Polypyrrole-coated needle as an electrospray emitter for ambient mass spectrometry

Nylon 6-cellulose composite hosted in a hypodermic needle: Biofluid extraction and analysis by ambient mass spectrometry in a single device

This study proposes a hypodermic needle (HN) as a sorbent holder and an electrospray (ESI) emitter, thus combining extraction and analysis in a single device. A novel nylon 6-cellulose (N6-Cel) composite sorbent is proposed to extract methadone from oral fluid samples. The cellulosic substrate provides the composite with high porosity, permitting the flow-through of the sample, while the polyamide contributes to the extraction of the analyte. The low price of the devices (considering the holder and the sorbent) contributes to the affordability of the method, and their small size allows easy transportation, opening the door to on-site extractions. Under the optimum conditions, the analyte can be determined by high-resolution ambient ionization mass spectrometry at a limit of detection (LOD) as low as 0.3 μg/L and precision (expressed as relative standard deviation, RSD) better than 9.3%. The trueness, expressed as relative recovery (RR), ranged from 90% to 109%. As high-resolution mass spectrometers are not available in many laboratories, the method was also adapted to low-resolution spectrometers. In this sense, the direct infusion of the eluates in a triple quadrupole-mass spectrometry provided an LOD of 2.2 μg/L. The RSD was better than 5.3%, and the RR ranged from 96% to 121%.

Polydopamine inner wall-coated hypodermic needle as microextraction device and electrospray emitter for the direct analysis of illicit drugs in oral fluid by ambient mass spectrometry

In this article, polydopamine inner wall-coated hypodermic needles (PDA-HNs) are evaluated as both microextraction devices and electrospray ionization (ESI) emitters for determining selected illicit drugs (methamphetamine, cocaine, and methadone) in oral fluid samples. The PDA film, located in the inner wall of the needle, allows the extraction of the analytes at alkaline pH, where their hydrophobic character is promoted. The extracted analytes are finally eluted in a methanol/formic acid mixture that also acts as ESI solution. For this purpose, a dedicated interface based on the connection of a PEEK tube with the needle hub is proposed. This assembly allows delivering the ESI solution by the infusion syringe pump of the mass spectrometer, providing an efficient ESI on the tip of the needle. The double use of the PDA-HNs as microextraction devices and ESI emitters permits the determination of the target analytes with limits of detection and precision (expressed as relative standard deviation) values better than 2.4 μg/L and 17.6%, respectively. The accuracy was evaluated by analyzing independent spiked oral fluid samples, obtaining good results.

Electrospray ionization mass spectrometry with wooden tips: A review

Electrospray ionization (ESI) is a powerful ionization technique in mass spectrometry (MS). There has been an increasing interest for the new development of ESI technique to extend its applications. ESI-MS with wooden tips (wooden-tip ESI-MS), an ESI technique invented in 2011, enabled not only new applications but also new insights into the ESI mechanism. In this review, the technical aspects of wooden-tip ESI-MS are described, the new features of wooden-tip ESI-MS for sampling and ionization of analytes are highlighted, and the important applications of wooden-tip ESI-MS in various fields in the past 10 years, including food safety, forensic investigation, environmental analysis, biomedical analysis and protein study, are summarized. The perspectives on the further development and applications of wooden-tip ESI-MS are also discussed.

Direct analysis of naphthenic acids in produced water and crude oil by NH2-surface-modified wooden-tip electrospray ionization mass spectrometry

This work describes the surface coating of wooden toothpicks with amino groups (NH₂) for electrospray ionization mass spectrometry (MS) analysis of naphthenic acids (NAs) in produced water samples and crude oil fractions. NH₂ was introduced into the cellulosic material through a silanization reaction using aminopropyltriethoxysilane. An NH₂-modified toothpick was inserted into the analyte extraction sample and was subsequently used as an electrospray emitter for MS analysis. The extraction conditions were optimized by analyzing NAs (benzoic acid, 1-naphthoic acid, decanoic acid, 3,5-dimethyladamantane-1-carboxylic acid, and 3,5-dimethyladamantane-1-acetic acid) in pure water, and the best condition was using 5 min of extraction time with the samples under agitation. Modified and unmodified wooden toothpicks were compared, and the intensities of all NAs were higher when using the modified substrates than when using the unmodified ones. Limit of detection (LOD), limit of quantification (LOQ), linearity, precision, and recovery were determined by analyzing decanoic acid in seawater samples. The LOD and LOQ were 2 and 5 μg mL^-1, respectively, and a linear correlation (R² = 0.9927) was obtained with concentrations ranging from 5 to 250 μg mL^-1. Precision values ranged from 6 to 13% and recoveries from 89 to 106%. The technique was also employed to analyze three produced water samples, in which decanoic acid was semi-quantified, and the concentrations ranged from 10 to 13 μg mL^-1. High abundances of acidic compounds of class O2 with DBEs (double bond equivalents) ranging from 1 to 3 and carbon numbers going from 8 to 12 were detected in the produced water samples. The results suggest that the modification of wooden toothpicks with NH₂ might offer a significant advancement in the knowledge of cheap substrates that can improve the sensitivity of analysis of NAs in water samples.