A Novel Technique for the Pre-Concentration and Extraction of Inositol Hexakisphosphate from Soil Extracts with Determination by Phosphorus-31 Nuclear Magnetic Resonance

Abstract

Inositol hexakisphosphate (IP 6 ) is often the dominant form of soil organic phosphorus (P), but is rarely investigated because of the analytical difficulties encountered in its extraction, separation, and detection in environmental samples. In particular, recent advances in the study of soil organic P with 31 P nuclear magnetic resonance (NMR) have been of limited use for the study of IP6, because the technique does not discriminate between IP 6 and other forms of P. This was addressed by developing a novel analytical procedure using the retentive properties of gel-filtration gels for IP 6, which allows the combined selective extraction and pre-concentration of IP 6 from soil extracts with determination by 31 P NMR. While the technique is still in the developmental stage, the results demonstrate that the gel does not interfere with 3113 NMR analysis and retains IP6 to concentrations well above those required to give clear spectral signals. The technique has considerable potential for application to the study of IP 6 in soil extracts and water samples and, with development, could help to answer fundamental questions regarding the dynamics of organic P in the environment.T HE MOST ABUNDANT CLASS of organic phosphorus (P) compounds in the environment is the inositol phosphates, a family of six congeners of hexahydroxy cyclohexane (inositol) that exist as inositol in various states of phosphorylation (bound to between 1 and 6 phosphate ions) (Fig. 1). Nine stereoisomers of inositol phosphates exist; the myo stereoisomer is by far the most common in nature, although neo-, scyllo-, and chiro-inositol phosphates have been reported in terrestrial and aquatic environments (Cosgrove, 1980). The dominant form of inositol phosphate in the environment is myo-inositol hexakisphosphate (IP 6 ), which constitutes the major organic P compound in soils and aquatic sediments (Harrison, 1987; Suzumura and Kamatani, 1995). Despite its abundance, it remains poorly understood and little reliable information exists on the sources, pools, and dynamics of IP6 in the environment (Turner et al., 2002). The role of IP6 in supplying P to plants and algae is largely unknown and even its origins remain unclear in many cases (L'Annunziata, 1975). Research into IP6 has been limited by the lack of suitable analytical techniques for its determination in environmental samples, the main problems being poor recoveries of IP6 from soils by conventional extractants and from anion exchange columns during sample cleanup and separation (Anderson, 1964;Martin, 1970;Irving

Phosphorus Speciation of Sequential Extracts of Organic Amendments Using Nuclear Magnetic Resonance and X‐ray Absorption Near‐Edge Structure Spectroscopies

“…Detailed studies of inorganic and organic P pool in manures have been performed recently using solution 31 P nuclear magnetic resonance (NMR) on alkaline extracts of manures (Cade‐Menun and Preston, 1996; Turner, 2004; Turner and McKelvie, 2002; Toor et al, 2005a; Turner et al, 2005). This technique provided direct molecular and structural characterization of organic P in alkaline solution with environmental relevance.…”

Phosphorus transformation in poultry litter and litter-treated Oxisol of Brazil assessed by 31P-NMR and wet chemical fractionation

“…Although the C/N and C/P molar ratios were similar as in the other poultry litters, factors such as elevated concentration of lignin and phenolic compounds present in the wood chips may have limited the decomposer activity of soil microorganisms (Oglesby & Fownes, 1992;Entry & Backman, 1982;Cortez et al, 1996). Possibly, high concentrations of orthophosphate monoesters, such as inositol hexaphosphate (phytic acid), with a high affinity for the soil colloids (Leytem et al, 2002;Gebrim et al, 2004), could have reduced the availability to soil microbes and thus decreased decomposition (Bowman & Cole, 1978;Evans, 1985;Turner & McKelvie, 2002). It is suspected that this phenomenon may favor the persistence of P in organic compounds for a longer period of time and be more prone to be transported to water bodies (Eghball et al, 1996;Chardom et al, 1997), increasing the risk of eutrophication.…”

“…In some litters, a complete peak absence at -0.5 to 2 ppm after incubation suggested complete mineralization of diester P (Figure 1 and Table 4). The more intensive mineralization of orthophosphate diesters may be attributed to the presence of compounds such as phospholipids, nucleic acids and sugar phosphates (Turner & McKelvie, 2002 Table 2.…”

“…On the other hand, the CC and GN litter, with a slower Po mineralization rate, would better meet the demands of perennial crops or plants with a smaller initial P demand. Although some organic P forms, such as phytic acid, are more stable in the soil environment (Turner & McKelvie, 2002), it appears that some perennial plants are able to acquire them. Chen et al (2004) reported that pine (Pinus radiata) trees are able to acquire P from phytic acid from soils, but faster-growing plants, including some annual grasses and legumes, are not efficient in acquiring P from such organic sources (Hayes et al, 2000).…”

Evaluation of Bioavailability of Phosphorus Accumulated in Arable Soils

“…특히 인산의 형태중 유기태 인산 (Organic P)은 토양 용액뿐만 아니라 침출수 및 배출수 중 총인산 (Total P)의 많은 부분을 차지하고 있어 인산 동태 에 중요한 형태로 평가되고 있다 (Turner and McKelvie, 2002 …”