Minimum detectables amount

The feasibility of the fast neutron bulk activation detection system and of other bulk nitrogen measurement systems is in serious question. The nitrogen present in innocent, common, and completely legitimate materials to be found in suitcases varies sufficiently that the estimated minimum detectable amount of explosive in this system is around 25 to 50 sticks of 40% dyji3=... 

Attenuation Injection volume Retention time Minimum detectable amount... 

The limit of detection of hymexazol in vegetables is 0.01 mgkg, as shown below. Minimum detectable amount 0.1 ng... 

Column and detector properties determine the minimum amount of a component that can be reliably distinguished from the background noise. If we arbitrarily select a signal to noise ratio of 4 as the minimum value for the confident determination of a peak in a chromatogram then for a mass sensitive detector the minimum detectable amount is given by... 

Where Q, is the minimum detectable amount, R the detector noise level and s the detector sensitivity [135,146,151,152]. For a concentration sensitive detector the minimum detectable concentration is the product of Q, and the volumetric gas flow rate through the detector. The minimum detectable amount or concentration is proportional to the retention time, and therefore, directly proportional to the column radius for large values of n. it follows, then, that very small quantities can be detected on narrow-bore columns. 

The gaseous atmosphere was then vented through a trap at -78° (to remove most of the benzene vapor) into an evacuated vessel. Samples were removed by gas-tight syringe and injected into a Hewlett-Packard 5790 gas chromatograph, equipped with a U ft, 1/8 in Porapak P column and a flame ionization detector. Use of known samples of hydrocarbons (methane and ethane) established that the minimum detectable amounts of product by this procedure were about 0.5-1 0 % (based on starting Nb complex). Several of the reactions (Mo(CO)g, W(C0)g and Ru (CO) p) gave small amounts (around 1-2 %) of these alkanes only with Cr(C0)g was a substantial yield of hydrocarbon product consistently observed (see below). 

Note that Vg is proportional to the square of the inner radius of the column. It is important to have a rough idea of the void volume of the column since it often dictates the operating flow-rate range, sampleloading capacity, and mass sensitivity (the minimum detectable amount) of the assay. For instance, a typical analytical column (150mm x 4.6mm i.d.) has a Vg of about 1.5 mL and is operated at 1.0mL/min. In contrast, by reducing the inner diameter to 2.0 mm, a typical LC/MS column (150mm X 2.0mm i.d.) has a Vg of about 0.3mL and is operated at... 

Compound Type Reagent Type of Positive Text Minimum Detectable Amount(pig)... 

Devine et al. [188] adjust the water sample (1L) to pH2 with hydrochloric acid and extract it with benzene (100, 50 and 50mL). The extract is dried over sodium sulphate, concentrated to 0.1 mL and methylated by the addition of diazomethane in ethyl ether (lmL). After lOmin, the volume is reduced to about O.lmL, acetone is added and an aliquot is analysed by gas chromatography on one of three columns (1) 5% SE-30 on 60-80 mesh Chromosorb W at 175°C, (2) 2% QF-1 on 90-100 mesh Anakron ABS at 175°C or (3) 20% Carbowax 20m on 60-80 mesh Chromosorb W at 220°C In each instance nitrogen is the carrier gas and detection is by electron capture. The minimum detectable amount of pesticide in water was 2 parts per 109 for MCPA (4-chloro-2-methyl-phenoxyacetic acid) and 0.01-0.05 parts per 109 for 2,4-D (2,4-dichloro-... 

Species Method Minimum detectable amount Method sensitivity (pg mL )a. 

Interfacing the TEA to both a gas and a HPLC has been shown to be selective to nitro-based explosives (NG, PETN, EGDN, 2,4-DNT, TNT, RDX and HMX) determined in real world samples, such as pieces of explosives, post-blast debris, post-blast air samples, hand swabs and human blood, at picogram level sensitivity [14], The minimum detectable amount for most explosives reported was 4-5 pg injected into column. A pyrolyser temperature of 550°C for HPLC-TEA and 900°C for GC/TEA was selected. As the authors pointed out, GC uses differences in vapour pressure and solubility in the liquid phase of the column to separate compounds, whereas in HPLC polarity, physical size and shape characteristics determine the chromatographic selectivity. So, the authors reported that the use of parallel HPLC-TEA and GC-TEA techniques provides a novel self-confirmatory capability, and because of the selectivity of the technique, there was no need for sample clean-up before analysis. The detector proved to be linear over six orders of magnitude. In the determination of explosives dissolved in acetone and diluted in methanol to obtain a 10-ppm (weight/volume) solution, the authors reported that no extraneous peaks were observed even when the samples were not previously cleaned up. Neither were they observed in the analysis of post-blast debris. Controlled experiments with handswabs spiked with known amounts of explosives indicated a lower detection limit of about 10 pg injected into column. 

Compound type Reagent Type of positive test Minimum detectable amount (Mg) Compounds tested... 

Pentafluorophenylhydrazine, in a condensation reaction with 27 carbonyl compounds, gave quantitative results for most of them [59]. The minimum detectable amount was 0.01 ng, the derivatives being separated in a column coated with SE-30 or PEG 20M. Hoshika [60] used derivatives containing sulphur for the GC analysis of benzaldehyde, which were prepared by condensation with 2- and 3-methylthioaniline (Scheme 5.7). 

Minimum detectable amount and upper limit of linearity delimit LR... 

Diltiazem hydrochloride and its related compounds can be separated in both bulk drug and finished tablets using a Waters pBondapak C18 column (10 pm particle size, 300 mm x 3.9 mm I.D.) and a mobile phase of buffer methanol acetonitrile (50 25 25, v/v) at a flow rate of about 1.6 mL/minute. The buffer is 0.1 M aqueous sodium acetate containing 5mM d-camphorsulfonic acid (99%) adjusted to pH 6.2 with 0.1 M aqueous sodium hydroxide. Detection of the compounds is achieved using UV absorbance at 240 nm. The method provides for the resolution of trans-diltiazem and seven known and unidentified related compounds. Diltiazem hydrochloride elutes at approximately 21 minutes under these conditions. The minimum detectable amounts are less than 0.1% for all related compounds except for one of the synthetic intermediates for which there is a limit of about 2% (27). 

Compound k minimum detectable amount Inal Compound k ... 

Fluorescence detection has alo been applied in the analysis of Psiiocybe alkaloids (Fig.8.11). The minimum detectable amount was for fluorimetric detection 250 pg (excitation 267 nm, emission 335 nm) and for UV detection 30 ng (267 nm) for psilocybin, for psilocin... 

Column packing was SE30 on Chromosorb W(100-120 mesh). Retention time at 235° is given as 3.7 minutes, and the minimum detectable amount at attenuation X20 is 0.2 J.g in 1 Hi of ethanol. 

Chapter 11. By analogy to the ECD data for the esters of simple acids, the ECD temperature dependence for derivatives of the amino acids is predicted. The temperature dependence of derivatives used to analyze nucleic acids and amino acids will be estimated based on the calculated data for the parent compounds and reported minimum detectable amounts [43—48]. 

The sensitivity of the x-ray method in determining small amounts of retained austenite is limited chiefly by the intensity of the continuous background present. The lower the background, the easier it is to detect and measure weak austenite lines. With filtered radiation the minimum detectible amount is about 2 volume percent austenite, and with crystal-monochromated radiation probably about 0.2 percent. The error in the austenite content, originating in the calculation of R and the measurement of I, is probably about 5 percent of the amount present, in the absence of preferred orientation (Sec. 14-12). 

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