High-performance liquid chromatographic determination of glyoxylic acid in urine

Petrarulo, Michele; Pellegrino, Sergio; Bianco, Ornella; Marangella, Martino; Linari, F; Mentasti, Edoar̈do

doi:10.1016/s0378-4347(00)80631-3

“…In the case of the phenylhydrazone of pyruvate, which was isolated following an identical protocol, the species observed at ≈ 149 was absent and a mass of 178.07462 was obtained (calculated 178.07423). We also tried to identify the compound by NMR spectroscopy of its phenylhydrazone derivative, but the spectra could not be interpreted, probably as a result of the known instability of the phenylhydrazones of pyruvate [20] and the large number of acquisitions required to obtain a meaningful result when using a very limited amount of material.…”

Section: Resultsmentioning

confidence: 99%

The biosynthesis of ovothiol A (N¹‐methyl‐4‐mercaptohistidine)

Vogt

¹

,

Spies

²

,

Steenkamp

³

2001

European Journal of Biochemistry

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Crude extracts of Crithidia fasciculata catalyse the formation of 4‐mercapto‐l‐histidine, an intermediate in the biosynthesis of ovothiol A (N1‐methyl‐4‐mercaptohistidine), in the presence of histidine, cysteine, Fe2+ and pyridoxal phosphate. This activity was present in a 35–55% ammonium sulfate fraction that was shown to produce a transsulfuration intermediate in the absence of pyridoxal phosphate. The transsulfuration intermediate was isolated and identified as S‐(4′‐l‐histidyl)‐l‐cysteine sulfoxide. The synthase activity, partially purified by anion‐exchange chromatography, was shown to require oxygen and could be used to synthesize a number of isotopically labeled S‐(4′‐l‐histidyl)‐l‐cysteine sulfoxides. Sulfoxide lyase activity was partially resolved from the synthase by anion‐exchange chromatography. The phenylhydrazone of the product derived from the cysteine moiety of the sulfoxide coeluted with the phenylhydrazone of pyruvate on HPLC, but this assignment could not be confirmed by mass spectral analysis. S‐(4′‐[14C]l‐histidyl)‐[U‐13C3,15N]l‐cysteine sulfoxide was synthesized and converted to products of the lyase reaction in the presence of lactate dehydrogenase and NADH. The 13C‐labeled product was identified by 13C‐NMR spectroscopy as lactate and the primary product of the lyase reaction is therefore pyruvate. With S‐(4′[3H]l‐histidyl)‐[14C]l‐cysteine sulfoxide as the substrate [14C]lactate, [14C]cysteine and [3H]4‐mercaptohistidine could be detected as products of the lyase reaction, but the sum of the two thiol species exceeded the amount of sulfoxide substrate used. Evidence is presented that this anomaly was due to the utilization of sulfur from dithiothreitol for the formation of cysteine.

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“…a-Keto acids (e.g., glycolic, glyoxylic acids) are detectable with UV light after derivatization with phenylhydrazine [287], [288].…”

Section: Derivatizationmentioning

confidence: 99%

Sample Preparation for Trace Analysis

Begerow

¹

,

Dunemann

²

2006

Ullmann's Encyclopedia of Industrial Chemistry

2

0

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The article contains sections titled: 1. Introduction 1.1. A Strategy Appropriate to Trace Analysis 1.2. Avoidance of Systematic Errors 1.2.1. Trace Losses and Contamination 1.2.2. Uncertainty 2. Sample Preparation and Digestion in Inorganic Analysis 2.1. Sample Treatment after the Sampling Process 2.1.1. Stabilization, Drying, and Storage 2.1.2. Homogenization and Aliquoting 2.1.3. Requirements with Respect to Materials and Chemicals 2.2. Sample‐Preparation Techniques; General Considerations 2.2.1. Special Factors Associated with Microwave‐Assisted Digestion 2.2.2. Safety Considerations 2.3. Wet Digestion Techniques 2.3.1. Wet Digestion at Atmospheric Pressure 2.3.2. Pressure Digestion 2.3.2.1. Thermally Convective Pressure Digestion 2.3.2.2. Microwave‐Assisted Pressure Digestion 2.4. “Dry” Digestion Techniques 2.4.1. Combustion in Air 2.4.2. Combustion in Oxygen 2.4.3. Cold‐Plasma Ashing 2.4.4. Fusion 2.5. Illustrative Examples 2.5.1. Sample Preparation as a Function of Analytical Method 2.5.2. Combined Use of Multiple Decomposition Techniques 2.5.3. Comparative Merits of the Various Sample‐Preparation Techniques 2.5.4. Decomposition Procedures for Determining Nonmetals 2.6. Evaluation Criteria 2.6.1. Completeness 2.6.2. Uncertainty 2.6.3. Time Factors 2.6.4. The Final Result 2.7. Concentration and Separation of Inorganic Trace Materials 2.8. Automation and Direct Analysis 2.8.1. Automation 2.8.2. Direct Analysis 2.9. Analysis of Element Species 3. Sample Preparation in Organic Analysis 3.1. Sample Treatment after the Sampling Process 3.1.1. Stabilization, Drying, and Storage 3.1.2. Homogenization and Aliquoting 3.1.3. Requirements with Respect to Materials and Chemicals 3.2. Separation of the Analyte 3.2.1. Hydrolysis 3.2.2. Liquid ‐ Liquid Extraction 3.2.3. Soxhlet Extraction 3.2.4. Microwave‐Assisted Solvent Extraction 3.2.5. Supercritical Fluid Extraction (SFE) 3.2.6. Solid‐Phase Extraction (SPE) 3.2.7. Solid‐Phase Microextraction (SPME) 3.2.8. Stir‐Bar Adsorptive Extraction (SBSE) 3.2.9. Miscellaneous Techniques 3.3. Headspace Techniques 3.3.1. Static Headspace Technique 3.3.2. Dynamic Headspace Technique (Purge and Trap) 3.4. Determination of Trace Organic Materials in Air Samples 3.5. Analyte Concentration 3.6. Derivatization 3.7. Coupled Techniques Trace analysis is a very relevant and applications‐oriented branch of analytical chemistry. The sample preparation for trace analysis must be custom‐tailored to the problem at hand. Systematic errors can arise by contact with vessel materials, reagents, or the ambient atmosphere, as well as any change in chemical or physical state. In inorganic analysis, sample preparation has to meet the requirements for a substantially trouble‐free determination of the analyte. Digestion of the matrix (microwave digestion, wet digestion, dry digestion techniques) and subsequent careful comparison of several decomposition techniques is therefore an essentially important step. Some separation and concentration techniques of the analytes are liquid –liquid extraction, solid‐phase extraction, special precipitation reactions, and electrolytic deposition. The introduction of laboratory robots should make it possible to incorporate a significant degree of automation into the time‐consuming, labor‐intensive area of sample preparation as well, leading to more efficient, reliable, and reproducible sample work‐up. The goal of sample preparation in organic trace analysis is to isolate the analyte from the sample matrix (e.g., liquid‐liquid extraction, Soxhlet extraction, microwave‐assisted solvent extraction, steam distillation) and then concentrate it and convert it into a form suitable for analysis by the selected method. Separation and concentration of an analyte must often be followed by some type of derivatization. Various coupled sample preparation and determination processes are increasingly utilized in trace organic analysis.

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“…α-Keto acids (e.g., glycolic, glyoxylic acids) are detectable with UV light after derivatization with phenylhydrazine [268,269]. Fluorescent compounds are obtained by reacting carboxylic acids with 4bromomethyl-7-methoxycoumarin [270][271][272][273] or 4-bromomethyl-7-acetoxycoumarin [274,275].…”

Section: Derivatizationmentioning

confidence: 99%