Advancement in Determination of Phthalate Metabolites by Gas Chromatography Eliminating Derivatization Step

Abstract

A gas chromatography-mass spectrometry (GC-MS) method to determine polar and thermally unstable phthalate metabolites [monomethyl phthalate-MMP, monoethyl phthalate-MEP, mono-n-butyl phthalate-MnBP, mono-(2-ethylhexyl) phthalate-MEHP] has been developed. This is the first report presenting the separation of monophthalates without derivatization step and any additional equipment or special injection port. Injection parameters (temperature, pressure, time, and volume of injection), chromatographic separation (retention gap, temperature program), and MS detection/identification (working parameters, ion selection) were investigated. Mechanisms and phenomena occurring under different conditions in the GC injector were evaluated and discussed. The limits of detection (LODs) of MMP, MEP, MnBP, MEHP in the protocol were 0.049, 0.036, 0.038, and 0.029 ng (per 2 µL of injection), respectively. The response of the monophthalates was found to be linear in the tested concentration range (for MMP: 0.15-100 ng, MEP and MnBP: 0.11-100 ng, MEHP: 0.087-100 ng per 2 µL) with the coefficient of determination higher than 0.9817 and inter-day precision in the range of 1.4-5.4%. The developed method is fast, easy and repeatable. Moreover, it allows for the elimination of derivatization agents, reduction of toxic waste production and simplification of analytical procedure.

Comprehensive Insight from Phthalates Occurrence: From Health Outcomes to Emerging Analytical Approaches

“…Consequently, to overcome the contamination problems, the step involved in the sample preparation, as well as solvent amounts, glassware, extraction time, and exposure of the sample to air, should be minimized [ 118 ]. Some studies have been performed to reduce the contamination level in laboratory material [ 11 , 119 , 120 , 121 , 122 ]. Reid et al [ 119 ] performed a screening of common laboratory equipment and components, and the results indicated that plastic syringes, pipette tips produced maximum leaching of 0.36 µg/cm 2 of DEHP and 0.86 µg/cm 2 of DiNP, plastic filter holders releases maximum leaching of 2.49 µg /cm 2 of DBP from polytetrafluoroethylene (PTFE) and Parafilm ® leached levels up to 0.50 µg/ cm 2 of DEHP.…”

“…Gas chromatography is the most used analytical approach for PAEs determination since these target analytes present low molecular weight (e.g., DMP, DEP, DBP, and DEHP), relatively low polarity, and thermally stable and appropriately volatility [ 118 ]. In the case of phthalates with high molecular weight, a derivatization step is required to convert phthalates to their volatiles through the methylation (-COOCH 3 ) or silylation (-COOSiR 3 ) process of the carboxylic acid group [ 120 ]. Nevertheless, excess derivatization agents or byproducts should be removed prior to GC analysis to avoid the deterioration of the stationary phase (column) [ 120 ].…”

“…In the case of phthalates with high molecular weight, a derivatization step is required to convert phthalates to their volatiles through the methylation (-COOCH 3 ) or silylation (-COOSiR 3 ) process of the carboxylic acid group [ 120 ]. Nevertheless, excess derivatization agents or byproducts should be removed prior to GC analysis to avoid the deterioration of the stationary phase (column) [ 120 ]. Generally, the PAEs separation is carried out using apolar fused-silica capillary columns coated with 5% phenyl and 95% dimethylpolysiloxane, under temperature programs starting from 60 °C up to 330 °C, in total run time analysis ranging from 20 to 51 min [ 66 , 67 , 69 , 79 , 85 , 86 , 91 , 100 , 103 ].…”

Chemical Composition and Antioxidant, Anti-Inflammatory, and Enzyme Inhibitory Activities of an Endemic Species from Southern Algeria: Warionia saharae

“…GC–MS analysis is the most suitable technique to assess plant extracts′ lipophilic profile [ 34 , 35 ]. It requires, in some cases, a derivatization procedure to convert many secondary metabolites to volatile derivatives [ 36 ], and silylation is the most recent derivatization procedure [ 37 , 38 ]. The GC–MS analysis of the hydromethanolic extract of W. saharae allowed the identification of four families of compounds: sugars (214.735 µg/mg), alcohols (128.520 µg/mg), carboxylic acids and esters (124.6 µg/mg), and fatty acids (11.364 µg/mg).…”

Lineage-Selective Disturbance of Early Human Hematopoietic Progenitor Cell Differentiation by the Commonly Used Plasticizer Di-2-ethylhexyl Phthalate via Reactive Oxygen Species: Fatty Acid Oxidation Makes the Difference

“…The column was initially heated to 70 • C for 3 min, then increased at a rate of 13 • C/min to 280 • C; the temperature was held at 280 • C for 15.83 min. DEHP, MEHP, and deuterated internal standards were detected in the SIM mode using 149 m/z or 153 m/z fragments as quantifiers as previously described [38,39]. All materials used for this analysis were tested for the absence of DEHP and MEHP prior to use.…”