Signal Enhancement of Cadmium in Lettuce Using Laser-Induced Breakdown Spectroscopy Combined with Pyrolysis Process.

Fast detection of heavy metals in lettuce is significant for food market regulation and the control of heavy metal pollution. Advanced methods like laser-induced breakdown spectroscopy (LIBS) technology have been tried to determine the cadmium (Cd) content. To retard the negative effect of complex matrix composition from samples and improve quantitative performance of LIBS technology, the pyrolysis process combined with LIBS was adopted to determine the cadmium (Cd) content of lettuce. Adaptive iteratively reweighted penalized least squares (airPLS) was used to preprocess the LIBS spectra and solve the baseline drift. For multivariate linear regression based on the three selected Cd emission lines correlation coefficient in the prediction set Rp2 increased from 0.9154 to 0.9969, and the limit of detection (LOD) decreased from 9.1 mg/kg to 0.9 mg/kg after the pyrolysis process. The partial least squares (PLS) regression and support vector regression (SVR) were applied to construct calibration models based on full spectra. In addition, the least absolute shrinkage and selection operator (LASSO) was implemented to choose limited lines to predict the Cd content. The PLS model with the pyrolysis process obtained the best results with Rp2 = 0.9973 and LOD = 0.8 mg/kg. The results indicated that the pyrolysis method could enhance the spectral signal of cadmium and thus significantly improve the analysis results for all the models. It is shown in this experiment that proper sample preprocessing could effectively amplify the Cd signal in LIBS and make LIBS measurement an efficient method to assess Cd contamination in the vegetable industry.

Rapid Determination of Cadmium Contamination in Lettuce Using Laser-Induced Breakdown Spectroscopy.

Quick access to cadmium (Cd) contamination in lettuce is important to supervise the leafy vegetable growth environment and market. This study aims to apply laser-induced breakdown spectroscopy (LIBS) technology for fast determination of Cd content and diagnosis of the Cd contamination degree in lettuce. Emission lines Cd II 214.44 nm, Cd II 226.50 nm, and Cd I 228.80 nm were selected to establish the univariate analysis model. Multivariate analysis including partial least squares (PLS) regression, was used to establish Cd content calibration models, and PLS model based on 22 variables selected by genetic algorithm (GA) obtained the best performance with correlation coefficient in the prediction set Rp² = 0.9716, limit of detection (LOD) = 1.7 mg/kg. K-Nearest Neighbors (KNN) and random forest (RF) were used to analyze Cd contamination degree, and RF model obtained the correct classification rate of 100% in prediction set. The preliminary results indicate LIBS coupled with chemometrics could be used as a fast, efficient and low-cost method to assess Cd contamination in the vegetable industry.

[Virtual image-guided minimal incision sugary unicondylar knee arthroplasty].

OBJECTIVE: To investigate the curative effect of virtual image-guided minimal incision sugary unicondylar knee arthroplasty (MIS-UKA). METHODS: Twenty-six patients of knee osteoarthritis (with 26 knees) received virtual image-guided MIS-UKA and followed up for (8.2 +/- 2.4) months. The incision length, operative time, hemorrhage, and 48 h drainage were calculated. The patients were evaluated by hand injury severity score (HISS) system knee score. X-ray film of the whole lower limb was taken to observe the line of force and range of motion of knee. RESULTS: MIS-UKA was successfully performed on the 26 knees with the average incision length of 7.4 +/- 0.6 cm, the average operative time of 78 +/- 12 min, the average hemorrhage of 114 +/- 18 ml, and the 48 h drainage of 122 +/- 13 ml. Two weeks after the operation, the average HISS hip score was 98, higher than that before the operation (72), the hip-knee-ankle angle was 0.8 degree +/- 0.6 degree, larger than that before the operation (7.6 degrees +/- 1.8 degrees), the flexion contraction angle was 1.8 degrees +/- 1.1 degrees, smaller than that before the operation (6.8 degrees +/- 1.6 degrees), and the joint range of motion of knee was 132.6 degrees +/- 3.5 degrees, larger than that before the operation (107.5 degrees +/- 6.2 degrees). No infection, prosthesis cacothesis, and patellofemoral joint pain were found. CONCLUSION: The surgical navigation system surmounts the disadvantage of small visual field, observes the line of force of the lower limbs, knee joint rotational apposition, and ligament balance dynamically with digital 3D bone mode, provide geometry and morphology data, and rebuilds knee joint vitodynamically and anatomically, and heightens the accuracy of prostheses replacement, thus having important clinic value in MIS-UKA.