Derivatization with diazomethane

The scope of the multi-residue method is extended permanently by testing and then including further active substances that can be determined by GC. Acidic analytes (such as phenoxyacetic acids or RCOOH metabolites) are included into the homogeneous partitioning by acidifying the raw extracts to a pH below the pKs value of the carboxylic acids. To include these analytes in the GC determination scheme they have to be derivatized with diazomethane, diazoethane, trimethylsilyldiazomethane, acidic esterification or benzylation, or by silanizing the COOH moiety. 

Water samples of 500-1000 mL are extracted and purified simultaneously through an SPE cartridge such as Carbograph-1, Cig and RP-18, usually followed either by HPLC with ultraviolet (UV) or photoconductivity detection or by GC/ECD. The acidic-type diphenyl ether herbicides are derivatized with diazomethane and various kinds of chloroformates and determined by GC and HPLC. 

In the above-mentioned method by Hodgeson el acifluorfen was determined by GC/ECD after the extraction with a 47-mm PS-DVB disk and derivatization with diazomethane. The conditions for GC/ECD were as follows column, DB-5 fused silica (30 m X 0.32-mm i.d., 0.25-p.m film thickness) He carrier gas velocity, 25 cm s (210°C), detector makeup gas, methane-argon (5 95), 30mLmin column temperature, 50 °C (5 min), 10°Cmin to 210 °C (5 min) and to 230 °C (10 min) injection port and detector temperature, 220 and 300 °C, respectively injection method, splitless mode. The recovery of acifluorfen from purified water, dechlorinated tap water and high humic content surface water fortified at 0.5-2.0 ug was 59-150% and the LOD was 25 ngL Acifluorfen after derivatization with various chlorofor-mates was also determined by GC/MS using an SE-54 column (25 m x 0.20-mm i.d., 0.32- um Aim thickness), and the average recovery of acifluorfen fortified between 0.05 and 0.2 ugL was 78%. ... 

A method involving SPE was developed for the determination of ten A-nitroso amino acids in cured meat products. These compounds were derivatized with diazomethane followed by O-acylation of hydroxyl groups with acetic anhydride-pyridine reagent. The methyl esters and their acylated derivatives were separated by GC on a DB-5 fused silica capillary column and quantified with a TEA-CLD specific for the nitric oxide derived from the thermal denitrosation of nitrosamines recovery exceeded 75% at the 10 ppb level579. 

Gas chromatographic methods have been successfully used for the determination of penicillin molecules bearing neutral side-chains in milk and tissues (95, 97), but cannot be used for amphoteric -lactams. Gas chromatography of penicillin residues is further complicated by the necessity for derivatization with diazomethane. This derivatization step is particularly important because it not only leads to formation of the volatile penicillin methyl esters but also improves their chromatographic properties (thermal stability and decreased polarity). Using a fused-silica capillary column in connection with a thermionic nitrogen-selective detector, excellent separation and sensitivity figures were obtained. 

G1azko 7 reviewed same early studies on the gas chromatographic assay of phenytoin. These included derivatization with diazomethane S, the use of trimethylsilyl derivative /50, on col linn methyl at ion using tetramethyl ammonium hydroxide51 and trimethylanilinium hydroxide5. ... 

Phosphoramidothiolates a and 7b. with MCPBA yield thermally-unstable products in contrast to the more stable obtained on oxidation of 6a. Neutral aqueous hydrolysis of the reaction products of 7a then derivatization with diazomethane yields many... 

Dissolved nitrite in natural waters was determined at subnanomolar levels by derivatization with 2,4-dinitro-phenylhydrazine followed by hplc (102). The method has a detection limit of 0.1 nM, with an average precision of 4% RSD at ambient natural water concentrations. Irgasan 300 ((2,4-dichlorophenoxy)-phenol) has been determined in the wastewater of a slaughterhouse, using gc/ecd after derivatization with diazomethane (103). The detection limit was found to be 0.2 ng/L. 

Nick K, Schoeler HF. 1992. Gas-chromatographic determination of nitrophenols after derivatization with diazomethane. Fresenius J Anal Chem 343(3) 304-307. 

Determination of Irgasan DP 300 (41) in slaughterhouse wastewater involved alkaliniza-tion to pH 11, removal of fats and oils by LEE with petroleum ether, acidification to pH 1, LEE with benzene, further purification by sodium sulfate/silica gel adsorption, desorption, derivatization with diazomethane and end analysis by GC with electron capture detection (LCD). LOD was 8.2 ngL" recovery was better than 88% regardless of concentration. ... 

Bupivacaine (49a) and its phenolic metabolites (49b-c) were detected in urine after the samples underwent hydrolysis, LLE with ether, concentration by evaporation and derivatization with diazomethane, to obtain the methyl ethers (49d). End analysis was by GC-MS in the SIM mode". Another methylation reaction with this reagent was mentioned in Section III.A.2 . On-site methylation with tetramethylammonium hydroxide was proposed for the analysis of phenolic additives in polymeric materials, by the pyrolysis-GC method" . Pressurized LLE using phenytrimethylammonium hydroxide (50) or trimethylsulfonium hydroxide (51) for simultaneous methylation was applied to the... 

Rractically the same list of phenols can be determined by analysis of municipal and industrial wastewater detailed in ERA Method 604 (GC/FID or GC/ECD) and 625 (GC/MS) . Method 8041 for determination of phenols in wastewater, presented by the ERA Office of Waste Water, describes the determination of ca 40 phenols specifying extraction and cleanup conditions, derivatization with diazomethane or pentafluorobenzyl bromide and analytical determination by GC/FID, GC/ECD or GC/MS . ... 

Klaffenbach and Holland (1993) analyzed sulfourea herbicides in soil water extracts and in water samples using disk extraction. They found that the thermally unstable sulfourea herbicides could be extracted onto the C-18 disks eluted with ethyl acetate and derivatized with diazomethane for GC/MS confirmation. The method also worked well for aqueous soil extracts that could also be passed through the C-18 disks for rapid concentration, derivatization, and analysis. 

Urine (BAA) Addition of external standard to 50 inL urine, adjustment of pH to 1-2 and removal of cationic impurities by cation-exchange. Isolation of BAA by adsorption onto XAD-4 resin and elution using diethyl ether. Evaporation of solvent followed by derivatization with diazomethane. GC/FID 0.02 mg/L (0.02 ppm, w/v) 100.9% (%RSD ranged from 4.8 to 12.6) Begerow et al. 1988... 

PDMS and PA + derivatization with diazomethane Derivatization with benzyl bromide + PDMS PA... 

Derivatization with diazomethane, evaporation of excess regent... 

It is known that methylation with diazomethane selectively methylates FFAs in the presence of FA esters. Caution is required, as diazomethane is a dangerous substance. Under inappropriate conditions, derivatization with diazomethane leads to the formation of artifacts. Functional groups such as phenol, enol, and carbonyl, or olefinic bonds can be affected. The less-dangerous methylation agents such as trimethylsilyldiazomethane (TMS-CHN2) and lit-hiated TMS-CHN2 have been suggested to replace diazomethane. Benzyl esters can be produced by the use of phenyldiazomethane. 

Pharmaceuticals (acid and neutral) SPE (Oasis HLB sorbent) derivatization with diazomethane GC-MS... 

Similarly, detection of phenoxy acid herbicides by GC is complicated by the fact that these compoimds exhibit low volatilities due to the H bonding of their carboxylic acid and phenol fimctionalities. To convert phenoxy acid to esters, derivatization with diazomethane [96,103], dimethyl sulfate [23], and benzyl bromide before extraction [95] was adopted by some authors. Rodriguez et al. [94] developed a method to derivatize phenoxy acid herbicides and dicamba on an SPME fiber phenoxy acid herbicides and dicamba, using N-methyl-N-(ferf-butyldimethylsilyl)-trifluoroacetamide as reagent for silylation. 

Normal phase HPLC-UV (277 nm) for ethoxy distribution and nonylphenol RP-HPLC-UV (277 nm) for other phenols headspace GC for CO2 Derivatization with diazomethane (for determination of carboxylates) and GC-MS GC-MS, with or without diazomethane derivatization... 

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