Lithium citrate

Atkin, G. E., and Ferdinand, W., Accelerated amino acid analysis studies on the use of lithium citrate buffers and the effect of //-propanol, in the analysis of physiological fluids and protein hydrolyzates, Anal. Biochem., 38, 313,1970. 

Five milliliters of lithium citrate syrup contain the equivalent of 8 milliequivalents of Li+. Calculate the equivalent, in terms of milligrams, of lithium carbonate (Li2C03 M.W. = 74) in each 5-mL dose of the syrup. 

The composition and pH of the buffer should be accurate to 0.001 mol l-1 and 0.01 pH units. Most methods rely on the sequential application of a series of buffer solutions of increasing pH and molarity, with the initial pH around 3.2. Sodium citrate or, preferably, lithium citrate buffers are used, which incorporate a detergent (BRH 35), an antioxidant (thiodiglycol) and a preservative... 

Figure 10.19 Amino acid analyser trace. Separation of a complex physiological standard mixture of amino acids in 3.5 hours using lithium citrate buffers and ninhydrin detection 10 nmol of each amino acid, including the internal standard, nor-leucine, were applied to the column (0.3 X 35 cm) in a total volume of 50 ml. 

A 0.05M NaOAc buffer (pH 6.85)71% MeOH/ 0.8% THE B 0.05M NaOAc buffer (pH 5.35)765% MeOH flow rate 1.6mL7min Lithium citrate buffer... 

Brand Name(s) (lithium citrate) Cibalith-S Cfiemical Class Monovalent cation... 

Tyrer, S.P., Peat, M.A., Minty, P.S., Luchini, A., Glud, V., and Am-disen, A. (1982) Bioavailability of lithium carbonate and lithium citrate a comparison of two controlled-release preparations. Pharmatherapeutica 3 243-246. 

Lithium salts are used in the treatment of bipolar affective disorder (i.e., manic depression) and occasionally in mania (but its slow onset of action is somewhat of a disadvantage in this case). Its mechanism of action is still open to debate, but lithium has effects on brain monoamines, on neuronal transmembrane sodium flux, and on cellular phosphatidylinositides related to second messenger systems. Lithium is administered in two salt forms, lithium carbonate (8.98) and lithium citrate (8.99). Side effects are common and include diarrhea, kidney failure, and drowsiness with tremor. 

Lithium salts lithium carbonate lithium citrate... 

Lithium preparations include lithium carbonate, sustained-release preparations, and the liquid form, lithium citrate. The sustained-release preparations allow for a more gradual absorption of the drug, leading to blunted peak plasma levels. Because lithium has a slow onset of action, it can take weeks, and occasionally longer, to obtain an optimal clinical response. Thus, it is important to avoid a premature abandonment in those who are simply slower to respond. 

Lithium carbonate and lithium citrate are the most commonly used compounds. Lithium has effects on cation transport, on individual neurotransmitters (including 5-HT) and on intracellular second messenger systems. Which of these is key to its therapeutic efficacy is not entirely clear but, as for the antidepressant drugs, the net effects seem to be to enhance serotonin function and to stabilise the noradrenergic system. Once lithium treatment is established it is very important that it is not suddenly stopped as this may result in rebound hypomania. 

Each 5 mL of syrup for oral administration contains lithium ion 8 mEq (equivalent to amount of lithium in 300 mg of lithium carbonate), alcohol 0.3% v/v. Lithium citrate syrup is a palatable oral dosage form of lithium ion. 

Lithium citrate is prepared in solution from lithium hydroxide and citric acid in a ratio approximately dilithium citrate. 

Amino acids can be separated without prior derivatization on a cation-exchange resin column. The elution buffers are classically lithium citrate buffers with different pH values and salt concentrations, which are applied stepwise. There is usually a programmed increase in column temperature. Consequently, there are numerous variables affecting the separation of the individual amino acids [6]. For the detection of the amino acids, the column effluent is mixed with the ninhydrin reagent. Nowadays there are only very few manufacturers of AAAs left. The considerable cost of purchase and the operation costs are a potential threat to the widespread application of this technique, although it is still considered to be the definitive method for diagnosing disorders of amino acid metabolism. 

The buffers are uniformly made up of lithium citrate solutions of various pH and salt concentrations. The composition of the buffers is absolutely essential for a reproducible analysis and the supply companies are expected to meet the highest criteria in this respect. Due to impurities in the chemicals, the water, and the mixing devices, different lot numbers of buffers may have slightly different properties. A few tricks have been added over the years to improve the quality of the analysis, including the addition of methylcellosolve (methoxy ethanol) to the first buffer, and antioxidants to preserve methionine from oxidation to methionine sulfoxide. 

In brief, a 200-pl sample will be deproteinized with 20 pi 5% SSA containing internal standard. Following precipitation and centrifugation, 150 pi supernatant is diluted with 150 pi of the lithium citrate buffer and placed in the autosampler. The derivatization step takes 40 pi of sample and 20 pi of the OPA reagent, which are mixed and left to react for 30 s. A 20-pl aliquot is injected. 

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