Thermal Desorption-atmospheric Pressure Chemical Ionization Research Articles

Development of a High-Throughput Affinity Mass Spectrometry (AMS) Platform Using Laser Diode Thermal Desorption Ionization Coupled to Mass Spectrometry (LDTD-MS).

Affinity selection mass spectrometry (MS) or, simply, affinity mass spectrometry (AMS) is a label-free technology that has been used to identify high-affinity ligands of target proteins of interest by screening against small-molecule compound libraries and identifying molecules that are enriched in the presence of the target protein. We have previously applied Agilent Technology's (Santa Clara, CA) RapidFire solid-phase extraction (SPE)-based high-throughput MS technology to screen small-molecule libraries using AMS. However, SPE-based technologies rely on fluidics for desalting and separation prior to mass analysis with attendant high solvent consumption, relatively high sample volume requirements, risk of sample carryover, and frequent maintenance. To address these challenges, we have established an AMS platform using a laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) ionization source (Phytronix, Quebec, Canada) coupled with a SCIEX 5600+ TripleTOF MS (Framingham, MA). We also validated a data-independent acquisition (DIA) Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) method for the robust detection and analysis of small-molecule affinity hits. An informatics platform developed in-house has resulted in a streamlined data analysis workflow for high-throughput AMS screening campaigns and reduced data processing time without compromising data quality. Finally, 68,000 compounds were screened in a single plate and affinity selected hits were confirmed in an orthogonal enzyme activity assay.

Reagent approaches for improved detection of chlorate and perchlorate salts via thermal desorption and ionization.

Techniques for improving the detectability of chlorate and perchlorate salts with thermal desorption based ionizers (i.e. radioactive, corona discharge and photoionization-based) are desired. This work employs acidic reagents to chemically transform chlorate and perchlorate anions into traces of chloric and perchloric acid. These high vapor pressure acids are easier to detect than the originating salts. The efficacy of the reagent chemistry was quantified with a triple-quadrupole mass spectrometer interfaced with a custom-built thermal-desorption atmospheric-pressure chemical ionization (TD-APCI) source. Additional experiments were conducted using tandem IMS/MS instrumentation. Reagent pKa and pH values were varied in order to gain a better understanding of how those parameters affect the degree of observed signal enhancement. Samples of chlorates and perchlorates treated with liquid acidic reagents exhibit signal enhancement of up to six orders of magnitude compared with signals from untreated analytes. Three orders of magnitude of signal enhancement are demonstrated using solid-state reagents, such as weakly acidic salts and polymeric acids. Data is presented that demonstrates the compatibility of the solid-state approach with both MS and IMS/MS platforms. Several methods of acidification were demonstrated for enhanced vaporization and detection of chlorates and perchlorates. For applications where rapid surface collection and analysis for chlorates and perchlorates are desired, the solid-state approaches offer the simplest means to integrate the reagent chemistry into MS or IMS detection.

Total Analysis of Microcystins in Fish Tissue Using Laser Thermal Desorption-Atmospheric Pressure Chemical Ionization-High-Resolution Mass Spectrometry (LDTD-APCI-HRMS).

Microcystins (MCs) are cyanobacterial toxins encountered in aquatic environments worldwide. Over 100 MC variants have been identified and have the capacity to covalently bind to animal tissue. This study presents a new approach for cell-bound and free microcystin analysis in fish tissue using sodium hydroxide as a digestion agent and Lemieux oxidation to obtain the 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) moiety, common to all microcystin congeners. The use of laser diode thermal desorption-atmospheric pressure chemical ionization coupled with Q-Exactive mass spectrometry (LDTD-APCI-HRMS) led to an analysis time of approximately 10 s per sample and high-resolution detection. Digestion/oxidation and solid phase extraction recoveries ranged from 70 to 75% and from 86 to 103%, respectively. Method detection and quantification limits values were 2.7 and 8.2 μg kg(-1), respectively. Fish samples from cyanobacteria-contaminated lakes were analyzed, and concentrations ranging from 2.9 to 13.2 μg kg(-1) were reported.

High resolution/accurate mass (HRMS) detection of anatoxin-a in lake water using LDTD–APCI coupled to a Q-Exactive mass spectrometer

A new innovative analytical method combining ultra-fast analysis time with high resolution/accurate mass detection was developed to eliminate the misidentification of anatoxin-a (ANA-a), a cyanobacterial toxin, from the natural amino acid phenylalanine (PHE). This was achieved by using the laser diode thermal desorption–atmospheric pressure chemical ionization (LDTD–APCI) coupled to the Q-Exactive, a high resolution/accurate mass spectrometer (HRMS). This novel combination, the LDTD–APCI–HRMS, allowed for an ultra-fast analysis time (<15s/sample). A comparison of two different acquisition modes (full scan and targeted ion fragmentation) was made to determine the most rigorous analytical method using the LDTD–APCI interface. Method development focused toward selectivity and sensitivity improvement to reduce the possibility of false positives and to lower detection limits. The Q-Exactive mass spectrometer operates with resolving powers between 17500 and 140000FWHM (m/z 200). Nevertheless, a resolution of 17500FWHM is enough to dissociate ANA-a and PHE signals. Mass accuracy was satisfactory with values below 1ppm reaching precision to the fourth decimal. Internal calibration with standard addition was achieved with the isotopically-labeled (D5) phenylalanine with good linearity (R2>0.999). Enhancement of signal to noise ratios relative to a standard triple-quadrupole method was demonstrated with lower detection and quantification limit values of 0.2 and 0.6μg/L using the Q-Exactive. Accuracy and interday/intraday relative standard deviations were below 15%. The new method was applied to 8 different lake water samples with signs of cyanobacterial blooms. This work demonstrates the possibility of using an ultra-fast LDTD–APCI sample introduction system with an HRMS hybrid instrument for quantitative purposes with high selectivity in complex environmental matrices.

Total microcystins analysis in water using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry

A new approach for the analysis of the cyanobacterial microcystins (MCs) in environmental water matrices has been developed. It offers a cost efficient alternative method for the fast quantification of total MCs using mass spectrometry. This approach permits the quantification of total MCs concentrations without requiring any derivatization or the use of a suite of MCs standards. The oxidation product 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) was formed through a Lemieux oxidation and represented the total concentration of free and bound MCs in water samples. MMPB was analyzed using laser diode thermal desorption-atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). LDTD is a robust and reliable sample introduction method with ultra-fast analysis time (<15ssample−1). Several oxidation and LDTD parameters were optimized to improve recoveries and signal intensity. MCs oxidation recovery yield was 103%, showing a complete reaction. Internal calibration with standard addition was achieved with the use of 4-phenylbutyric acid (4-PB) as internal standard and showed good linearity (R2>0.999). Limits of detection and quantification were 0.2 and 0.9μgL−1, respectively. These values are comparable with the WHO (World Health Organization) guideline of 1μgL−1 for total microcystin-LR congener in drinking water. Accuracy and interday/intraday variation coefficients were below 15%. Matrix effect was determined with a recovery of 91%, showing no significant signal suppression. This work demonstrates the use of the LDTD-APCI-MS/MS interface for the screening, detection and quantification of total MCs in complex environmental matrices.

A comparative study of ultrasonication, Fenton's oxidation and ferro-sonication treatment for degradation of carbamazepine from wastewater and toxicity test by Yeast Estrogen Screen (YES) assay

A comparative study of ultrasonication (US), Fenton's oxidation (FO) and ferro-sonication (FS) (combination of ultrasonication and Fenton's oxidation) advanced oxidation processes (AOPs) for degradation of carbamazepine (CBZ) from wastewater (WW) is reported for the first time. CBZ is a worldwide used antiepileptic drug, found as a persistent emerging contaminant in many wastewater treatment plants (WWTPs) effluents and other aquatic environments. The oxidation treatments of WW caused an effective removal of the drug. Among the various US, FO and FS pre-treatments carried out, higher soluble chemical oxygen demand (SCOD) and soluble organic carbon (SOC) increment (63 to 86% and 21 to 34%, respectively) was observed during FO pre-treatment process, resulting in higher removal of CBZ (84 to 100%) from WW. Furthermore, analysis of by-products formed during US, FO and FS pre-treatment in WW was carried out by using laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). LDTD-APCI–MS/MS analysis indicated formation of two by-products, such as epoxycarbamazepine and hydroxycarbamazepine due to the reaction of hydroxyl radicals (OH) with CBZ during the three types of pre-treatment processes. In addition, the estrogenic activity of US, FO and FS pre-treated sample with CBZ and its by-products was carried out by Yeast Estrogen Screen (YES) assay method. Based upon the YES test results, none of the pre-treated samples showed estrogenic activity.

Carbamazepine in municipal wastewater and wastewater sludge: Ultrafast quantification by laser diode thermal desorption-atmospheric pressure chemical ionization coupled with tandem mass spectrometry

In this study, the distribution of the anti-epileptic drug carbamazepine (CBZ) in wastewater (WW) and aqueous and solid phases of wastewater sludge (WWS) was carried out. A rapid and reliable method enabling high-throughput sample analysis for quicker data generation, detection, and monitoring of CBZ in WW and WWS was developed and validated. The ultrafast method (15s per sample) is based on the laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). The optimization of instrumental parameters and method application for environmental analysis are presented. The performance of the novel method was evaluated by estimation of extraction recovery, linearity, precision and detection limit. The method detection limits was 12ngL−1 in WW and 3.4ngg−1 in WWS. The intra- and inter-day precisions were 8% and 11% in WW and 6% and 9% in WWS, respectively. Furthermore, three extraction methods, ultrasonic extraction (USE), microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) with three different solvent condition such as methanol, acetone and acetonitrile:ethyle acetate (5:1, v/v) were compared on the basis of procedural blank and method recovery. Overall, ASE showed the best extraction efficiency with methanol as compared to USE and MAE. Furthermore, the quantification of CBZ in WW and WWS samples showed the presence of contaminant in all stages of the treatment plant.

High throughput analysis of solid-bound endocrine disruptors by LDTD-APCI-MS/MS

The development of a high-throughput method for the analysis of 14 endocrine-disrupting substances in environmental solid matrices has been investigated. Selected compounds were: hormones (estrogens and progestogens), parabens and triclocarban. The ultrafast method (15 s per sample) is based on the laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). This novel approach was tested and validated in three different solid matrices (municipal sludge cakes, aquatic sediments and agricultural soils) and its performance was evaluated by estimation of extraction recovery, linearity, precision, and detection limits. In contrast to other methods based on LC-MS/MS, a cleanup step is not necessary or minimal for the municipal sludge cake matrix. Extraction recoveries ranged from 80 to 109% for all compounds in all matrix types except for estriol which was 60-75%. The intra- and inter-day precisions, as indicated by % RSD, were ≤ 14% and ≤ 16%, respectively. The method detection limits ranged from 0.7 to 4.0 ng g⁻¹ in sediments and soil matrices and 2.8 to 16.8 ng g⁻¹ for municipal sludge cake samples. The results for real environmental samples collected in different areas of Quebec (Canada) are illustrated.