Bone, mass spectrometry

The previous discussion has centered on how to obtain as much molecular mass and chemical structure information as possible from a given sample. However, there are many uses of mass spectrometry where precise isotope ratios are needed and total molecular mass information is unimportant. For accurate measurement of isotope ratio, the sample can be vaporized and then directed into a plasma torch. The sample can be a gas or a solution that is vaporized to form an aerosol, or it can be a solid that is vaporized to an aerosol by laser ablation. Whatever method is used to vaporize the sample, it is then swept into the flame of a plasma torch. Operating at temperatures of about 5000 K and containing large numbers of gas ions and electrons, the plasma completely fragments all substances into ionized atoms within a few milliseconds. The ionized atoms are then passed into a mass analyzer for measurement of their atomic mass and abundance of isotopes. Even intractable substances such as glass, ceramics, rock, and bone can be examined directly by this technique. 

The three techniques — laser desorption ionization, laser ablation with secondary ionization, and matrix-assisted laser desorption — are all used for mass spectrometry of a wide variety of substances from rock, ceramics, and bone to proteins, peptides, and oligonucleotides. 

Gillespie, R., Hedges, R.E.M. and Wand, J.O. 1984 Radiocarbon dating of bone by Accelerator Mass Spectrometry. Journal of Archaeological Science 11 165-170. 

Coplen, T.B. (2011). Guidelines and recommended terms for expression of stableisotope-ratio and gas-ratio measurement results. Rapid Gommunications in Mass Spectrometry, 25, 2538-2560. DOl 10.1002/rcm.5129 Cormie, A.B., Luz, B., Schwarcz, H.P. (1994a). Relationship between the hydrogen and oxygen isotopes of deer bone and their use in the estimation of relative humidity. Geochimica et Cosmochimica Acta, 58, pp. 3439-49. 

The low concentrations of lead in plasma, relative to red blood cells, has made it extremely difficult to accurately measure plasma lead concentrations in humans, particularly at low PbB concentrations (i.e., less than 20 pg/dL). However, more recent measurements have been achieved with inductively coupled mass spectrometry (ICP-MS), which has a higher analytical sensitivity than earlier atomic absorption spectrometry methods. Using this analytical technique, recent studies have shown that plasma lead concentrations may correlate more strongly with bone lead levels than do PbB concentrations (Cake et al. 1996 Hemandez-Avila et al. 1998). The above studies were conducted in adults, similar studies of children have not been reported. 

McCullagh, J. S. O., Juchelka, D. and Hedges, R. E. M. (2006) Analysis of amino acid 13C abundance from human and faunal bone collagen using liquid chromatography/isotope ratio mass spectrometry. Rapid Communications in Mass Spectrometry 20, 2761 2768. 

Roberts, N.B, Walsh, H.P.J., Klenerman, L., Kelly, S.A., and Helliwell, T. R. (1996). Determination of elements in human femoral bone using inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Journal of Analytical Atomic Spectroscopy 11 133-138. 

De Muynck, David, Christophe Cloquet, Elisabeth Smits, Frederik A. de Wolff, Ghylaine Quitte, Luc Moens, and Frank Vanhaecke. Lead Isotopic Analysis of Infant Bone Tissue Dating from the Roman Era Via Multicollector ICP-Mass Spectrometry. Analytical and Bioana-lytical Chemistry 390 (2008) 477-486. The researchers used isotope analysis to show that high concentrations of lead in the bones of Roman infants probably did not come from the soil or other objects in the graves. 

Phosphorus-32, for example, produced by irradiating sulphur or natural phosphorus ( P) with high-energy particles, has a half-life of 14.8 days and can be rapidly taken up (in the form of phosphate) by body tissues such as muscles, the liver, bones, and teeth. De Hevesy found that different phosphorus compounds would be incorporated in a tissue-specific manner certain compounds were concentrated in the liver, for example. One can use stable isotopes as biological tracers too, since they are detectable atom by atom using mass spectrometry. De Hevesy observed that it takes deuterium twenty-six minutes to pass from ingested heavy water into urine. 

To learn whether people from the ancient British coastal town of Barton-on-Humber ate mainly plants or fish, cholesterol from the bones of 50 people was extracted with organic solvent, isolated by gas chromatography, combusted to convert it into COz, and its 13C/I2C ratio measured by mass spectrometry. Observed 13C/12C ratios differ from that of a standard material by about —21 to —24 parts per thousand. A diet of local plants yields a 5I3C value (defined in Box 22-3) in cholesterol of —28 parts per thousand. Values more positive than —28 parts per thousand are indicative of a marine diet. It appears that the population got much of its food from the sea. 

Use of inductively coupled plasma-mass spectrometry (1CP-MS) coupled to a laser-ablation sample introduction system (LA-ICP-MS) as a minimally destructive method for chemical characterization of archaeological materials has gained favor during the past few years. Although still a relatively new analytical technique in archaeology, LA-ICP-MS has been demonstrated to be a productive avenue of research for chemical characterization of obsidian, chert, pottery, painted and glazed surfaces, and human bone and teeth. Archaeological applications of LA-ICP-MS and comparisons with other analytical methods are described. 

DPD and PYD are the only markers of bone remodeling for which the exactly characterized primary referential material is available. This material is a preparation isolated from bovine bone submitted to intensive purification, and characterized with molar absorption coefficients, elementary organic analysis, mass spectrometry, and NMR spectra (R5). The values of critical differences of DPD/PYD measurements are summarized in Table 2. 

UV and fluorescent spectroscopy can be employed down to 190 nm because there is no solvent interference. Mass spectrometry is easy because the water provides good ionization. Flame ionization detection (FID) is of particular interest because potentially it offers a sensitive and universal detector. A number of different interfaces have been used, including heated capillaries, which have been examined by Miller and Hawthorne [62], Ingelse et al. [63], and others [64, 65], who separated a range of analytes including alcohols, amino acids, and phenols. An alternative method employing a cold nebuliza-tion of the eluent has been introduced by Bone et al. [66]. They were able to detect both aliphatic and aromatic alcohols, polymers, carbohydrates, parabens, and steroids. 

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