Abstract: Precolumn derivatization applying o-phthaldialdehyde (OPA) was used to analyze free lysine, histidine, and ornithine, precursors of the respective biogenic amines cadaverine, histamine, and putrescine, which are considered indicators of fish quality and safety. This method uses 75% methanol to eliminate the use of strong acids as the extraction solution. Each analysis took 35 min, was reproducible, and allowed separation of primary amino acids in fish samples. A binary solvent delivery system coupled with a fluorescence detector and an Ultrasphere ODS column were utilized for HPLC separation. Linearity of the calibration curves was very good (r2 = 0.99) for the amino acids of interest. Minimum concentrations of detection were 40 pmol/mL for histidine and lysine and 70 pmol/mL for ornithine. Average recoveries were 72% for lysine, 93% for histidine, and 98% for ornithine. This method used solvent gradient elution to study the levels of these analytes in mahi-mahi, bigeye tuna, and flounder. Keywords: Free ...

Abstract: Partial Table of Contents: 1. Pretreatment for Real Sample Analysis and Choice of Suitable Reagent 2. Reagent for UV--VIS detection 3. Reagent for FL Detection 4. Reagents for CL detection 5. Reagents for electrochemical detection 6. Derivatization for resolution of chiral compounds References Subject index.

Abstract: New applications for your mass spectrometer-use it to measure enantiomeric excess! The enantiomeric content of very small quantities of chiral alcohols and amines has been determined by derivatization with chiral acylating agents in which mass is correlated to absolute configuration. The resultant esters and amides were then analyzed by electrospray ionization mass spectrometry (ESI-MS; shown schematically). The technique requires surprisingly low levels of diastereoselectivity in the acylation step, and is therefore generally applicable.

Abstract: This paper describes a new detection method that uses a six-potential waveform to detect all amino acids without derivatization. The detection limits are less than 1 pmol for most of the analytes. The anion-exchange separation uses a ternary gradient with water, 0.25 M sodium hydroxide, and 1.0 M sodium acetate. We present results of waveform optimization experiments designed to minimize gradient artifacts and to achieve optimum conditions for the quantitative analysis of common amino acids. Analytical results for protein hydrolysates are discussed and compared with those obtained by cation exchange followed by ninhydrin derivatization and spectrophotometric detection.

Abstract: Modern derivatization methods for separation science , Modern derivatization methods for separation science , کتابخانه دیجیتال جندی شاپور اهواز

Abstract: Publisher Summary This chapter discusses the size separation of condensed tannins by normal-phase high performance liquid chromatography (HPLC). Condensed tannins are also called “proanthocyanidins” because they release anthocyanins when heated in acidic conditions. They are ubiquitous plant components, consisting of chains of flavan-3-ol units. Tannin properties—including radical scavenging effects protein binding ability—depend largely on their structure and particularly on the number of constitutive units. Several methods have been developed to determine oligomeric and polymeric proanthocyanidins. Separation of lower molecular weight proanthocyanidins is usually achieved by reversed-phase HPLC, but the elution order is unrelated to the degree of polymerization. Various other techniques have been used to separate proanthocyanidins following this criterion—for instance, liquid chromatography on sephadex LH-204 or fractogel. HPLC method presented in this chapter allows separation of proanthocyanidins on a molecular weight basis, without derivatization. Although this method is suitable in most cases, it may require modifications, depending on the nature of tannins to be extracted and on the presence of other plant constituents. In particular, the extraction yield may be improved by sonicating and the samples may be protected against oxidation at this stage—for instance, by sulfiting or working under inert gas and/or at low temperature.

Abstract: Aminoglycosides are antimicrobial agents used frequently in treatment of human and animal diseases caused by aerobic, gram-negative bacteria. Because of the toxicity of these compounds, considerable effort has been attributed to analysis of aminoglycoside content in drug preparations, in serum and urine specimen in therapeutic drug monitoring, and in edible animal tissues in residue control. The present review emphasizes the analytical problems associated with aminoglycoside analysis. Screening methods based on microbiological and immunological procedures were briefly discussed. Gas chromatography and especially high-performance liquid chromatography appeared the most widely used chemical methods for the analysis of these compounds. Due to lack of volatility, chromophore, and hydrophility of aminoglycosides, most methods applied derivatization for enhancement of their chromatographic characteristics. The applicability and advantages of the various derivatization procedures were discussed in detail. A wide variety of detection methods, including mass spectrometry have been used. Packed column separation was generally used for gas chromatographic separation. In liquid chromatography, reversed phase, ion pair, ion exchange, and normal phase separation has been employed. Mass spectrometry, as a detection method, was discussed in detail. Extraction procedures from body fluids and tissues were emphasized. The performance and the operational conditions of the methods were described and detailed information of the data was provided also in table format.

Abstract: Pre-column conversion of ammonia and a number of aliphatic amines into phenylthiourea or its derivatives by reaction with phenyl isothiocyanate, followed by HPLC, has been used for their determination in environmental waters. Optimum conversion was found when the reaction was carried out in sodium hydrogencarbonate–carbonate medium at 40°C for 15 min. Well separated peaks were obtained on a C18 column with an acetonitrile–water gradient (1 ml min–1) of 30% acetonitrile for an initial 5 min which was increased linearly to 100% over 15 min and then maintained isocratic for 5 min, the acetonitrile ratio finally being returned to 30% in 5 min. The derivatized analytes were subjected to off-line solid phase extraction on C18 sorbent. A linear calibration graph was obtained for 0.01–10 mg l–1 analytes with a correlation coefficient of 0.9954 for ammonia and in the range 0.9982–0.9996 for amines. The limit of detection for ammonia was 0.2 µg l–1 and for amines in the range 0.3–0.6 µg l–1. The method was applied to tap, underground, river and aquarium waters, the recovery being in the range 97–106% (RSD 1.8–4.5%). Many of the samples were found to contain more than the permissible limit of ammonia. Phenyl isothiocyanate is stable for long periods in aqueous medium over wide ranges of pH and temperature, and the resulting phenylthioureas have adequate retention on C18 sorbent and strong UV absorption, making this reagent suitable for the determination of amines in water.

Abstract: The α-diketones glyoxal, methylglyoxal, and diacetyl were determined in selected beer and wine using a procedure involving the use of C18 solid phase extraction columns to remove interferences and derivatization of the compounds with o-phenylenediamine to form quinoxalines, which are separated by HPLC and detected using UV spectrophotometric detection. Interferences were more difficult to remove in the case of beer, due to the higher complexity of the matrix and because the concentrations of the compounds were lower (higher for methylglyoxal and lower for diacetyl, but all in the 10−7 M region). The determination was easier to implement in the case of wine as the typical concentrations of the compounds were about ten times higher, with methylglyoxal being the more abundant compound found.

Abstract: This chapter reviews methods for the analysis of free amino acids particularly during cheese ripening. Two commonly used methods are described in more detail. The most accurate results are obtained using the ion exchange chromatography method with postcolumn ninhydrin derivatization and photometry detection at 570 and 440 nm for primary and secondary amino acids, respectively. Because the majority of dairy laboratories are not equipped with such an amino acid analyser, another method has been developed using high performance liquid chromatography with reverse phase separation of OPA and FMOC derivatives for primary and secondary amino acids, respectively. These derivatives can be detected by photometry or by fluorescence at very low concentration. The use of several other derivatives is discussed.

Abstract: Dissolved formaldehyde in aqueous samples was determined at submicromolar levels by derivatization with Nash's reagent followed by liquid chromatography. The method requires little sample preparation, and the chromatogram is simple even in the presence of other aldehydes and ketones. The isocratic HPLC analysis is rapid with a low limit of detection (0.1 μM) and a precision of 1% RSD at 150 μM. The derivative is stable for at least 3 days at room temperature. Accuracy of the method was verified by intercomparison with an alternate, completely independent method, which utilizes another derivatizing agent.

Abstract: A sensitive method for the determination of ultratrace organotin species in seawater is described. The merits and demerits of derivatization methods using Grignard reagent or sodium tetraethylborate (NaBEt4) were evaluated in terms of derivatization efficiency, applicability to the programmed temperature vaporization (PTV) method, and procedural blanks. The sensitivity of the gas chromatography/inductively coupled plasma mass spectrometry (GC/ICPMS) was improved by more than 100-fold by operating the shield torch at normal plasma conditions, compared with that obtained without using it. The absolute detection limit as tin reached subfemtogram (fg) levels. Furthermore, the detection limit in terms of relative concentration was improved 100-fold by using the PTV method, which enabled the injection of a large sample volume of as much as 100 microL without loss of analyte. When the organotin species in seawater were extracted into hexane with a preconcentration factor of 1000 after ethylation with NaBEt4 and a 100 microL aliquot of the extract was injected into the GC, the instrumental detection limit in relative concentration reached 0.01 pg/L in original seawater. Sources of contamination of organotin species during the sample preparation were examined, and a purification method of NaBEt4 was developed. Finally, the method was successfully applied to open ocean seawater samples containing organotin species at the level of 1-100 pg/L.