On-site Immunoassay Research Articles

Drug Use during Incarceration: A Comprehensive Quality and Prevalence Study in Three Danish Prisons

Background Drug use in Danish prisons has previously not been investigated in detail using confirmatory, laboratory analysis. The objective of the present quality study, initiated by the Danish Prison and Probation Service, was to i) evaluate the performance of an initial, on-site drug screening strategy; ii) gain insights into emerging drug trends; and iii) suggest evidence-based strategies for future drug testing. Methods Over a two-year period, routine urine samples (n = 1952 from 710 inmates) from three Danish prisons were subjected to comprehensive drug testing. Immunoassay screening was conducted on-site. A parallel sample aliquot was forwarded to laboratory analysis by confirmatory methods: High-performance liquid chromatography and tandem mass spectrometry (LC-MS/MS) and gas chromatography and mass spectrometry (GC-MS) targeting 56 drugs-of-abuse/medical drugs, 26 key metabolites, 41 new psychoactive substances (NPS), including specific biomarkers for heroin, crack cocaine, or ethanol (a total of 123 target analytes/sample). Results The on-site immunoassay method showed a sensitivity from 66 to 100%; specificity was above 98%; accuracy was above 95%. Laboratory analysis detected compounds not screened for including tramadol, oxycodone, buprenorphine, ketamine, MDMA, 4-fluoroamphetamine, and GHB. The prevalence of drug use was in the order: cannabis > ethanol > cocaine > benzodiazepines > amphetamine. Conclusion The performance of the immunoassay was found acceptable; however, the screening program was inadequate for detecting other significant substances. Based on these findings, a broader screening method will be implemented in future at Danish Prisons to minimize false negative results. The data did not indicate a trend of using NPS in Danish prisons.

A miniaturized platform based on reciprocating-flowing immunobinding for ultrafast, highly-sensitive and on-site immunoassay

Immunoassays are considered important methods for detecting disease biomarkers for biomedical diagnosis. Particularly, enzyme-linked immunosorbent assay (ELISA) is a commonly-used immunoassay method due to its high reliability and low cost. Nowadays, automatic analyzers integrating all steps of ELISA can achieve detection without manual operation to save labor, increase detection efficiency and avoid manual error. However, most ELISA analyzers require more than 30 min for one detection, which are not fast enough for on-site point-of-care testing (POCT). Herein, based on the reciprocating-flowing immunobinding strategy, we developed a miniaturized reciprocating-flowing POCT platform (RF-POCT platform) for rapid immunodetection. RF-POCT platform, which included an electronic control module, a fluid control module, a mechanical control module and a detection module, enabled fast immunobinding of antigen and antibody. Taking ELISA as an example of immunoassay methods for RF-POCT platform, we developed a miniaturized reciprocating-flowing ELISA analyzer (RF-ELISA analyzer) to automatically detect SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 N protein) and dust mite-specific immunoglobulin E (DM-IgE), with the LOD of 5.2–6.6 pg/mL and the CV less than 3 %. The detection required only 3.5 min. Afterwards, we detected the SARS-CoV-2 N protein in nasal swab samples and the DM-IgE in serum samples; the specificities were 85.7–100 %, the sensitivities were 96.3–100 %. The quantitative results from RF-ELISA analyzer were generally-consistent with those from large ELISA analyzers in hospitals. Therefore, RF-ELISA analyzer demonstrated excellent performance on ultrafast, highly-sensitive, and on-site immunoassay, with potential to support on-site POCT for primary hospitals and community clinics.

Reciprocating-flowing on-a-chip enables ultra-fast immunobinding for multiplexed rapid ELISA detection of SARS-CoV-2 antibody

The worldwide epidemic of novel coronavirus disease (COVID-19) has led to a strong demand for highly efficient immunobinding to achieve rapid and accurate on-site detection of SARS-CoV-2 antibodies. However, hour-scale time-consumption is usually required to ensure the adequacy of immunobinding on expensive large instruments in hospitals, and the common false negative or positive results often occur in rapid on-site immunoassay (e.g. immunochromatography). We solved this dilemma by presenting a reciprocating-flowing immunobinding (RF-immunobinding) strategy. RF-immunobinding enabled the antibodies in fluid contacting with the corresponding immobilized antigens on substrate repeatedly during continuous reciprocating-flowing, to achieve adequate immunobinding within 60 s. This strategy was further developed into an immunoassay method for the serological detection of 13 suspected COVID-19 patients. We obtained a 100% true negative and true positive rate and a limit of quantification (LOQ) of 4.14 pg/mL. Our strategy also can be a potential support for other areas related to immunorecognition, such as proteomics, immunopharmacology and immunohistochemistry.

Multiplex Immunoassay Techniques for On-Site Detection of Security Sensitive Toxins.

Biological toxins are a heterogeneous group of high molecular as well as low molecular weight toxins produced by living organisms. Due to their physical and logistical properties, biological toxins are very attractive to terrorists for use in acts of bioterrorism. Therefore, among the group of biological toxins, several are categorized as security relevant, e.g., botulinum neurotoxins, staphylococcal enterotoxins, abrin, ricin or saxitoxin. Additionally, several security sensitive toxins also play a major role in natural food poisoning outbreaks. For a prompt response to a potential bioterrorist attack using biological toxins, first responders need reliable, easy-to-use and highly sensitive methodologies for on-site detection of the causative agent. Therefore, the aim of this review is to present on-site immunoassay platforms for multiplex detection of biological toxins. Furthermore, we introduce several commercially available detection technologies specialized for mobile or on-site identification of security sensitive toxins.

Efficacy of drug screening in forensic autopsy: retrospective investigation of routine toxicological findings.

Toxicological analysis is indispensable in forensic autopsy laboratories, but often depends on the limitations of individual institutions. The present study reviewed routine drug screening data of forensic autopsy cases (n=2996) during an 18.5-year period (January 1996-June 2014) at our institute to examine the efficacy of the procedures and findings in autopsy diagnosis and interpretation. Drug screening was performed using on-site immunoassay screening devices and gas chromatography/mass spectrometry (GC/MS) in all cases, followed by re-examination using GC/MS and liquid chromatography/tandem mass spectrometry (LC/MS/MS) at a cooperating institute in specific cases in the last 4 years. GC/MS detected drugs in 486 cases (16.2%), including amphetamines (n=160), major tranquilizers (n=72), minor tranquilizers (n=294), antidepressants (n=21), cold remedies (n=77), and other drugs (n=19). Among these cases, fatal intoxication (n=123) involved amphetamines (n=73), major tranquilizers (n=37), minor tranquilizers (n=86), antidepressants (n=3), and cold remedies (n=9); most cases involved self-administration, alleged suicide and accidental overdose, while homicide was not included. These drugs were also identified in other manners of death, including homicide (n=40/372), suicide (n=34/226), accidental falls (n=27/129), and natural death (n=72/514). In these cases, on-site immunoassay screening of drugs of abuse showed negative findings in 2440 cases (81.4% in all cases), while GC/MS detected other drugs in 218 cases (7.3% in all cases), including several antipsychotic drugs, acetaminophen and salicylic acid. Further analysis using LC/MS/MS detected low concentrations of benzodiazepines in 32 cases, and also anti-diabetic and hypertensive drugs in a case of fatal abuse. These observations indicate the efficacy of systematic routine toxicological analysis to investigate not only the cause of death but also the background of fatalities in forensic autopsy. The provision of extensive drug screening is needed for forensic and social risk management, considering the marked diversity of medical and illicit drugs.

Liquid chromatography tandem mass spectrometry determination of selected synthetic cathinones and two piperazines in oral fluid. Cross reactivity study with an on-site immunoassay device

Since the past few years, several synthetic cathinones and piperazines have been introduced into the drug market to substitute illegal stimulant drugs such as amphetamine and derivatives or cocaine due to their unregulated situation. These emerging drugs are not usually included in routine toxicological analysis. We developed and validated a LC–MS/MS method for the determination of methedrone, methylone, mephedrone, 3,4-methylenedioxypyrovalerone (MDPV), fluoromethcathinone, fluoromethamphetamine, 1-(3-chlorophenyl)piperazine (mCPP) and 3-trifluoromethylphenylpiperazine (TFMPP) in oral fluid. Sample extraction was performed using Strata X cartridges. Chromatographic separation was achieved in 10min using an Atlantis® T3 column (100mm×2.1mm, 3μm), and formic acid 0.1% and acetonitrile as mobile phase. The method was satisfactorily validated, including selectivity, linearity (0.2–0.5 to 200ng/mL), limits of detection (0.025–0.1ng/mL) and quantification (0.2–0.5ng/mL), imprecision and accuracy in neat oral fluid (%CV=0.0–12.7% and 84.8–103.6% of target concentration, respectively) and in oral fluid mixed with Quantisal™ buffer (%CV=7.2–10.3% and 80.2–106.5% of target concentration, respectively), matrix effect in neat oral fluid (−11.6 to 399.7%) and in oral fluid with Quantisal™ buffer (−69.9 to 131.2%), extraction recovery (87.9–134.3%) and recovery from the Quantisal™ (79.6–107.7%), dilution integrity (75–99% of target concentration) and stability at different conditions (−14.8 to 30.8% loss). In addition, cross reactivity produced by the studied synthetic cathinones in oral fluid using the Dräger DrugTest 5000 was assessed. All the analytes produced a methamphetamine positive result at high concentrations (100 or 10μg/mL), and fluoromethamphetamine also at low concentration (0.075μg/mL).

On-site ethyl glucuronide immunoassay monitoring of alcohol use in cocaine-dependent outpatients

On-site ethyl glucuronide immunoassay monitoring of alcohol use in cocaine-dependent outpatients

A compact immunoassay platform based on a multicapillary glass plate.

A highly sensitive, rapid immunoassay performed in the multi-channels of a micro-well array consisting of a multicapillary glass plate (MCP) and a polydimethylsiloxane (PDMS) slide is described. The micro-dimensions and large surface area of the MCP permitted the diffusion distance to be decreased and the reaction efficiency to be increased. To confirm the concept of the method, human immunoglobulin A (h-IgA) was measured using both the proposed immunoassay system and the traditional 96-well plate method. The proposed method resulted in a 1/5-fold decrease of immunoassay time, and a 1/56-fold cut in reagent consumption with a 0.05 ng/mL of limit of detection (LOD) for IgA. The method was also applied to saliva samples obtained from healthy volunteers. The results correlated well to those obtained by the 96-well plate method. The method has the potential for use in disease diagnostic or on-site immunoassays.

A nanosensor based on quantum-dot haptens for rapid, on-site immunoassay of cyanotoxin in environmental water

A nanoprobe based on quantum-dot (QD) haptens was synthesized by conjugating carboxyl quantum dots with aminoethyl-microcystin (MC)–leucine–arginine (LR). A two-alkyl group was introduced to supply a spacer between the QD nanoprobe and anti-MC–LR antibody to reduce the steric hindrances of immunoreaction. The sensor system based on a portable optofluidic platform exhibited a liner range of 0.10–4.0µg/L for MC–LR with a detection limit of 0.03µg/L. The proposed sensor has potential application in the rapid, on-site detection of MC–LR in real water samples.

Does duration of wearing a disposable diaper in newborns influence testing for methamphetamine from urine absorbed in the diaper when using conventional immunoassay devices?

Although the actual number of pregnant women who abuse methamphetamine (MAP) in Japan remains unknown, it appears to be increasing [1]. Thus, rapid screening for MAP in newborns with on-site immunoassay devices is essential for protecting the health of both the mother and child. Urine is the most popular specimen of choice for drug testing, because it can usually be collected noninvasively in a large volume [2]. However, a special bag is required to collect urine from newborns. Sometimes this can be problematic, because skin dermatitis can be induced in newborns as a result of contact with adhesives used to fix the bag to the skin. As an alternative to urine specimens, meconium and hair can also be used for noninvasive drug testing in newborns [3–7]. However, use of these sample types requires liquid– liquid or solid-phase extraction before analysis for the drug via immunoassay devices or instruments such as a gas chromatograph–mass spectrometer or liquid chromatograph–mass spectrometer. Thus, these latter specimens are not practical for bedside drug testing. Moreover, interpretation of hair results can sometimes be confusing because of extreme contamination of the hair by external drug exposure [8]. However, visual demonstration of drugs by matrix-assisted laser desorption ionization time-of-flight mass spectrometry has been shown to be able to discriminate between deliberate drug use and passive exposure to drugs [9]. Recently, we developed a screening method for MAP in urine absorbed in a disposable diaper, with the analysis using the conventional immunoassay devices, Instant View M-1 (Alfa Scientific Designs, Poway, CA, USA) and Triage DOA (Biosite, San Diego, CA, USA) [10]. Our method makes it possible to quickly test newborns for MAP at the bedside. Our previous study results demonstrated that MAP could be completely recovered from disposable diapers, which means that MAP is not adsorbed nonspecifically onto the polymers (sodium polyacrylate) of the diapers. However, when urine is excreted into a disposable diaper, it is exposed to the infant’s body temperature until the diaper is exchanged for a new one. In addition, when the newborn continues to wear the same diaper, there is slight decomposition of the urine retained in the diaper due to proliferation of bacteria at body temperature. Nagata et al. [11] reported that MAP in bodily fluids and tissues was stable against decomposition at room temperature for a long period of time. However, the stability of urinal MAP in the polyacrylate environment of the diaper at body temperature has yet to be determined. Due to the metabolism of bacteria, putrefactive amines are produced in biological specimens left at room temperature [12]. In addition, there is a variable cross-reaction between the anti-MAP antibodies used for immunoassay devices and some putrefactive amines such as phenethylamine and tyramine, which is frequently problematic when screening for MAP in forensic autopsy cases [13]. Moriya et al. [14] reported that the anti-MAP antibodies used for the Triage DOA cross-react with phenethylamine at a concentration of 5000 ng/ml or higher in an aqueous T. Shiotsuki F. Moriya (&) Department of Nursing, Faculty of Health and Welfare, Kawasaki University of Medical Welfare, Matsushima, Kurashiki, Okayama 701-0193, Japan e-mail: moriyaf@mw.kawasaki-m.ac.jp

Use of on-site immunoassay devices to screen urine absorbed in disposable diapers for methamphetamine: a preliminary study with artificial urine

The aim of this preliminary study was to establish a simple, rapid method for recovering urine absorbed in disposable diapers in order to test for methamphetamine (MAP) using the Instant-View™ M-1 and Triage® DOA on-site immunoassay devices. A 4-ml aliquot of drug-free artificial urine was absorbed into a disposable diaper (Pampers®) that had been cut into 3 × 3 cm pieces. Further addition of 4 ml of saturated KCl solution to the piece of diaper led to the recovery of substantial amounts (c.a. 2 ml) of fluid sample within 3–5 min. After diluting recovered fluids two-fold with distilled water, both immunoassays showed all samples were negative for all drug classes. After absorption of artificial urine containing 500–5,000 ng/ml of MAP in similar-sized pieces of diaper using the identical processing method, positive results were observed with Instant-View™ M-1 for artificial urine containing 2,000 ng/ml or more of MAP and with Triage® DOA for urine containing 4,000 ng/ml or more of MAP. Diapers dosed with artificial urine containing 500, 2,500, and 5,000 ng/ml of MAP were further examined by gas chromatography–mass spectrometry, with recoveries of MAP of 98.6 ± 36.7 % (n = 6), 115 ± 22.4 % (n = 6), and 102 ± 15.1 % (n = 6), respectively. Use of this new sample preparation method may be applicable for analyzing infant urine absorbed in disposable diapers. Additionally, the sensitivity of the method along with the availability of Instant-View™ M-1 screening suggests the potential usefulness of this technique in clinical settings.

Passive fluidic chip composed of integrated vertical capillary tubes developed for on-site SPR immunoassay analysis targeting real samples.

We have successfully developed a surface plasmon resonance (SPR) measurement system for the on-site immunoassay of real samples. The system is composed of a portable SPR instrument (290 mm(W) × 160 mm(D) × 120 mm(H)) and a microfluidic immunoassay chip (16 mm(W) × 16 mm(D) × 4 mm(H)) that needs no external pump system. An integrated vertical capillary tube functions as a large volume (150 μL) passive pump and a waste reservoir that has sufficient capacity for several refill operations. An immunoassay was carried out that employed the direct injection of a buffer and a test sample in sequence into a microfluidic chip that included 9 antibody bands and 10 reference reagent bands immobilized in the flow channel. By subtracting a reliable averaged reference sensorgram from the antibody, we effectively reduced the influence of the non-specific binding, and then our chip successfully detected the specific binding of spiked IgG in non-homogeneous milk. IgG is a model antigen that is certain not to be present in non-homogeneous milk, and non-homogeneous milk is a model of real sample that includes many interfering foreign substances that induce non-specific binding. The direct injection of a real sample with no pretreatment enabled us to complete the entire immunoassay in several minutes. This ease of operation and short measuring time are acceptable for on-site agricultural, environmental and medical testing.

A pilot study of the accuracy of onsite immunoassay urinalysis of illicit drug use in seriously mentally ill outpatients

Objectives: This pilot study investigated the accuracy of onsite immunoassay urinalysis of illicit drug use in 42 outpatients with co-occurring substance use disorders and serious mental illness. Methods: Up to 40 urine samples were submitted by each participant as part of a larger study investigating the efficacy of contingency management in persons with co-occurring disorders. Each sample was analyzed for the presence of amphetamine, methamphetamine, cocaine, marijuana, and opiates or their metabolites using onsite qualitative immunoassays. One onsite urinalysis was randomly selected from each participant for confirmatory gas chromatography–mass spectrometry (GC–MS) analyses. Results: Agreement between immunoassay and GC–MS was calculated. Agreement was high, with 98% agreement for amphetamine, methamphetamine, opiate, and marijuana. Agreement for cocaine was 93%. Conclusions: Results of this pilot study support the use of onsite immunoassay screening cups as an assessment and outcome measure in adults with serious mental illness. Scientific significance: Data suggest that onsite urinalysis screenings may be a helpful assessment tool for measuring clinical and research outcomes.

An Improved Rapid On-Site Immunoassay for Triazophos in Environmental Samples

The suitability of enzyme-linked immunosorbent assay for rapid and on-site determination of triazophos in environmental samples was investigated. The optimized rapid ELISA can be completed in around 10 min at ambient temperature. A rapid sample preparation procedure was developed which can be performed on field site for fresh water and soil samples. The rapid assays can process 40 samples within 1 h including the sample preparation time. It can be concluded that this rapid assay would be a potential, effective method for monitoring triazophos in the environment, especially when quick Judgment regarding low or high contamination is critical.

Liquid Chromatography/Quadrupole Ion Trap/Time-of-Flight Determination of the Efficacy of Drug Test Kits for Rapid Screening of Food

The goal of this study was to evaluate the plausibility and accuracy of commercially available on-site immunoassay urinalysis kits for the screening of compounds of interest within food matrices. In conjunction with this study, a sensitive, robust, and reproducible analytical method, utilizing solid-phase extraction liquid chromatography/quadrupole ion trap/time-of-flight mass spectrometry for confirmation analysis, was developed. The food matrices analyzed were tomato juice, apple juice, milk, beer, white wine, ground beef, powdered milk, and all-purpose flour. Compounds fortified into the food matrices included heroin, phencyclidine, cocaine, benzoylecgonine, methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine, imipramine, doxepin, nitrazepam, diazepam, oxazepam, temazepam, alprazolam, flunitrazepam, clonazepam, and lorazepam. Standard curves were prepared for each matrix from 10 to 500 ng/ml for each analyzed compound. All liquid chromatography/tandem mass spectrometry samples were fortified with 20μl of deuterated internal standard at 90 ng/ml. Quality control standards were prepared at 20 and 400 ng/ml, and >90% were within 2 SD of the mean for each analyte. The test kits were found to produce up to 85% of the expected results based on concentration levels of adulterants (i-Screen in milk). This study shows that lateral-flow immunoassay test kits are plausible as a rapid, accurate, and reliable screening method in the event of adulteration of the food supply.

Comparison of Urinary On-Site Immunoassay Screening and Gas Chromatography-Mass Spectrometry Results of 111 Patients With Suspected Poisoning Presenting at an Emergency Department

On-site tests based on immunoassay techniques are widely used for toxicologic screening analysis in patients with suspected poisoning. However, such assays usually have been validated using urine samples with known concentrations of the investigated substances. In the present investigation, on-site screening results were evaluated in a clinical setting. This was a retrospective study of patients with suspected poisoning from January to December 2003 in the emergency department of a tertiary urban hospital. Urine samples were analyzed using the Triage 8 panel and gas chromatography-mass spectrometry (GC-MS). A total of 111 patients were included (54 female, 57 male; average age 37.8 +/- 19.7 years). A total of 3.8% of the patients showed no symptoms, 45.2% minor, 24.0% moderate, and 26.9% serious symptoms. In 50 patients (45.0%), Triage 8 results corresponded well with GC-MS results. In 17 patients (15.3%), the Triage 8 results were confirmed by GC-MS, but additional substances were determined that could not be detected by the Triage 8 panel. A completely negative Triage 8 screening result was obtained in 23 patients (20.7%) who showed toxicologically relevant findings in GC-MS. In 21 patients (18.9%), Triage 8 results could not be confirmed by GC-MS. The analysis of the results in view of the patients' medical histories revealed that in 20 patients (18.0%), no relevant toxic substance could be detected. Additionally, 8 patients (7.2%) showed intoxication with alcohol, which could not be detected by the presently applied toxicologic screening investigations. On-site screening results in suspected poisoning were not very helpful in the present study because practically every second patient ingested substances that were not detectable by the Triage 8 device. In addition, every fifth result was not in line with GC-MS findings. On-site test findings should be interpreted very carefully, and in critical cases, a GC-MS screening should be performed.

An analytical device for on-site immunoassay. Demonstration of its applicability in semiquantitative detection of aflatoxin B1 in a batch of samples with ultrahigh sensitivity.

A simple analytical device has been developed for performing noninstrumental immunofiltration-based assay on a batch of samples. The device consists of membrane strips, with antibody-immobilized zones, attached to a polyethylene card. A moist filter paper placed between the membrane and the polyethylene card acts as the absorbent body. The device was used to estimate very low concentrations of aflatoxin B1 (AFB1) present in food samples by using an improved catalyzed reporter deposition (Super-CARD) method of signal amplification involving biotinylated tyramine (B-T) and avidin-horseradish peroxidase conjugate. 4-chloro-1-naphthol was used as the substrate for visualization. Semiquantitative results are obtained by visual comparison of the color intensity (inversely related to the analyte concentration) of a sample spot with those of reference standards. Quantitative estimation is possible by densitometric analysis (detection limit 0.25 pg/spot, 0.01 ng mL(-1)). Dilute samples can be assayed by in situ concentration with improved dose-response characteristics. A batch of 12 extracted samples can be analyzed in a single test card within 12 min. Spiked and contaminated samples of groundnut, corn, wheat, cheese, and chilli were analyzed without sample cleanup. The matrix interferences were eliminated by using appropriate dilution of the aqueous methanol extracts. Mean recoveries from different food samples were between 91 and 104%. The values obtained for infected corn and groundnut samples correlated well (R2=0.99) with the estimates by HPLC. The method is well-suited for visual screening of agricultural and food samples for AFB1 under field conditions.

Development of a microparticle-based on-site immunoassay for the detection of atrazine in soil and water samples.

Atrazine is widely used as a herbicide in agriculture and has been identified as a major groundwater contaminant in the US. Because of the possible hazard associated with its usage, there is a need for an efficient and economic screening method for on-site field testing of atrazine and other s-triazine herbicides in soil and water. We have developed a rapid, on-site test for the detection of atrazine based on the principle of microparticle agglutination inhibition immunoassay. The test detects 50 microg kg(-1) (0.050 ppm) atrazine in soil samples with direct extraction and 1.0 microg L(-1) atrazine in water samples when coupled with solid phase extraction.

Excretion and Detection of Cathinone, Cathine, and Phenylpropanolamine in Urine after Kath Chewing

The stimulating herbal drug kath is uncommon in most countries, and information on its detection and interpretation of analytical results is limited. Therefore, a study with kath was carried out to compare the efficiencies of different analytical techniques used to detect drug use. Four volunteers chewed kath leaves for 1 h; urine samples were collected up to 80 h afterward and analyzed by the Abbott fluorescence polarization immunoassay (FPIA), the Mahsan-AMP(300) on-site immunoassay, the Bio-Rad Remedi HS HPLC system with photodiode array detection (DAD), and gas chromatography-mass spectrometry (GC-MS). FPIA gave negative results, whereas positive results were obtained with the Mahsan test during the first day. With HPLC, one peak could be observed up to 50 h, but its DAD spectrum could not be identified by the system. Further investigations indicated that the kath alkaloids coeluted and produced a mixed DAD spectrum. With GC-MS, the specific kath ingredient cathinone was detected up to 26 h, whereas cathine and norephedrine were still detectable in the last samples. Maximum concentrations of cathinone, cathine, and norephedrine in urine samples from the study were 2.5, 20, and 30 mg/L, respectively, whereas in authentic cases the concentrations were much higher. GC-MS is superior to the screening techniques Mahsan-AMP(300) and Remedi with respect to specificity and sensitivity for the detection of kath use in urine.

Rapid on-site immunoassay for diflubenzuron in grains

An antibody-based test for field use has been developed to enable a screening test for diflubenzuron in animal feed grain. In this test, a pesticide containing methanol extract of the grain sample and an HRP-labeled diflubenzuron derivative are separately added to the antibody-precoated 8-well strip. After a brief incubation period, the strip is washed and a substrate for the enzyme is added. The color development is stopped by acidification, and the test result can be read either by plate reader or a portable field photometer. Diflubenzuron could be extracted efficiently by blending ground grain for 2 min using methanol. The overall test time is around 15 min. The test had a limit of detection of 3 ppb (0.75 ppm in grain) and gave quantitative estimates in the range of 0.75–25 ppm in the grain. No significant matrix effect was observed after methanol extraction of the residue was diluted 1/50 with 1%BSA–PBS. The results correlated well with those obtained using either laboratory immunoassay or HPLC method.