High-Throughput GC/MS and HPLC/MS/MS Techniques for the Multiclass, Multiresidue Determination of 653 Pesticides and Chemical Pollutants in Tea

An effcient and sensitive method has been established for simultaneous determination of 653 pesticides in teas by GC/MS and HPLC/MS/MS. The method involved extraction with acetonitrile followed by cleanup using Cleanert-TPT SPE and subsequent identifcation and quantitation of 490 pesticides by GC/MS and 448 pesticides by HPLC/MS/MS. The LODs for pesticides determined by GC/MS were between 1.0 and 500 µg/kg, and those determined by HPLC/MS/MS were between 0.03 and 4820 µg/kg. At the low fortifcation levels of 0.01–100 µg/kg, the average recoveries of 94% of the pesticides determined by GC/MS were between 60 and 120%, 77% of which had an RSD below 20%. For 91% of pesticides determined by HPLC/MS/MS, the average recoveries were between 60 and 120%, 76% of which had an RSD below 20%. The paper also reports a novel SPE column, Cleanert TPT, which comprised graphitized carbon black (PestiCarb), polyamine silica, and amide polystyrene for purifying the tea samples. The results indicated good repeatiblity and reproducibility.

High-Throughput Analytical Techniques for the Determination of the Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VII: A GC-MS, GC-MS/MS, and LC-MS/MS Study of the Degradation Profiles of Pesticide Residues in Green Tea

GC-MS, GC-tandem MS (MS/MS), and LC-MS/MS were used to mathematically define the degradation profiles of pesticide residues in two field trials. Nineteen pesticides were studied in the first field trial and 11 in the second. The results of the field trials demonstrated that the degradation profiles of pesticide residues in green tea can be described with power functions to successfully estimate the amount of time, following pesticide application, pesticide residues appearing in tea in concentrations at and/or above the maximum residue limit (MRL) decrease to concentrations below the MRL. Stability tests on green tea samples stored at room temperature were conducted to determine whether pesticide-incurred green tea samples prepared according to the method used in the field trials would be suitable for the preparation of reference standards for laboratory-proficiency testing trials. This paper reports the results of a GC-MS, GC-MS/MS, and LC-MS/MS study, as well as the suitability of the samples prepared under these conditions for use as pesticide reference standards in tea analysis.

High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VI: Study of the Degradation of 271 Pesticide Residues in Aged Oolong Tea by Gas Chromatography-Tandem Mass Spectrometry and Its Application in Predicting the Residue Concentrations of Target Pesticides

The degradation rate of 271 pesticide residues in aged Oolong tea at two spray concentrations, named a and b (a < b), were monitored for 120 days using GC-tandem MS (GC-MS/MS). To research the degradation trends and establish regression equations, determination days were plotted as horizontal ordinates and the residue concentrations of pesticide were plotted as vertical ordinates. Here, we consider the degradation equations of 271 pesticides over 40 and 120 days, summarize the degradation rates in six aspects (A-F), and discuss the degradation trends of the 271 pesticides in aged Oolong tea in detail. The results indicate that >70% of the determined pesticides coincide with the degradation regularity of trends A, B, and E, i.e., the concentration of pesticide will decrease within 4 months. Next, 20 representative pesticides were selected for further study at higher spray concentrations, named c and d (d > c > b > a), in aged Oolong tea over another 90 days. The determination days were plotted on the x-axis, and the differences between each determined result and first-time-determined value of target pesticides were plotted on the y-axis. The logarithmic function was obtained by fitting the 90-day determination results, allowing the degradation value of a target pesticide on a specific day to be calculated. These logarithmic functions at d concentration were applied to predict the residue concentrations of pesticides at c concentration. Results revealed that 70% of the 20 pesticides had the lower deviation ratios of predicted and measured results.

High Throughput Analytical Techniques for the Determination and Confirmation of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea by GC/MS, GC/MS/MS, and LC/MS/MS: Collaborative Study, First Action 2014.09

Thirty laboratories from fom North and South America, Europe, and Asia participated in this AOAC collaborative study (15 from China; five from Germany; two each from Italy and the United States; and one each from the Republic of Korea, Canada, Spain, Japan, Belgium, and India). Participants represented government regulatory, commercial testing, university, research institute, and private laboratories. The single-laboratory validated (SLV) tea method was evaluated in the collaborative study to determine the recovery and reproducibility of the method under multilaboratory conditions. Since there were no restrictions regarding the type of analytical instrumentation to use for the analyses, laboratories used a combination of equipment that included GC/MS, GC/MS/MS, and LC/MS/MS instruments from 22 different manufacturers, 21 brands of GC and LC columns, 13 different GC temperature programming profiles, 11 LC gradient elution programs, and six different vendor manufactured SPE cartridges. Even though all the analytical performance parameters for all the 653 compounds had been determined in the SLV study, guidance was obtained from an expert review panel of the AOAC Method-Centric Committee on Pesticide Residues to conduct the multilaboratory collaborative study based on 20 selected compounds that can be analyzed by GC/MS and 20 compounds that can be analyzed by LC/MS/MS. Altogether, 560 samples covering the 40 selected pesticides were analyzed in the study. These samples included green tea and oolong tea samples fortified typically at the European Union maximum residue limit for regulatory guidance and compliance, aged tea samples incurred with 20 pesticides, and green tea and oolong tea samples incurred with five pesticides. The analysis of the 560 samples generated a total of 82 459 test results by the 30 participating laboratories. One laboratory failed to meet the proficiency requirements in the precollaborative study. Therefore, its data submitted for the collaborative study were excluded from further analysis and interpretation. The results presented are therefore the 6638 analytical results obtained from the 29 remaining laboratories, which included 1977 results generated by GC/MS, 1704 results by GC/MS/MS, and 2957 results by LC/MS/MS. It was determined after application of the Grubbs and Dixon tests for outliers to the data sets that there were 65 outlier results from the 1977 GC/MS results (3.3%), 65 outlier results from the 1704 GC/MS/MS results (3.8%), and 57 outlier results out of 2957 LC/MS/MS results (1.9%), representing 0.98, 0.98, and 0.86%, respectively, of the 6638 results generated in the study. Analysis with the AOAC statistical software package also confirmed that the method is rugged, and average recovery, average concentration, RSDr, RSDR, and HorRat values all meet recovery and reproducibility criteria for use in multiple laboratories. The Study Director is recommending this method for adoption as an AOAC First Action Official MethodSM.

High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea--Part V: A Comparative Study of the Influence of Tea Hydration on the Efficiency of Pesticide Multiresidue Determination Using Three Sample Preparation Methods and GC/MS/MS

This paper describes a comparative study of the influence of three sample preparation techniques (M1: hydration+oscillating extraction+partial extraction solution hexane partitioning cleanup; M2: hydration+oscillating extraction+overall extraction solution SPE cleanup; and M3: pure acetonitrile homogeneous extraction+overall extraction SPE cleanup) on the determination efficiency of 456 pesticide multiresidues in tea. First, it was discovered from the mathematical correlation equation of 329 pesticide recoveries established and log Kow values that the extraction efficiency of hydration method M1 has obvious correlation with pesticide log Kow, making the extraction efficiency of M1 take the shape of an arc trend line with a certain arc hanging down from both ends of polar pesticides and nonpolar pesticides. Second, regarding the M1 method, the interfering matter after co-extraction increased in large quantities, which markedly lowered the S/N of the target pesticides and method sensitivity, leading to an obvious decrease of the method efficiency. The fortification experiment of the uniform limit 0.010 mg/kg proved that with the M1 hydration method there are 23 pesticides with recoveries between 70 and 120% and RSD<20%, accounting for only 5.0%, while with nonhydration method M3 there are 229 pesticides, making up 50%.

High-Throughput Analytical Techniques for Multiresidue, Multiclass Determination of 653 Pesticides and Chemical Pollutants in Tea-Part IV: Evaluation of the Ruggedness of the Method, Error Analysis, and Key Control Points of the Method

A 3 month study was conducted on the ruggedness of a multiresidue method for accuracy and stability. The results indicate that in terms of Youden pair ratios of 201 pesticide aged tea samples falling approximately within 1.00-1.20 of the ratio of theoretical spraying concentrations, the differences do not exceed 5% for percentages made up by ratios of the fixed values obtained by two kinds of instruments for two teas and those made up by 18 circular determinations. However, regarding two kinds of SPE cartridges, the Cleanert TPT cartridge is higher than the ENVI-CARB+primary secondary amine (PSA) cartridge by 10%. Pertaining to RSD values of "parallel samples" and whether it is green tea or Woolong tea, the percentages of RSD≤15% values of the parallel samples all exceed 88%. Whether it is the first or circular determination for two teas and analytical results from two kinds of instruments, the percentages of RSD≤15% values have a difference of less than 6%, while the TPT cartridge is better than ENVI-CARB+PSA by above 6% for the two cartridges. Concerning RSDs of Youden pair ratios, RSD≤15% values have a proportion exceeding 85% for both green tea and Woolong tea, and the percentage is greater than 87% whether it is for two kinds of SPE cartridges or two kinds of instruments. In terms of Youden pair ratios and the classified statistical analysis of the ruggedness data of parallel samples, the proportion of RSD≤15% values of Youden pair ratios is 8% higher for the TPT cartridge than the ENVI-CARB+PSA cartridge; the proportion of RSD≤15% values of parallel samples is 6.2% higher for the TPT cartridge than the ENVI-CARB+PSA cartridge. Data show no marked differences for two teas and two kinds of instruments. A comparison of the aforementioned aspects finds that good ruggedness was obtained with both SPE cleanup methods, and the results from the TPT cartridge are better than those from the ENVI-CARB+PSA cartridge.

Determination of trace elements in rape honey and its corresponding rape flower and stem by ICP-MS

The determination of 10 trace elements including Na, Mg, P, K, Ca, Mn, Zn, Rb, Sr and Ba, in rape honey and its corresponding rape flower and stem gathered from nine sampling sites was carried out by inductively coupled plasma mass spectrometry (ICP-MS). The contents of K, P, Ca, Mg and Na were obviously higher than Zn, Rb, Mn, Sr and Ba in rape honey, rape flower and rape stem. For the first five elements, K had the highest content, followed by P, Ca, Mg and Na. However, the order of content for latter five elements was not the same in different matrixes. The contents of K, P and Ca were all higher than 1 000 mg x kg(-1) in rape flower and rape stem, while the contents of P, Ca, Mn, Zn and Rb in rape flower were slightly higher than in rape stem. It can be concluded that rape flower showed slightly higher concentrating ability for trace elements than rape stem. Based on these results, radar chart was firstly applied to research the relationship of 10 elements in rape honey and its corresponding rape flower and stem. The aim of the present work was to study the possibility of using trace elements contents in rape flower to trace the geographical and botanical origin of honey instead of rape honey. It can be found from the radar charts that the stars of rape honey, rape flower and rape stem were similar to each other. This research not only provides the basic data of trace elements in comparative study of rape honey, but also gives scientific basis for tracing the origin of rape honey according to the trace elements in corresponding rape flower that replaces those of rape honey.

High-throughput GC/MS and HPLC/MS/MS techniques for the multiclass, multiresidue determination of 653 pesticides and chemical pollutants in tea

An efficient and sensitive method has been established for simultaneous determination of 653 pesticides in teas by GC/MS and HPLC/MS/MS. The method involved extraction with acetonitrile followed by cleanup using Cleanert-TPT SPE and subsequent identification and quantitation of 490 pesticides by GC/MS and 448 pesticides by HPLC/MS/ MS. The LODs for pesticides determined by GC/MS were between 1.0 and 500 microg/kg, and those determined by HPLC/MS/MS were between 0.03 and 4820 microg/kg. At the low fortification levels of 0.01-100 microg/kg, the average recoveries of 94% of the pesticides determined by GC/MS were between 60 and 120%, 77% of which had an RSD below 20%. For 91% of pesticides determined by HPLC/MS/MS, the average recoveries were between 60 and 120%, 76% of which had an RSD below 20%. The paper also reports a novel SPE column, Cleanert TPT, which comprised graphitized carbon black (PestiCarb), polyamine silica, and amide polystyrene for purifying the tea samples. The results indicated good repeatiblity and reproducibility.

Simultaneous determination of 346 multiresidue pesticides in grapes by PSA-MSPD and GC-MS-SIM

The article demonstrates a method of simultaneous determination for 352 pesticide residues in grapes using primary-secondary amine (PSA) matrix solid phase dispersion (MSPD) cleanup and gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). Grape samples (15 g) were mixed with 6 g of anhydrous magnesium sulfate and 1.5 g of sodium chloride, and then extracted with acetonitrile (15 mL) and cleaned up with 0.3 g of dispersive PSA. The analytes were determined by GC-MS-SIM. Four injections for one sample were acquired to cover a total of 352 pesticides. The limit of detection (LOD) for the method was 0.0017-0.2667 mg kg(-1), depending on the nature of compounds. The linear correlation coefficient (r) was equal to or greater than 0.95; at low, medium, and high fortification levels, recoveries ranged from 45% to 136% for 352 pesticides, among which the recoveries between 60%-120% accounted for 97%. The pesticides for which the relative standard deviations (RSD) were equal to or below 20% accounted for 95%. A positive of nine varieties of grape samples was detected out, one of which was abtained Changli city, Hebei province, China. Pesticides were identified by the retention time, molecule ions, fragment ions, and the abundance ratio of the selected ions. The analytical method was rugged, quick, cheap and effective, and suitable for the determination of a wide scope of 346 pesticides in grapes.

Effect of manual acupuncture and transcutaneous electrical nerve stimulation on the H-reflex

Several studies find that manual acupuncture and transcutaneous electrical nerve stimulation (TENS) are via different mechanisms and generate different effect on the central nervous system, therefore, the aim of the present study was to compare the effect of manual acupuncture (MA) and TENS on the spinal cord using H-reflex recordings. A total of 13 healthy adult volunteers were studied. The electrical stimuli were delivered to the posterior tibial nerve transcutaneously at the left popliteal fossa to evoke the soleus H-reflex. MA, 2Hz TENS, 100 Hz TENS, respectively, was applied to the surface of the right first dorsal interosseous muscle exactly at the Hegu acupoint (LI.4). Four assessments were performed randomly, separated by an interval of at least three days in all the subjects as follows: 1) Control assessment: a pair of electrodes placed on the surface of the right Hegu acupoint (LI.4), but no electrical stimulation was delivered throughout the test; 2) MA assessment: MA was done at the right Hegu acupoint (LI.4) for 15 minutes; 3) TENS assessment at 2Hz: electrical stimulation (40 mA in intensity) at 2Hz was applied to the surface of the right Hegu acupoint (LI.4) for 15 minutes; 4) TENS assessment at 100 Hz: electrical stimulation (20 mA in intensity) at 100 Hz was applied to the surface of the right Hegu acupoint (LI.4) for 15 minutes. Each assessment was divided into three periods as follows: 1) Baseline period: H-reflexes recorded prior to MA or TENS; 2) TENS period: six H-reflex recordings after MA or TENS for a duration of 4-5 min, 9-10 min and 14-15 min, respectively; 3) Post TENS period: H-reflex recordings of 6 after TENS period 4-5 min and 9-10 min, respectively. Our results indicate that both 2Hz TENS and 100 Hz TENS increased the amplitude of the H-reflex, and that these increases may be retained longer with 100 Hz TENS than with 2 Hz TENS, whereas MA could not increase the amplitude of the H-reflex. MA, TENS at 2 Hz or 100 Hz didn't change the latencies of the H-reflexes. We conclude that both 2Hz and 100 Hz TENS increased the amplitude of the H-reflex, suggesting that TENS enhances the excitability of the motoneuron pool in the spinal cord, and 100 Hz TENS has a greater effect than 2Hz TENS, whereas MA was not similar effect to TENS on spinal cord.

Changes of pulse rate and skin temperature evoked by electroacupuncture stimulation with different frequency on both Zusanli acupoints in humans

The purpose of this study was to investigate the effect of electroacupuncture stimulation (EA) of different frequency on pulse rate and skin temperature. Sixteen healthy male medical student volunteers received EA of 2 Hz, and 100 Hz, respectively on the both Zusanli acupoints (St-36) while resting. Their pulse rates were measured on the middle finger, and skin temperature was taken between the thumb and index finger before, during, and after EA stimulation. Each test took 35 minutes. The initial 10 min were defined as baseline period (no EA), the following 15 min as the EA period and the last 10 min as the post-EA period. Three assessments were performed on each subject as follows: A) control assessment: no EA was done throughout the test; B) 2 Hz EA assessment: 2 Hz EA was applied to both Zusanli acupoints during the EA period; and C) 100 Hz EA assessment: 100 Hz EA was applied to both Zusanli acupoints during the EA period. Our results indicate that both 2 Hz EA and 100 Hz EA decreased pulse rates during the EA period, and these changes remained throughout the post-EA period in 2 Hz EA assessment, but not in 100 Hz EA assessment. Both 2 Hz and 100 Hz EA resulted in decreases of skin temperature during the EA period. Our conclusions are that 2 Hz EA and 100 Hz EA applied to both Zusanli acupoints resulted in the decrease of pulse rate, which possibly evoked greater parasympathetic nerve activity on heart beats. 2 Hz EA had a more sustained effect on heart beats than 100 Hz EA. Decreased skin temperatures in the EA period may have resulted from cutaneous vasoconstriction caused by EA induced sympathetic stress response, suggesting EA at least remains for 15 min in clinical application.

Cerebral cortex participation in the physiological mechanisms of acupuncture stimulation: a study by auditory endogenous potentials (P300)

Although acupuncture has traditionally used the acupoints formula to treat diseases, the physiological mechanisms involved and the effectiveness of therapy remain unclear. This study investigated the physiological mechanism(s) and response to acupuncture stimulation using the acupoints formula. Scalp-recorded potentials P300 were evoked by auditory stimulation of non-target and target in 13 normal adult volunteers. Latencies and amplitudes were measured. Three assessments were performed in each subject over a period of at least one week. Each assessment was divided into a control period with no acupuncture stimulation, followed by an acupuncture period and then a post-acupuncture period. Acupuncture needles were inserted into the body as follows: 1) non-acupoint: acupuncture needles were inserted 2 cm lateral to both Zusanli acupoints; 2) acupoint: acupuncture needles were inserted into both Zusanli acupoints; 3) acupoints formula: acupuncture needles were inserted into both Zusanli and Shousanli acupoints. Our results showed that both acupoint and acupoints formula assessments resulted in a significant decrease of P300 amplitudes during the acupuncture and post-acupuncture periods. However, there was significant difference in P300 amplitudes in the non-acupoint assessment during these periods. P300 changes in latencies and amplitudes were not significantly different between the acupoint assessment and the acupoints formula assessment. We concluded that acupuncture stimulation of both Zusanli acupoints resulted in a decrease of P300 amplitudes, suggesting the involvement of the cerebral cortex in sensory interaction when simultaneous sensations of the two types are received. No similar changes were observed in the non-acupoint assessment, which have been suggested to be related to so-called acupoint specificity. Results obtained using the acupoints formula were not significantly different from those using acupoints alone. These findings suggested that neuropsychological effects from stimulation of Zusanli acupoints and Shousanli acupoints are different.