Preparation Magnesium citrate

Since the use of alcohol in the sol-gel process can lead to aggregation of the colloidal metal, Au/SiC>2 catalysts have been prepared without alcoholic solution, using tetramethyl orthosilicate (TMOS) as a water-soluble silicic precursor and colloidal gold by reducing aqueous HAuCLi with magnesium citrate.114 However, the size of the gold particles was not reported, but reduction by citrate ion does not usually produce small particles. 

Regev A, Fraser G, Delpre G, Leiser A, Neeman A, Maoz E, Anikin V, Niv Y. Comparison of two bowel preparations for colonoscopy sodium picosulphate with magnesium citrate versus sulphate-free polyethylene glycol lavage solution. Am J Gastroenterol 1998 93(9) 1478-82. 

Despite the large amount of published studies on CTC, there is no consensus about the optimum regimen for bowel preparation. Two commonly used bowel-deansing regimens are polyethylene glycol electrolyte (PEG) lavage solution and saline cathartics such as phospho-soda and magnesium citrate, both of which are available in commercial preparations. Table 17.1 details the most common preparation schemes. 

Several studies have evaluated the effect of these two bowel preparations on the amount of residual fluid present within the colon at the time of CTC. The standard PEG solution usually leaves a large quantity of residual fluid within the colon that may hamper visibility for the radiologist, but it poses no problems to the endoscopist, since fluid maybe easily aspirated by the endoscope. Radiologists prefer a dry colon, such as that produced by phospho-soda and/or magnesium citrate, as this generally results in a smaller amount of residual fluid compared to the electrolyte lavage solutions (Macari et al. 2001). Furthermore, patients usually tolerate saline cathartics better than they do PEG (Kolts et al. 1993 Oliveira et al. 1997). 

Magnesium Citrate Oral Solution 80 mg/mL ENA (Table 18.14) is a supersaturated solution of magnesium citrate. The patient should be warned that crystallisation can take place after about 2 weeks, or earlier when the preparation is stored in the refrigerator. Magnesium citrate mixture USP has a similar formula. 

Magnesium citrate has been used with a reduced total volume of polyethylene glycol lavage solution prior to colonoscopy as a strategy to improve patient compliance and tolerance. This has also been found to improve the quality of colonic cleansing and to decrease preparation times (Sharma et al. 1998). 

There are two main bowel preparations available cathartics, such as magnesium citrate and phos-phosoda, and gut lavage solutions, such as polyethylene glycol (PEG). 

The following substance, namely magnesium acetate potassium citrate potassium hydroxide potassium nitrate and sodium chloride can also be assayed for their respective elements as shown in Table 25.1 below. However, all the respective solutions of the said pharmaceutical substance and their standard solutions must be prepared as prescribed in BP (1993) strictly to obtain the best results. 

Antacid preparations based on aluminium hydroxide sometimes contain magnesium salts (and carbonate or oxide) to offset the constipating effect of the alumina. This laxative effect of salts such as magnesium sulphate (or citrate) and other saline cathartics such as potassium sodium tartrate is due to their incomplete absorption from the digestive tract so that, by osmotic forces, they retain water in the intestinal lumen. 

Magnesium ascorbyl phosphate (6) was used as reference compound for the RP-HPLC-UVD determination of sodium risedronate (68) in pharmaceutical preparations . Co(II) reacts with 2,2 -bipyridylketone-2-picolylimine in the presence of Na L-ascorbate in a weakly alkaline solution to form a blue water-soluble complex with the absorption maximum at ca 580 nm. The absorbance at 580 nm is proportional to the concentration of Co(II) in the range 0.05-2.5 mg L , with RSD = 0.46%. Ni(II) and Cu(II) were tolerated up to 20 and 10 mg L , respectively, in the presence of Na citrate . 

In t ie case of animal plasma preparation, an anticoagulant is necessary to maintain solubility of blood components, and sodium citrate or lithium heparin would be preferable over any alternatives that contain EDTA. EDTA will chelate magnesium and zinc ions and require much higher concentrations of the two ions in the assay buffer for acceptable hnal ion concentrations, possibly to the point of precipitation. 

BufFer-Salt-Mixture To induce phase separation, the following mixture of salts is required per sample test portion (containing approx. 10 g of water) 4 g magnesium sulfate anhydrous grit, 1 g of sodium chloride, 1 g of disodium hydrogen citrate sesquihydrate, and 0.5 g of trisodium citrate dihydrate. It is advisable to prepare in advance a sufficient number of portions of this mixture, the preparation of which is immensely facilitated if a sample divider (see apparatus) is used. 

The surface ions of the apatite crystals are therefore readily exchanged with ions of the medium capable of replacing calcium e.g., magnesium), phosphate e.g., carbonate or citrate), or the hydroxyl e.g., fluorine). As we shall see, the surface reaction assumes particular importance in the process of mineralization, and some investigators claim that the lack of stoichiometry in apatite preparations can be entirely explained by such surface reactions. 

An alternative sample preparation is based on the QuEChERS (Quick Easy Cheap Effective Rugged Safe) technique [14]. In this the sample is extracted into acetonitrile and magnesium sulfate, sodium chloride and citrate buffer salts at pH 5-5.5 are added, the mixture is shaken and then centrifuged to separate the phases. When applied to honey [15] the samples, containing isoproturon-d6 as an internal standard, were diluted with water and homogenized before addition of the QuEChERS salts described above, and acetonitrile. After extraction, centrifugation... 

Silver hydrosols prepared by Lea s method exhibit peculiar reactions that deserve further elucidation. Alkali sulfates, nitrates, and citrates precipitate soluble silver, while iron, nickel, and magnesium sulfates, and barium or silver nitrates, throw down silver that is insoluble in water. The insoluble form may sometimes be peptised with borax and ammonium sulfate, but these reactions are not always reproducible, and it often happens that the repetition gives totally unexpected results. 

---