Phosphate analytical techniques

Sodium and chloride may be measured using ion-selective electrodes (see Electro analytical techniques). On-line monitors exist for these ions. Sihca and phosphate may be monitored colorimetricaHy. Iron is usually monitored by analysis of filters that have had a measured amount of water flow through them. Chloride, sulfate, phosphate, and other anions may be monitored by ion chromatography using chemical suppression. On-line ion chromatography is used at many nuclear power plants. 

Part—IV has been entirely devoted to various Optical Methods that find their legitimate recognition in the arsenal of pharmaceutical analytical techniques and have been spread over nine chapters. Refractometry (Chapter 18) deals with refractive index, refractivity, critical micelle concentration (CMC) of various important substances. Polarimetry (Chapter 19) describes optical rotation and specific optical rotation of important pharmaceutical substances. Nephelometry and turbidimetry (Chapter 20) have been treated with sufficient detail with typical examples of chloroetracyclin, sulphate and phosphate ions. Ultraviolet and absorption spectrophotometry (Chapter 21) have been discussed with adequate depth and with regard to various vital theoretical considerations, single-beam and double-beam spectrophotometers besides typical examples amoxycillin trihydrate, folic acid, glyceryl trinitrate tablets and stilbosterol. Infrared spectrophotometry (IR) (Chapter 22) essentially deals with a brief introduction of group-frequency... 

Schmidt M, Botz R, Stoffers P, Anders T, Bohrmann G (1997) Oxygen isotopes in marine diatoms a comparative study of analytical techniques and new results on the isotope composition of recent marine diatoms, Geochim Cosmochim Acta 61 2275-2280 Schmidt M, Botz R, Rickert D, Bohrmann G, Hall SR, Mann S (2001) Oxygen isotopes of marine diatoms and relations to opal-A maturation. Geochim Cosmochim Acta 65 201-211 Schmitt AD, StUle P, Vennemann T (2003) Variations of the Ca/ °Ca ratio in seawater during the past 24 milhon years evidence from 5 Ca and 5 0 values of Miocene phosphates. Geochim Cosmochim Acta 67 2607-2614... 

Sissingh, H.A. (1983) Estimation of plant-avail-able phosphate in tropical soils A new analytical technique. Note 235, Institute for Soil Fertility, Haren, Netherlands Skinner, H.G.W. Fitzpatrick, R.W (eds.)... 

A number of instrumental analytical techniques can be used to measure the total phosphorus content of organophosphorus compounds, regardless of the chemical bonding of phosphorus within the molecules, as opposed to the determination of phosphate in mineralized samples. If the substances are soluble, there is no need for their destruction and for the conversion of phosphorus into phosphate, a considerable advantage over chemical procedures. The most important methods are flame photometry and inductively coupled plasma atomic emission spectrometry the previously described atomic absorption spectrometry is sometimes useful. 

Food additives - [FOOD ADDITIVES] (Vol 11) -analysis of [BIOPOLYMERS - ANALYTICAL TECHNIQUES] (Vol 4) -iron compounds as [IRON COMPOUNDS] (Vol 14) -oxo chemicals for [OXO PROCESS] (Vol 17) -phosphoric acids as [PHOSPHORIC ACID AND PHOSPHATES] (Vol 18) -propylene oxide m mfg of [PROPYLENE OXIDE] (Vol 20) -regulatory agencies [REGULATORY AGENCIES - PPIARMACEUTICALS AND COSMETICS] (Vol21) -role m food processing [FOOD PROCESSING] (Vol 11)... 

Although a great variety of analytical techniques have been applied to the simultaneous determination of methylxanthines in various matrices, HPLC is the one most frequently used nowadays. Most of the methods are based on reversed-phase HPLC, using ACN, MeOH, or THF in acetate or phosphate buffer as mobile phase and UV spectrophotometric detection (256 -270). Some RP-HPLC methods were proposed in combination with solid-surface room-temperature phosphori-metric detection (271), mass spectrometry (272), or amperometric (273) detection. The separation can also be achieved by RP ion-pair or ion-interaction HPLC (274-277) or micellar HPLC (278). In contrast, in recent years few normal-phase HPLC methods (279) were reported (see Table 5). 

Both zinc and iron sulfides have to be present in a mixed Fe/Zn polyphosphate matrix and iron sulfide is present in the more severe tribological conditions. The XANES analytical technique is considerably more chemically sensitive than XPS, and the degree of phosphate polymerization was quantified for sodium phosphate glasses (Fuller et al., 2002 Yin et al., 1995), zinc phosphate glasses (Kasrai et al., 1995), and the antiwear tribofilms. 

The tribofilm composition On the basis of Table 4.1, what analytical surface techniques were used to evaluate the tribofilm composition after ZDDP degradation The tribofilm conditions include the following (a) the tribofilm consists of Zn, P, S, O and Fe and (b) the tribofilm contains mostly of a mixture of short-and long-chain phosphates and sulfur is present as zinc sulfide. What analytical technique has the ability to identify elements and their chemical state, e.g., Fe° or Fe2+, in case (a), and compounds in case (b) More about analytical techniques for evaluation of the metal surfaces can be found in chapter 4.3. 

It is clear that the analytical techniques presently available are superior to those used in the past, and therefore may enable more detailed insight into the mechanism of the phosphate effect. It was decided therefore to start a reinvestigation into the phosphate effect using the latest techniques, e.g. High Performance Liquid Chromatography (HPLC). 

Although several elements are necessary to sustain life, traditionally in oceanography the term nutrients has referred to nitrogen (notably, but not exclusively, nitrate), phosphorus (usually as phosphate), and silicon (as silicate). The rationale for this classification was that analytical techniques had long been available that allowed the precise determination of these constituents despite their relatively low concentrations. They were observed to behave in a consistent and explicable manner, but quite differently to the major constituents in seawater. 

Measurement of labelling yield and subsequent radiochemical purity requires a suitable analytical technique, and the method of choice for radio-labelled peptides is reversed phase HPLC with on-line UV and radiometric detection. It is important to use as stringent a separation method as possible with isocratic or slow mobile phase composition gradients over the peptide peak. Ideally, more than one mobile phase system should be used (e.g. a phosphate buffer-methanol system in addition to the standard water-acetonitrile system), since these may show the presence of new impurities. It is important to recognize that HPLC analyses only measure those components that elute from the column. Insoluble, highly lipophilic or positively charged species may bind to the solid phase. It is very important to verify the absence of these species by a complimentary technique such as thin layer chromatography (TLC) and to ensure that the two techniques produce similar results. 

Other groups also used gel filtration exchange to measure middle molecules and perform in vitro toxicity tests (C7, D21). However, many of the middle molecular weight substances isolated by these techniques proved to be much smaller than anticipated. This discrepancy was due to the intrinsic inadequacies of the standard gel filtration techniques for the isolation of middle molecules, as pointed out by Furst et al. (F13) and later by Schoots et al. (S13). These investigators used analytical techniques to demonstrate that middle molecular fractions obtained by gel filtration comprised many low-molecular-weight solutes, such as carbohydrates, amino acids, polyols, aromatic substances, and other UV-absorbing solutes, and also sodium chloride, acetate, phosphate, and sulfate (S10). Thus these fractions do not exclusively represent middle molecules. 

In this chapter common methods to evaluate chemical properties and phase composition of bioceramic coatings will be briefly described that are available in many laboratories including X-ray diffraction (XRD), vibrational spectroscopy techniques such as infrared (FTIR) and Raman spectroscopy and nuclear magnetic resonance spectroscopy (NMR). These methods provide a host of information on bulk phase composition, degree of crystallinity and crystallite size. Some special techniques including cathodoluminescence serve to reveal intrinsic coating properties that cannot be assessed by conventional analytical techniques, for example to distinguish between amorphous calcium phosphate (ACP) and crystalline calcium phosphates. 

This, in fact, was the case for detection of a hemiketal phosphate intermediate formed in the KD08P synthase reaction pathway described in Section 8.18.5. Other potential limitations of rapid chemical quench methodology include the need for radiolabeled substrates and the need for subsequent analytical techniques, for example, NMR, to elucidate structural information on enzyme intermediates. An earlier article focusing on New Concepts in Bioorganic Chemistry has highlighted the potential of using high-resolution MS coupled with electrospray ionization (ESI) to examine rapid enzyme reactions. ... 

---