Influence of intraoral scanning duration on data accuracy.

STATEMENT OF PROBLEM: The use of intraoral scanners (IOSs) correlates with clinical outcome and patient satisfaction. While the accuracy of IOSs has been well evaluated, studies on the effect of scanning duration on data accuracy are limited. PURPOSE: The purpose of this in vitro study was to investigate the relationship between different scanning durations and the accuracy of the scanned data. MATERIAL AND METHODS: Two experienced operators used the same intraoral scanner (TRIOS 3; 3Shape A/S) to scan a gypsum cast, but with 5 different scanning durations (30 seconds, 60 seconds, 90 seconds, 120 seconds, and 180 seconds), and the trueness of the scanned data was assessed. Ten scans for each duration group were performed, and all the acquired data were evaluated for precision analysis. In addition, each scanned complete arch cast was divided into anterior and posterior regions at the canine teeth, and the 3-way ANOVA test was used to assess the scanning trueness and precision of the scanned anterior and posterior dental arch. RESULTS: The intraoral scanning results between the 2 operators were highly consistent. The data of the 30-second group showed the lowest trueness and precision (P<.001), whereas no significant difference was found among the other groups (P>.05). The trueness and precision of the scanning data in the posterior region was inferior to that in the anterior region (P<.001). CONCLUSIONS: The duration time of the intraoral scanning (ranging from 60 seconds to 180 seconds) did not influence the accuracy of the acquired data, while excessively rapid scanning adversely affected accuracy.

Facile synthesis of magnetic molybdenum disulfide@graphene nanocomposite with amphiphilic properties and its application in solid-phase extraction for a wide polarity of insecticides in wolfberry samples.

A novel magnetic molybdenum disulfide@graphene (Fe3O4/MoS2@G) nanocomposite with amphiphilic properties was prepared via a co-mixing solvothermal method. To demonstrate the feasibility of Fe3O4/MoS2@G as a sorbent during sample preparation, it was employed for the magnetic solid phase extraction (MSPE) of ten pyrethroids, three triazoles and two acaricide pyridaben and picoxystrobin in an emulsified aqueous solution. Dichloromethane was used as the extractant to form an emulsified aqueous solution. Subsequently, the Fe3O4/MoS2@G sorbent with amphiphilic properties was used to retrieve 15 wide polarity insecticides from dichloromethane via MSPE. The proposed method has the advantage of being applicable to different polar pesticides, strengthening the capacity of enrichment and purification of target analytes. The π-π interaction between the hydrophilic and hydrophobic moieties of Fe3O4/MoS2@G and the aromatic rings of target analytes were responsible for the efficient sorption. Thus, a reliable, convenient, and efficient method for the analysis of 15 insecticides with wide polarity in wolfberry samples was established by coupling Fe3O4/MoS2@G nanocomposite MSPE with gas chromatography-mass spectrometry (GC-MS) analysis. The obtained linearity of this method was in the range from 1 to 5000 ng mL-1 for 15 analytes, with determination coefficients (R2) ≥0.9907. The limit of detection (LOD) for 15 insecticides was in the range from 0.1 to 5.0 ng g-1. The recoveries of 15 insecticides from spiked wolfberry samples were in the range from 71.41% to 110.53%, and RSD was less than 14.8%.

[Determination of pesticide residues in wolfberry using QuEChERS-gas chromatography-tandem mass spectrometry].

A method based on QuEChERS-gas chromatography-tandem mass spectrometry (GC-MS/MS) was established for the determination of 20 pesticide residues in wolfberry. The samples were extracted with acetonitrile. The extract was purified with PSA (primary secondary amine), GCB (graphite carbon black) and C18 to suppress the matrix in wolfberry. The analytical results showed that the calibration curves for the 20 pesticides obtained by GC-MS/MS were linear in the range of 5-500 µg/L, with the correlation coefficients higher than 0.99. The recoveries ranged from 70.02% to 110.78% with relative standard deviations (RSDs) ranging from 2.05% to 9.53%. This method has the advantages of being time-saving, convenient and sensitive. The proposed method can simultaneously detect organic phosphorus and organic chlorine pesticides residues with a good performance in terms of qualitative and quantitative detection.

[Determination of metformin hydrochloride, melamine and dicyandiamide in metformin hydrochloride preparations by tandem dual solid phase extraction cartridges-high performance liquid chromatography-electrospray ionization multi-stage mass spectrometry].

A method for the confirmation and quantification of metformin hydrochloride and its relative substances melamine and dicyandiamide using tandem dual solid phase extraction (SPE) cartridges and high performance liquid chromatography-electrospray ionization multi-stage mass spectrometry (HPLC-ESI-MSn) was developed. The samples were extracted with anhydrous ethanol containing 0.1% (v/v) acetic acid under ultrasound-assisted conditions. The extracts were concentrated and purified using Cleanert PCX and C18 tandem dual solid phase extraction cartridges, and eluted with 5% (v/v) ammonia methanol solution. The separation was performed on a Kromasil-C18 column (100 mm×4.6 mm, 3.5 µm) with gradient elution. The detection was performed in selected ion monitoring (SIM) mode using electrospray ionization multi-stage mass spectrometry. The external standard method was used for quantification. The extraction solvents, types of SPE cartridges and eluents were optimized by comparing the recoveries under different conditions. The results showed that the detector response of each target compound was linear in corresponding mass concentration ranges with the correlation coefficients (r2) ≥ 0.9992. The limits of detection (LODs) and the limits of quantification (LOQs) of the three analytes were 1.48-13.61 µg/kg and 5.96-45.67 µg/kg, respectively. The recoveries of the three analytes were 65.02%-118.33% spiked at low, medium and high levels. The relative standard deviations (RSDs) were no more than 13.41%. The method is reliable, easy, and has a better purification effect. The method can be applied to the routine analysis of metformin hydrochloride and its relative substances melamine and dicyandiamide in different preparations of metformin hydrochloride.