FOLIN’s reagent

A iridine traces in aqueous solution can be determined by reaction with 4-(p-nitroben25l)pyridine [1083-48-3] and potassium carbonate [584-08-7]. Quantitative determination is carried out by photometric measurement of the absorption of the blue dye formed (367,368). Alkylating reagents interfere in the determination. A iridine traces in the air can be detected discontinuously by absorption in Folin s reagent (l,2-naphthoquinone-4-sulfonate) [2066-93-5] (369,370) with subsequent chloroform extraction and hplc analysis of the red dye formed (371,372). The detection limit is ca 0.1 ppm. Nitrogen-specific thermal ionisation detectors can be used for continuous monitoring of the ambient air. 

Fluorescence stabilization, porphyrins la 100-101 Fluorophors la 57 Flupentixol lb 354 Fluphenazine la 104 lb 354-356 Fluspirilen lb 354 Fluvalinates lb 86 Foam bath, brominated la 64 Folic acid la 223,225 Folin-Ciocalteu s reagent lb 180 Folin s reagent lb 321 Formaldehyde la 299,351 -, vapor la 86 Formazan lb 65... 

In Goiffon s method (G3) peptides are precipitated with phospho-tungstic acid from a trichloroacetic acid filtrate. The precipitate is dissolved and color is developed by a reaction with Folins phenol reagent. This method, however, is not only specific for peptides and a separate assay of uric acid has to be made since this substance also reacts with Folin s reagent. 

Lincomycin hydrochloride formed a molybdenum blue heteropolycomplex with Folin s reagent This method was used to monitor lincomycin in the workplace air of antibiotic manufacturing plant at wavelength 600 nm (47). 

H15. Herriott, R. M., Reaction of Folin s reagent with proteins and biuret compounds in the presence of cupric ions. Proc. Soc. Exptl. Biol. Med. 46, 642-644 (1941). 

A number of other reagents have been used to give colored derivatives of amino acids, among these being Folin s reagent, 1,2-naphthoquinon-4-sulfonic acid and o-phthalaldehyde. However, the ninhydrin reaction is so easy to perform and sensitive that other reactions are of very limited importance. Derivatization of amino acids to give colored and/or fluorescent products subsequently subjected to chromatographic procedures can be mentioned in connection with the discussion of color reactions for amino acids. 

Other highly sensitive reagents are 2,4,6-trinitro-benzosulfonic acid, l,2-naphthoquinone-4-sulfonic acid (Folin s reagent), and 4,4 -tetramethyldiaminodi-phenylmethane (TDM). Intensely fluorescing amino acid derivatives are formed by reaction with o-phthal-aldehyde in the presence of reducing agents with pyr-idoxal and zinc ions and with dansyl chloride (5-di-methylaminonaphthalene sulfonyl chloride). 

Folin s phenol reagent was prepared as reported by Lowry et al., J. Biol. Chem., 193 (1951) 265. Samples containing 5-100 /ig of fresh citrinin (in 0.15% sodium carbonate) were pipetted out into a series of test tubes. The final volume was brought to 3 ml with carbonate/bicarbonate buffer. To this, 1 ml of Folin s reagent was added, followed by 1 ml of 15% sodium carbonate soln. The tubes were then gently shaken once and incubated at 37°C for IS min. The blue color developed was read at 640 nm... 

Folin s Reagent, for uric acid and phenols. Boil under a reflux condenser for two hours a mixture of 100 gm. sodium tungstate, 102 ml. ort -phosphoric acid (B.P. 66 3 per cent.), and 750 ml. of water. When the mixture has cooled, sufficient bromine is added to bleach completely any blue colour. The mixture is then boiled... 

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