Smartphone-based colorimetric detection of formaldehyde in the air

Adverse impacts of exposure to formaldehyde on human health significantly increases attention in monitoring formaldehyde concentrations in the air.Conventional formaldehyde detection methods typically rely on large and costly instruments and requires high skills of expertise,preventing it from being widely accessible to civilians.This study introduced a novel approach utilizing smartphone-based colorimetric analysis.Changes of green channel signals of digital images by a smartphone successfully capture variation of purple color of 4-amino-3-hydrazino-5-mercapto-1,2,4-triazol solution,which is proportional to formaldehyde concentrations.It is because that green and purple are complimentary color pairs.A calibration curve was established between green channel signals and formaldehyde concentrations,with a correlation coefficient of 0.98.Detection limit of the smartphone-based method is 0.008 mg/m^(3).Measurement errors decrease as formaldehyde concentrations increase,with median relative errors of 34%,17%,and 6%for concentration ranges of 0–0.06 mg/m^(3),0.06–0.12 mg/m^(3),and 0.12–0.35 mg/m^(3),respectively.This method replaced scientific instrumentation with ordinary items,greatly reducing cost and operation bars.It would provide an opportunity to realize onsite measurements for formaldehyde by occupants themselves and increase awareness of air quality for better health protection.

Identification of Colored Dyes that are Resistant to Fading on Exposure to Ethylene Oxide;Use with Indicating FTA™Sample Collection Cards

Regulatory Standards and Forensic Communities are expressing an expectation for HID products to be certified as“DNA‑free.”Recently,“DNA‑free”status was described for HID‑related products using ethylene oxide(EtO);this gas reduces the presence of amplifiable DNA and causes minimal interference to downstream HID‑analytical methods.During sample collection,indicating cards,for example,Indicating FTA™(GE Healthcare Life Sciences,UK),are used to collect and store buccal cell DNA.These cards contain a dye which changes color on application of a colorless sample.Generating“DNA‑free”indicating cards using EtO should not impact the dyes’ability to indicate sample location or the efficacy of the card in downstream HID‑analytical methods.This study was initiated to identify alternative dyes to those currently used with sample indicating collection cards.The most promising,dyes when applied to cellulose papers exhibited a uniform color distribution and excellent sample indicating properties even when mixed with chemicals associated with FTA™.When dyed cellulose papers were exposed to EtO,ultraviolet radiation,elevated temperature,and humidity,negligible fading or discoloration was observed.The presence of these dyes on cellulose papers did not interfere with direct short tandem repeat(STR)profiling.Allelic concordance,first pass success rate,and mean peak heights were comparable to samples applied to Indicating FTA.Biological samples applied to EtO‑treated dyed cellulose papers and stored>1 month produced full STR profiles of sufficient quality to allow submission to DNA databases,confirming negligible interference from EtO treatment.These alternative sample indicating dyes resist EtO‑mediated fading while fulfilling the Forensic Community’s expectation for“DNA‑free”with negligible impact on collection card performance.

Design of tooth color measurement system based on silicon double P-N junction color sensor

Working principles of silicon double P-N junction color sensor are introduced and a color measurement system to distinguish tooth color difference is designed in this paper.This system consists of silicon double P-N junction,a small optical fiber probe,signal process circuit and an MSP430FG439 single-chip system.Small in size,this system can measure different parts of the tooth in a fast and convenient way with high-accuracy.Thus,this system will be very promising in building prosthodontics and tooth fabrication.