Citrate-phosphate

Fig. 10.3.1 Bioluminescence spectrum of the centipede Orphaneus brevilabiatus (left panel), and the influence of pH on the luminescence of the exudate of the same centipede in 0.1 M potassium citrate/phosphate buffers (right panel). From Anderson, 1980, with permission from the American Society for Photobiology.

An interesting paper that attempted to relate dissolution of a poorly soluble acidic drug (naproxen) to simulated gastrointestinal flow in the presence of buffers was published by Chakrabarti and Southard [17]. In addition to showing that buffer type (citrate, phosphate, or acetate) had a significant impact on naproxen dissolution, these authors unexpectedly found that elevating a solid tablet into the flow channel of the flow-between-two-plates apparatus resulted in a substantial... 

The rate of y -alumina island formation essentially depends on the nature of the electrolyte used. If outwards migrating (in the terms of Xu et al.102) anions, such as tungstates and molybdates, are used in the anodization process, y- alumina seed crystals are surrounded by pure alumina and crystallization occurs easily. In the case of inwards migrating anions (e.g., citrates, phosphates, tartrates), the oxide material surrounding the y-nuclei is enriched... 

We used outdated human CPD (citrate-phosphate-dextrose) blood from the Dayton Community Blood Center. At 21 days, CPD blood still retains 78% survival of the red blood cells and would fairly well simulate in vivo physiological conditions. During these tests, many enzymes and proteins may denature and/or precipitate. Even after suffering that trauma, the resulting fluid is more suitable for material testing than other pseudo-physiological fluids, since it still contains most of the salts, lipids, hormones, oligomers, nucleotides, saccharides, etc., found in whole blood in vivo. 

Whole blood is blood that has been aseptically withdrawn from humans. A suitable anticoagulant is added (often heparin or a citrate-dextrose-based substance), although no preservative is present. The blood is usually stored at temperatures ranging from 1-8 °C, and has a short shelf life (48 h after collection if heparin is used as the anticoagulant, or up to 35 days if citrate-phosphate-dextrose with adenine is employed). 

Assay conditions. 700 pL citrate-phosphate buffer pH 5.0, 100 pL enzyme solution (dilution if required) and 200 pL mandelonitrile stock solution (60 mmol L in citrate-phosphate buffer pH 3.5) were mixed in a cuvette with 1 cm pathlength and the increase of absorbance at 280 nm was measured for 2 min. 

CE instrumentation is quite simple (see Chapter 3). A core instrument utilizes a high-voltage power supply (capable of voltages in excess of 30,000 V), capillaries (approximately 25—lOOpm I.D.), buffers to complete the circuit (e.g., citrate, phosphate, or acetate), and a detector (e.g., UV-visible). CE provides simplicity of method development, reliability, speed, and versatility. It is a valuable technique because it can separate compounds that have traditionally been difficult to handle by HPLC. Furthermore, it can be automated for quantitative analysis. CE can play an important role in process analytical technology (PAT). For example, an on-line CE system can completely automate the sampling, sample preparation, and analysis of proteins or other species that can be separated by CE. 

The sodium acetate-acetic acid combination is one of the most widely used buffers, and is usually referred to simply as acetate buffer. Other buffer combinations commonly employed in chemistry and biochemistry include carbonate-bicarbonate (sodium carbonate-sodium hydrogen carbonate), citrate (citric acid-trisodium citrate), phosphate (sodium dihydrogen phosphate-disodium hydrogen phosphate), and tris [tris(hydroxymethyl)amino-methane-HCl]. 

Cellulase solution - dissolve 6.25 g cellulase from Trichoderma viride (Merck Ltd) in 1 I citrate-phosphate buffer, pH 4.6, immediately before use. 

Ca is a comparatively difficult element for the body to absorb and digest. It is essentially only available for consumption associated with various other moieties (e.g., citrate, phosphate, and other anions). Each Ca source has unique physical, structural, and chemical properties such as mass, density, coordination chemistry, and solubility that are largely determined by the anions associated with the Ca +. Aqueous solubility of various Ca salts can vary markedly and comparisons are frequently made under standardized conditions. The water solubility of CCM is moderate when ranked versus other Ca sources frequently used as dietary supplements and food/beverage fortificants. The solubility of CCM (6 2 3 molar ratio) is 1.10-g salt in 100 ml of H2O at 25 °C (Fox et ah, 1993a). Table 6.4 lists the solubility of various Ca sources in water at specific temperatures, and also includes some information on potential sensory characteristics. 

Homogenization with MeOH, CH2CI2 addition of citrate-phosphate buffer centrifugation filtration... 

Figure 2. Heat stability of nisin after treatment at 100°C at pH 4.0, 6.0, and 8.0. Nisin was obtained from culture supernatant broth of Lc. lactis 11454 and resuspended in citrate-phosphate buffer.

Figure 3. Heat stability of bacteriocins from Lc, lactis FS 84, FS 90, FS 91-1, and FS 97 In citrate-phosphate buffer at pH 4.0 and 8.0.

Citrate/phosphate-buffer 1.78 g Na2HP04-2H20 (Merck) is dissolved in 50 ml demineralized water and the pH is adjusted to 5.0 with citrate solution. Subsequently, demineralized water is added until a total volume of 100 ml is obtained. 

Substrate buffer 3.79 mg 4-methylumbelliferyl-N-acetyl-a-D-glucosaminide (Moscerdam Substrates) is dissolved in 10 ml citrate/phosphate buffer. For faster dissolution, the mixture is sonicated (1 min). The substrate buffer is stored at -20°C and protected from light. 

Calcium and magnesium. Some calcium and magnesium in milk exist as complex undissociated ions with citrate, phosphate and bicarboante, e.g. Ca Citr-, CaP04, Ca HCOj. Calculations by Smeets (1955) suggest the following distribution for the various ionic forms in the soluble phase ... 

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