Determination of lactate

The determination of lactate is important in medicine, because certain disorders are related to lactic acidosis, and in industry, for the control of milk and other food products. A lactate sensor can be constructed by coupling amperometric transducers with various enzymes, such as lactate dehydrogenase, cytochrome b2, lactate oxidase and lactate monooxygenase. Lactate dehydrogenase requires NAD as a cofactor, whereas cytochrome b2 uses potassium ferricyanide, which is much cheaper [173]. Cytochrome b2 catalyses the following reaction  

The ferrocyanide formed from the oxidation of lactate into pyruvate is electiDchemically reoxidized into ferricyanide at an applied potential on a corrosion-proof electrode. 

Lactate is generally determined by immobilizing lactate oxidase on an amperometric transducer, such as a p02 electrode [174, 175], to detect the oxygen consumption, or a platinum electrode [176], to detect 

The pyruvate formed is recycled into lactate using lactate dehydrogenase OLDH)  

The coupling of these two enzymes amplifies the response of the lactate-sensitive electrode by up to 60 times, which gives a detection limit of 8 X 10 M lactate [174]. 

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Amplification of the sensitivity of substrate or co-en me recycling is especially efficient in thermometric analysis since all the reactions involved frequently contribute to increasing the overall temperature change. One case in point is the determination of lactate or pyruvate by substrate recycling using co-immobilized lactate oxidase and lactate dehydrogenase [160]. 

Deproteinisation using acids is required to avoid glycolysis, but has to be performed as soon as possible after sampling (within 5 min). Simultaneous determination of lactate, pyruvate, ACAC and is possible using this sample. 

Artuch R, Vilaseca MA, Farre C, Ramon F (1995) Determination of lactate, pyruvate, beta-hydroxybutyrate and acetoacetate with a centrifugal analyser. Eur J Clin Chem Clin Biochem 33 529-533... 

R. C.H. Kwan, P.Y.T. Hon, K.K.W. Mak and R. Renneberg, Amperomet-ric determination of lactate with novel trienzyme/poly(carbamoyl) sulfonate hydrogel-based sensor, Biosens. Bioelectron., 19(12) (2004) 1745-1752. 

Extraction of minced meat into buffer was used immediately prior to determination of lactate in meat by screen-printed sensors mounted in a FIA system [17]. The sensors were similar in design to those used for dairy product analysis [31] although they were constructed completely by screen-printing rather than having the outer membrane applied... 

L(+)-Lactate dehydrogenase is specific for l(+)-lactate and does not react with d(—)-lactate. LDH is used in coupled enzyme assays, for example in the determination of ATPase (Penefsky and Bruist 1984), myokinase (Brolin 1983), and pyruvate kinase (Beutler 1971). It may also be used in the determination of lactate (Noll 1984), pyruvate (Lamprecht and Heinz 1984), and various other metabolites. 

Samples for determination of lactate dehydrogenase activity (LDH) are taken every 30 minutes and they are a measure for the viability and integrity of the isolated organ. A continuous bile flow throughout the perfusion time is the best measure of the functionally integrity of the organ (typically bile flow of four livers are shown in Fig. 2). Isolated livers without bile flow should be excluded from the final evaluation of the data. 

Lactate The same assessment is true for the determination of lactate in ascitic fluid. The increase in this acid residue in infected ascitic fluid (>4.5 mmol/1) is proportional to the decrease in the pH value. Malignant ascites generally yields values of <4.5 mmol/1. (21,58, 63, 79) (s. fig. 16.10)... 

E659 Marx, A.M. and Gressner, A.M. (1990). On the performance of the determination of lactate and iron with the Kodak Ektachem 700XR analyzer. Clin. Chem. 36, 1199, Abstr. 1153. 

Zipp, A., Watson, C. and Greyson, J. (1978). Reflectance spectroscopy as an analytical tool in the clinical laboratory Application to the quantitative determination of lactate dehydrogenase in serum. Clin. Chem. 24, 1009, Abstr. 105. 

Metrohm Application Note S-12, Determination of lactate, chloride, nitrate, sulfite and phosphate in wine, Metrohm Ltd, Hcrisau, Switzerland, 1999. 

The LMO sensor has also been applied to the sequential determination of lactate and LDH activity. When the current decrease resulting from lactate oxidation was complete, NADH and pyruvate were added to the measuring cell. The subsequent current decrease reflects the lactate formation by the LDH-catalyzed reaction. The time required for one sequential measurement was 4 min. The CV for 20 LDH determinations was 1.2%. 

Fig. 87. Response curve of the sequential determination of lactate, pyruvate, and creatine kinase activity with a LMO-LDH-PK sensor. CP = creatine phosphate, lactate 3.4 mmol/1, pyruvate 245 pmol/1, CK 504 U/l.

At present the determination of lactate does not belong to the most frequently performed analyses in clinical chemistry yet its popularity in the diagnosis of shock and myocardial infarction and in neonatology and sports medicine is increasing. Strong efforts are therefore being made to develop sensor-based lactate analyzers which may be readily used at the bedside. 

Fig. 7.9 Scheme of instrument for enzymatic determination of lactate by differential amperometric measurements. The chief difference between the measurement (top) and reference manifold (bottom) is the absence of an oxidant from the latter. (Reproduced from [8] with permission of Elsevier). 

T. Toyoda, S. S. Kuan, and G. G. Guilbault, Determination of Lactate Dehydrogenase Isoenzyme (LD-1) Using Flow Injection Analysis with Electrochemical Detection after Immunochemical Separation. Anal. Lett., 18 (1985) 345. 

The determination of lactate is becoming increasingly popular in the diagnosis of shock and myocardial infarction and in neonatology and sports medicine. Therefore, great efforts are being made to develop sensor-based lactate analyzers which may readily be used at the bedside. The first enzyme electrode-based lactate analyzer was developed in 1976 by La Roche (Switzerland) (see Thble 14-8). It contains cytochrome in a small reaction chamber in front of a platinum electrode polarized at +0.25-0.40 V. The lactate values measured with the analyzer correlate fairly well with those obtained with the spectrophotometric reference method using deproteinized blood ... 

Xue, Q. Yeung, E. S. Indirect fluorescence determination of lactate and pyruvate in single erythrocytes by capillary electrophoresis. J. Chromatogr. A 1994, 661, 287-295. 

Enzyme nylon tube reactor for routine determination of lactate in serum Active immobilized enzyme evaluation of potential of immobilized enzyme in the iodination of small molecules Investigation of the active site of the immobilized enzyme... 

Parker C, Milosevic M, Toi A, Sweet J, Panzarella T, Bristow R, Catton C, Catton P, Crook J, Gospodarowicz M, McLean M, Warde P, Hill RP (2004) Polarographic electrode study of tumor oxygenation in clinically localized prostate cancer. Int J Radiat Oncol Biol Phys 58 750-757 Paschen W (1985) Regional qiuintitative determination of lactate in brain sections. A bioluminescent approach. J Cerebral Blood Flow Metab 5 609-612 Paschen W, Djuricic B, Mies G, Schmidt-Kastner R, Linn F (1987) Lactate and pH in the brain Association and dissociation in different pathophysiological states. J Neuro-chem 48 154-159... 

Metrohm AG, Metrohm Application Note No. S-131 Determination of Lactate, Acetate, Chloride, Methyl sulfate. Bromide, and Sul te. Metrohm... 

Metrohm AG, 1C Application Note No. S-12 Determination of Lactate, Chloride, Nitrate, Sulfite, and Phosphate in Wine. Metrohm AG, Herisau, Switzerland. 

Electrochemical biosensor performance such as sensitivity, protein stability, selectivity or reproducibility have been improved due to the use of different carbonaceous materials and combination of them. To improve the sensitivity of a electrochemical biosensor is necessaiy to increase the enzyme amount in a proper immobilization manner. CNTs are good candidates and in this regard, some authors combine carbon nanomaterials with conducting polymers, which gives rise the biosensor special properties due to the synergic effect of the individual components. The electrochemical determination of lactate by the use of lactate oxidase (LOx) based SPE platform takes advantages of the combination of MW-CNT and conductive polysulfone polymer, and such an electrochemical biosensor was successfully applied for the quantification of lactate in wine and beer. In some cases, the inconvenient is the low stability associated with the deleterious interaction of the enzyme LOx with the composite CNT/polymer substrate. 

For the determination of lactate in buttermilk and denaturated milk powder, the use of a lot of filters (12 in total) gives significant information. The need for so many filters is caused by the variation in physical and chemical composition of the samples and by the few specific NIR bands of lactate in relation to the overall NIR spectrum. 

Kwan, R. C. H., Hon, P. Y.T., Mak, K. K. W. and Renneberg, R. (2004a) Amperometric determination of lactate with novel trienzyme/poly(carbamoyl) sulfonate hydrogel-based sensof. Biosensors and Bioelectronics, 19,1745-1752. 

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