Evaluation of multistep derivatization methods for identification and quantification of oxygenated species in organic aerosol

• Published in: Journal of Chromatography Vol. 1418; no. C; pp. 1 - 11
• Main Authors: Flores, Rosa M., Doskey, Paul V.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.10.2015; Elsevier
• Subjects: Aerosols; Alcohols - analysis; Alcohols - chemistry; Aldehydes - analysis; Aldehydes - chemistry; Carboxylic Acids - analysis; Carboxylic Acids - chemistry; Esters; Gas Chromatography-Mass Spectrometry - methods; GC × GC-ToF-MS; Ketones - analysis; Ketones - chemistry; Multistep derivatization; Organic aerosol; Oximes - chemistry; Oxygen; Oxygenated organics; Secondary organic aerosol; Trimethylsilyl Compounds - chemistry; Organic aerosol; Secondary organic aerosol; Multistep derivatization; GC×GC-ToF-MS; Oxygenated organics
• ISSN: 0021-9673; 1873-3778
• DOI: 10.1016/j.chroma.2015.09.041

•A 3-step derivatization technique was developed for mono- and multi-functional species.•Carbonyls were converted to methyloximes with O-methyhlhydroxylamine hydrochloride.•Carboxylic acids were converted to methyl esters with (Trimethylsilyl)diazomethane/methanol.•Alcohols were converted to trimethylsilyl ethers with N,O-bis(TMS)-trifluoroacetamide.•The average derivatization efficiency was 88.0±7.4% for 34 model compounds. Two, 3-step methods for derivatizing mono- and multi-functional species with carbonyl (CO), carboxylic acid (–COOH), and alcohol (–OH) moieties were compared and optimized. In Method 1, the CO, –COOH, and –OH moieties were converted (1) to methyloximes (R–CN–OCH3) with O-methylhydroxylamine hydrochloride (MHA), (2) to methyl esters (OC–R–OCH3) with (trimethylsilyl)diazomethane in methanol (TMSD/MeOH), and (3) to trimethylsilyl ethers [R-OSi(CH3)3] with N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) containing 1% trimethylchlorosilane (TMCS), respectively. Steps 1 and 3 of both methods were identical; however, in Step 2 of Method 2, –COOH moieties were derivatized with 10% (v/v) boron trifluoride (BF3) in MeOH or n-butanol (n-BuOH). The BF3/MeOH and BF3/n-BuOH were ineffective at converting species with more than 2-OH moieties. Average standard deviations for derivatization of 36 model compounds by the 3-step methods using TMSD/MeOH and BF3/(MeOH) were 7.4 and 14.8%, respectively. Average derivatization efficiencies for Methods 1 and 2 were 88.0 and 114%, respectively. Despite the lower average derivatization efficiency of Method 1, distinct advantages included a greater certainty of derivatization yield for the entire suite of mono- and multi-functional species and fewer processing steps for sequential derivatization. Detection limits for Method 1 using GC×GC-ToF-MS were 0.3–54pgm−3. Approximately 100 oxygenated organic species were identified and quantified in aerosol filtered from 39m3 of air in an urban location. Levels of species were 0.013–17ngm−3 and were nearly all above the Method 1 limit of detection.