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High time-resolution monitoring of nitrogen dioxide (NO2) is of great importance for studying the formation mechanism of aerosols and improving air quality. Based on the Griess–Saltzman (GS) reaction, a portable NO2 optical sensor was developed by employing a porous polypropylene membrane tube (PPMT) integrated gas permeation collector and detector. The PPMT was filled with GS reagents and covered with a coaxial jacket tube for gas collection. Its two ends were respectively fixed with a yellowish-green light-emitting diode and a photodiode for optic signal reception. NO2 was automatically introduced through the collector by two air pumps cooperating with a homemade gas injector. Under the optimized conditions, the device presented good performance for monitoring NO2, such as a limit of detection of 5.1 ppbv (parts per billion by volume), an intraday precision of 4.1% (RSD, relative standard deviation, n = 11, c = 100 ppbv), an interday precision of 5.7% (RSD, n = 2–3 per day for 5 days, c = 100 ppbv), an ...

The endoplasmic reticulum (ER) has a central role in the fine-tuning of environmental and internal stimuli. We herein report a ratiometric fluorescent probe, α-Naph, capable of determining basal H2O2 in the ER. The probe specifically responds to H2O2. The limit of detection of the probe is as low as 38 nM, making it a feasible sensor to image intracellular basal H2O2. In addition, utilizing its ratiometric property, we are able to measure the concentration of H2O2 in the ER quantitatively, eliminating the error caused by the probe concentration and environment. The intracellular concentration of H2O2 in the ER is calculated to be 0.692 μM under normal conditions and 1.26 μM under the stimulation of phorbol myristate acetate.

Rapid detection of ultratrace pollutants in complex matrixes is a great challenge for studying their environmental behaviors and impacts. In this work, a method is developed by combining covalent organic framework (COF) based solid phase microextraction (SPME) with constant flow desorption ionization mass spectrometry for rapid detection of trace tetrabromobisphenol A (TBBPA) in multiple water media. The limits of detection and qualification are 0.92 and 3.1 ng L–1 for TBBPA, respectively. The linear range is between 0.01 and 10 μg L–1 (R2 = 0.9992), and the relative standard deviations with single fiber and multiple fibers are 6.4% and 6.7% (0.1 μg L–1, n = 9), respectively. The detection of nanogram per liter levels of TBBPA in tap water, river water, seawater, and beverage can be achieved in 7 min.

The endoplasmic reticulum (ER) has a central role in the fine-tuning of environmental and internal stimuli. We herein report a ratiometric fluorescent probe, α-Naph, capable of determining basal H

Real time online calibration of mass shift and intensity fluctuation to improve the accuracy of measurements for identification and quantitation in trace mass spectrometric analysis was demonstrated using extractive electrospray ionization mass spectrometry (EESI-MS). The signals of authentic compounds (e.g., lysine (Lys), proline (Pro), and histidine (His)) spiked into the extractive solution for the EESI process were used as the references to calibrate the signal of analytes (e.g., methionine (Met)) in the untreated sample solution. The intensity of the analyte signal was recorded simultaneously with the reference signals. The analyte signals at a given time point were calibrated on the basis of these correlation factors and real time signal response of the reference. The calibrated signal of Met at 10 μg L(-1) was improved with a better signal-to-noise ratio (S/N from 2.3 to 4.3), better linearity (R(2) from 0.9758 to 0.9980), and reduced relative standard deviation (RSD from 9.8% to 6.0%). The shift of mass-to-charge ratio of Met signal between the detected and theoretical values was decreased from 247 ± 133 to -7 ± 167 ppm for 50 min of detection using a linear ion trap mass analyzer and was reduced from -0.27 ± 0.60 to -0.12 ± 0.23 ppm for 50 min of detection using an Orbitrap mass analyzer (P = 95%). This method has been validated using a certified standard amino acids solution (GBW(E)100062) and applied for quantitative detection of amino acids in chicken feed, urine, nutritional drink, and facial mask samples, showing that the method is useful to improve the accuracy of mass spectrometric analysis.