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There is a steady increase in the number of overweight and obese people worldwide and increasingly, younger people. Excess adipose tissue impairs the action of insulin, leading to insulin resistance (IR). Tissue IR is a major factor in relation to cardiovascular disease, metabolic syndrome and diabetes. Thus, it is important to recognize at the pre-disease stage with the possibility of therapeutic intervention. IR is assessed using indicators of epidemiological significance, most often calculated from fasting and postprandial glucose and insulin values, so-called indirect indicators of insulin resistance. The most commonly used parameter is the Homeostatic Model Assessment (HOMA). Although the Quantitative Insulin Sensitivity Check Index (QUICKI), Matsuda Index and the Insulin Secretion-Sensitivity Index-2 (ISSI-2) are also used, the values of these indices established for IR vary for different age, sex, populations and ethnic groups. Thus, appropriate reference values of indirect indices should be determined for such groups, and when this is precluded, data from published studies carried out on the most ethnically, socio-economically and age-matched populations should be applied.

Background: In human medicine, extremely high CRP (C-reactive protein) concentrations > 100 mg/l are indicators of bacterial infection and the need of antibiotic treatment. Similar decision limits for septic pneumonia are recommended for dogs but have not yet been evaluated for other organ systems. The aim of the retrospective study was to investigate the prevalence and evaluate dogs with CRP concentrations > 100 mg/l regarding the underlying etiology, the affected organ system and the prognostic significance. Results: Prevalence of CRP > 100 mg/l was investigated in dogs presented between 2014 and 2015 and was 12%. For evaluation of etiology and organ systems, dogs with CRP > 100 mg/l presented between 2014 and 2016 were enrolled. Dogs were classified into 4 main disease categories, i.e. inflammatory, neoplastic, tissue damage or "diverse". Diseases were assigned to the affected organ system. If an organ classification was not possible, dogs were classified as "multiple". 147 dogs with CRP 101–368 mg/l were included and classified into disease categories: 86/147 (59%) with inflammatory etiology (among these, 23/86 non-infectious, 44/86 infectious (33/44 bacterial), 19/86 inflammation non-classifiable), 31/147 (21%) tissue damage, 17/147 (12%) neoplastic (all malignant) and 13/147 (9%) diverse diseases. The affected organ systems included 57/147 (39%) multiple, 30/147 (20%) trauma, 21/147 (14%) gastrointestinal tract, 10/147 (7%) musculoskeletal system, 8/147 (5%) respiratory tract, 7/147 (5%) urinary/reproductive tract, 6/147 (4%) skin/subcutis/ear, 6/147 (4%) central/peripheral nervous system and 2/147 (1%) heart. The disease group (p = 0.081) or organ system (p = 0.17) did not have an impact on CRP. Based on CRP, a detection of bacterial infection was not possible. The prognostic significance was investigated by determining the 3-months survival and hospitalization rate in a subgroup with known outcome. The 3-months survival rate was 46/73 (63%) while the majority 66/73 (90%) of patients was hospitalized. Conclusions: CRP concentrations > 100 mg/l are occasionally seen in a clinic population. They indicate a severe systemic disease of various etiologies with guarded prognosis. Extremely high CRP concentrations do not allow a conclusion of the underlying etiology or an identification of bacterial inflammation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel method for estimating of detection capability in a qualitative analysis. • The method is based on the concept of Classification Analytical Signal. • The method is presented by a simple algorithm and each step is described in depth. • The method is mostly relevant for detection of low concentrations of the analyte. This paper presents a new methodology for the estimation of the limit of detection and other related parameters in qualitative analysis. Estimation of the detection limit is important in special cases when a small amount of an illegal ingredient can significantly affect the quality of the product or the presence of even a small amount of an extraneous analyte is significant. The approach is based on a recently introduced concept of an analytical signal in qualitative analysis, called the Classification Analytical Signal (CAS). A detailed algorithm to calculate the detection capability for a one-class classification method Data-Driven Soft Independent Modeling of Class Analogy (DD-SIMCA) is described and illustrated with two real-world examples. Both examples consider cases where the detection of low analyte concentrations is important and corresponding samples should be considered as non-compliant. The first case presents adulteration of wheat flour with talcum powder, where the samples were specially prepared with various concentrations of the analyte. The second case uses a publicly available dataset devoted to the estimation of tetracycline in blood serum. The latter case is used to compare the limits of detection estimated for multivariate calibration with those presented for qualitative analysis. [ABSTRACT FROM AUTHOR]

There is a steady increase in the number of overweight and obese people worldwide and increasingly, younger people. Excess adipose tissue impairs the action of insulin, leading to insulin resistance (IR). Tissue IR is a major factor in relation to cardiovascular disease, metabolic syndrome and diabetes. Thus, it is important to recognize at the pre-disease stage with the possibility of therapeutic intervention. IR is assessed using indicators of epidemiological significance, most often calculated from fasting and postprandial glucose and insulin values, so-called indirect indicators of insulin resistance. The most commonly used parameter is the Homeostatic Model Assessment (HOMA). Although the Quantitative Insulin Sensitivity Check Index (QUICKI), Matsuda Index and the Insulin Secretion-Sensitivity Index-2 (ISSI-2) are also used, the values of these indices established for IR vary for different age, sex, populations and ethnic groups. Thus, appropriate reference values of indirect indices should be determined for such groups, and when this is precluded, data from published studies carried out on the most ethnically, socio-economically and age-matched populations should be applied. [ABSTRACT FROM AUTHOR]

Objectives: Sysmex UN series fully automated urine analyzer reports a series of research parameters besides routine parameters including the "atypical cells" parameter. An automated instrument in clinical use capable of detecting neoplastic cells of the urinary tract will have paramount significance. Case presentation: A 73 years old male patient with a recurrent high grade urothelial carcinoma admitted to our urology outpatient clinic due to hematuria. Urinalysis showed +3 hemoglobin, +3 leukocyte esterase, 200/HPF red blood cells, 300/HPF white blood cells. The instrument also reported atypical cells (7.6/µL or 1.3/HPF) under the heading of "research parameters." Presence of atypical cells was confirmed by the manual microscopy. The patient has undergone transurethral resection of papillary lesions and the pathology report confirmed a recurrence. On follow-up, atypical cells fell to 0.1/µL after 40 days. Conclusions: This case report presents a patient with atypical cells in urine, detected by a fully automated urine analyzer. The atypical cells presented on the screen of the analyzer were confirmed by the manual microscopy. This presentation may influence future studies pertaining to the subject. [ABSTRACT FROM AUTHOR]

• The original serum free light chain ratio diagnostic range is no longer acceptable. • The diagnostic range for serum free light chains does not align with gammopathy risk. • Replace serum FLC diagnostic range with institution-specific reference intervals. • International guidelines for free light chain decision limits need updating. Recent reference interval studies of the serum free light chain (FLC) test using contemporary instruments display divergence with the diagnostic range generally adopted as the international standard. In this study, we perform a retrospective reference interval analysis with risk predictions for monoclonal gammopathy. Retrospective laboratory and clinical data for 8,986 patients were included in the study. Reference intervals were generated against a set of inclusion/exclusion criteria for two time periods representing the use of different instruments. The presence of monoclonal gammopathy was established from diagnostic test interpretations and EHR diagnosis codes in the patient problem lists and medical history. The 95% FLC ratio reference intervals were 0.76–2.38 for SPAPLUS®, and 0.68–1.82 for Optilite® instruments. These intervals varied considerably from the current diagnostic range of 0.26–1.65 and mapped approximately to the FLC ratios beyond which risk of monoclonal gammopathy substantially increased. These findings corroborate recent reference interval studies and support recommendations for independent re-evaluation of intervals by institutions as well as an update of international guidelines. [ABSTRACT FROM AUTHOR]

A large body of literature exists on the limit of detection (LOD), but there is still a lot of confusion about this important validation parameter. This confusion mainly stems from its statistically complex background. The goal of this two-part tutorial is to discuss and clarify the topic of LOD for practitioners. The two main conclusions of this tutorial are: (1) the choice of how to estimate LOD should be based on the purpose of the analytical method that is being validated (e.g. considerable effort should not be made to estimate LOD for a method that is not used for detecting traces in the vicinity of LOD), and (2) LOD estimates are strongly dependent on different assumptions and the approach used, and therefore caution must be exercised when using the estimate or when comparing different estimates. Part I of the tutorial contains a theoretical discussion (without excessively sophisticated statistics) and part II contains examples based on experimental data. In Part I, LOD and other definitions related to it are reviewed, and their estimation and use are discussed. The assumptions and practicality of different approaches to estimate LOD are compared. Different aspects of the analytical method that strongly influence LOD estimates (e.g. linearity, scedasticity and day-to-day variability of LOD) together with experimental design considerations when estimating LOD are discussed. In part II, LOD is estimated for the LC-MS/MS analysis method to detect pesticides on separate days. The performance of different tests on the data necessary for LOD estimation are discussed and the results of different approaches under review in this tutorial are compared. In conclusion, a decision tree is proposed for estimating and monitoring LOD. A detailed working procedure for estimating LOD is presented. Several topics are pointed out in which further research and discussion is needed. [ABSTRACT FROM AUTHOR]

In part II of this tutorial, the investigated approaches of estimating the limit of detection (LOD) are applied to experimental data from LC-MS measurements. Important practical aspects specific to LC-MS and related to LOD are reviewed. The results of different tests of estimating linearity and scedasticity are compared. LOD estimates obtained with different approaches (for both simple characterization of the analysis method and accurate interpretation of the results) are applied to the data and the obtained values are compared. As a conclusion, a decision tree is proposed for estimating LOD for analytical methods using the LC-MS technique. [ABSTRACT FROM AUTHOR]

Background Laboratories often adopt new methods. It would be useful to have a statistical procedure to estimate the incremental impact of a change in assay. Methods Mathematical modeling, statistical analysis, and case example. Results We derived equations to estimate the proportion of discordant results that can be attributed to the new laboratory method. The calculations were demonstrated by comparing eGFR values based on creatinine values determined using the enzymatic method (existing method) and Jaffe method (new method). The discordance rate at the 60 ml/min eGFR decision limit was 3.15%. In this example, we estimated that 60% of the discordant results could be attributed to the Jaffe method. Conclusion The sources of discordance in a laboratory method comparison study can be divided into three categories: The baseline discordance due to imprecision in the established method, the incremental discordance due to imprecision in the new method, and lack of analytical specificity. Discordance due to imprecision can be attributed to each individual method. Discordance due to bias can be attributed to individual methods if information is available to estimate the rate of biased observations in either method. Such information can be used to estimate the incremental cost effectiveness associated with the adoption of a new method. [ABSTRACT FROM AUTHOR]

The article discusses a study which evaluates the clinical decision limit and performance of cardiac troponin (cTn) I assay. The study uses immunoassay and serum analysis for blood sample examination. The study reveals that the cTn assay has improved low-end analytical performance for myocardial injury detection.

Background: Peripheral smear review is a critical, but labor intensive adjunct for evaluation of lymphocytosis. Standard practice based on consensus guidelines is to review cases with absolute lymphocyte count (ALC) >5×109/L. We hypothesize that identifying cases for review by applying appropriately adjusted ALC and age discriminators will decrease laboratory workload without compromising patient care. Methods: 1170 complete blood counts with ALCs >5×109/L analyzed in the core laboratory during a 2-year period were included. Patients were categorized into diagnostic groups based on follow-up criteria. A total of 402 patients with new onset lymphocytosis who met criteria for reactive lymphocytosis (82%) or lymphoproliferative disorder (18%) were used to establish optimal ALC and age thresholds from receiver operating characteristic (ROC) curve analysis. Results: ALC as a discriminator for neoplastic lymphocytosis had an ROC area under the curve (AUC) of 0.732. Selecting cases with ALC >10×109/L enriched the proportion of neoplastic cases in the review pool (90% specificity); however, many cases with ALC below this threshold were also neoplastic (52% sensitivity). For cases with ALC between 5 and 10×109/L, age as a discriminator had an ROC AUC of 0.886. Selecting patients >50 years old in this group for review captured the neoplastic cases while excluding the reactive cases (93% sensitivity, 62% specificity). When applied to a validation cohort, the predictive performance of the thresholds was maintained while reducing smears reviewed by 50%. Conclusions: We show that modifying the standard 5×109/L ALC smear review threshold through retrospective analysis of institutional data can reduce laboratory workload without compromising quality. [ABSTRACT FROM AUTHOR]

The decision limit ( CCα), capability of detection ( CCβ) and quantification limit ( QL) are importance performance characteristics in method validation. The TLC-Scanner 3 from Camag provides the possibility to choose the slit dimension of light to determine the peak chromatogram of a substance. The influence of the slit dimension for determination of CCα, CCβ and QL of paracetamol has been carried out. Paracetamol was spotted onto plates of AL-TLC Si G 60 F254 by linomat 4 in the range of 50-400 ng/spot and 10-400 ng/band, then on twin chambers eluted with TAEA (toluene:acetone-ethanol:conc.ammonia, 45 + 45 + 7 + 3 v/v) for 45 mm. Eluted spots were scanned in different slit dimensions at 248 nm. The CCα, CCβ and QL of paracetamol were estimated through the linear regression (LRM) and signal-to-noise (S/N) methods. Slit lengths between 50 and 133 % of the band width of the spots, and with the noise factor of the slit under 2.6, produced good precision measurements of TLC-densitometry between plates, while slit lengths between 50 and 83 % of the band width of the spots introduced a higher sensitivity response of the detector. The estimated CCα, CCβ and QL were determined by how the data were collected, the analytical optical setting, and the usage method for the estimation of both validation parameters. [ABSTRACT FROM AUTHOR]

Abstract: The proposed procedure is described by applying it to develop an analytical method which fulfils the SANCO specifications. Nevertheless, the procedure would be valid for any other legal specification that requires the identification of the analyte by means its m/z values and retention time. To demonstrate the procedure, three herbicides (simazine, Sz; atrazine, Az; propazine, Pz), with terbuthylazine, Tz, as internal standard (IS) have been analysed by gas chromatography with mass spectrometry detection (GC/MS). The procedure consists of the following steps: (i) To record the data in the full scan mode (201 m/z ratios). (ii) To select four characteristic ions which make possible the unequivocal identification of each triazine according to the criteria established in the Document SANCO/12495/2011 by means of principal components and hierarchical clustering of variables; (iii) To build a calibration based on the PARAFAC decomposition with the data recorded in SIM mode at the four m/z ratios selected for each triazine. Afterwards several figures of merit have been evaluated. Bearing in mind that triazines are one of the most frequently used group of herbicides in agriculture and atrazine and simazine are included in the list of priority substances in Annex II of Directive 2008/105/EC, in this work, these analytes have been analysed in three natural waters. Prior to determination by gas chromatography with mass spectrometry detection (GC/MS) a step with solid phase extraction (SPE) has been carried out. The calibration set is made up of 40 standards 33 are external standards prepared in acetone and seven matrix matched prepared in deionised water subjected to the SPE procedure. Moreover, each kind of water, stream, well, and river, is analysed both unspiked and spiked. For the triazine determination, the second order PARAFAC advantage allows the use of samples prepared in acetone together with those prepared in deionised water subjected to SPE. The decision limit, CCα, and the capability of detection, CCβ, are calculated according to ISO 11843-2, assessing the false positive and false negative. The m/z ratios chosen fulfils the SANCO identification criteria and also the spectrum obtained in the PARAFAC decomposition, which is common in all samples for each triazine. However, when the same experimental data are used to carry out a univariate calibration with the abundance of the base peak of each triazines, a lot of samples lie outside the permitted tolerances depending on the reference experimental spectra used, despite the fact that all of them have a triazine content above the detection limit. Also, the PARAFAC calibration allows us to detect the test samples which are not similar to the calibration samples and in this way their mistaken quantification is avoided. [Copyright &y& Elsevier]

Abstract: For obtaining reliable results of a chemical analysis, the method of analysis must be validated first, before it can be used routinely in a QC-laboratory. Therefore the availability of an acceptable transfer analytical method to QC-laboratory is very essential. Assessment of the accuracy of an analytical method can be improved by applying the concept of accuracy profile, which derived from the uncertainty of the analytical results. Selectivity of the analytical method is the most important parameter for univariate calibration. This present review summarized and discussed some new aspects of validation method which have been recently published. [Copyright &y& Elsevier]

Abstract: The problem of setting the limit of detection is considered for censored samples and heterogeneous errors. After formal definitions of the critical level and of the method detection limit, we obtain simplified maximum likelihood-type estimators. The estimation problem of the truncation parameter and its uncertainty are reviewed. Upper confidence bounds for the limit of detection are derived and some simulation results are given. [Copyright &y& Elsevier]

Abstract: Uncertainty is inherent in all experimental determinations. Nevertheless, these measurements are used to make decisions including the performance of the own measurement systems. The link between the decision and the true implicit system that generates the data (measurement system, production process, category of samples, etc.) is a representation of this uncertainty as a probability distribution. This representation leads to the probabilistic formalization of the possibility of making errors. In the context of regulations established by official agencies, it is important to use these statistical decision methods in some cases because the own norm makes them mandatory and, in general, because this is the way of reasonably evaluating whether a working hypothesis is rejected on the basis of the experimental data. The aim of the present tutorial is to introduce some ideas and basic methods for the critical analysis of experimental data. With this goal, the basic elements of the Neyman–Pearson theory of hypothesis testing are formally introduced in connection with the common problems in chemical analysis and, if this is the case, their relation to the norms of regulatory agencies. The notion of decision with ‘enough quality’ is modelled when explicitly considering: (1) the null, H 0, and alternative, H 1, hypotheses. (2) The significance level of the test, which is the probability, α, of rejecting H 0 when it is true, and the power of the test, 1− β, β being the probability of accepting H 0 when it is false. (3) The difference between H 0 and H 1 that has to be detected with experimental data. (4) The needed sample size. These four concepts should be explicitly defined for each problem and, under the usual assumption of normal distribution of the data, the mathematical relations among these concepts are shown, which allow the analyst to design a decision rule with pre-set values of α and β. To illustrate the unifying character of this inferential methodology, several situations are exposed along the tutorial: the design of a hypothesis test to decide on the performance characteristics of analytical methods, the capability of detection of both quantitative and qualitative analytical methods (including its generalization to the case of multivariate and/or multiway signals), the analytical sensitivity with multivariate signals, the class-modelling and the process control. [Copyright &y& Elsevier]

Matrix-matched calibration allows to quantify accurately without the necessity of correcting results for the bias error caused by matrix effects. In this work, an approach to estimate the decision limit CCa and the detection capability CCb using matrix-matched calibration data series that were obtained at different times and under different conditions is described. The basic idea underlying the approach is to consider the set of the calibration submodels to be an ensemble of equally probable events. By way of illustration, the methodology is applied to a data set acquired within a validation study of an LC-MS assay for the determination of the aminoglycoside antibiotic dihydrostreptomycin in kidney. [ABSTRACT FROM AUTHOR]

Estimation of measurement uncertainty (MU) for quantitative results is a requirement of ISO/IEC17025. This concept is well established for chromatographic methods in doping control and forensic analysis. For non-chromatographic methods, however, very few practical methodologies have been published. In this paper, the applicability of a top-down model, established for estimating uncertainty in chromatography, was evaluated for two other methodologies with different sets of raw data as a starting point. The first case study involves the estimation of MU for the determination of haematological parameters. In this case, a large data set of quality control material and proficiency testing results was available to establish MU. The second case study involves the estimation of MU for the recently approved method for the determination of human growth hormone misuse. In this case the amount of data available to establish MU was limited to results from method validation and a basic set of analysis data. In both cases a methodology based upon long-term bias, long-term imprecision and-eventually-a correction for standard impurity is proposed. The proposed methodology can be regarded as a dynamic procedure, which allows re-evaluation of MU on a regular basis. Finally, a concept for the verification and evaluation of MU estimations using proficiency testing results is proposed. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Thyreostatic compounds could be illegally administered to animals in order to obtain a weight gain due to a higher retention of water in the edible tissue and the gastro-intestinal tract. In the European Union their use for animal production is banned since 1981. Recently a highly sensitive method exploiting the determination of thyreostats with 3-iodobenzylbromide prior to purification to determine thyreostats in urine and other matrices was reported. For the first time, the UPLC instrumentation was used to separate the 3-iodobenzyl derivatives of various thyreostats. The deuterated internal standards tapazole-d3 and propylthiouracil-d5 were for the first time used for the quantification of tapazole, thiouracil, methylthiouracil, propylthiouracil, phenylthiouracil and mercaptobenzimidazole. The confirmative quantitative liquid chromatographic tandem mass spectrometric (LC–MS/MS) method was validated according to Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) were found to be for all compounds below the recommended value of 10μgkg−1. [Copyright &y& Elsevier]

A confirmatory method has been developed and validated that allows for the simultaneous detection of medroxyprogesterone acetate (MPA), megestrol acetate (MGA), melengestrol acetate (MLA), chlormadinone acetate (CMA) and delmadinone acetate (DMA) in animal kidney fat using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The compounds were extracted from kidney fat using acetonitrile, defatted using a hexane wash and subsequent saponification. Extracts were then purified on Isolute™ CN solid-phase extraction cartridges and analysed by LC-MS/MS. The method was validated in animal kidney fat in accordance with the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCα) was calculated to be 0.12, 0.48, 0.40, 0.63 and 0.54 µg kg-1, respectively, for MPA, MGA, MLA, DMA and CMA, with respective detection capability (CCβ) values of 0.20, 0.81, 0.68, 1.07 and 0.92 µg kg-1. The measurement uncertainty of the method was estimated at 16, 16, 19, 27 and 26% for MPA, MGA, MLA, DMA and CMA, respectively. Fortifying kidney fat samples (n = 18) in three separate assays showed the accuracy of the method to be between 98 and 100%. The precision of the method, expressed as % RSD, for within-laboratory reproducibility at three levels of fortification (1, 1.5 and 2 µg kg-1 for MPA, 5, 7.5 and 10 µg kg-1 for MGA, MLA, DMA and CMA) was less than 5% for all analytes. [ABSTRACT FROM AUTHOR]

Abstract: A rapid method has been developed to analyse for firocoxib (FIRO) residue in bovine milk. Milk samples were extracted with acetonitrile and sample extracts were purified on Evolute™ ABN solid phase extraction cartridges. Aliquots were analysed by rapid resolution liquid chromatography tandem mass spectrometry (RRLC–MS/MS). The method was validated in bovine milk, according to the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCα) was 1.18ng/mL and for the detection capability a (CCβ) value of 2.02ng/mL was obtained. The measurement uncertainty of the method was 27%. Fortifying bovine milk samples (n =18) in three separate assays, show the accuracy of the method to be between 96 and 105%. The precision of the method, expressed as RSD values for the within-lab reproducibility at the three levels of fortification (5, 7.5 and 10ng/mL) was less than 11% respectively. [Copyright &y& Elsevier]

Abstract: In this work, a four-way tensor is used to model the quenching effect in fluorescent measurements. By means of the analysis of excitation–emission matrices obtained in the determination of tetracycline in tea, which acts as quencher, it is shown as the impossibility to use a calibration, or an addition standard based on a three-way model. It is analysed the quencher multiplicative effect made on the tetracycline signal by means of an ANOVA. However, by arranging the experimental data in a four-way tensor, it is viable to perform a calibration based on the parallel factor analysis, PARAFAC, decomposition and a four-way partial least squares, 4-PLS, regression to quantify the tetracycline in the presence of the matrix quencher effect. 4-PLS calibration provides better results. In the range from 40 to 220μgL−1 gives an average of relative errors in absolute value equal to 8.02% in prediction (3.40% in calibration). The repeatability as standard deviation in this range is 5.08μgL−1 and the method is accurate, slope and intercept being statistically equal to 1 and 0, respectively when a regression calculated versus true concentration is performed. Moreover, it has a decision limit (CCα) of 13.87μgL−1 for a probability of false positive, α, equal to 0.05 and a capability of detection (CCβ) of 26.63μgL−1 (for probabilities of false positive, α, false negative, β, equals to 0.05). [Copyright &y& Elsevier]

A simple and inexpensive liquid chromatographic method for the determination of seven sulphonamides in animal tissues was validated. The measurement uncertainty of the method was estimated using two approaches: a 'top-down' approach based on in-house validation data, which used either repeatability data or intra-laboratory reproducibility; and a 'bottom-up' approach, which included repeatability data from spiking experiments. The decision limits (CCα) applied in the European Union were calculated for comparison. The bottom-up approach was used to identify critical steps in the analytical procedure, which comprised extraction, concentration, hexane-wash and HPLC-UV analysis. Six replicates of porcine kidney were fortified at the maximum residue limit (100 μg kg-1) at three different stages of the analytical procedure, extraction, evaporation, and final wash/HPLC analysis, to provide repeatability data for each step. The uncertainties of the gravimetric and volumetric measurements were estimated and integrated in the calculation of the total combined uncertainties by the bottom-up approach. Estimates for systematic error components were included in both approaches. Combined uncertainty estimates for the seven compounds using the 'top-down' approach ranged from 7.9 to 12.5% (using reproducibility) and from 5.4 to 9.5% (using repeatability data) and from 5.1 to 9.0% using the bottom-up approach. CCα values ranged from 105.6 to 108.5 μg kg-1. The major contributor to the combined uncertainty for each analyte was identified as the extraction step. Since there was no statistical difference between the uncertainty values obtained by either approach, the analyst would be justified in applying the 'top-down' estimation using method validation data, rather than performing additional experiments to obtain uncertainty data. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the selection of experimental conditions and how the signals obtained in these conditions influence the fitted Partial Least Squares calibration model. The multivariate signals come from a flow analysis system with amperometric detection when determining sulfadiazine, sulfamerazine and sulfamethazine in milk. The solution (carrier plus analyte) was pumped through the system to provide a continuous supply of analyte to the cell. The detector was programmed for a scan mode operation being the multivariate signal the hydrodynamic voltammogram. To obtain an analytical signal of enough analytical quality, the Net Analyte Signal and its standard deviation have been optimised by using an experimental design. The conflicting behaviour of the two responses has been solved by estimating the Pareto-optimal front. The multivariate signals recorded in the optimal conditions found have been calibrated by Partial Least Squares regression and their figures of merit validated according to the criteria established in European Decision 2002/657/EC. In relation to the permitted limit, 100 µg l−1 in milk, for the total content of sulfonamides established in the Commission Regulation EC no. 281/96 the proposed method has a decision limit of 109.1 µg l−1 and the capability of detection is 117.9 µg l−1 for both probability of false non-compliance and of false compliance equal to 5%. A recovery of 86.5%±2.4% (n =5) has been obtained. [Copyright &y& Elsevier]

Abstract: A sensitive and cheap FIA, with amperometric detection, analytical procedure is developed in this paper to determine sulfadiazine, sulfamethazine and sulfamerazine in milk. A multicriteria optimization based on the use of a desirability function is used for optimizing two analytical responses (peak height and its variability) since single-objective optimizations lead to conflicting experimental conditions. In the optimum conditions, the determination of the three sulfonamides in milk samples is carried out, the analytical procedure being validated according to Commission Decision 2002/657/EC. The decision limit at 0 and 100μgL−1 (which is the maximum residue limit in milk) are 13.9 and 110.2, 9.5 and 107.1 and 9.1 and 107.1μgL−1 for sulfadiazine, sulfamethazine and sulfamerazine, respectively. Whereas the values of capability of detection, CCβ, obtained at 0 and 100μgL−1 were 26.9 and 119.8, 18.2 and 113.6, and 17.5 and 113.7μgL−1 for sulfadiazine, sulfamethazine and sulfamerazine, respectively. Recovery values between 67.4% and 119.1% are found for milk test samples of two brands of milk. The accuracy of the method is confirmed. The ruggedness of the procedure is evaluated by means of a Plackett–Burman design. The relative errors were lower than 2.5% (n =7). [Copyright &y& Elsevier]

Abstract: This paper reports an experimental design optimization of a recently proposed silylation procedure that avoids the introduction of false positives and false negatives in the simultaneous determination of steroid hormone estrone (E1) and 17-α-ethinylestradiol (EE2) by gas chromatography–mass spectrometry (GC/MS). The figures of merit for several calibration procedures were evaluated under optimum conditions in the silylation step. Internal standardization strategies were applied and global models were constructed by gathering signals recorded on three non-consecutive days. Three calibration models were examined: a univariate model with a sum of six monitorized ions and a three-way PARAFAC-based model (the analyte scores were standardized on the basis of the scores of the internal standard). The global PARAFAC-based calibration model showed the best performance with detection capabilities of 4.3μgl−1 and 7.0μgl−1 for E1 and EE2, respectively, when the probability of false positives was fixed at 1% and that of false negatives at 5%. Mean relative error in absolute terms for E1 and for EE2 was 11.1% and 8.5%, respectively, and trueness was likewise confirmed. The proposed optimized derivatization procedure using a three-way calibration function was also applied in the determination of E1, 17-β-estradiol (E2) and EE2 in bovine urine samples: recovery values were 68.5%, 40.4% and 43.4%, respectively, and the detection capability was 18.4, 19.3 and 18.6μgl−1 when the probability of false positives was fixed at 1% and that of false negatives at 5%. Mean relative error in absolute terms for E1, E2 and EE2 was 7.4%, 9.4% and 8.6%, respectively, and trueness was likewise confirmed. [Copyright &y& Elsevier]

Abstract: A method for the detection and determination of nitrofuran derivatives in egg by liquid chromatography–tandem mass spectrometry (LC–MS/MS) was validated with the software InterVal and can be applied for the confirmation of nitrofuran metabolites in fresh or lyophilised eggs. The validation study comprises variations in operator, storage condition, breeding, equipment and duration of sample preparation. A comprehensive overview of the robustness of the method is obtained by analysing eight samples at six concentration levels. First results of short- and medium-term investigations for stability of analytes in solution show that standard solutions of nitrofuran metabolites are stable for at least 1 year when stored at +4°C in the dark. The decision limit CCα expressed for the underivatised metabolite is 0.05μgkg−1 for 3-amino-5-methyl-morpholino-2-oxazolidinone, 0.03μgkg−1 for 3-amino-2-oxazolidinone, 0.20μgkg−1 for semicarbazide and 0.22μgkg−1 for 1-amino-hydantoin. [Copyright &y& Elsevier]

Abstract: The use of gestagens in animal fattening is prohibited within the European Union. Recently, the use of spectrometric methods for the detection and confirmation of banned substances was made obligatory. Therefore, conventional high-performance liquid chromatographic (HPLC) methods have been superseded. It has been possible to couple a previously described HPLC method for the determination of acetyl-gestagens in kidney fat to tandem mass spectrometry (LC-MS/MS). The decision limits CCα and the detection capability CCβ are found to be below the minimum required performance limit (MRPL) established for medroxyprogesterone acetate (MPA) at 1μgkg−1. The calculated values for CCα are as follows: megestrol acetate (MGA)—0.15μgkg−1, melengesterol acetate (MLA)—0.15μgkg−1, chlormadinone acetate (CMA)—0.37μgkg−1 and for medroxyprogesterone acetate (MPA)—0.24μgkg−1. The CCβ values for these compounds have been determined as 0.19, 0.19, 0.47 and 0.32μgkg−1, respectively. [Copyright &y& Elsevier]