Chengyin Shen

Thermal desorption extraction proton transfer reaction mass spectrometer (TDE-PTR-MS) for rapid determination of residual solvent and sterilant in disposable medical devices.

Thermal desorption extraction proton transfer reaction mass spectrometer (TDE-PTR-MS) has been exploited to provide rapid determination of residual solvent and sterilant like cyclohexanone (CHX) and ethylene oxide (EO) in disposable medical devices. Two novel methods are proposed for the quantification of residual chemicals in the polyvinyl chloride infusion sets with our homemade PTR-MS. In the first method, EO residue in the solid infusion sets (y, mgset(-1)) is derived through the determination of EO gas concentration within its packaging bag (x, ppm) according to the correlative equation of y=0.00262x. In the second one, residual EO and CHX in the solid infusion sets are determined through a time integral of their respective mass emission rates. The validity of the proposed methods is demonstrated by comparison with the experimental results from the exhaustive extraction method. Due to fast response, absolute concentration determination and high sensitivity, the TDE-PTR-MS is suggested to be a powerful tool for the quality inspection of disposable medical devices including the quantitative determination of residual solvent and sterilant like CHX and EO.

Control of solvent use in medical devices by proton transfer reaction mass spectrometry and ion molecule reaction mass spectrometry

A homemade proton transfer reaction mass spectrometer (PTR-MS) and a commercial ion molecule reaction mass spectrometer (IMR-MS) have been applied to detect volatile organic compounds (VOCs) in the packaging bags of infusion sets made of polyvinylchloride (PVC) plastic. The most abundant characteristic ions in the PTR-MS and IMR-MS measurements are observed at m/z 99 and 98 respectively, which are the results of soft ionizations that a residual chemical undergoes the proton transfer reaction in PTR-MS and the charge transfer reaction in IMR-MS. On the basis of ionic intensity dependence on the reduced-field in the PTR-MS investigation, the residue can be unambiguously identified as cyclohexanone, a commonly used adhesive agent in PVC medical device manufacture. Quantitative measurement by PTR-MS shows that concentrations of cyclohexanone in the packages of two types of infusion sets are 11 and 20 ppm respectively. Due to fast response, absolute concentration detection, and high sensitivity, the PTR-MS and IMR-MS detection methods are proposed for the quality control of medical devices including the detection of illegal or excessive uses of chemical solvents like cyclohexanone.

Exhaled gases online measurements for esophageal cancer patients and healthy people by proton transfer reaction mass spectrometry

Esophageal cancer is a prevalent malignancy. There is a considerable demand for developing a fast and noninvasive method to screen out the suspect esophageal cancer patients who may undergo further clinical diagnosis.

Spray Inlet Proton Transfer Reaction Mass Spectrometry (SI-PTR-MS) for Rapid and Sensitive Online Monitoring of Benzene in Water

Rapid and sensitive monitoring of benzene in water is very important to the health of people and for environmental protection. A novel and online detection method of spray inlet proton transfer reaction mass spectrometry (SI-PTR-MS) was introduced for rapid and sensitive monitoring of trace benzene in water. A spraying extraction system was coupled with the self-developed PTR-MS. The benzene was extracted from the water sample in the spraying extraction system and continuously detected with PTR-MS. The flow of carrier gas and salt concentration in water were optimized to be 50 sccm and 20% (w/v), respectively. The response time and the limit of detection of the SI-PTR-MS for detection of benzene in water were 55 s and 0.14 μg/L at 10 s integration time, respectively. The repeatability of the SI-PTR-MS was evaluated, and the relative standard deviation of five replicate determinations was 4.3%. The SI-PTR-MS system was employed for monitoring benzene in different water matrices, such as tap water, lake water, and wastewater. The results indicated that the online SI-PTR-MS can be used for rapid and sensitive monitoring of trace benzene in water.

Discrimination of isomers and isobars by varying the reduced-field across drift tube in proton-transfer-reaction mass spectrometry (PTR-MS)

Proton-transfer-reaction mass spectrometry (PTR-MS) is a powerful technique for the real time trace gas analysis of volatile organic compounds (VOCs). However, quadrupole mass spectrometer (MS) used in PTR-MS has a relatively low mass resolution and is therefore not suitable for differentiating isobars. Furthermore, because of the lack of chemical separation before analysis, isomers can not be identified, either. In the present study, by varying the reduced-field E/N in the reaction chamber with a range of 50–180 Td in PTR-MS, we studied the product ion distribution (PID) of three sets of isobars/isomers, i.e. n-propanol/iso-propanol/acetic acid, propanal/acetone and four structural isomers of butyl alcohol. The profiles of the reduced-field dependence (PFD) of the PID under the chosen E/N-values show obvious differences which can be used to discriminate between these isobars/isomers thus enabling the titled method. Noticeably, we have observed that even the isomers, in the case of four structural isomers of butyl alcohol, which show little difference with each other at high reduced-field, can be discriminated easily at low reduced-field. Finally, two examples for the application of this method are discussed: (1) cyclohexanone was identified to be a major compound in the headspace of medical infusion sets; and (2) the differentiation and quantification of propanal and acetone in three synthetic mixtures with different ratios. This study presents a potential method to distinguish and quantify isobars/isomers conveniently in practical applications of PTR-MS analysis without additional instrumental configurations.

Detection of Ketones by a Novel Technology: Dipolar Proton Transfer Reaction Mass Spectrometry (DP-PTR-MS)

AbstractProton transfer reaction mass spectrometry (PTR-MS) has played an important role in the field of real-time monitoring of trace volatile organic compounds (VOCs) due to its advantages such as low limit of detection (LOD) and fast time response. Recently, a new technology of proton extraction reaction mass spectrometry (PER-MS) with negative ions OH– as the reagent ions has also been presented, which can be applied to the detection of VOCs and even inorganic compounds. In this work, we combined the functions of PTR-MS and PER-MS in one instrument, thereby developing a novel technology called dipolar proton transfer reaction mass spectrometry (DP-PTR-MS). The selection of PTR-MS mode and PER-MS mode was achieved in DP-PTR-MS using only water vapor in the ion source and switching the polarity. In this experiment, ketones (denoted by M) were selected as analytes. The ketone (molecular weight denoted by m) was ionized as protonated ketone [M + H]+ [mass-to-charge ratio (m/z) m + 1] in PTR-MS mode and deprotonated ketone [M – H]– (m/z m – 1) in PER-MS mode. By comparing the m/z value of the product ions in the two modes, the molecular weight of the ketone can be positively identified as m. Results showed that whether it is a single ketone sample or a mixed sample of eight kinds of ketones, the molecular weights can be detected with DP-PTR-MS. The newly developed DP-PTR-MS not only maintains the original advantages of PTR-MS and PER-MS in sensitive and rapid detection of ketones, but also can estimate molecular weight of ketones. Graphical Abstractᅟ

Application of a self-developed proton transfer reaction-mass spectrometer to on-line monitoring trace volatile organic compounds in ambient air

Real-time and on-line monitoring volatile organic compounds(VOCs) are valuable for real-time evaluating air quality and monitoring the key source of pollution. A self-developed proton transfer reaction-mass spectrometer( PTR-MS) was constructed and applied to on-line monitoring trace VOCs in ambient air in Hefei. With the help of a self-developed catalytic converter, the background signal of the instrument was detected and the stability of the instrument was evaluated. The relative standard deviation of signal at m/z 21 was only 0.74% and the detection limit of PTR-MS was 97 part per trillion(97×10–12, volume ratio). As a case of the air monitoring in Hefei, the ambient air at Dongpu reservoir spot was on-line monitored for 13 d with our self-developed PTR-MS. Meanwhile, a solid-phase micro-extraction(SPME) technique coupled to gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS) was also used for the off-line detection of the air. The results show that our self-developed PTR-MS can be used for the on-line and long-term monitoring of VOCs in air at part per trillion level, and the change trend of VOCs concentration monitored with PTR-MS was consistent with that detected with the conventional SPME-GC-MS. This self-developed PTR-MS can fully satisfy the requirements of air quality monitoring and real-time monitoring of the key pollution sources.

Rapid identification of false peaks in the spectrum of Hadamard transform ion mobility spectrometry with inverse gating technique

With the application of Hadamard transform (HT) technique, the signal to noise ratio of ion mobility spectrometry (IMS) has been improved significantly. Nevertheless, possibly due to the modulation defects, false peaks appear in the demultiplexed data and demonstrate similar features to those of the real signal peaks, which makes them hard to be discriminated. Facing this challenge, a novel method has been presented in this work and achieved the rapid identification of the false peaks in Hadamard multiplexing IMS. Simply by introducing the inverse gating technique to Hadamard multiplexing, the novel inverse Hadamard transform (IHT) method is developed. With the application of this novel method in IMS, most of the false peaks are changed to opposite to the real signal peaks, which makes them easy to be classified as the false peaks. Furthermore, with the help of the single “code” extended method, the amount of the false peaks in inverse Hadamard transform ion mobility spectrometry (IHT-IMS) decreases dramatically, and this makes the identification more accurate. The sample tests further demonstrate that the inverse Hadamard transform (IHT) method is an effective way to address the problem of rapid identification of the false peaks and upgrade the quality analysis of Hadamard multiplexing ion mobility spectrometry.

Negative photoionization chloride ion attachment ion mobility spectrometry for the detection of organic acids

A novel negative photoionization chloride ion attachment ion mobility spectrometry (NP-CA-IMS) instrument has been developed. In this technique, chloride ion attachment technology is first applied to photoionization ion mobility spectrometry in a negative detection mode. The reactant ions are chloride ions, which are generated from the reaction between carbon tetrachloride (CCl4) and low energy electrons induced by the photoionization of acetone (CH3COCH3) with a commercial vacuum ultraviolet Krypton lamp. The generation efficiency of chloride ions was investigated. Subsequently, the performance of the instrument was investigated. A series of volatile straight chain organic carboxylic acids were detected in the order of magnitude of ppb, including acetic acid (CH3COOH), propionate acid (CH3CH2COOH), butyric acid (CH3(CH2)2COOH), valeric acid (CH3(CH2)3COOH), isovaleric acid (2-CH3(CH2)3COOH), hexanoic acid (CH3(CH2)4COOH), heptanoic acid (CH3(CH2)5COOH), and octanoic acid (CH3(CH2)6COOH). Besides, the concentration of acetic acid was calibrated and a mixture of the investigated acids was also studied. Finally, the new methods capability to detect acetic acid in five different brands of edible white vinegar was evaluated. The experimental results show that negative photoionization chloride ion attachment is an excellent nonradioactive source for IMS.

Detection of Volatile Organic Compounds in a Drop of Urine by Ultrasonic Nebulization Extraction Proton Transfer Reaction Mass Spectrometry

Detection of volatile organic compounds (VOCs) in human urine has potential application value in screening for disease and toxin exposure. However, the current technologies are too slow to detect the concentration of VOCs in fresh urine. In this study, we developed a novel ultrasonic nebulization extraction proton transfer reaction mass spectrometry (UNE-PTR-MS) technology. The urinary VOCs can be rapidly extracted to gaseous VOCs using the UNE system and then delivered using a carrier gas to the PTR-MS instrument for rapid detection. The carrier gas flow and sample size were optimized to 100 mL/min and 100 μL, respectively. The limits of detection (LODs) and response time of the UNE-PTR-MS were evaluated by detecting three VOCs that are common in human urine: methanol, acetaldehyde, and acetone. The LODs determined for methanol (4.47 μg/L), acetaldehyde (1.98 μg/L), and acetone (3.47 μg/L) are 2-3 orders of magnitude lower than the mean concentrations of that in healthy human urine. The response time of the UNE-PTR-MS is 34 s and only 0.66 mL of urine is required for a full scan. The repeatability of this UNE-PTR-MS was evaluated, and the relative standard deviations of 5 independent determinations were between 4.62% and 5.21%. Lastly, the UNE-PTR-MS was applied for detection of methanol, acetaldehyde, and acetone in real human urine to test matrix effects, yielding relative recoveries of between 88.39% and 94.54%. These results indicate the UNE-PTR-MS can be used for the rapid detection of VOCs in a drop of urine and has practical potential for diagnosing disease or toxin exposure.