Josette Alary

Effect of geographic origin, variety and storage on tocopherol concentrations in walnuts by HPLC

Abstract Retinol, tocopherols and carotenes were extracted from walnut kernels. Three walnut extraction procedures were compared. Direct hexane extraction was selected. The fat-soluble vitamin separation was achieved by reversed-phase high performance liquid chromatography equipped with a ternary mobile phase gradient (methanol, butanol, water), and wavelength programming. The chromatographic run was under 35 minutes. This technique allowed a good resolution of α, γ, δ tocopherols, α and β carotenes and retinol. Two walnut varieties (Franquette and Hartley) from two geographical origins (France, USA) were analyzed. Retinol, and carotenes were not identified in walnuts. The amounts of α, γ, δ tocopherols ranged respectively from 1.08 to 4.05, 21.78 to 26.46, and 2.51 to 4.23 (mg/100 g). Significant differences related to variety and geographical origin were observed. A decrease in tocopherols (about 30%) was observed after 3 month refrigerated storage.

Mineral composition of two walnut cultivars originating in France and California

Mineral composition of two walnut cultivars (Franquette and Hartley) originating both in France and California was determined. Microwave assisted mineralisation was followed by atomic absorption spectrometry for all minerals except selenium which was quantified by gas chromatography–mass spectrometry (GC–MS), and phosphorus by a colorimetric method. Three elements presented major level differences linked to variety or origin. For origin, potassium levels of the French walnuts were higher (Franquette: 487 and Hartley: 466 mg 100 g−1) than those of the Californian walnuts (Franquette: 358 and Hartley: 372 mg 100 g−1). Inversely, sodium level was higher in the Californian Hartley than in the French Hartley (6.7 vs 0.3 mg 100 g−1). For variety, high levels of magnesium were observed for the Franquette cultivars (French: 191 and Californian: 202 mg 100 g−1) while the Hartley levels were lower (French: 129 and Californian: 134 mg 100 g−1). The same observation could be made for zinc, but the differences were weaker. Nevertheless, these data could not differentiate the walnuts according to origin or variety.

HPLC analysis of antioxidants.

Qualitative and quantitative HPLC methods are described for the analysis of mixtures of twelve antioxidants. For identification of the components present, gradient elution with a convex profile from 35:65 v/v water-methanol to pure methanol is used, on a Waters 5 mum C(18) Resolve column, with an ultraviolet detector. Propyl gallate and methyl p-hydroxybenzoate cannot be separated, however. For quantitative analysis, with ultraviolet and electrochemical detectors in series, the 35:65 water-methanol mixture or pure methanol is used as the eluent, under isocratic conditions, with lithium perchlorate as supporting electrolyte. An applied potential ranging from +0.8 to + 1.7 V allows detection of all the antioxidants tested. Both modes of detection are very sensitive, with limits of detection as low as 61 pg (UV, methyl p-hydroxybenzoate) and 360 pg (electrochemistry, butylhydroxyanisole).

Dansyl amino acid enantiomer separation on a teicoplanin chiral stationary phase : effect of eluent pH

The retention and separation of a series of D,L dansyl amino acids (used as test solutes) on a teicoplanin stationary phase were investigated over a wide range of mobile phase (citrate buffer-methanol, 90:10, v/v) pH. An approach based on the development of various equilibria was carried out in order to describe the retention behavior of the solute in the chromatographic system. The equilibrium constants corresponding to the transfer of the anionic and zwitterionic forms of the dansyl amino acids from the mobile to the stationary phase were determined. These values allowed one to explain the decrease in the retention factor and the associated increase in the separation factor as the eluent pH was increased. Thermodynamic parameter variations were calculated so that the driving forces of the solute association with the teicoplanin phase were derived. This approach indicated that the chiral discrimination was principally controlled by the interaction between the anionic form of the solute and the stationary phase.

Effect of temperature on DNA fractionation in slalom chromatography.

Slalom chromatography is an alternative chromatographic procedure for the analysis of relatively large double-stranded DNA molecules and is based on a hydrodynamic principle. The retardation of the DNA fragments from the cleavage of the Lambda DNA by the KpnI restriction enzyme was studied using an acetonitrile-phosphate buffer as a mobile phase (flow rate equal to 0.3 ml/min) and a C1 column as a stationary phase at various temperatures. It was shown that the temperature constituted an important parameter for the separation of the DNA fragments in slalom chromatography. The DNA hydrodynamic behavior with the temperature was related to the variation in the fluid viscosity and the modification of the elastic properties of the biopolyrner.

Zinc determination in human milk by flameless atomic absorption spectrometry after dry ashing

A zinc determination method, using a dry ashing step and flameless atomic absorption spectrometry is described. Milk samples were dry ashed at 400°C. Then, the ash was dissolved in 0.1 m nitric acid (final dilution = 1 + 99). The within-run precision was found to be 8%. The between-run was found to be 5%. The recovery of standard addition was found to be 109 ± 9%. The linear range was 122 nmol litre−1 to 2 μmol litre−1. The analytical variables (dry ashing temperature, dilution rate, acid, furnace, calibration) are discussed. A significant loss of zinc was observed at temperature <450°C. The dilution rate and acid used for dissolution of dry ash had an important effect on the validity of the method. A comparison of the proposed method with a direct method without an ashing step was performed. The results obtained from these two methods were similar. From these results, it is concluded that flameless atomic absorption spectrometry after dry ashing is a reliable technique for the determination of zinc in solid foods or tissues.

Fatty Acid Nutriture in Hospitalized Elderly Women

OBJECTIVE The aim of this study was to measure the fatty acid (FA) dietary intakes and the FA composition of plasma total lipids in a selected group of hospitalized elderly patients. METHODS Twenty-three women aged 76 to 99 years were recruited. FA were analyzed in 5-day duplicate portions and in plasma by gas liquid chromatography. RESULTS The hospitalized elderly women ingested an average of 5.22 megajoules (MJ) and 45.9 g of lipids per day. Polyunsaturated fatty acids (PUFA) represented 11.0% and saturated fatty acids (SFA) 53.6% of the lipid intake. Minimal recommendations for linoleic acid intake were reached in average, but 32% of the patients ingested less than 3 g of linoleic acid/d. Eighty-six percent received less than 0.5% of energy for alpha-linolenic acid and 64% had low intakes in very long-chain n-3 FA. In parallel, these patients presented several biochemical signs of essential fatty acids (EFA) insufficiency (decrease in linoleic acid, increase in monounsaturated fatty acids (MUFA), in n-7 FA and in indexes of delta-6 and delta-9 desaturase activities). CONCLUSIONS Hospitalized elderly patients have low PUFA intakes and show biochemical indices of EFA insufficiency. These patients might benefit from a nutritional supplementation providing both EFA and antioxidant micronutrients to limit the risk of skin troubles, immune system impairment and vascular disease often observed in institutionalized elderly subjects.

Determination of zinc in human milk by electrothermal atomic absorption spectrometry

An electrothermal atomic absorption spectrometric method has been developed for determining zinc in human milk. Milk samples were analysed after 1+99 dilution with 0.1% Triton X-100. The within-run precision was found to be 4.6%. The accuracy was ascertained by recovery of standard additions, and was found to be 96 ± 10%(n= 85 milk samples). The accuracy was also checked against National Institute of Standards and Technology Standard Reference Material 1549 Non-Fat Milk Powder. The results were 713 ± 35 µmol g–1(n= 38)(certified value: 705 ± 34 µmol g–1). The detection limit was found to be 0.052 µmol l–1. The calibration graph was linear up to 3 µmol l–1. The choice of experimental parameters (diluent, dilution rate, background correction, graphite furnace tube, etc.) are discussed. Normal values for colostrum and transitional milk varied from 45 to 318 and from 30 to 146 µmol l–1, respectively.

FLOW RATE DEPENDENCE ON THE BIOPOLYMER RETENTION IN HYDRODYNAMIC CHROMATOGRAPHY. COMPARISON BETWEEN THE BEHAVIORS OF PROTEINS AND PLASMIDS

Hydrodynamic chromatography (HDC) in a packed column is a useful chromatographic mode for the rapid separation of polymers. This paper compared the retention of various circular double-stranded DNA molecules (3, 5 and 10 kbp) and proteins (keyhole lumpet hemocyanin, ferritin, thyroglobulin, and catalase) in a chromatographic system using a C1 stationary phase and a acetonitrile-phosphate buffer mixture as a mobile phase. For a similar molecular weight, the protein was retained more than the corresponding plasmid. This was attributed to the difference in the compactness between the two species. As well, the retention dependence on the flow rate (0.03 to 1.5 mL/min) exhibited a different behavior in relation to the type of biopolymer. The protein retention curve showed a decrease in the relative retention time until 0.2 mL/min, followed by an increase for the high size polymers, only, while the plasmid retention increased over the entire flow rate range. This observation confirmed that the migration in HDC was dependent on two antagonist phenomena, i. e. stress induced diffusion and polymer deformation. This work demonstrated that the HDC separation of protein was optimal for a flow rate equal to 0.2 mL/min.

Sucrose effect on reversed-phase liquid chromatography solute retention

The reversed-phase liquid chromatography retention of a series of benzoate ester molecules was investigated over a wide range of sucrose concentrations (c) 0.01‐0.8 M using a C18 as the stationary phase and a methanol‐water mixture with high organic fraction (60/40, v/v) as the mobile phase. A theoretical treatment was developed to investigate the effect of sucrose molecules on the equilibrium between the solutes and the C18 phase and the methanol‐water medium, respectively. This was found to be adequate to accurately describe the benzoate ester retention behavior when c varied. It was expected that the addition of sucrose was responsible for two main opposite contributions to solute retention, (i) a net interaction between the solute and the modifier in the mobile phase determining a decrease in k 0 values with c up to 0.2 M; and (ii) an increase in the solute affinity for the C18 stationary phase due to the salting-out effect governing a retention increase above 0.2 M. Thermodynamic parameter variations were calculated using van’t Hoff plots and discussed in relation to this retention model to confirm the respective effects of the modifier on the solute affinity towards the two phases.