Outcompeting GC for the detection of legacy chlorinated pesticides: online-SPE UPLC APCI/MSMS detection of endosulfans at part per trillion levels

Abstract

Endosulfan, the last remaining organochlorine pesticide, has been the subject of a number of international regulations and restriction/banning action plans worldwide. Occurrence of endosulfan residues in South Florida environments has been widely described in the literature for more than two decades. This work describes a selective, sensitive, and fast online solid-phase extraction (SPE) method coupled with liquid chromatography separation and tandem mass spectrometry (LC-MS/MS) for the determination of endosulfan isomers and endosulfan sulfate in water samples at low part per trillion levels with very little sample preparation. A negative atmospheric pressure chemical ionization source was carefully optimized to produce reproducible spectra of the target compounds with no adduct ion formation. Selected reaction monitoring transitions were monitored and quantitation was performed against a per-deuterated internal standard β-endosulfan (d4). The automated online SPE clean-up was performed using only 20 mL of untreated water sample prior to LC-MS/MS analysis. The method was capable of separating and quantifying endosulfan within a 24-min run using acetonitrile and water as mobile phases and presenting statistically calculated method detection limits of 3, 10, and 7 ng/L for endosulfan sulfate, α-endosulfan, and β-endosulfan, respectively. In addition, a QuEChERS method was successfully developed and applied for endosulfan determination in sediments/soils, floating and submerged algal mats, and small fish. Minimal matrix effects were observed in all matrices analyzed and recoveries for all analytes ranged from 50-144 %. The developed methodology was applied to monitor the occurrence and to assess the potential transport of endosulfan in the Loveland Slough watershed, an area adjacent to Everglades National Park showing long-term contamination with endosulfans.

Online solid phase extraction liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS) method for the determination of sucralose in reclaimed and drinking waters and its photo degradation in natural waters from South Florida

“…Preliminary tests on sucralose standards through direct injection into the LC/MS/MS were performed using HESI and APCI sources. The APCI source showed better sensitivity than HESI, moreover ESI and/or HESI spectrum generally contains abundant and extensive series of adducts ions with methanol and inorganic ions [24,38]. The APCI source was then selected and carefully optimized to produce reproducible spectra of the target compound.…”

“…The ionization process associated with APCI is one of the most efficient, being considered more energetic or less soft than ESI, where gas phase reactions leading to the loss of net charge on the analyte may generate more fragment ions relative to the parent ion [28]. In fact, for certain classes of compounds that are traditionally very difficult to ionize or tend to show low sensitivity in LC-MS/MS techniques, electron capture negative APCI has provided increased sensitivity for these ‘tough to ionize’ compounds [24,29]. APCI has been reported to be more sensitive than ESI for triazines, phenylurea herbicides and organochlorine pesticides [24,30,31].…”

“…In fact, for certain classes of compounds that are traditionally very difficult to ionize or tend to show low sensitivity in LC-MS/MS techniques, electron capture negative APCI has provided increased sensitivity for these ‘tough to ionize’ compounds [24,29]. APCI has been reported to be more sensitive than ESI for triazines, phenylurea herbicides and organochlorine pesticides [24,30,31]. Another advantage is that signal suppression in ESI is significantly more intense than that occurring in APCI for several compounds in different matrices [32], where ionization suppression involves mainly changes in the droplet solution properties caused by the presence of non-volatile solutes in ESI ionization [33].…”

Photo Degradation of Cotnaminants of Emerging concern (CECs) under Simulated Solar Radiation: Implications for their Environmental Fate

“…Suppressive effects of formic acid were also observed for the analysis of other compounds such as endosulfan (Quinete et al, 2013). Therefore formic acid was eliminated and the mobile phase was switched to acetonitrile and water resulting in a 20-fold increase in sensitivity.…”

“…More recently, studies employing liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) have been published for the analysis of sucralose in water samples by direct injection (higher detection limits) or offline SPE (Loos et al, 2009b;Scheurer et al, 2009b;Ferrer and Thurman, 2010a;Mawhinney et al, 2011b;Minten et al, 2011b;Ordonez et al, 2012a). Nowadays the use of online SPE has shown important improvements such as higher sensitivity, analysis of smaller sample volumes, limited sample loss, no carry-over and robust and reproducible detection, while increasing sample throughput (Neset et al, 2010;Heeb et al, 2012;Panditi et al, 2013;Quinete et al, 2013).…”