Importance of Sample Form and Surface Temperature for Analysis by Ambient Plasma Mass Spectrometry (PADI)

Heat Pulse Desorption of Low-Volatility Compounds by a Heated N2 Gas Pulse with Mass Spectrometry

For the thermal desorption of low-volatility compounds, rapid heating followed by instant cooling is desirable to suppress thermal decomposition. In this work, a new thermal desorption method, heat pulse desorption (HPD), was developed. A heated N₂ gas pulse (350 °C, 50 ms) was directed to the solid sample surface, and desorbed analytes were ionized by DC corona discharge and mass analyzed by an Orbitrap mass spectrometer. Because heat transfer from the heated N₂ gas to the solid surface is not very efficient, desorption of the solid sample occurs at a certain temperature before reaching 350 °C. In short, there is a self-controlling desorption depending on the volatility of each analyte. Because the exit of the copper tube for gas blowing is separated from the sample surface, no carryover occurs, enabling the repetitive analysis of samples. HPD was applied to various compounds such as narcotics, pharmaceutical tablets, and explosives. Because analysis is completed within a few seconds per sample, this method is highly useful for quick and consecutive analysis of real samples, having potential utility in food quality control, counterfeit drugs analysis, and the detection of explosives for safety and security.

Rapid Analysis of Trace Phthalates by Spray-Inlet Microwave Plasma Torch Ionization-Tandem Mass Spectrometry in Commercial Perfumes

BACKGROUND

The less volatile fraction of perfumes can be easily contaminated by phthalates esters (PAEs) which are endocrine-disrupting chemicals during the production, bottling and transportation processes. It is necessary to establish an innovative and rapid method to determine the trace PAEs in commercial perfumes.

OBJECTIVE

Hence, self-built spray-inlet microwave plasma torch ionization coupled with a quadrupole time-of-flight tandem mass spectrometer (QTOF-MS) was developed for direct analysis of PAEs in perfumes with no sample pretreatment.

METHODS

Perfumes were sprayed to the MPT's flame directly by sampling pump in 10 µL/min and the ions produced by MPT were introduced into QTOF-MS, the MPT worked at 2450 MHz and 40 W in the 800 ml/min flow rate of argon.

RESULTS

For the developed method, excellent linearities were obtained and the correlation coefficient of Di-n-pentyl Phthalate was 0.9799 and the rest were larger than 0.99. The LODs and LOQs were obtained in the ranges of 1.452-18.96 ng/g and 4.839-63.19 ng/g, respectively. The spiked recoveries of PAEs were in the range of 100.1-105.2% with satisfied intra-day RSDs and inter-day RSDs ranging from 1.51-4.34% and 3.45-5.65%, respectively. PAEs in commercial perfumes were successfully detected by spray-inlet MPT-MS2 with low concentrations from 0.036-1.352 µg/g.

CONCLUSIONS

The method is a promising tool in field analysis of PAEs in cosmetic solutions where rapid qualitative and quantitative analysis in needed.

HIGHLIGHTS

The method was satisfactorily applied to the analysis of commercial perfume samples within 30 s, and earned merits such as simplicity, sensitivity, environmental friendliness and ease operation.

A methodological inter-comparison study on the detection of surface contaminant sodium dodecyl sulfate applying ambient- and vacuum-based techniques

Biomedical devices are complex products requiring numerous assembly steps along the industrial process chain, which can carry the potential of surface contamination. Cleanliness has to be analytically assessed with respect to ensuring safety and efficacy. Although several analytical techniques are routinely employed for such evaluation, a reliable analysis chain that guarantees metrological traceability and quantification capability is desirable. This calls for analytical tools that are cascaded in a sensible way to immediately identify and localize possible contamination, both qualitatively and quantitatively. In this systematic inter-comparative approach, we produced and characterized sodium dodecyl sulfate (SDS) films mimicking contamination on inorganic and organic substrates, with potential use as reference materials for ambient techniques, i.e., ambient mass spectrometry (AMS), infrared and Raman spectroscopy, to reliably determine amounts of contamination. Non-invasive and complementary vibrational spectroscopy techniques offer a priori chemical identification with integrated chemical imaging tools to follow the contaminant distribution, even on devices with complex geometry. AMS also provides fingerprint outputs for a fast qualitative identification of surface contaminations to be used at the end of the traceability chain due to its ablative effect on the sample. To absolutely determine the mass of SDS, the vacuum-based reference-free technique X-ray fluorescence was employed for calibration. Convex hip liners were deliberately contaminated with SDS to emulate real biomedical devices with an industrially relevant substance. Implementation of the aforementioned analytical techniques is discussed with respect to combining multimodal technical setups to decrease uncertainties that may arise if a single technique approach is adopted. Graphical abstract ᅟ.

Spray-inlet microwave plasma torch ionization tandem mass spectrometry for the direct detection of drug samples in liquid solutions

RATIONALE

Drug abuse or dependence results in a series of social problems, including crime and traffic accidents. Spray-inlet microwave plasma torch tandem mass spectrometry (MPT-MS/MS) was developed and used for the direct detection of such drugs in liquid solutions.

METHODS

Drug sample solutions were directly sprayed into the flame of an MPT by a sampling pump and the ions produced by Penning ionization and ion-molecule reactions were guided into a quadrupole time-of-flight (QTOF) tandem mass spectrometer for mass analysis. The MPT was operated at 40 W and 2.45 GHz in a 700 mL/min argon flow both for the inner and middle plasma.

RESULTS

Intact quasi-molecular and molecular ions of various drugs were successfully characterized by spray-inlet MPT-MS/MS. The analysis of one sample was finished within 30 s. Furthermore, the method exhibited excellent efficiency, precision and sensitivity, and the limits of detection and limits of quantification of the samples in methanol were in the range of 5.25-60.0 and 17.5-200 ng g^-1 , respectively. Excellent linearities with coefficients of determination (R² ) of 0.9627-0.9980 were verified in the range 0.05-50 μg g^-1 . Four different beverages purchased locally were also analyzed with spray-inlet MPT-MS/MS, and caffeine was directly determined in two of the beverages. By adding six standard drug samples to sport drinks (each drug was 1 μg g^-1 ) and Chinese spirit (each drug was 0.1 μg g^-1 ), all the drugs except for caffeine were detected successfully.

CONCLUSIONS

This study indicates that spay-inlet MPT-MS/MS is an effective method for direct and rapid identification of drug solutions, and it has substantial potential for fast and sensitive drug residue detection.

Solid Sampling with a Diode Laser for Portable Ambient Mass Spectrometry

A hand-held diode laser is implemented for solid sampling in portable ambient mass spectrometry (MS). Specifically, a pseudocontinuous wave battery-powered surgical laser diode is employed for portable laser diode thermal desorption (LDTD) at 940 nm and compared with nanosecond pulsed laser ablation at 2940 nm. Postionization is achieved in both cases using atmospheric pressure photoionization (APPI). The laser ablation atmospheric pressure photoionization (LAAPPI) and LDTD-APPI mass spectra of sage leaves (Salvia officinalis) using a field-deployable quadrupole ion trap MS display many similar ion peaks, as do the mass spectra of membrane grown biofilms of Pseudomonas aeruginosa. These results indicate that LDTD-APPI method should be useful for in-field sampling of plant and microbial communities, for example, by portable ambient MS. The feasibility of many portable MS applications is facilitated by the availability of relatively low cost, portable, battery-powered diode lasers. LDTD could also be coupled with plasma- or electrospray-based ionization for the analysis of a variety of solid samples.

Low-pressure barrier discharge ion source using air as a carrier gas and its application to the analysis of drugs and explosives

In this work, a low-pressure air dielectric-barrier discharge (DBD) ion source using a capillary with the inner diameter of 0.115 and 12 mm long applicable to miniaturized mass spectrometers was developed. The analytes, trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), 1,3,5,7-tetranitroperhydro-1,3,5,7-tetrazocine (HMX), pentaerythritol tetranitrate (PETN), nitroglycerine (NG), hexamethylene triperoxide diamine (HMTD), caffeine, cocaine and morphine, introduced through the capillary, were ionized by a low-pressure air DBD. The ion source pressures were changed by using various sizes of the ion sampling orifice. The signal intensities of those analytes showed marked pressure dependence. TNT was detected with higher sensitivity at lower pressure but vice versa for other analytes. For all analytes, a marked signal enhancement was observed when a grounded cylindrical mesh electrode was installed in the DBD ion source. Among nine analytes, RDX, HMX, NG and PETN could be detected as cluster ions [analyte + NO3 ](-) even at low pressure and high temperature up to 180 °C. The detection indicates that these cluster ions are stable enough to survive under present experimental conditions. The unexpectedly high stabilities of these cluster ions were verified by density functional theory calculation.

Comparison of three plasma sources for ambient desorption/ionization mass spectrometry

Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.