Identity Efficiency for High-Performance Ambient Pressure Ion Mobility Spectrometry.

A new approach to reduce the false-positive responses commonly encountered in the field when drugs and explosives are detected is reported for an electrospray ionization high-performance ion mobility spectrometry (ESI-HPIMS). In this article, we report on the combination of reduced mobility and the width-at-half-height of a peak to give a new parameter called conditional reduced mobility (CRM). It was found that the CRM was capable of differentiating between real drugs peaks from that of a false-positive peak and may help to reduce false-positive rates. This effect was demonstrated using 11 drugs (amphetamine, cannabidiol, cocaine, codeine, heroine, methamphetamine, morphine, phentermine, L-phenylepherine, proglitazone, and rosiglitazone) and seven interferences chosen from off-the-shelf products. This report determined and compared CRM, resolving power (R(m)), and diffusion-limited conditional theoretical reduced mobility (DLCTRM) for ESI-HPIMS. The most important parameters for determining CRM are reduced mobility and width-at-half-height of a peak. There is a specific optimum voltage, gate pulse width, resolving power, and now CRM for each ion. DLCTRM indicate the optimum reduced mobility that is not normally possible under field conditions. CRM predicts the condition at which a target compound can be differentiated from a false-positive response. This was possible because different ions exhibits different drifting patterns and hence a different peak broadening phenomenon inside an ion mobility tube. Reduced mobility for target compounds reported were reproducible to within 2% for ESI-HPIMS. The estimated resolving power for the ESI-HPIMS used in this study was 61 ± 0.22. Conditional reduced mobility introduced in this paper show differences between target compounds and false-positive peaks as high as 74%, as was the case for cannabidiol and interference #1 at 70 µs gate pulse width.

Analysis of psychoactive cathinones and tryptamines by electrospray ionization atmospheric pressure ion mobility time-of-flight mass spectrometry.

The ability to use positive ion monitoring mode with an atmospheric pressure ion mobility time-of-flight mass spectrometer (APIM(tof)MS) to detect psychoactive cathinones and tryptamines from aqueous phase samples was evaluated. The study used a traditional electrospray ionization (ESI) source for sample introduction and ionization. A total of four cathinones (mephedrone, butylone, 4-Me-PPP, and 4-MEC) and five tryptamines (5-EtO-DPT, 5-EtO-DALT, 5-EtO-MIPT, 5-EtO-ALCHT, and 5-EtO-2MALET) were investigated, and we report on parent ions, collision induced dissociation (CID) fragment ions, reduced mobility (Ko), mass flight times, and detection limits obtained from a single instrument run for the psychoactive substances. Detection limits reported ranged from 3 to 11 µM concentration for the compounds studied. This detection limit range corresponded to 1-5 ng of material needed for improved detection on the instrument. This article demonstrates that it was possible to use a single instrument platform for the separation, detection, and identification of cathinones and tryptamines in less than 1 min. The application holds great promise for detecting and identifying a new class of drugs often referred to as "bath salts" or "legal highs" distributed over the Internet.

Recent developments in sample preparation techniques combined with high-performance liquid chromatography: A critical review.

This review article compares and contrasts sample preparation techniques coupled with high-performance liquid chromatography (HPLC) and describes applications developed in biomedical, forensics, and environmental/industrial hygiene in the last two decades. The proper sample preparation technique can offer valued data for a targeted application when coupled to HPLC and a suitable detector. Improvements in sample preparation techniques in the last two decades have resulted in efficient extraction, cleanup, and preconcentration in a single step, thus providing a pathway to tackle complex matrix applications. Applications such as biological therapeutics, proteomics, lipidomics, metabolomics, environmental/industrial hygiene, forensics, glycan cleanup, etc., have been significantly enhanced due to improved sample preparation techniques. This review looks at the early sample preparation techniques. Further, it describes eight sample preparation technique coupled to HPLC that has gained prominence in the last two decades. They are (1) solid-phase extraction (SPE), (2) liquid-liquid extraction (LLE), (3) gel permeation chromatography (GPC), (4) Quick Easy Cheap Effective Rugged, Safe (QuEChERS), (5) solid-phase microextraction (SPME), (6) ultrasonic-assisted solvent extraction (UASE), and (7) microwave-assisted solvent extraction (MWASE). SPE, LLE, GPC, QuEChERS, and SPME can be used offline and online with HPLC. UASE and MWASE can be used offline with HPLC but have also been combined with the online automated techniques of SPE, LLE, GPC, or QuEChERS for targeted analysis. Three application areas of biomedical, forensics, and environmental/industrial hygiene are reviewed for the eight sample preparation techniques. Three hundred and twenty references on the eight sample preparation techniques published over the last two decades (2001-2021) are provided. Other older references were included to illustrate the historical development of sample preparation techniques.

Comparison of PGE2, prostacyclin and leptin release by human adipocytes versus explants of adipose tissue in primary culture.

The present studies were designed to investigate the sites of PGE(2), prostacyclin and leptin formation in human adipose tissue. Most of the PGE(2) and prostacyclin formation by adipose tissue explants from obese humans after 48 h in primary culture was due to blood vessels and other tissues not digested by collagenase. However, there was appreciable PGE(2) formation by adipocytes over a 48 h incubation and leptin formation was only seen in adipocytes. An increase in COX-2 immunoreactive protein was also seen after incubation of isolated human adipocytes for 48 h. The release of PGE(2) by adipocytes incubated for 48 h was about 4% that by intact adipose tissue explants while the release of prostacyclin was about 1.5% that by tissue. However, in a different experimental design where PGE(2) formation was measured over 2 h in the presence of 20 microM arachidonic acid the formation of PGE(2) by adipocytes after 48 h prior incubation in primary culture was 38% of that by tissue explants. Dexamethasone enhanced leptin release by adipocytes while inhibiting PGE(2) release and COX-2 up-regulation. The mechanisms involved in up-regulation of COX-2 activity during primary culture of adipocytes and the inhibition of this by dexamethasone do not appear to involve p38 MAPK or p42-44 MAPK. Interleukin I(beta) further enhanced PGE(2) formation by adipocytes but did not affect leptin formation. In conclusion, these data indicate that leptin release is exclusively a function of adipocytes while prostanoids are made by both adipocytes and the other cells present in human adipose tissue

Health discussions between college students and parents: results of a Delphi study.

College students' perspectives on health discussions with parents were examined in a survey of students from 5 US universities. Topics important for promoting students' and parents' health as well as guidelines for promoting productive discussions between college students and their parents were identified, using the Delphi technique to reach consensus. Sex, drugs, alcohol, and HIV/AIDS ranked as the most important discussion topics related to students' health; family relationships, physical fitness, and stress management ranked as most important topics dealing with parental health. Guidelines for profitable discussion were that the individual be honest, open, respectful of others' opinions, and a good listener. Parent education, health education activities that promote student-parent discussion, and further research on the topic are suggested.

Rapid screening of 2-[18F]-fluoro-2-deoxy-D-glucose infusions for volatile organic compound contaminants by solid phase microextraction with gas chromatography-selective ion monitoring mass spectrometry (SPME-GC-SIMMS).

A method compatible with radioactive samples, capable of detecting trace volatile components in a sample volume of ca. 1cm(3) of 2-[18F]-fluoro-2-deoxy-D-glucose solution is described. The approach, based on solid phase micro-extraction gas chromatography-mass spectrometry with a carboxen/polydimethylsiloxane based fibre, was optimised with respect to extraction time (10 min), extraction temperature (60 degrees C) and phase volume ratio (1). The analysis time, including extraction, was less than 20 min with linear responses for acetonitrile and ethanol over the ranges: 0.09-80 microg cm(-3) (22 degrees C, acetonitrile) and 0.78-79 microg cm(-3) (22 degrees C, ethanol). The detection limits were estimated to be ca. 0.78 microg cm(-3) for ethanol and 0.09 microg cm(-3) for acetonitrile. Stability studies indicated analyte losses of up to 75% over 24h and analysis of aged 2-[18F]FDG samples showed that levels of ethanol and acetonitrile were not less than 100 microg cm(-3), indicative of levels substantially greater than this in the original infusions given to human subjects.

Internally heated membrane interfaced to a gas chromatography flame ionization detector.

Volatile Organic Compounds (VOCs) mixtures in aqueous solutions have been investigated using a simple and efficient all-in-one on-line sampling, isolation, enrichment and pre-concentration internally heated membrane connected to a gas chromatography flame ionization detector (GC-FID). In our previous study with the internally heated membrane, no GC column was used in the instrument. In this new study, we introduce a GC column in the instrument design and this makes it possible for mixtures to be investigated. This new experimental design enabled high resolution separation of analyte mixtures capable of being adsorbed, diffused, and desorbed from the device for detection with an FID. With the new design we present data from investigation of competitive adsorption effects on the membrane. The data showed that analyte adsorption and diffusion onto the membrane can be affected when mixtures of analytes are introduced. The application of multiple linear regressions approach to the data enabled us to correct for the problem of competitive adsorption. Analyte adsorption and diffusion was affected by the diffusion coefficients of the analytes; the higher the diffusion coefficient the better the extraction from the membrane. Increasing the sampling time from 1 to 4 min increases the response by 77%. The sampling time responses were linear up to 4 min sampling time. Above 4 min sampling time, the data deviate from linearity. The effect of adding salt to standards has no effect on analyte absorption onto the membrane. The detection limits for key VOCs studied with an internal standard calibration ranged from 0.2 to 194 ng cm(-3).

Separation and preconcentration phenomena in internally heated poly(dimethylsilicone) capillaries: preliminary modelling and demonstration studies.

The concept of achieving low-resolution separations in internally heated capillary membranes is discussed in terms of controlling the diffusion coefficients of volatile organic compounds in poly(dimethylsilicone) membranes in space and time. The behaviour of 1,1,1-trichloroethane in polydimethylsilicone was used in conjunction with a mixed-physics finite element model, incorporating second order partial differential equations, to describe time and spatial variations of mass-flux, membrane temperature and diffusion coefficients. The model, coded with Femlab, predicted highly non-linear diffusion coefficient profiles resulting from temperature programming a 500 [micro sign]m thick membrane, with an increase in the diffusion coefficient of approximately 30% in the last 30% of the membrane thickness. Simulations of sampling hypothetical analytes, with disparate temperature dependent diffusion coefficient relationships, predicted distinct thermal desorption profiles with selectivities that reflected the extent of diffusion through the membrane. The predicted desorption profiles of these analytes also indicated that low resolution separations were possible. An internally heated poly(dimethylsilicone) capillary membrane was constructed from a 10 cm long, 1.5 mm od capillary with 0.5 mm thick walls. Thirteen aqueous standards of volatile organic compounds of environmental significance were studied, and low-resolution separations were indicated, with temperature programming of the membrane enabling desorption profiles to be differentiated. Further, analytically useful relationships in the [micro sign]g cm(-3) concentration range were demonstrated with correlation coefficients >0.96 observed for linear regressions of desorption profile intensities to analyte concentrations.