Average Relative Standard Deviation Research Articles

Occurrence, distribution, and ecological risk assessment of potentially toxic elements in surface sediments of Lake Awassa and Lake Ziway, Ethiopia

Microwave-assisted acid digestion and modified aqua regia (HNO3:HCl:HF:H3BO3) leaching techniques were used for the determination of 15 potentially toxic elements (V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Se, Ag, Cd, Sn, Hg and Pb) in sediment samples from Lake Awassa and Lake Ziway, Ethiopia. The digests were subsequently analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Mercury was directly determined in the solid samples using an elemental mercury analyzer. The precision and accuracy of the digestion procedures were verified using certified reference materials. The experimental results were in good agreement with the certified values (P < 0.05) and the recoveries were quantitative (>90%). The average relative standard deviations were below 10%. There is significant correlation between the two lakes at the 0.01 level (2-tailed). Using the sediment quality guidelines, both lakes are heavily polluted with Zn and some of the sites are heavily polluted with Cu, Ni and Pb. Based on effect range low (ERL) – effect range medium (ERM), in both lakes for Ag were greater than the ERM, indicating that the areas could be toxic to aquatic organisms, while for Cr, Cu, As and Hg the values were less than ERL.

Detection Dicyandiamide in Environmental Water by Liquid Chromatography–Mass Spectrometry Combined with Solid Phase Extraction Method

A new analytical method has been developed to determine dicyandiamide in environmental water. Residues of dicyandiamide were extracted from the environmental water samples by solid phase extraction using Waters Sep-Pak AC2 Cartridge. The extraction procedure condition (included loading, washing, and eluting) of flow rate of 1.0 mL/min, and dicyandiamide was eluted with 20 mL of acetonitrile and methanol (v/v = 60:40) mixture solution, and preconcentrated using nitrogen evaporation followed by analysis with liquid chromatography–mass spectrometry. Laboratory method validation data was collected in water samples at concentration down to 1.0 ng/mL. Average recovery and relative standard deviation using spiked calibration standard curve were 89% and 2.9%, respectively. The method provides a effective approach to monitor the contaminant in environmental water samples.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the direct detection of 2-monochloropropanediol (2-MCPD) esters in edible oils.

A new analytical method has been developed and validated for the detection and quantification of 2-monochloropropanediol (2-MCPD) esters in edible oils. The target compounds are potentially carcinogenic contaminants formed during the processing of edible oils. As the 2-MCPD esters that occur most frequently in refined edible oils were not commercially available, standards were synthesized with identity and purity (95+%) confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and (1)H NMR. Target analytes are separated from edible oil matrices using a two-step solid-phase extraction (SPE) procedure. The extracts are then analyzed using LC-MS/MS with electrospray ionization (ESI). The method has been validated for 11 2-MCPD diesters and 3 2-MCPD monoesters in soybean oil, olive oil, and palm oil using an external calibration curve. The ranges of average recoveries and relative standard deviations (RSD) across the three oil matrices at three spiking concentrations are 79-106% (3-13% RSD) for the 2-MCPD diesters and 72-108% (4-17% RSD) for the 2-MCPD monoesters, with limits of quantitation at or below 30 ng/g for the diesters and 90 ng/g for the monoesters.

Anodic stripping voltammetry of gold nanoparticles at boron-doped diamond electrodes and its application in immunochromatographic strip tests

Anodic stripping voltammetry (ASV) of colloidal gold-nanoparticles (AuNPs) was investigated at boron-doped diamond (BDD) electrodes in 50mM HClO4. A deposition time of 300s at−0.2V (vs. Ag/AgCl) was fixed as the condition for the ASV. The voltammograms showed oxidation peaks that could be attributed to the oxidation of gold. These oxidation peaks were then investigated for potential application in immunochromatographic strip tests for the selective and quantitative detection of melamine, in which AuNPs were used as the label for the antibody of melamine. Linear regression of the oxidation peak currents appeared in the concentration range from 0.05–0.6μg/mL melamine standard, with an estimated LOD of 0.069μg/mL and an average relative standard deviation of 8.0%. This indicated that the method could be considered as an alternative method for selective and quantitative immunochromatographic applications. The validity was examined by the measurements of melamine injected into milk samples, which showed good recovery percentages during the measurements.

Detection of Hepatitis B virus antigen from human blood: SERS immunoassay in a microfluidic system

A highly sensitive immunoassay utilizing surface-enhanced Raman scattering (SERS) has been developed with a new Raman reporter and a unique SERS-active substrate incorporated into a microfluidic device. An appropriately designed Raman reporter, basic fuchsin (FC), gives strong SERS enhancement and has the ability to bind both the antibody and gold nanostructures. The fuchsin-labeled immuno-Au nanoflowers can form a sandwich structure with the antigen and the antibody immobilized on the SERS-active substrate based on Au–Ag coated GaN. Our experimental results indicate that this SERS-active substrate with its strong surface-enhancement factor, high stability and reproducibility plays a crucial role in improving the efficiency of SERS immunoassay. This SERS assay was applied to the detection of Hepatitis B virus antigen (HBsAg) in human blood plasma. A calibration curve was obtained by plotting the intensity of SERS signal of FC band at 1178cm−1 versus the concentration of antigen. The low detection limit for Hepatitis B virus antigen was estimated to be 0.01IU/mL. The average relative standard deviation (RSD) of this method is less than 10%. This SERS immunoassay gives exact results over a broad linear range, reflecting clinically relevant HBsAg concentrations. It also exhibits high biological specificity for the detection of Hepatitis B virus antigen

Determination of trace analytes based on diffuse reflectance spectroscopic techniques: development of a multichannel membrane filtration-enrichment device to improve repeatability

The determination of trace analytes based on membrane filtration-enrichment and diffuse reflectance spectroscopic techniques has gained increasing interest in the past decade due to its simplicity, rapidity and high sensitivity. However, poor repeatability primarily attributed to the differences of characteristics between membrane filters limits the development of this technique. In the current study, a simple and effective multichannel device is specially designed for the membrane filtration-enrichment process. The device is able to enrich six samples simultaneously on different positions of a membrane filter and allows the spectroscopic measurement of six samples with only one membrane filter. The proposed approach avoided the effects caused by the nonuniform membrane filters on the performance of the enrichment process. Accuracy and repeatability have been improved significantly for the subsequent on-line spectroscopic detection. A case study was carried out to assess this method utilizing the carcinogenic dye rhodamine B (RhB) as a model analyte. Under the optimal conditions, linearity of the calibration curve based on the Kubelka–Munk function was achieved in the concentration range of 2–30 μg L−1 with the correlation coefficient (R2) of 0.9924. Good repeatability was achieved with three average relative standard deviation (RSD) values of 3.6%, 3.8% and 3.8% corresponding to the solutions of 30, 10 and 5 μg L−1 RhB, respectively. The presented method was successfully employed to quantify RhB in soft drink and river water samples.

Application of a Spectrum Standardization Method for Carbon Analysis in Coal Using Laser-Induced Breakdown Spectroscopy (LIBS)

Measurement of coal carbon content using laser-induced breakdown spectroscopy (LIBS) is limited by its low precision and accuracy. A modified spectrum standardization method was proposed to achieve both reproducible and accurate results for the quantitative analysis of carbon content in coal using LIBS. The proposed method used the molecular emissions of diatomic carbon (C2) and cyanide (CN) to compensate for the diminution of atomic carbon emissions in high volatile content coal samples caused by matrix effect. The compensated carbon line intensities were further converted into an assumed standard state with standard plasma temperature, electron number density, and total number density of carbon, under which the carbon line intensity is proportional to its concentration in the coal samples. To obtain better compensation for fluctuations of total carbon number density, the segmental spectral area was used and an iterative algorithm was applied that is different from our previous spectrum standardization calculations. The modified spectrum standardization model was applied to the measurement of carbon content in 24 bituminous coal samples. The results demonstrate that the proposed method has superior performance over the generally applied normalization methods. The average relative standard deviation was 3.21%, the coefficient of determination was 0.90, the root mean square error of prediction was 2.24%, and the average maximum relative error for the modified model was 12.18%, showing an overall improvement over the corresponding values for the normalization with segmental spectrum area, 6.00%, 0.75, 3.77%, and 15.40%, respectively.

Characteristics and sources of atmospheric mercury speciation in a coastal city, Xiamen, China

Semi-continental monitoring of gaseous elemental mercury (GEM), particulate mercury (Hgp), and reactive gaseous mercury (RGM) was conducted in the Institute of Urban Environment, CAS in Xiamen, China from March 2012 to February 2013. The average concentrations and relative standard deviations (RSD) were 3.50 (34.6%) ngm−3, 174.41 (160.9%) pgm−3, and 61.05 (113.7%) pgm−3 for GEM, Hgp, and RGM, respectively. The higher concentrations of GEM and Hgp were observed in spring and winter months, indicating the combustion source, while RGM showed the different seasonal variation with highest concentration in spring and the minimum value in winter. The concentrations of Hg species were generally elevated in nighttime and low in daytime to reflect the diurnal changes in meteorology, especially the mixing condition of the air masses. The high Hg concentrations were observed in SWW–NW sectors due to calm wind while the low levels in NE–SE due to high speed wind, and the amplitude was much larger for Hgp and RGM. Backward trajectories calculation indicated that summer air masses were much more from ocean with lower Hg while the air masses were mainly from inland area in other seasons. Principal component analysis suggested that combustion and road traffic emissions were the dominant anthropogenic mercury sources for the study area, and the temporal distribution of atmospheric mercury was mainly the result of climatological change.

Analytical Use of Prussian Blue to the Assay of Hydroxyurea in Capsule

The research involves a simple and sensitive spectrophotometric method for the determination of hydroxyurea in aqueous solution by two steps. The first step depends on the reduction of ferric ions by hydroxyurea to ferrous ions, and in the second step the later reacts with potassium ferricyanide to form a stable prussian blue. This dye is soluble in water and gives absorption maxima at 700 nm. Beer's law was obeyed over the range 1-100 µg of hydroxyurea per 20 ml (i.e 0.05 – 5 ppm) with a corresponding molar absorptivity of 2.4×1041.mol-1.cm-1, Sandell's sensitivity index of 0.0032 µg cm-2 and average relative standard deviation of ± 0.33%, depending on the concentration level, and the t-test value comes to be (0.91) which is less than its table value (2.361) at a confidence level of 95% for 8 degrees of freedom which applies credibility to the suggested method. The method had been applied successfully to determination of hydroxyurea in capsule.

On-line detection and quantification of trace impurities in vaporisable samples by direct liquid introduction process mass spectrometry

A thermal vaporiser has been designed for analysis of liquid streams by a process mass spectrometer normally used for gas analysis. Concentrations of benzene, toluene and o-xylene at mg kg−1 levels in ethanol were determined from continuous vaporisation of the liquid. Ions with m/z values of 39, 57, 73, 77, 78, 91, 92 and 106 were selected and the optimal regression model (multiple linear regression with mean-centring) was found using an automated design of experiments approach to calibration model selection. It was discovered that the linearity of the response allowed excellent calibration to be performed using only four standards (at 0 and 110 mg kg−1 for each of the three analytes) and that there were minimal inter-analyte interferences. The detection limit of benzene, toluene and o-xylene was 0.5, 0.8 and 0.5 mg kg−1, respectively. Average differences between the actual and predicted concentrations, expressed as a percentage of the actual concentrations, for 27–82 mg kg−1 of benzene, toluene and o-xylene were 0.5–1.4%, 0.0–0.4% and 0.3–1.6%, respectively, while the average relative standard deviations were 1.3–2.6%, 1.0–2.5% and 1.1–2.3%, respectively. Detection of 3 mg kg−1 changes in the concentration of each of the analytes (at the 36 mg kg−1 level) was also demonstrated, indicating the sensitivity of the technique and the potential ability of the procedure to detect minor deviations in the specification of process streams from continuous analysis.

Insights from analysis for harmful and potentially harmful constituents (HPHCs) in tobacco products

A total of 20 commercial cigarette and 16 commercial smokeless tobacco products were assayed for 96 compounds listed as harmful and potentially harmful constituents (HPHCs) by the US Food and Drug Administration. For each product, a single lot was used for all testing. Both International Organization for Standardization and Health Canada smoking regimens were used for cigarette testing. For those HPHCs detected, measured levels were consistent with levels reported in the literature, however substantial assay variability (measured as average relative standard deviation) was found for most results. Using an abbreviated list of HPHCs, statistically significant differences for most of these HPHCs occurred when results were obtained 4–6months apart (i.e., temporal variability). The assay variability and temporal variability demonstrate the need for standardized analytical methods with defined repeatability and reproducibility for each HPHC using certified reference standards. Temporal variability also means that simple conventional comparisons, such as two-sample t-tests, are inappropriate for comparing products tested at different points in time from the same laboratory or from different laboratories. Until capable laboratories use standardized assays with established repeatability, reproducibility, and certified reference standards, the resulting HPHC data will be unreliable for product comparisons or other decision making in regulatory science.

Precise determination of hypochlorite in commercial bleaches with established traceability using automatic potentiometric titration

A measurement procedure is proposed for precisely determining hypochlorite in commercial bleaches, with established traceability and a full description of its uncertainty sources. The procedure is based on automatic volumetric titration with potentiometric detection and was evaluated in the analysis of several commercial bleach samples, with Na-hypochlorite mass fractions in the range 0.002–0.027 g g−1, with an average expanded uncertainty (k = 2) of 0.00027 g g−1 and an average relative standard deviation between measurement triplicates of 0.36 %. Compared with a standard procedure based on manual volumetric titration with visual colorimetric detection, the improved procedure produced equivalent results with a lower average expanded uncertainty (0.00029 g g−1 as compared to 0.0015 g g−1 for the standard procedure). This was related to better precision of the volume measurement using an automatic buret and to better precision of the titration endpoint determination using potentiometric detection. Compared with other studies reported in the literature, the improved procedure presented a lower average relative standard deviation between measurement replicates (0.36 % as compared to 1.00–11.53 %).

Screening and quantification of pesticide residues in fruits and vegetables making use of gas chromatography-quadrupole time-of-flight mass spectrometry with atmospheric pressure chemical ionization.

An atmospheric pressure chemical ionization source has been used to enhance the potential of gas chromatography coupled with quadrupole time-of-flight (QTOF) mass spectrometry (MS) for screening and quantification purposes in pesticide residue analysis. A screening method developed in our laboratory for around 130 pesticides has been applied to fruit and vegetable samples, including strawberries, oranges, apples, carrots, lettuces, courgettes, red peppers, and tomatoes. Samples were analyzed together with quality control samples (at 0.05 mg/kg) for each matrix and for matrix-matched calibration standards. The screening strategy consisted in first rapid searching and detection, and then a refined identification step using the QTOF capabilities (MS(E) and accurate mass). Identification was based on the presence of one characteristic m/z ion (Q) obtained with the low collision energy function and at least one fragment ion (q) obtained with the high collision energy function, both with mass errors of less than 5 ppm, and an ion intensity ratio (q/Q) within the tolerances permitted. Following this strategy, 15 of 130 pesticides were identified in the samples. Afterwards, the quantitation capabilities were tested by performing a quantitative validation for those pesticides detected in the samples. To this aim, five matrices were selected (orange, apple, tomato, lettuce, and carrot) and spiked at two concentrations (0.01 and 0.1 mg/kg), and quantification was done using matrix-matched calibration standards (relative responses versus triphenyl phosphate used as an internal standard). Acceptable average recoveries and relative standard deviations were obtained for many but not all pesticide-matrix combinations. These figures allowed us to perform a retrospective quantification of positives found in the screening without the need for additional analysis. Taking advantage of the accurate-mass full-spectrum data provided by QTOF MS, we searched for a higher number of compounds (up to 416 pesticides) in a second stage by performing extra data processing without any new sample injection. Several more pesticides were detected, confirmed, and/or tentatively identified when the reference standard was unavailable, illustrating in this way the potential of gas chromatography-QTOF MS to detect pesticides in addition to the ones targeted in quantitative analysis of pesticides in food matrices.

Fermentation in 24-well plates is an efficient screening platform for filamentous fungi.

Fermentation by filamentous fungi in Erlenmeyer flasks is a favoured method for comparing different fermentation conditions. However, significant inter-flask variation often occurs when using Erlenmeyer flasks, which makes the comparison of fermentation product levels less reliable. We have investigated the use of a 24-well plate method for citric acid, ethanol and glycerol batch fermentation using the filamentous fungi Aspergillus carbonarius and compared the relative standard deviation (RSD) from sextuplicates obtained using Erlenmeyer flasks and 24-well plates. The production levels using the Erlenmeyer flasks showed a combined average RSD of 29%, which is two and a half-fold higher than what was measured using the 24-well plates showing an average RSD of 12%. We conclude that fermentation in 24-well plates is a more reliable screening method for metabolite production by filamentous fungi and possibly for screening metabolites in general. Fermentation studies with filamentous fungi and especially screening experiments often struggle with high inter-vessel variations in metabolite production. This study compares two different types of frequently used screening methods namely batch fermentation in Erlenmeyer flasks with batch fermentation in 24-well plates. The results demonstrate that the variance potentially can be reduced two and a half-fold using 24-well plates leading to improved resolution when testing the impact of varying fermentation parameters on product formation.

Cold column trapping-cloud point extraction coupled to high performance liquid chromatography for preconcentration and determination of curcumin in human urine

A cold column trapping-cloud point extraction (CCT-CPE) method coupled to high performance liquid chromatography (HPLC) was developed for preconcentration and determination of curcumin in human urine. A nonionic surfactant, Triton X-100, was used as the extraction medium. In the proposed method, a low surfactant concentration of 0.4% v/v and a short heating time of only 2min at 70°C were sufficient for quantitative extraction of the analyte. For the separation of the extraction phase, the resulted cloudy solution was passed through a packed trapping column that was cooled to 0 °C. The temperature of the CCT column was then increased to 25°C and the surfactant rich phase was desorbed with 400μL ethanol to be directly injected into HPLC for the analysis. The effects of different variables such as pH, surfactant concentration, cloud point temperature and time were investigated and optimum conditions were established by a central composite design (response surface) method. A limit of detection of 0.066mgL−1 curcumin and a linear range of 0.22–100mgL−1 with a determination coefficient of 0.9998 were obtained for the method. The average recovery and relative standard deviation for six replicated analysis were 101.0% and 2.77%, respectively. The CCT-CPE technique was faster than a conventional CPE method requiring a lower concentration of the surfactant and lower temperatures with no need for the centrifugation. The proposed method was successfully applied to the analysis of curcumin in human urine samples.

Simultaneous determination of ethyl carbamate, chloropropanols and acrylamide in fermented products, flavoring and related foods by gas chromatography–triple quadrupole mass spectrometry

A simultaneous determination method was established by gas chromatography–triple quadrupole mass spectrometry (GC–MS/MS) for ethyl carbamate, acrylamide and chloropropanols (1,3-dichloropropane-2-ol (1,3-DCP), 2,3-dichloropropane-1-ol (2,3-DCP), 3-monochloropropane-1,2-diol (3-MCPD) and 2-monochloropropane-1,3-diol (2-MCPD)) in fermented products, flavoring and related foods. Ethyl carbamate-d5, 1,3-DCP-d5, 3-MCPD-d5 and acrylamide-d3 were used as isotope internal standards for ethyl carbamate, DCPs, MCPDs and acrylamide, respectively. The sample was extracted and cleaned in one single step by a combined clean-up column packed with Extrelut™ NT and primary secondary amine (PSA). The concentrated extract was directly injected without derivatization, separated by an Innowax (cross-bonded polyethylene glycol) capillary column and measured by GC–MS/MS. The calculated limits of detection (LODs) in the sample matrix were 1.8, 1.0, 2.1, 5.3, 5.1 and 5.0 μg kg−1 for ethyl carbamate, 1,3-DCP, 2,3-DCP, acrylamide, 3-MCPD and 2-MCPD, respectively. The average recoveries in different matrices at three spiked concentration levels (20, 100 and 400 μg kg−1) were 88.6–112, 92.6–103, 92.1–106, 86.2–107, 90.4–109 and 91.0–105% with relative standard deviations (RSDs) (Average RSDs in bracket) of 4.4–10.2 (6.4%), 3.7–7.3 (5.4%), 3.9–7.7 (5.2%), 4.4–9.3 (6.4%), 4.1–10.7 (6.3%) and 3.7–7.9% (5.6%), respectively. Two to six contaminants were simultaneously found in some of the soy sauce samples. Ethyl carbamate, acrylamide, 3-MCPD and 2-MCPD were found in the instant noodle flavoring. Trace levels (<12 μg kg−1) of ethyl carbamate, acrylamide or 3-MCPD were detected in tomato sauce and salad dressing. Both ethyl carbamate and acrylamide were found in some of the curry products and Chinese yellow rice wine. Only ethyl carbamate was found in beer and grape wine.

High‐performance thin layer chromatography to assess pharmaceutical product quality

To assess the sustainability, robustness and economic advantages of high-performance thin layer chromatography (HPTLC) for quality control of pharmaceutical products. We compared three laboratories where three lots of cotrimoxazole tablets were assessed using different techniques for quantifying the active ingredient. The average assay relative standard deviation for the three lots was 1.2 with a range of 0.65-2.0. High-performance thin layer chromatography assessments are yielding valid results suitable for assessing product quality. The local pharmaceutical manufacturer had evolved the capacity to produce very high quality products.

Direct Electrochemical Tyrosinase Biosensor based on Mesoporous Carbon and Co3O4 Nanorods for the Rapid Detection of Phenolic Pollutants

AbstractA novel tyrosinase (Tyr) biosensor based on a graphitized ordered mesoporous carbon/cobaltosic oxide nanorod (GMC/Co3O4) nanocomposite is developed for the rapid detection of phenolic pollutants. By applying the GMC/Co3O4 nanocomposite as an enzyme immobilization matrix, rapid direct electron transfer between Tyr and the electrode is achieved. The biosensor exhibits a wide linear response for catechol, ranging from 5.0×10−8 to 1.3×10−5 M, with a limit of detection down to 25 nM and a response time of less than 2 s. The sensitivity of the biosensor based on the GMC/Co3O4 nanocomposite (6.4 A M−1 cm−2) is higher than that of the biosensor based on GMC (5.0 A M−1 cm−2) or Co3O4 (3.5 A M−1 cm−2), which can be attributed to the synergistic effect of the GMC/Co3O4 nanocomposite. The biosensor is further used to systematically detect mixed phenolic samples (phenol, catechol, m‐cresol, p‐cresol, and 4‐chlorophenol) and real water samples. The biosensor‐based detection results for river water and tap water samples show outstanding average recovery (92.2–103.3 %) and relative standard deviations (0.9–7.8 %). In comparison with the conventional spectrophotometric method, the biosensor method is more rapid, sensitive, accurate, and convenient. Furthermore, the detection limit of the biosensor method is about 20 times lower than that of the spectrophotometric method. This novel biosensor is proven to be a promising alternative tool for the rapid and on‐site monitoring of environmental phenolic pollutants.

Determination of gold in ore samples by energy dispersive X-ray fluorescence after separation and preconcentration on polyurethane foam

A sensitive and selective method to determine gold in ore samples was developed. It was based upon gold extraction from hydrochloric acid medium by unloaded polyether type polyurethane foam (PUF). After that direct measurement on the solid sorbent by energy dispersive X-ray fluorescence (EDXRF) was done. The main parameters that control the gold sorption on PUF were evaluated. HCl concentration, sorption kinetic, amount of PUF and influence of foreign ions are some examples of these parameters. No variation in the gold system sorption was observed in the concentration range of 10−2 to 1mol L−1 of HCl. A 0.3mol L−1 HCl concentration was selected. The sorption kinetics of Au (III) is rapid with a half-life of adsorption (t1/2) of 0.83min. The curve fitted by EDXRF measurement of gold Lα intensity signal on PUF was linear in the mass range of 0 to 25μg. The calibration sensitivity was 0.0860 CPS μg−1. The detection and quantification limits of gold in ore samples were 1.36 and 4.53μg .g−1, respectively. It was observed that Al, Cu (II), Fe (III), Mn (II) and Ni have no significant effect on gold sorption. The method was successfully applied to determine gold in ore reference materials. The results are in good agreement with the certified gold values at a 95% confidence level. The average relative standard deviation (RSD) was 6%.

Periodic silver nanodishes as sensitive and reproducible surface-enhanced Raman scattering substrates

Highly ordered silver nanodishes which consist of nanorings and a film were fabricated as surface-enhanced Raman scattering (SERS) substrates. Numerical simulation reveals the bottom film can dramatically enhance the local electromagnetic (EM) field in the ring cavity, due to the plasmonic interaction between the nanorings and the film. Raman results show that the nanodishes can produce about sevenfold stronger signal than the nanorings alone, in accordance with the theoretical simulation. The detection limit for Rhodamine 6G (R6G) in the order of 10−12 M and the average relative standard deviation (RSD) of less than 12% indicate the excellent sensitivity and reproducibility of silver nanodishes. The SERS enhancement factor (EF) of R6G on the nanodishes was calculated to be 6.17 × 107. For practical application, the silver nanodishes were also used to detect thiram, one dithiocarbamate fungicide that has been extensively used as a pesticide in agriculture. The detection limit of thiram molecules is as low as 1 × 10−7 M, which can meet the requirements for ultra trace detection of pesticide residues. The resulting substrate with high SERS activity, stability and reproducibility makes it a perfect choice for practical SERS detection applications.