[Evaluation of the efficacy of medial open wedge high tibial osteotomy combined with anterior cruciate ligament reconstruction in the treatment of varus knee osteoarthritis with anterior cruciate ligament injury]

Objective: To evaluate the efficacy of medial open wedge high tibial osteotomy (MOWHTO) combined with anterior cruciate ligament (ACL) reconstruction in the treatment of varus knee osteoarthritis (OA) with ACL injury. Methods: A follow-up study. The study retrospectively analyzed the patients underwent MOWHTO combined with ACL reconstruction for treatment of varus knee OA with ACL injury in Tianjin Hospital between April 2018 and September 2022. The preoperative and postoperative posterior slope angle (PSA), hip-knee-ankle angle (HKA), visual analog scale (VAS) pain scores, Lysholm score, International Knee Documentation Committee (IKDC) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Tegner score were compared. The follow-up indicators were recorded at 6 weeks, 3 months and 1 year after operation, and the complications were recorded. Results: The study included 32 patients (23 males, 9 females) with a mean age of (50.7±8.4) years. The mean follow-up time was (21.2±4.8) months. PSA increased from 9.2°±1.8° preoperatively to 11.1°±2.4° postoperatively, and HKA increased from 168.7°±2.2° to 181.5°±2.2° (both P<0.01). The indicators such as VAS score (6.8±1.1 vs 1.8±0.4), Lysholm score (52.6±7.1 vs 82.0±6.4), IKDC score (64.7±6.2 vs 80.3±10.0), WOMAC score (51.8±6.3 vs 81.8±6.5), and Tegner score (1.9±0.6 vs 5.0±1.0) were all improved after the operation (all P<0.01). Complications occurred in 5 patients (15.6%), including hematomas, sensory abnormalities, intermuscular vein thrombosis and correction angle loss. Conclusion: MOWHTO combined with ACL reconstruction is a safe and effective approach for the treatment of varus knee OA with ACL injury.

Design of multi-frequency point, high-isolation switches for micro-channel plate data acquisition

In order to replace the phosphor screen of a proximity-gated x-ray framing camera with a readout circuit using a time-interleaved structure, this paper carries out the design of a high-isolation RF switch. In this paper, a Metal-Oxide-Semiconductor Field Effect Tube (MOSFET) switching circuit is designed to achieve high isolation and low insertion loss at 0.5-3 GHz. This solves the problem that the switching circuit cannot be turned off properly due to the parasitic capacitance of MOSFETs in the process of RF signal transmission, resulting in signal feedthrough. It also ensures that the input signal can be transmitted to the output intact when the switching circuit is turned on. High isolation is achieved by using parallel resonance to increase the voltage division and series resonance to leak the current. The switch achieves 76 dB isolation and 0.07 dB insertion loss at 1 GHz frequency. Isolation is increased by adding parallel branches near the 2 and 3 GHz frequency points, achieving greater than 33 dB isolation from 0.5 to 3 GHz.

A large-format streak tube for compressed ultrafast photography

Streak cameras are powerful imaging instruments for studying ultrafast dynamics with the temporal resolution ranging from picosecond to attosecond. However, the confined detection area limits the information capacity of streak cameras, preventing them from fulfilling their potential in lidar, compressed ultrafast photography, etc. Here, we designed and manufactured a large-format streak tube with a large-size round-aperture gate, a spherical cathode, and a spherical screen, leading to an expanded detection area and a high spatial resolution. The simulation results show that the physical temporal resolution of the streak tube is better than 45 ps and the spatial resolutions are higher than 14 lp/mm in the whole area of 24 × 28 mm² on the cathode. The experiments demonstrate the streak tube's application potential in weak light imaging benefiting from the imaging magnification of 0.79, a photocathode radiance sensitivity of 37 mA/W, a radiant emitting gain of 11.6 at the wavelength of 500 nm, and a dynamic range higher than 512:1. Most importantly, in the photocathode area of Φ35 mm, the static spatial resolutions at the center and the edge along the slit (R = 16 mm) reach 32 and 28 lp/mm, respectively, and are higher than 10 lp/mm in the whole area of 24 × 28 mm² on the cathode, allowing for a considerable capacity for spatial information.

[Efficacy and safety of intravenous combined with topical administration of tranexamic acid in reducing blood loss after intramedullary fixation of intertrochanteric femoral fractures]

Objective

To investigate the efficacy and safety of intravenous combined with topical administration of tranexamic acid (TXA) in reducing blood loss after intramedullary fixation of intertrochanteric femoral fractures by a prospective controlled trial.

Methods

Patients with intertrochanteric femoral fractures, who were admitted for intramedullary fixation between June 2015 and July 2019, were selected as the study subjects, 120 of whom met the selection criteria. The patients were randomly assigned to 3 groups: intravenous administration group (group A, 41 cases), topical administration group (group B, 40 cases), and combined administrations group (group C, 39 cases). In group A, 4 patients occurred deep vein thrombosis of lower extremity before operation, 1 patient died of myocardial infarction on the 5th day after operation, and 1 patient developed severe pulmonary infection after operation. In group B, 2 patients occurred deep vein thrombosis of lower extremity before operation and 1 patient had iatrogenic fracture during operation. In group C, 3 patients occurred deep vein thrombosis of lower extremity before operation and 1 patient developed pulmonary infection before operation and gave up surgical treatment. All the above patients were excluded from the study, and the remaining 107 cases were included in the analysis, including 35, 37, and 35 cases in groups A, B, and C, respectively. There was no significant difference in gender, age, height, body mass, injury cause, fracture side and type, the interval between injury and operation, and preoperative hemoglobin (Hb), hematocrit between groups ( P>0.05). Intraoperative TXA (15 mg/kg) was injected intravenously in group A at 30 minutes before operation, and 1 g of TXA was injected into the medullary cavity in group B after the proximal femur was grooted and before the intramedullary nail implantation, respectively. TXA was given in group C before and during operation according to the administration methods and dosage of groups A and B. Total blood loss, maximum Hb decrease, blood transfusion rate, operation time, fracture healing time, and the incidence of complications were recorded and compared between groups. The hip joint function were evaluated by Harris score.

Results

There was no significant difference in operation time between groups ( P>0.05). The total blood loss, the maximum Hb decrease, and the blood transfusion rate in group B were the highest, followed by group A and group C, and the differences between groups were significant ( P<0.05). No incision infection or pulmonary embolism occurred in the 3 groups after operation. The incidence of anemia in group C was significantly lower than that in groups A and B, the difference was significant ( P<0.05). There was no significant difference in the incidence of subcutaneous hematoma, aseptic exudation, and deep vein thrombosis of lower extremity between groups ( P>0.05). All patients in the 3 groups were followed up 8-35 months, with an average of 16.2 months. The fracture healing time of groups A, B, and C was (6.12±1.78), (5.89±1.63), and (5.94±1.69) months, respectively, and there was no significant difference between groups ( P>0.05). At last follow-up, the Harris scores of the hip joints in groups A, B, and C were 83.18±7.76, 84.23±8.01, and 85.43±8.34, and the difference was not significant ( P>0.05).

Conclusion

Preoperative intravenous injection combined with intraoperative topical application of TXA can effectively reduce blood loss and blood transfusion after intramedullary fixation of femoral intertrochanteric fracture, without increasing the risk of deep vein thrombosis, and the efficacy is better than that of intravenous injection or topical administration.

[Short-term effectiveness comparison of unipedicular versus bipedicular percutaneous kyphoplasty for osteoporotic vertebral compression fractures with posterior wall broken]

Objective

To compare the short-term effectiveness and safety of unipedicular versus bipedicular percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fracture (OVCF) with posterior wall broken.

Methods

The clinical data of 68 patients with OVCF with posterior wall broken and without posterior ligament complex injury and spinal cord nerve injury between June 2013 and December 2018 were retrospectively analyzed. According to the different operative approaches, the patients were divided into two groups: group A (36 cases received PKP via bilateral pedicle puncture) and group B (32 cases received PKP via unilateral pedicle paracentesis). There was no significant difference between the two groups in gender, age, fracture vertebra distribution, time from injury to operation, preoperative pain visual analogue scale (VAS) score, Oswestry disability index (ODI), and height of injured vertebra ( P>0.05). The operation time, intraoperative fluoroscopy times, and bone cement volume were recorded and compared between the two groups. The VAS score and ODI score were used to evaluate the effectiveness before operation, at 1 day and 6 months after operation; the height of injured vertebra was measured on the lateral X-ray film, and the recovery height of injured vertebra at 1 day after operation and the loss height of injured vertebra at 6 months after operation were calculated; the intraoperative and postoperative complications of the two groups were recorded.

Results

The operation time, intraoperative fluoroscopy times, and bone cement volume of group B were significantly less than those of group A ( P<0.05). All patients were followed up 10-35 months, with an average of 18 months. During the operation, there were 2 cases (5.56%) of cement leakage in group A and 9 cases (28.13%) in group B, showing significant difference ( χ ²=4.808, P=0.028). There was no adverse reactions of bone cement, iatrogenic spinal cord injury, infection of puncture port, or other complications in the two groups. During the follow-up period, there were 3 cases (8.3%) of adjacent vertebral fractures in group A and 2 cases (6.3%) in group B, showing no significant difference between the two groups ( χ ²=0.027, P=0.869). The height of injured vertebra of the two groups at 1 day and 6 months after operation were significantly improved when compared with preoperative ones ( P<0.05). There was no significant difference in the height of injured vertebrae and the recovery height of injured vertebra at 1 day after operation between the two groups ( P>0.05). However, at 6 months after operation, the height of injured vertebra in group B was significantly lower than that in group A ( P<0.05), and the loss height of injured vertebra in group B was significantly higher than that in group A ( P<0.05). The VAS score and ODI score at 1 day and 6 months after operation were significantly improved when compared with preoperative ones in both groups ( P<0.05), but there was no significant difference between the two groups ( P>0.05).

Conclusion

Both bipedicular and unipedicular PKP can obtain satisfactory effectiveness for the treatment of OVCF with posterior wall broken, but the former may have advantages of lower cement leakage rate and less height loss.

[Clinical study for preoperative traction on impact of osteonecrosis of femoral head in patients with femoral neck fractures]

OBJECTIVE

To explore the impact of preoperative traction on the osteonecrosis of the femoral head (ONFH) in patients with femoral neck fractures.

METHODS

Between February 2013 and May 2016, 120 patients with femoral neck fractures, who were treated with screw fixation, were collected. Sixty patients with fractures of Garden type Ⅰ and Ⅱ were non-displaced fracture group; 60 cases with fractures of Garden type Ⅲ and Ⅳ were displaced fracture group. The patients in 2 groups were randomly divided into traction and non-traction subgroups ( n=30). There was no significant difference in gender, age, injury mechanism, damage side, the time from injury to operation, and fracture classification between 2 subgroups ( P>0.05). Intracapsular pressure was recorded before operation. The quality of fracture reduction and the satisfaction ratio of screw implant were evaluated during operation. Visual analogue scale (VAS), Harris score, joint mobility, and the incidence of ONFH would be evaluated at 6 months, 1 year, and 2 years after operation.

RESULTS

All incisions of 2 groups healed by first intention after operation. There was no infection or deep vein thrombosis of lower extremity. All patients were followed up 2 years. In displaced and non-displaced fracture groups, the intracapsular pressure of traction subgroups were higher than that of non-traction group ( P<0.05); the differences of the quality of fracture reduction and the satisfaction ratio of screw implant were not significant ( P>0.05) between 2 subgroups. At 6 months, 1 year, and 2 years after operation, VAS scores were higher in traction subgroup than in non-traction subgroup ( P<0.05); and the joint mobility and Harris scores were lower in traction subgroup than in non-traction subgroup ( P<0.05). X-ray films showed all fractures healed. Except for the non-displaced group at 6 months, the incidences of ONFH were higher in traction subgroup than in non-traction subgroup at other time points ( P< 0.05).

CONCLUSION

Preoperative traction may increase the risk of ONFH, which can increase the intracapsular pressure and affect the blood supply of femoral head.

High-Sensitivity and Long-Life Microchannel Plate Processed by Atomic Layer Deposition

As a key component of electron multiplier device, a microchannel plate (MCP) can be applied in many scientific fields. Pure aluminum oxide (Al₂O₃) as secondary electron emission (SEE) layer were deposited in the pores of MCP via atomic layer deposition (ALD) to overcome problems such as high dark current and low lifetime which often occur on traditional MCP. In this paper, we systematically investigate the morphology, element distribution, and structure of samples by scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS), respectively. Output current of different thickness of Al₂O₃ was studied and an optimal thickness was found. Experimental tests show that the average gain of ALD-MCP was nearly five times better than that of traditional MCP, and the ALD-MCP showed better sensitivity and longer lifetime.

[Effect of functional exercise at different time and different immobilization positions on functional recovery of elbow joint with type C distal humeral fractures]

Objective

To investigate the effect of functional exercises at different time and different immobilization positions on the functional recovery of elbow joint with type C distal humeral fractures.

Methods

A total of 120 patients with type C distal humeral fractures admitted to the hospital between June 2013 and July 2015 were included in the study. They were randomly allocated to 3 groups, 40 patients in each group. Group A: functional exercises began immediately after the operation; Group B: the affected elbow was fixed at 90° flexion for 1 week and then began functional exercises after 1 week of immobilization; Group C: the affected elbow was fixed at 30° extension for 1 week and then began functional exercises after 1 week of immobilization. There was no significant difference in gender, age, fracture pattern, fracture side, injury time, and surgical approach between groups ( P>0.05).

Results

In groups A and B, 1 case had incision redness and swelling respectively, and the other incisions healed by first intention. Five patients occurred myositis ossificans in group A, 4 cases in group B, and 5 cases in group C. The incidence of complications in groups A, B, and C was 15.0% (6/40), 12.5% (5/40), and 12.5% (5/40), respectively. There was no significant difference between groups ( χ²=0.144, P=0.930). All patients were followed up 6-25 months, with an average of 9.8 months. At 2 weeks after operation, the Mayo elbow joint function score of group A was significantly higher than those of groups B and C ( P<0.05), and the visual analogue scale (VAS) of group A was significantly lower than those of groups B and C ( P<0.05). There was no significant difference between groups B and C ( P>0.05). At 6 months after operation, there was no significant difference in Mayo elbow joint function score and VAS score between groups ( P>0.05). At 2 weeks and 6 months after operation, the flexion and extension activities of elbow joint in groups A and C were better than that in group B ( P<0.05), and there was no significant difference between groups A and C ( P>0.05). There was no significant difference in forearm rotation between groups ( P>0.05). All fractures of 3 groups achieved clinical healing, and there was no significant difference in healing time between groups ( P>0.05).

Conclusion

Early functional exercises can relieve pain and obtain better elbow flexion and extesion activities after operation. The elbow joint fixed at 30° extension is better than at 90° flexion in elbow flexion and extension activitis.

Protein Arginine Methyltransferase PRMT1 Is Essential for Palatogenesis

Cleft palate is among the most common birth defects. Currently, only 30% of cases have identified genetic causes, whereas the etiology of the majority remains to be discovered. We identified a new regulator of palate development, protein arginine methyltransferase 1 (PRMT1), and demonstrated that disruption of PRMT1 function in neural crest cells caused complete cleft palate and craniofacial malformations. PRMT1 is the most highly expressed of the protein arginine methyltransferases, enzymes responsible for methylation of arginine motifs on histone and nonhistone proteins. PRMT1 regulates signal transduction and transcriptional activity that affect multiple signal pathways crucial in craniofacial development, such as the BMP, TGFβ, and WNT pathways. We demonstrated that Wnt1-Cre;Prmt1 ^fl/fl mice displayed a decrease in palatal mesenchymal cell proliferation and failure of palatal shelves to reach the midline. Further analysis in signal pathways revealed that loss of Prmt1 in mutant mice decreased BMP signaling activation and reduced the deposition of H4R3me2a mark. Collectively, our study demonstrates that Prmt1 is crucial in palate development. Our study may facilitate the development of a better strategy to interrupt the formation of cleft palate through manipulation of PRMT1 activity.

Smad6 Methylation Represses NFκB Activation and Periodontal Inflammation

The balance between pro- and anti-inflammatory signals maintains tissue homeostasis and defines the outcome of chronic inflammatory diseases such as periodontitis, a condition that afflicts the tooth-supporting tissues and exerts an impact on systemic health. The induction of tissue inflammation relies heavily on Toll-like receptor (TLR) signaling, which drives a proinflammatory pathway through recruiting myeloid differentiation primary response gene 88 (MyD88) and activating nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). TLR-induced production of proinflammatory cytokines and chemokines is reined in by anti-inflammatory cytokines, including the transforming growth factor β (TGFβ) family of cytokines. Although Smad6 is a key mediator of TGFβ-induced anti-inflammatory signaling, the exact mechanism by which TGFβ regulates TLR proinflammatory signaling in the periodontal tissue has not been addressed to date. In this study, we demonstrate for the first time that the ability of TGFβ to inhibit TLR-NFκB signaling is mediated by protein arginine methyltransferase 1 (PRMT1)-induced Smad6 methylation. Upon methylation, Smad6 recruited MyD88 and promoted MyD88 degradation, thereby inhibiting NFκB activation. Most important, Smad6 is expressed and methylated in the gingival epithelium, and PRMT1-Smad6 signaling promotes tissue homeostasis by limiting inflammation. Consistent with this, disturbance of Smad6 methylation exacerbates inflammation and bone loss in experimental periodontitis. The dissected mechanism is therapeutically important, as it highlights the manipulation of PRMT1-Smad6 signaling as a novel promising strategy to modulate the host immune response in periodontitis.

Osteoimmunology in orthodontic tooth movement

The skeletal and immune systems share a multitude of regulatory molecules, including cytokines, receptors, signaling molecules, and signaling transducers, thereby mutually influencing each other. In recent years, several novel insights have been attained that have enhanced our current understanding of the detailed mechanisms of osteoimmunology. In orthodontic tooth movement, immune responses mediated by periodontal tissue under mechanical force induce the generation of inflammatory responses with consequent alveolar bone resorption, and many regulators are involved in this process. In this review, we take a closer look at the cellular/molecular mechanisms and signaling involved in osteoimmunology and at relevant research progress in the context of the field of orthodontic tooth movement.

Three-dimensional reconstruction of laser-imploded targets from simulated pinhole images

This paper proposes an integral method to achieve a more accurate weighting matrix that makes very positive contributions to the image reconstruction in inertial confinement fusion research. Standard algebraic reconstruction techniques with a positivity constraint included are utilized. The final normalized mean-square error between the simulated and reconstructed projection images is 0.000365%, which is a nearly perfect result, indicating that the weighting matrix is very important. Compared with the error between the simulated and reconstructed phantoms, which is 2.35%, it seems that the improvement of the accuracy of the projection image does not mean the improvement of the phantom. The proposed method can reconstruct a simulated laser-imploded target consisting of 100×100×100 voxels.

[An animal model of Perthes disease and an experimental research of VEGF expression]

OBJECTIVE

To make a rabbit model of Perthes disease and to explore the change and its significance of VEGF expression in the femoral head.

METHODS

Twenty-four 3-month-old New Zealand rabbits (weighing 1.6-1.8 kg) were randomly divided into experimental group (n=16) and control group (n=8). A rabbit model of Perthes disease was made by excision of left ligamentum teres and retinacular blood supplies of femoral head. The gross appearance, X-ray film and histological observations were made and the immunohistochemistry and VEGF mRNA in situ hybridization were carried out 1, 2, 4, 8 weeks after operation.

RESULTS

The rabbit model of Perthes disease was made successfully; only 1 was infected 5 days after operation and was made quit. The gross appearance: The femoral heads had no necrosis changes in control group at every time. The femoral heads became coarse, tarnish and smaller, and even collapsed in experimental group. The HE staining observation: The femoral heads had no necrosis changes in control group at every time after operations. New vessels and granulation tissues grew into the necrosis part in the experimental group 4 weeks and 8 weeks after operations. New bone could be seen in repaired bone. Immunohistochemistry staining: In the epiphyseal cartilage of the femoral heads in control group, an intensive VEGF immunoreactivity (VEGF-IR) was found in the hypertrophic zone with a low level of VEGF-IR in the proliferative zone. At 1 week after operation, the percentage of VEGF+ cells in the proliferative zone of the femoral heads in experimental group was increased compared with that of the femoral heads in control group. The percentage of VEGF+ cells in the hypertrophic zone of the femoral heads in experimental group was significantly decreased compared with that of the femoral heads in control group. At 8 weeks after operation, VEGF-IR was observed throughout the epiphyseal cartilage surrounding the bony epiphysis in the femoral heads in experimental group. The percentage of VEGF-positive cells in the proliferative zone of the femoral heads in experimental group was significantly increased compared with that of the normal heads. The hypertrophic zone of the femoral heads in experimental group had a similar percentage of the VEGF+ cells to the femoral heads in control group when endochondral ossification was restored at 8 weeks. There were statistically significant differences in the ratios of VEGF+ cells in the proliferative zone of femoral head 1, 2, 4, 8 weeks after operations (P < 0.01); in the ratios of VEGF+ cells in the hypotrophic zone of femoral head 1, 2, 4 weeks after operations (P < 0.01) between experimental group and control group. In situ hybridization results: The results were similar to that of histology. VEGF mRNA expression in the hypertrophic zone of epiphyseal cartilage after necrosis were lower. VEGF mRNA expression in the proliferative zone of epiphyseal cartilage after necrosis increased. VEGF mRNA expression in the hypertrophic zone of epiphyseal cartilage in experimental group could be seen again after endochondral ossification was repaired.

CONCLUSION

It is possible that VEGF may act as a key regulator that couples angiogenesis, cartilage remodeling, and ossification after ischemic damage to restore endochondral ossification in the epiphyseal cartilage.

[Nondestructive quantitative analysis of Paracetamoli powder pharmaceutical by artificial neural network and near-infrared spectroscopy]

The application of artificial neural network for pharmaceutical nondestructive quantitative analysis were investigated. Real data set from near infrared reflectance spectra of Paracetamoli powder pharmaceutical were used to build up artificial network to predict unknown samples. The parameters affecting network were discussed. A new network evaluation criterion, the degree of approximation, was employed. Owing to good nonlinear multivariate calibration nature of ANN, the predicted results was reliable.

[A strain of influenza A H9N2 virus repeatedly isolated from human population in China]

OBJECTIVE

To understand the subtype of surface proteins (hemagglutinin and neuraminidase) and antigenic character of the isolate of influenza virus, as well as to know its origin.

METHODS

The virus isolation was performed on MDCK cells. The identification and antigenic analysis of the isolate were carried out with HI and NI tests. The serum antibody in population against the isolate was detected with HI and neutralization assays. The individual investigation of the patient from whom the H9N2 virus was isolated was followed.

RESULTS

The isolate was H9N2 subtype of influenza A virus. It was G9 like strain. Its antigenicity was different from that of H9N2 viruses which were previously found in humans, chickens and pigeons. The HI and neutralization titers to H9N2 virus in convalescent serum of the patient reached 1:400 and > or =1: 640, respectively. The HI antibody titer 1:25 to H9N2 virus was also detected in the serum of patient's mother.

CONCLUSIONS

The isolate is H9N2 subtype of influenza A virus and belongs to G9 like strain. The antigenic character of the isolate was different from that of H9N2 viruses found previously in humans, chickens and pigeons. The greatest possibility was that her mother had contacted with birds, especially chickens carrying H9N2 virus, then transmitted to her or she breathed in the air borne with H9N2 virus particles directly.

In-tube solid-phase microextraction coupled to capillary LC for carbamate analysis in water samples

Recently, the on-line sample preparation technique, intube solid-phase microextraction (SPME), was successfully implemented with a Hewlett-Packard 1100 HPLC system for analysis of carbamates in water samples. This paper describes the coupling of in-tube SPME to capillary LC and explores its utility as a sample preparation method in that format, relative to conventional LC. The Hewlett-Packard HPLC system was upgraded to a capillary LC system using commercially available accessories from LC Packings. The combination of in-tube SPME with a capillary LC system was expected to build on the merits of both in-tube SPME and the capillary LC to generate a sensitive method with an easy, effective, and efficient sample preparation. Due to the relatively large effective injection volume of the in-tube SPME technique (30-45 microL), on-column focusing was employed in order to achieve good chromatographic efficiency. Excellent sensitivity was achieved with very good method precision. For all carbamates studied, the RSD of retention time was between 0.5 and 0.8% under 4 microL/min microgradient conditions. The RSD of peak area counts was between 1.5 and 4.6%. The detection limits for all carbamates studied were less than 0.3 microg/L and, for carbaryl, just 0.02 microg/L (20 ppt). Compared with the conventional in-tube SPME/LC method, the LODs were lowered for carbaryl, propham, methiocarb, promecarb, chlorpropham, and barban, by factors of 24, 45, 42, 81, 62, and 56, respectively. The optimized method was successfully applied to the analysis of carbamates in surface water samples.

Automated in-tube solid-phase microextraction-high-performance liquid chromatography for carbamate pesticide analysis

In-tube solid-phase microextraction (SPME) is an automated version of SPME that can be easily coupled to a conventional HPLC autosampler for on-line sample preparation, separation and quantitation. It has been termed "in-tube" SPME because the extraction phase is coated inside a section of fused-silica tubing rather than coated on the surface of a fused-silica rod as in the conventional syringe-like SPME device. The new in-tube SPME technique has been demonstrated as a very efficient extraction method for the analysis of polar and thermally labile analytes. The in-tube SPME-HPLC method used with the FAMOS autosampler from LC Packings was developed for detecting polar carbamate pesticides in clean water samples. The main parameters relating to the extraction and desorption processes of in-tube SPME (selection of coatings, aspirate/dispense steps, selection of the desorption solvents, and the efficiency of desorption solvent, etc.) were investigated. The method was evaluated according to the reproducibility, linear range and limit of detection. This method is simple, effective, reproducible and sensitive. The relative standard deviation for all the carbamates investigated was between 1.7 and 5.3%. The method showed good linearity between 5 and 10000 microg/l with correlation coefficients between 0.9824 and 0.9995. For the carbamates studied, the limits of detection observed are lower than or similar to that of US Environmental Protection Agency or National Pesticide Survey methods. Detection of carbaryl present in clean water samples at 1 microg/l is possible.