Alfredo Sanz Medel

Total determination of essential and toxic elements in milk whey by double focusing ICP-MS

A method is presented for the multielemental analysis of a wide range of elements in milk whey, using a double focusing ICP-MS instrument. Whey samples were diluted, 1 + 4 for minor and trace elements and 1 + 1999 for major elements, with ultrapure water and addition of Ga, Y, Rh, In and Tl as internal standards. Two different scans were used for the analysis. The first scan, m/Δm = 300, for the analysis of Sr, Cd, Hg and Pb and the second scan, m/Δm = 3000, for the analysis of Na, Al, Ca, Mg, Cr, Mn, Fe, Ni, Cu, Zn and Se. The lower background and greater sensitivity of double focusing instruments at low resolution mode provide better detection limits than quadrupole based instruments. A reference material, BCR Natural skim milk powder (CRM 063R), was analysed for the validation of the proposed method. The found levels show a good concordance with certified levels. The method was also applied to the multielemental analysis of human milk whey, cow milk whey and formula milk whey. The results obtained show considerable differences in trace element content on human, cow and formula milk whey.

High performance liquid chromatography methods for studying protein binding of aluminium in human serum in the absence and in the presence of desferrioxamine

Ion-exchange high performance liquid chromatography of serum proteins was combined with aluminium determination by electrothermal-atomisation-atomic-absorption spectroscopy and fluorimetry for studying the distribution of aluminium in human serum in the absence and in the presence of desferrioxamine. Aluminium was eluted as a single peak in the same fraction as transferrin. However, following the addition of desferrioxamine most of the aluminium was liberated from transferrin and become attached to the chelator.

Multi-elemental fractionation in milk whey by size exclusion chromatography coupled on line to ICP-MS

A fast hybrid technique based on HPLC coupled to ICP-MS was used to study elemental fractionation patterns in milk whey of different types of milk (human, cow and formula milk) taking advantage of the multi-elemental capability of ICP-MS. Milk whey was obtained from the corresponding whole milk samples by resorting to ultra-centrifugation. The method described separated the different fractions in a high-pressure column, based on size exclusion chromatography (SEC) on a TSK G 2000 SWXL column, coupled on-line to the inductively coupled plasma mass spectrometer for multi-elemental detection. After optimisation of the instrumental conditions, the method was applied to investigate the fractionation pattern of Fe, Cu, Zn, Mn, Sr, I, Br, Ca and Mg in four different samples of each kind of milk whey under study (human, raw cow, UHT cow and formula milk whey). As a result of this, it was found that the elemental binding patterns in human milk were different from those observed in cow and formula milks. This finding seems to indicate the presence in human milk of specific ligands. Thus, bioavailability of essential elements seems to be different in man. Therefore, more care and further study should be given to the characteristics of cow and formula milks used for human nutrition, particularly in babies and infants.

Enhanced semiquantitative multi-analysis of trace elements in environmental samples using inductively coupled plasma mass spectrometry

A semiquantitative procedure for the determination of trace metals in natural waters and sediments by ICP-MS was developed. The method is based on the establishment of the instrumental molar response curveversus mass using a multi-elemental solution containing elements from Mg to Bi with different ionisation potentials. The ionisation conditions in the plasma (electron density, ne, and ionisation temperature, Tion) were determined by least-squares fitting, using the Saha equation, by adjusting the molar response curve to a third-order polynomial. The effect of matrix constituents, such as Na+, K+, Ca2+, Mg2+, Cl– and SO42–, on both the shape of the molar response curve and on the plasma ionisation conditions was evaluated. It was observed that the ionisation degrees calculated in the plasma did not change significantly in the presence of the matrix constituents. However, the shape of the molar response curve was affected by high concentrations of matrix components and this effect was corrected by adding internal standards to the samples. The semiquantitative procedure was applied to the analysis of local natural waters and the results were compared with those obtained by external calibration and standard additions. Validation was performed by analysis of riverine water (SLRS-3) and sediment (PACS-1 and MESS-2) reference materials from the National Research Council of Canada with satisfactory results.

Flow injection ion-exchange pre-concentration for the determination of aluminium by atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

A flow injection ion-exchange pre-concentration procedure, using a micro-column loaded with Amberlite IRA-400, is outlined for the simple and quantitative determination of trace amounts of aluminium in the ng I–1 range by atomic absorption and/or inductively coupled plasma atomic emission spectrometry. The optimisation of the operating conditions and figures of merit are given and a possible retention mechanism for aluminium in the anion exchanger is discussed. Serum aluminium is so tightly bound by proteins that it is not retained by the resin in the flow procedure. The method can be used, however, for the rapid determination of free aluminium in waters and haemodialysis fluids.

Multimodal laser ablation/desorption imaging analysis of Zn and MMP-11 in breast tissues

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases. The main functions of these metalloproteinases are the degradation of the stromal connective tissue and basement membrane components. Recent data from model systems suggest that MMPs are involved in breast cancer (BC) initiation, invasion, and metastasis. Particularly, MMP-11 (stromelysin-3) is expressed in stromal fibroblasts adjacent to epithelial tumor cells, and high levels of this metalloproteinase were associated with tumor progression and poor prognosis of BC. Consequently, MMP-11 involved in these processes can be a candidate as a new potential prognostic biomarker in BC. Bioimaging techniques based on laser ablation/desorption and mass spectrometry are rapidly growing in biology and medicine for studies of biological systems to provide information of biomolecules (such as proteins, metabolites, and lipids) and metals with lateral resolution at the micrometer scale. In this study, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been used for the first time to investigate the distribution of MMP-11 in human breast cancer tissues in order to show a possible correlation between cancerous and healthy samples, by differential proteomics and using such differences for possible cancer diagnosis and/or prognosis. Additionally, those human breast tissue samples were analyzed in parallel by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in order to gather additional information about the elemental distribution of Zn and its possible associations with MMPs.

Rapid determination of eight elements in cement and its raw mixes by inductively coupled plasma atomic emission spectrometry

An investigation was carried out on the influence of the operating conditions and of the analytical performance characteristics of inductively coupled plasma atomic emission spectrometry for the determination of eight elements (Si, Al, Fe, Ti, Ca, Mg, Na and K) in the raw components of cement. The aim of this investigation was to develop a rapid method of quality control for such raw materials. The results showed that this technique is sensitive enough for each element of interest and no serious interferences were detected after a detailed inter-element interference study. Rapid determination by automatic sequential analysis of the eight elements in a single solution of the sample proved to be highly satisfactory. A suitable fusion method for non-clinkerised material, normally difficult to dissolve, is also given.