabean protein as measured in a previous study ()

We have evaluated urinary monitoring and erythrocyte analysis to determine Mg absorption in human subjects as alternatives to the conventional technique of faecal monitoring by stable-isotope techniques. Ten healthy adults received 2·2 mmol 25Mg in water, together with wheat bread, followed 15 min later by intravenous injection of 0·6 mmol 26Mg (day 1). Brilliant blue and Yb (given on day 0 and day 1 respectively) served as qualitative and quantitative faecal markers. Urine was collected for 6 d after test meal intake. Complete collections of faeces were made until excretion of the second brilliant blue marker (given on day 7). Mg isotope ratios were determined by thermal ionisation-MS in urine and faeces and by inductively coupled plasma-MS in erythrocytes. Absorption was determined based on: (1) 6 d urine pools; (2) 24 h urine pools (collected 22-46 h after test meal intake); (3) erythrocytes from a blood sample drawn on day 14; (4) complete 6 d faecal pools; (5) faecal pools based on the first three consecutive stools after excretion of the first brilliant blue marker. Differences in mean Mg absorption (42 44 %) were statistically insignificant between techniques, except when based on 6 d urine pools for which the value was significantly lower (33 (sd 7) %, P=0·0003, ANOVA). The results indicate that Mg absorption can be determined from 24 h urine pools or erythrocytes obtained 14 d after test meal intake, an alternative method to the more time-consuming and labour-intense faecal monitoring. The choice of technique depends on practical and financial considerations

The aim of the present study was to evaluate Mg absorption from a test meal served with an oxalate-rich vegetable, spinach, as compared with a test meal served with a vegetable with a low oxalate content, kale. Mg absorption was measured by a stable-isotope technique based on extrinsic labelling of the test meals and faecal monitoring of the excreted isotope labels. Nine healthy adults participated in the study. The test meals were based on 100g phytate-free white bread, served with 300g spinach (6·6mmol oxalate; 0·7mmol 25Mg label added, 5·0mmol total Mg) or 300g kale (0·1mmol oxalate; 1·2mmol 26Mg label added, 4·8mmol total Mg). The test meals were served on days 1 and 3, at breakfast and lunch, using a cross-over design. The results from the present study demonstrated that apparent Mg absorption was significantly lower from the meal served with spinach (26·7 (sd 10·4) %) than the meal served with kale (36·5 (sd 11·8) %) (P=0·01). However, the lower fractional apparent Mg absorption from the test meal served with spinach can be assumed to be, at least partly, counterbalanced by the higher native Mg content of spinach as compared with kale. Although based on indirect evidence, i.e. not based on an evaluation of added (or removed) oxalic acid, the difference in Mg absorption observed in the present study is attributed to the difference in oxalic acid content between the two vegetables

Ascorbic acid and Na2EDTA enhance Fe absorption from the water-soluble Fe compound FeSO4 but their effect on poorly water-soluble Fe compounds such as ferrous fumarate is less well established. In the present study, the effects of ascorbic acid and Na2EDTA on Fe absorption from ferrous fumarate were evaluated in adult women (ten women/study) from the erythrocyte incorporation of Fe stable isotopes (57Fe or 58Fe) 14 d after administration. Two separate studies were made with test meals of Fe-fortified infant cereal (5 mg Fe/meal). Data were evaluated by paired t tests and the results are presented as geometric means. In study 1a, the comparison between Fe absorption from ferrous fumarate- and FeSO4-fortified cereal showed that adult women absorb Fe as well from ferrous fumarate as from FeSO4 (3·0 and 3·1 % respectively, P=0·85). After addition of Na2EDTA (Na2EDTA:fortification Fe molar ratio of 1:1), Fe absorption from FeSO4 was significantly higher than from ferrous fumarate (5·3 v. 3·3 % respectively, P<0·01; study 1b). In study 2, Fe absorption was compared from ferrous fumarate-fortified meals with and without ascorbic acid added at a 4:1 molar ratio (relative to fortification Fe) and the results showed that ascorbic acid increased Fe absorption from ferrous fumarate significantly (6·3 v. 10·4 %, P=0·02). The results of the present studies show that Fe absorption from ferrous fumarate is enhanced by ascorbic acid but not by Na2EDTA, thus emphasising that not all findings from Fe absorption studies made with FeSO4 can be extrapolated to Fe compounds with different solubility properties