Depth profiling of inks in authentic and counterfeit banknotes by electrospray laser desorption ionization/mass spectrometry

An Overview of Security Materials in Banknotes and Analytical Techniques in Detecting Counterfeits

Counterfeiting or forged imitation of banknotes is a perpetual practice engulfing global economies. This not only poses challenges for the material scientists to come forth with advanced security materials but also demands veracious forensic examination to detect counterfeits. The present article pursues novel efforts in summarizing a study that lays focus on the recent optical and analytical examinations being used for the characterization and detection of chemical profiles of authentic and counterfeited banknotes. The article briefs the trends in banknote materials, security paper manufacturing process, security inks used for printing, and types of the security printing process in banknote practices. Reported literature shows the introduction of new anti-counterfeiting materials viz. magnetically-responsive photonic anti-counterfeiting watermarks, and fluorescent nanoparticles that can be used as anti-counterfeiting inks, anti-stokes inks, metameric inks, etc. Analytical techniques such as IR spectroscopy, Raman spectroscopy, Mossbauer spectroscopy, X-ray diffraction, X-ray fluorescence, LIBS, XRF, ELDI-MS, EASI/DESI-MS, HPLC, VSC, AFM, etc. in conjunction with different chemometrics approaches have been critically discussed. The study also presents the future scope in banknote examination like the use of hyper spectral imaging and sensor-based counterfeit detection systems.

Structural and optical characterization of banknotes using spectral-domain optical coherence tomography

Counterfeiting of banknotes remains a severe threat to economic security and social stability. The characterization of banknote has mainly relied on the assessment of various security features applied to the surface of the note. However, the surface features are easy to forge and contain insufficient information to discover the source. In this paper, a novel approach for banknote characterization has been proposed by employing spectral-domain optical coherence tomography (SD-OCT) that can provide structural and optical features. Three groups of counterfeit Chinese 100 Yuan banknotes produced by different printing manners and one group of authentic banknotes were examined by SD-OCT without any sample preparation and four distinct areas were selected for imaging. High-resolution tomographic and three-dimensional (3D) volumetric OCT images were obtained and a set of features were first revealed to characterize the banknotes qualitatively and quantitatively. The results demonstrated that SD-OCT was effective to detect and classify different types of counterfeit banknotes and could potentially be used to link counterfeit banknotes to their sources in a fast, simple and nondestructive manner.

Direct and rapid characterization of illicit drugs in adulterated samples using thermal desorption electrospray ionization mass spectrometry

Foods and drinks have been adulterated with illicit drugs to facilitate criminal activities. Unfortunately, conventional analytical methods are incapable of rapidly characterizing these drugs in samples, as serious interferences from sample matrices must be removed through tedious and time-consuming pretreatment. Ambient ionization mass spectrometry (AMS) generally does not require sample pretreatment and is thus a suitable tool for directly and rapidly detecting illicit drugs in samples in different physical states. In this study, thermal desorption electrospray ionization mass spectrometry (TD-ESI/MS), an AMS technique, was utilized to efficiently characterize illicit drugs spiked in samples including drinks, powders, and jelly candies. To perform sensitive analysis, the mass analyzer was operated in multiple reaction monitoring mode to monitor the molecular and fragment ions of the target analytes. The time required to complete a typical TD-ESI/MS analysis was less than 30 s. The limits of detection (LODs) for illicit drugs were found to be 100 ppb in drinks, 100–1000 ppb in instant powders, and 1.3–6.5 ng/mm² on stamp surfaces. FM2 and nitrazepam laced in the inner layer of a jelly candy were detected by TD-ESI/MS, showcasing the advantage of the technique for direct and rapid analysis as opposed to conventional methods.

Direct determination of trace phthalate esters in alcoholic spirits by spray-inlet microwave plasma torch ionization tandem mass spectrometry

A direct analytical method based on spray-inlet microwave plasma torch tandem mass spectrometry was applied to simultaneously determine 4 phthalate esters (PAEs), namely, benzyl butyl phthalate, diethyl phthalate, dipentyl phthalate, and dodecyl phthalate with extremely high sensitivity in spirits without sample treatment. Among the 4 brands of spirit products, 3 kinds of PAE compounds were directly determined at very low concentrations from 1.30 to 114 ng·g^-1 . Compared with other online and off-line methods, the spray-inlet microwave plasma torch tandem mass spectrometry technique is extremely simple, rapid, sensitive, and high efficient, providing an ideal screening tool for PAEs in spirits.

Rapid analysis of forensic-related samples using two ambient ionization techniques coupled to high-resolution mass spectrometers

RATIONALE

This paper highlights the versatility of interfacing two ambient ionization techniques, Laser Diode Thermal Desorption (LDTD) and Atmospheric Solids Analysis Probe (ASAP), to high-resolution mass spectrometers and demonstrate the method's capability to rapidly generate high-quality data from multiple sample types with minimal, if any, sample preparation.

METHODS

For ASAP-MS analysis of solid and liquid samples, the material was transferred to a capillary surface before being introduced into the mass spectrometer. For LDTD-MS analysis, samples were solvent extracted, spotted in a 96-well plate, and the solvent was evaporated before being introduced into the mass spectrometer. All analyses were performed using Atmospheric Pressure Chemical Ionization in positive mode.

RESULTS

Seven consumer "Spice" packets were combined and analyzed by both ASAP and LDTD, which identified 11 synthetic cannabinoids/cathinones by full MS and MS/MS experiments. To further show the usefulness of these techniques, black tar heroin was analyzed, which resulted in the identification of heroin and its impurities (monoacetylmorphine, papaverine, and noscapine). These experiments were performed on the LTQ-Orbitrap to demonstrate the ability to perform both parallel and serial MS and MSⁿ experiments.

CONCLUSIONS

Interfacing LDTD and ASAP to high-resolution mass spectrometers allows for expeditious analysis of a wide range of samples, with minimal or no sample preparation. Both allow for rapid full scan, MS/MS, and/or MSⁿ experiments from a single sample introduction. Published in 2017. This article is a U.S. Government work and is in the public domain in the USA.

Determination of elemental composition of metals using ambient organic mass spectrometry

Conventional inorganic mass spectrometric (MS) analysis of metals can require time-consuming and tedious sample preparation. We thus report the novel and direct characterization of metals in solid samples using an organic MS technique known as electrospray laser desorption ionization mass spectrometry (ELDI/MS). No sample pretreatment was needed, and results were rapidly obtained due to the ambient and laser-based nature of ELDI/MS. Metals from samples were desorbed and ionized by laser irradiation, after which they reacted with EDTA and then post-ionized and detected as metal-EDTA complexes. Aluminum, copper, iron, lead, nickel, and zinc from plates, foils, and coins were characterized in seconds. This study demonstrates that an ESI/MS system can be easily modified to analyze metal elements in solids by involving a chelating agent, indicating a potentially promising development in MS towards the analysis of metals using organic MS.