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Microneedles are widely used substrates for various chemical and biological sensing applications utilizing surface-enhanced Raman spectroscopy (SERS), which is indeed a highly sensitive and specific analytical approach. This article reports the fabrication of a nanoparticle (NP)-decorated microneedle substrate that is both a SERS substrate and a substrate-supported electrospray ionization (ssESI) mass spectrometry (MS) sample ionization platform. Polymeric ligand-functionalized gold nanorods (Au NRs) are adsorbed onto superhydrophobic surface-modified polydimethylsiloxane (PDMS) microneedles through the control of various interfacial interactions. We show that the chain length of the polymer ligands dictates the NR adsorption process. Importantly, assembling Au NRs onto the micrometer-diameter needle tips allows the formation of highly concentrated electromagnetic hot spots, which provide the SERS enhancement factor as high as 1.0 × 106. The micrometer-sized area of the microneedle top and high electromagnetic field enhancement of our system can be loosely compared with tip-enhanced Raman spectroscopy, where the apex of a plasmonic NP-functionalized sharp probe produces high-intensity plasmonic hot spots. Utilizing our NR-decorated microneedle substrates, the synthetic drugs fentanyl and alprazolam are analyzed with a subpicomolar limit of detection. Further analysis of drug-molecule interactions on the NR surface utilizing the Langmuir adsorption model suggests that the higher polarizability of fentanyl allows for a stronger interaction with hydrophilic polymer layers on the NR surface. We further demonstrate the translational aspect of the microneedle substrate for both SERS- and ssESI-MS-based detection of these two potent drugs in 10 drug-of-abuse (DOA) patient plasma samples with minimal preanalysis sample preparation steps. Chemometric analysis for the SERS-based detection shows a very good classification between fentanyl, alprazolam, or a mixture thereof in our selected 10 samples. Most importantly, ssESI-MS analysis also successfully identifies fentanyl or alprazolam in these same 10 DOA plasma samples. We believe that our multimodal detection approach presented herein is a highly versatile detection technology that can be applicable to the detection of any analyte type without performing any complicated sample preparation.

Surface-enhanced Raman scattering (SERS) is an ultrasensitive analytical technique, which is capable of providing high specificity; thus, it can be used for toxicological drug assay (detection and quantification). However, SERS-based drug analysis directly in human biofluids requires mitigation of fouling and nonspecificity effects that commonly appeared from unwanted adsorption of endogenous biomolecules present in biofluids (e.g., blood plasma and serum) onto the SERS substrate. Here, we report a bottom-up fabrication strategy to prepare ultrasensitive SERS substrates, first, by functionalizing chemically synthesized gold triangular nanoprisms (Au TNPs) with poly(ethylene glycol)-thiolate in the solid state to avoid protein fouling and second, by generating flexible plasmonic patches to enhance SERS sensitivity via the formation of high-intensity electromagnetic hot spots. Poly(ethylene glycol)-thiolate-functionalized Au TNPs in the form of flexible plasmonic patches show a twofold-improved signal-to-noise ratio in comparison to triethylamine (TEA)-passivated Au TNPs. Furthermore, the plasmonic patch displays a SERS enhancement factor of 4.5 ×107. Utilizing the Langmuir adsorption model, we determine the adsorption constant of drugs for two different surface ligands and observe that the drug molecules display stronger affinity for poly(ethylene glycol) ligands than TEA. Our density functional theory calculations unequivocally support the interaction between drug molecules and poly(ethylene glycol) moieties. Furthermore, the universality of the plasmonic patch for SERS-based drug detection is demonstrated for cocaine, JWH-018, and opioids (fentanyl, despropionyl fentanyl, and heroin) and binary mixture (trace amount of fentanyl in heroin) analyses. We demonstrate the applicability of flexible plasmonic patches for the selective assay of fentanyl at picogram/milliliter concentration levels from drug-of-abuse patients’ blood plasma. The fentanyl concentration calculated in the patients’ blood plasma from SERS analysis is in excellent agreement with the values determined using the paper spray ionization mass spectrometry technique. We believe that the flexible plasmonic patch fabrication strategy would be widely applicable to any plasmonic nanostructure for SERS-based chemical sensing for clinical toxicology and therapeutic drug monitoring.

Dissolvable tobacco products are smokeless, spit-free, made from finely milled tobacco, and dissolve in the mouth of a user. In 2009, R.J. Reynolds Tobacco Co. released a line of dissolvable tobacco products in several test markets. In late 2010, the dissolvables were reformulated and several changes in their composition were determined and are reported here. Our analytical approach featured gas chromatography-mass spectrometry preceded by four separate methods for sample preparation: solvent extraction using acetone, trimethylsilyl derivatization of sugars, solid-phase microextraction of semi-volatiles and liquid–liquid extraction for the quantitative analysis of nicotine. Taken together, these methods identified several changes in the formulation of the initial products and their reformulated versions. One major change in the new dissolvables is that “mellow” and “fresh” flavors have been replaced by a “mint” flavor. Additionally, the strips are no longer dominated by glycerol, but rather threitol. Total nicotine and (free nicotine) concentrations for the orbs, sticks, and strips were found to be 3.35 mg g−1(1.242 mg g−1), 2.6 mg g−1(0.850 mg g−1), and 2.74 mg g−1(0.572 mg g−1), respectively. Total nicotine and free nicotine concentrations have significantly increased in some cases.

Identification of the anions in inorganic explosives and their post-blast residues using ion chromatography (IC) and/or capillary electrophoresis (CE) is well established. However, IC and CE instrumentation are not as common in forensic science laboratories. Furthermore, coupling IC and CE to a mass spectrometer can be challenging as volatile buffers are required or ion suppressors must be used. Porous Graphitic Carbon (PGC) is a relatively new stationary phase type that is available for High Performance Liquid Chromatography (HPLC). PGC is known for its high retention of polar species and separation of anions using PGC has been demonstrated. In this work, a PGC (2.1 × 100 mm) column was coupled to an electrospray ionization mass spectrometer (ESI-MS) for the analysis and detection of anions. Several parameters of the method were optimized including ion source temperature (550 °C), MS cone voltage (75 V), injection volume (1 μL), solvent composition (1% formic acid in water), and column temperature (80 °C). This resulted in a method that separated 6 anions Cl−, NO3−, ClO3−, HSO4−, ClO4−, and dicyandiamide (DCDA) in less than 5 min. Several low explosive powders were analyzed intact and after burning. Finally, the post-blast residues of two black powder substitutes were extracted from pipe bomb container fragments and analyzed using this technique.

The analysis of organic material on the surface of human hair may indicate various subject characteristics such as age, race, gender, or the use of hair products. In addition, comparisons of hair chemical composition may be used to assess the potential for a common origin between a known and unknown sample. However, evidentiary hair samples are often extremely small, necessitating highly sensitive extraction and analysis techniques. In this communication, off‐line supercritical fluid extraction (SFE) followed by gas chromatography/mass spectrometry (GC/MS) using large volume injection (LVI) is demonstrated as a potential method for extracting and analyzing hair surface components. The retention gap technique was used to achieve large volume injections, allowing up to 30 μL of the off‐line extracts to be analyzed. Subsequent chemical analysis by GC/MS identified various natural components on the hair surface such as saturated and unsaturated free fatty acids, squalene, and cholesterol. Overall, off‐line SFE was quite efficient, allowing the measurement of surface components of sample amounts ranging from 0.22 mg to 0.24 mg. In addition, derivatization of free fatty acids using a silylating agent increased both chromatographic resolution and sensitivity. Results from two hair samples are discussed to demonstrate the technique.

The analysis of organic material on the surface of human hair may indicate various subject characteristics such as age, race, gender, or the use of hair products. In addition, comparisons of hair chemical composition may be used to assess the potential for a common origin between a known and unknown sample. However, evidentiary hair samples are often extremely small, necessitating highly sensitive extraction and analysis techniques. In this communication, off-line supercritical fluid extraction (SFE) followed by gas chromatography/mass spectrometry (GC/MS) using large volume injection (LVI) is demonstrated as a potential method for extracting and analyzing hair surface components. The retention gap technique was used to achieve large volume injections, allowing up to 30 μL of the off-line extracts to be analyzed. Subsequent chemical analysis by GC/MS identified various natural components on the hair surface such as saturated and unsaturated free fatty acids, squalene, and cholesterol. Overall, off-line SFE was quite efficient, allowing the measurement of surface components of sample amounts ranging from 0.22 mg to 0.24 mg. In addition, derivatization of free fatty acids using a silylating agent increased both chromatographic resolution and sensitivity. Results from two hair samples are discussed to demonstrate the technique.

In this work, a novel system has been designed, characterized, and validated for the determination of fluorescence quenching constants. Capillary flow injection methods are used to automate the preparation and mixing of the fluorophore and quencher solutions. Because of the small diameter of the capillary (75–200 μm), fluorescence measurements can be made without corrections for primary and secondary absorbance effects. The fluorescence spectrometer is equipped with a charge-coupled device (CCD) that has a detection limit of 3.0 × 10−9M (2.3 ppb) and a linear dynamic range of 105for integration times of 0.01–10 s. This spectrometer has a 300 nm spectral range with 1 nm resolution, allowing the fluorescence quenching constants to be calculated at single wavelengths or over integrated wavelength ranges. This system was validated by comparison to traditional methods for the determination of Stern–Volmer constants for alternant and nonalternant polycyclic aromatic hydrocarbons with nitromethane and triethylamine.