Urinary biomonitoring of fuel ether oxygenates using a needle trap device packed with a novel molecularly imprinted polymer surface modified Zeolite Y.

This study introduces an innovative needle trap device (NTD) featuring a molecularly imprinted polymer (MIP) surface-modified Zeolite Y. The developed NTD was integrated with gas chromatography-flame ionization detector (GC-FID) and employed for analysis of fuel ether oxygenates (methyl tert­butyl ether, MTBE, ethyl tert­butyl ether, ETBE, and tert­butyl formate, TBF) in urine samples. To optimize the key experimental variables including extraction temperature, extraction time, salt concentration, and stirring speed, a central composite design-response surface methodology (CCD-RSM) was employed. The optimal values for extraction in the study were found to be 51.2 °C extraction temperature, 46.2 min extraction time, 27 % salt concentration, and 620 rpm stirring speed. Under the optimized conditions, the calibration curves demonstrated excellent linearity within the range of 0.1-100 µg L-1, with correlation coefficients (R2) exceeding 0.99. The limits of detection (LODs) for MTBE, ETBE, and TBF were obtained 0.06, 0.08, and 0.09 µg L-1, respectively. Moreover, the limits of quantification (LOQs) for MTBE, ETBE, and TBF were obtained 0.18, 0.24, and 0.27 µg L-1, respectively. The enrichment factor was also found to be in the range of 98-129.The NTD-GC-FID procedure demonstrated a high extraction efficiency, making it a promising tool for urinary biomonitoring of fuel ether oxygenates with improved sensitivity and selectivity compared to current methods.

Exposure to BTEX and Ethers in Petrol Station Attendants and Proposal of Biological Exposure Equivalents for Urinary Benzene and MTBE.

OBJECTIVE: To assess exposure to benzene (BEN) and other aromatic compounds (toluene, ethylbenzene, m+p-xylene, o-xylene) (BTEX), methyl tert-butyl ether (MTBE), and ethyl tert-butyl ether (ETBE) in petrol station workers using air sampling and biological monitoring and to propose biological equivalents to occupational limit values. METHODS: Eighty-nine petrol station workers and 90 control subjects were investigated. Personal exposure to airborne BTEX and ethers was assessed during a mid-week shift; urine samples were collected at the beginning of the work week, prior to and at the end of air sampling. RESULTS: Petrol station workers had median airborne exposures to benzene and MTBE of 59 and 408 µg m(-3), respectively, with urinary benzene (BEN-U) and MTBE (MTBE-U) of 339 and 780 ng l(-1), respectively. Concentrations in petrol station workers were higher than in control subjects. There were significant positive correlations between airborne exposure and the corresponding biological marker, with Pearson's correlation coefficient (r) values of 0.437 and 0.865 for benzene and MTBE, respectively. There was also a strong correlation between airborne benzene and urinary MTBE (r = 0.835). Multiple linear regression analysis showed that the urinary levels of benzene were influenced by personal airborne exposure, urinary creatinine, and tobacco smoking [determination coefficient (R(2)) 0.572], while MTBE-U was influenced only by personal exposure (R(2) = 0.741). CONCLUSIONS: BEN-U and MTBE-U are sensitive and specific biomarkers of low occupational exposures. We propose using BEN-U as biomarker of exposure to benzene in nonsmokers and suggest 1457 ng l(-1) in end shift urine samples as biological exposure equivalent to the EU occupational limit value of 1 p.p.m.; for both smokers and nonsmokers, MTBE-U may be proposed as a surrogate biomarker of benzene exposure, with a biological exposure equivalent of 22 µg l(-1) in end shift samples. For MTBE exposure, we suggest the use of MTBE-U with a biological exposure equivalent of 22 µg l(-1) corresponding to the occupational limit value of 50 p.p.m.

Urinary BTEX, MTBE and naphthalene as biomarkers to gain environmental exposure profiles of the general population.

The aim of this work was to evaluate urinary benzene, toluene, ethylbenzene, m+p-xylene, o-xylene (BTEX), methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and naphthalene (NAP) as biomarkers of exposure to environmental pollutants. Personal air and urine samples from 108 subjects belonging to the Italian general population were compared. Urinary profiles were obtained by headspace gas chromatography-mass spectrometry. BTEX, MTBE, ETBE and NAP median airborne exposures during a 5-h sampling were 4.0, 25.3, 3.8, 9.3, 3.4, 3.4, <0.8, and 3.4 microg/m(3), respectively. Meanwhile, median urinary levels, as geometric means of three determinations were: 122, 397, 74, 127, 43, 49, <15, and 46 ng/L, respectively. Urinary benzene and toluene concentrations were 4.6- and 1.2-fold higher in smokers than in non-smokers. For most chemicals, significant positive correlations between airborne exposure (log-transformed) and the corresponding biological marker (log-transformed) were found, with Pearson's r values for correlation, ranging from 0.228 to 0.396. Multiple linear regression analysis showed that the urinary level of these chemicals was influenced by personal airborne exposure, urinary creatinine, and urinary cotinine, with R(2) 0.733 for benzene. Urinary chemicals are useful biomarkers of environmental exposure. Given the ease of rapidly obtaining urine samples, they represent a non-invasive alternative to blood chemical analysis. The possibility of obtaining urinary exposure profiles makes this method an appealing tool for environmental epidemiology.

Single-walled carbon nanotubes as an effective adsorbent in solid-phase microextraction of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether from human urine.

Carbon nanotubes (CNTs) are a kind of new carbon-based nano-materials which have drawn great attention in many application fields. The potential single-walled carbon nanotubes (SWCNTs) as solid-phase microextraction (SPME) adsorbents for the preconcentration of environmental pollutants have been investigated in recent years. The goal of this work was to investigate the feasibility of SWCNTs used as adsorbents for solid-phase microextraction of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) in human urine. SWCNTs were attached onto a stainless steel wire through organic binder. Potential factors affecting the extraction efficiency were optimized, including extraction time, extraction temperature, desorption time, desorption temperature, and salinity. The developed method showed good performance according to the ICH performance criteria for bioanalytical methods. The calibration curves of the ethers were linear (r(2)>or=0.992) in the range from 10 to 5000 ng L(-1). The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng L(-1) for all the analytes. In addition, compared with the commercial carboxen/polydimethylsiloxane (CAR/PDMS) fiber, the SWCNT fiber showed better thermal stability (over 350 degrees C) and longer life span (over 150 times). The developed method was applied successfully to determine trace level of the ethers in urine of 10 healthy male volunteers.

Determination of low level methyl tert-butyl ether, ethyl tert-butyl ether and methyl tert-amyl ether in human urine by HS-SPME gas chromatography/mass spectrometry.

Methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) are oxygenated compounds added to gasoline to enhance octane rating and to improve combustion. They may be found as pollutants of living and working environments. In this work a robotized method for the quantification of low level MTBE, ETBE and TAME in human urine was developed and validated. The analytes were sampled in the headspace of urine by SPME in the presence of MTBE-d12 as internal standard. Different fibers were compared for their linearity and extraction efficiency: carboxen/polydimethylsiloxane, polydimethylsiloxane/divinylbenzene, and polydimethylsiloxane. The first, although highly efficient, was discarded due to deviation of linearity for competitive displacement, and the polydimethylsiloxane/divinylbenzene fiber was chosen instead. The analysis was performed by GC/MS operating in the electron impact mode. The method is very specific, with range of linearity 30-4600 ng L(-1), within- and between-run precision, as coefficient of variation, <22 and <16%, accuracy within 20% the theoretical level, and limit of detection of 6 ng L(-1) for all the analytes. The influence of the matrix on the quantification of these ethers was evaluated analysing the specimens of seven traffic policemen exposed to autovehicular emissions: using the calibration curve and the method of standard additions comparable levels of MTBE (68-528 ng L(-1)), ETBE (<6 ng L(-1)), and TAME (<6 ng L(-1)) were obtained.

(2-Ethoxyethoxy)acetic acid: an unusual compound found in the gas chromatographic analysis of urinary organic acids.

An unknown acidic compound was detected in a number of urine samples from patients with a suspected metabolic disorder and some patients treated with chemotherapy. The structure of this compound has been characterized as (2-ethoxyethoxy)acetic acid, using a gas chromatography/mass spectrometry/computer system. The authentic compound was synthesized and compared with the unknown. Urinary (2-ethoxyethoxy)acetic acid is assumed to be formed endogenously from an exogenous precursor, probably 2-(2-ethoxyethoxy)ethanol.

Antibacterial activity of human urine.

The fate of bacteria in human urine was studied after inoculation of small numbers of Escherichia coli and other bacterial strains commonly implicated in urinary tract infection. Urine from normal individuals was often inhibitory and sometimes bactericidal for growth of these organisms. Antibacterial activity of urine was not related to lack of nutrient material as addition of broth did not decrease inhibitory activity. Antibacterial activity was correlated with osmolality, urea concentration and ammonium concentration, but not with organic acid, sodium, or potassium concentration. Between a pH range of 5.0-6.5 antibacterial activity of urine was greater at lower pH. Ultrafiltration and column chromatography to remove protein did not decrease antibacterial activity. Urea concentration was a more important determinant of antibacterial activity than osmolality or ammonium concentration. Increasing the urea of a noninhibitory urine to equal that of an inhibitory urine made the urine inhibitory. However, increasing osmolality (with sodium chloride) or increasing ammonium to equal the osmolality or ammonium of an inhibitory urine did not increase antibacterial activity. Similarly, dialysis to decrease osmolality or ammonium but preserve urea did not decrease inhibitory activity. Decreasing urea with preservation of ammonium and osmolality decreased antibacterial activity. Removal of ammonium with an ion exchanger did not decrease antibacterial activity, whereas conversion of urea to ammonium with urease and subsequent removal of the ammonium decreased antibacterial activity. Urine collected from volunteers after ingestion of urea demonstrated a marked increase in antibacterial activity, as compared with urine collected before ingestion of urea.