Amino compounds spectrophotometric

These principles appear to hold for nucleophilic catalysis of hydrolysis by other species also. The evidence for catalysis by amino-compounds is discussed below. Catalysis by a wide variety of oxyanions (and other anions) has been measured by several authors, particularly of the hydrolysis of p-nitrophenyl acetate. This is a convenient substrate kinetically, since the release of / -nitrophenoxide is easily followed spectrophotometrically at 400 nm, but perhaps not ideal mechanistically, since, as described above, at least some of its reactions involve a mixture of mechanisms. A selection of data, obtained under the same conditions in one laboratory283, is given in Tables 37 and 38. Some of these data are plotted logarithmically (in Fig. 17) against the... 

Diazo coupling involves the N exocyclic atom of the diazonium salt, which acts as an electrophilic center. The diazonium salts of thiazoles couple with a-naphthol (605). 2-nitroresorcinol (606), pyrocatechol (607-609), 2.6-dihydroxy 4-methyl-5-cyanopyridine (610). and other heteroaromatic compounds (404. 611) (Scheme 188). The rates of coupling between 2-diazothicizolium salts and 2-naphthol-3.6-disulfonic acid were measured spectrophotometrically and found to be slower than that of 2-diazopyridinium salts but faster than that of benzene diazonium salts (561 i. The bis-diazonium salt of bis(2-amino-4-methylthiazole) couples with /3-naphthol to give 333 (Scheme 189) (612). The products obtained from the diazo coupling are usuallv highly colored (234. 338. 339. 613-616). 

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

Methods for Determining Biomarkers of Exposure and Effect. Very few methods were located that could be used to determine exposure to 1,3-DNB or 1,3,5-TNB in humans. A spectrophotometric method exists (Dangwal and Jethani 1980) but is selective for nitro and amino benzene-based compounds, not for 1,3-DNB and 1,3,5-TNB specifically. The best methods for determination of exposure to 1,3-DNB and 1,3,5-TNB are HRGC/ECD (Bailey et al. 1988) and GC/MS (McEuen and Miller 1991). To date, only HRGC/ECD has been used quantitatively, and only for detection of... 

Many useful compounds such as amino acids, nucleic acids, alcohols, vitamins, antibiotics, foods, etc. are produced in fermentation industries. Furthermore, many organic and inorganic compounds are present in waste waters. The determination of these compounds is required for control of fermentation and environment. Analysis of these compounds can be done by spectrophotometric methods. However, complicated procedures and long reaction times are required. 

The expected result was obtained since n-amino acid oxidase converted )8-chloroalanine to pyruvate under anaerobic conditions, to chloropyruvate at high O2 concentrations, and to mixtures of these at intermediate O2 concentrations. Under steady state conditions, the reaction behaved as if cleavage of the a C-H bond were the rate-limiting process in turnover, although stopped-flow spectrophotometric measurements showed that this interpretation can not be entirely correct in this case (53) or in the case of )8-choloro-a-aminobutyrate (54), a-yS-Elimination has now been observed in three flavoprotein oxidase reactions (54) and can be considered strong circumstantial evidence for a-proton removal from compounds which closely resemble the physiological substrates. 

Other spectrophotometric organic reagents used for the determination of silver include 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) in the presence of the anionic surfactant lauryl sulphate (e = 7.7-10 ) [43] and dodecyl sulphate (e = 6-10 ) [44], 4-(3,5-dibromo-2 pyridylazo)-V,V-diethylaniline in the presence of dodecyl sulphate [45], Cadion 2B in the presence of Triton X-100 (e = 1.0-10 ) [46], 4-(2-quinolylazo)phenol [47], 4-(p-nitrophenylazo)-l-amino-3-pyridynol (e = 1.07-10 at 605 nm) [48], and thyrodine (after extraction of silver with the use of macrocyclic compounds) [5,49]. 

Measurement of total urinary metanephrines using spectrophotometric methods has also been reported." " After sample hydrolysis and isolation of metanephrines by ion-exchange chromatography, the hydroxyl- and amino-containing side-chains were oxidatively cleaved by periodate. Oxidation of both NM and MN resulted in the formation of a common end product, vanillin, which was measured spectrophotometricafly at 360 nm. This method was, however, susceptible to interferences from other compounds such as methylglucamine and the 4-hydroxylated metabolite of propranolol." Furthermore, the method did not differentiate between NM and MN, and results were only semi-quantitative for grossly increased concentrations of total metanephrines." " ... 

H.G. Higgins, D. Fraser, The reaction of amino acids and proteins with diazonium compounds. 1. A spectrophotometric study of azo-derivatives of histidine and tyrosine, Australian J., Sci. Res. Ser. A Phys. Sciences 1952, 5, 736-753. 

The chromatograms were treated with ninhydrin and developed by heating at 70 °C. for two hours. The spots of the individual amino acids were then cut out of the paper or scratched from the plate and extracted with methanol. The solutions were measured spectrophotometrically and the yields of the amino acids were calculated by means of calibration curves. Apart from this, special reagents were used for identification and detection of -SH and -SS- groups (3). The radioactivity measurements of the 85S-compounds formed were either carried out on a 27r-proport-tional flow counter or on a liquid scintillation counter. 

It has been reported that y3-CD could improve the selectivity of the color reactions of various metal ions with triphenylmethane, xanthene acid dyes and some other coloring reagents. The effect of fi-CD on the association compound system of metal (Mo, Zn, Co)-thiocyanate basic dyes such as malachite green, crystal violet, rhodamine B, rhodamine 6G and butyhhodamine B, has been investigated and the result shows that /3-CD could contribute to a more sensitive and stable system which improve the solubility of the basic dyes and produce a favorable microenviromnent for the color reactions [63]. /3-CD could be employed to solubilize the 1,2-amino anthraquinone in water due to the formation of inclusion complex which acts as a ligand for metal ions could be used for the determination of palladium at trace levels by spectrophotometry. In the spectrophotometric determination of microamounts of Zn based on the Zn-dithizone color reaction, -CD could increase the apparent molar absorptivity at 538 nm by 8.37 times. In the presence of cr-CD, the determination sensitivity of copper in leaves based on the color reaction of Cu(II) and mesotetrakis (4-methoxy-3-sulfophenyl) porphyrin was enhanced by 50% in the spectrophotometric analysis [64,65]. 

The p-nitrophenoxy group reacts readily with compounds that contain an aliphatic amino group, with the formation of an amide bond. The reaction may be easily detected spectrophotometrically in the UV... 

The scope of ion chromatography was considerably enlarged by newly designed electrochemical and spectrophotometric detectors. A milestone of this development was the introduction of a pulsed amperometric detector in 1983, allowing a very sensitive detection of carbohydrates, amino acids, and divalent sulfur compounds [19, 20]. 

The spectrophotometric method was calibrated with the l-fluoro-2,4-dinitrobenzene derivative of the model compound N,N -bis(p-amino-phenyl) terephthalamide. 

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