Determination of acetaldehyde in saliva by gas-diffusion flow injection analysis

The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-diffusion flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80 μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600 nm. Under the optimum working conditions the method is characterized by a sampling rate of 9 h⁻¹, a linear calibration range of 0.5–15 mg L⁻¹ (absorbance = 5.40 × 10⁻² [acetaldehyde, mg L⁻¹], R² = 0.998), a relative standard deviation (RSD) of 1.90% (n = 10, acetaldehyde concentration of 2.5 mg L⁻¹), and a limit of detection (LOD) of 12.3 μg L⁻¹. The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD = 93.0 μg L⁻¹ and sampling rate = 4 h⁻¹). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6–101.9%), comparable to those obtained by GC (96.4–102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.     

Determination of cholesterol by flow injection analysis with immobilized cholesterol oxidase

The injected sample passes through a column of enzyme immobilized on controlled pore glass, at pH 7.0, and the hydrogen peroxide produced is detected amperometrically. As little as 0.2 μg of cholesterol can be detected. The method is applied to blood serum, wax-wool alcohol and an extract of butter.     

Biochemical studies of soluble and immobilized aldehyde dehydrogenase from yeast

Aldehyde dehydrogenase from baker’s yeast was purified to homogeneity. The soluble and immobilized forms of this enzyme were characterized and compared biochemically. These included steady state kinetics, stability study, fluorescence, and NMR spectroscopy. Evidence of the coenzyme binding to this enzyme in the absence of aldehyde substrates was obtained by fluorescence and NMR studies. A significant quenching of protein fluorescence was observed upon the addition of coenzymes to the aldehyde-free enzyme solution. Significant shifts and broadening of coenzyme proton resonances in the presence of enzyme also indicate the enzyme-coenzyme interactions in the aldehyde-free solution. the enzyme was immobilized on glass beads by three different methods. The immobilized enzyme was found to exhibit physical and biochemical properties similar to those of the soluble enzyme. A system in which the immobilized alcohol, aldehyde, and steriod dehydrogenases are included in an enzyme reactor is described.     

Flow injection analysis for L-lactate with immobilized lactate dehydrogenase

Immobilized lactate dehydrogenase (LDH) is used for determination of L-lactate in a continuous flow system. The LDH is immobilized by reaction with glutaraldehyde onto the surface of alkylamino-bonded silica gel and packed into a column in the flow system. The reduction of NAD⁺ occurs simultaneously, and the NADH formed is detected amperometrically. The peak current is linearly related to the L-lactate concentration in the range 1–80 × 10^-6 M; 30 samples h^-1 can be analyzed with a r.s.d. of 0.5–1.5%. The immobilized LDH retains over 90% of its initial activity after repetitive use for 3 months.     

Determination of salicylate in blood serum by flow injection with immobilized salicylate hydroxylase

A flow injection (FI) enzymatic system, based on the use of immobilized salicylate hydroxylase in glass beads, was developed for the determination of salicylate. Salicylate hydroxylase and nicotinamide adenine dinucleotide (NADH) are used to convert salicylate to catechol. The reaction of catechol with 4-aminophenol at high pH yields a colored product which is detected spectrophotometrically at 565 nm. Ten samples of human serum containing from 5.0 x 10(-4) to 5.0 x 10(-3) mol/L added salicylate were analyzed and the recovery was determined. Eight additional serum samples containing salicylate were analyzed by the Trinder test and the proposed method. The results obtained with the 2 methods showed good agreement by the statistical Student's t-test. The relative precision of the method is about 3.4% (RSD of the mean recovery). Considering the lowest concentration analyzed, the quantitative limit of detection is about 0.2 x 10(-5) mol/L (3 x SD). The volume of the sample used was 150 microL. The proposed method was also used to analyze medicines containing acetylsalicylic acid. The results were statistically compared with those obtained through the U.S. Pharmacopoeia procedure and showed excellent agreement.     

Determination of glucose in blood by flow injection analysis and an immobilized glucose oxidase column

A flow-injection system for glucose determination is described. Glucose oxidase is immobilized on controlled porosity glass (CPG) and used in a glass column (2.5 mm diameter × 2.5 cm). The hydrogen peroxide produced by the enzymatic reaction (? 1 × 10^?6 M) is detected by the current produced in a flow-through cell, with two platinum electrodes having a potential difference of 0.6 V. Glucose (0–20 mmol l^?1) can be determined in blood plasma either with a dialyser in the system or, better, by incorporating a column of copper(II) diethyldithiocarbamate on CPG before the enzyme column. The results compared well with those obtained by a conventional analyser system. The glucose oxidase column showed little change in activity over a 10-month period.     

流动注射化学发光法测定茶饮料中的茶多酚

在碱性条件下,茶多酚对鲁米诺-KMnO4化学发光体系具有较强的抑制作用,据此建立了茶多酚的流动注射化学发光测定法。该法的化学发光抑制值ΔICL与茶多酚质量浓度在2.0×10-6~5.0×10-4mg/mL范围内,呈现出良好的线性关系,检出限为1.2×10-7mg/mL,对1.0×10-5mg/mL茶多酚测定的相对标准偏差为2.9%(n=11)。用于茶饮料中茶多酚的测定。     

流动注射化学发光法测定DL-酪氨酸

在甲醛存在下 ,高锰酸钾与DL 酪氨酸能够发生化学发光反应 ,产生很强的化学发光。据此采用流动注射技术 ,建立了一种测定DL 酪氨酸的化学发光分析法。方法的检出限为 2 .9× 1 0 - 8g/mL ,相对标准偏差为 1 .5 % ( 1 .0× 1 0 - 6g/mLDL 酪氨酸 ,n =1 1 ) ,线性范围为 1 .0× 1 0 - 7g/mL～ 5 .0× 1 0 - 6g/mL。     

流动注射-化学发光法测定非洛地平

基于非洛地平在碱性条件下对鲁米诺-K3Fe(CN)6化学发光体系具有很强的增敏作用,结合流动注射技术,建立了直接测定非洛地平的流动注射-化学发光新方法.方法的线性范围为6.0×10(-9)～3.0×10(-6)g/mL,检出限为2.1×10(-9)g/mL,对浓度为1.0×10(-7)g/mL非洛地平平行测定11次,其...     

Determination of total chromium by flow injection analysis

The determination of total chromium by flow injection analysis is described. Cerium(IV) and nitric acid are used to convert chromium(III) to chromium(VI); the oxidation rate is enhanced by placing the reaction coil in an 80°C oil bath. 1,5-Diphenylcarbazide is used to form a colored complex with chromium(VI) that is measured at 540 nm. For both chromium(III) and chromium(VI), relative standard deviation of less than 1% is achieved with a sampling rate of 40 per hour. Linear response is obtained for 0.5–10 mg l^?1 chromium.     

Determination of phenylephrine hydrochloride by flow injection analysis with chemiluminescence detection

A new method is proposed for the determination of phenylephrine hydrochloride by flow injection analysis with direct chemiluminescence detection. The method is based on the oxidation of the drug by potassium permanganate in sulfuric acid medium at 80 degrees C. The calibration graph is linear over the range 0.03-8 ppm phenylephrine hydrochloride, with a relative standard deviation (n = 51, 0.5 ppm) of 1.1% and sample throughput of 134/h. The influence of 38 different foreign compounds was tested, and the method was applied to the determination of phenylephrine hydrochloride in 8 different pharmaceutical formulations.     

流动注射-化学发光法测定富马酸依美斯汀

在酸性条件下,KMnO4与甲醛能够产生微弱的化学发光,而富马酸依美斯汀的存在能够大大增强该化学发光强度;结合流动注射技术,建立了测定富马酸依美斯汀的流动注射-化学发光新方法。该方法的线性范围分别为3.0×10-8～2.0×10-7g/mL,2.0×10-7～1.0×10-6g/mL和1.0×10-6～8.0×10-6g/mL。检出限为1.0×10-8g/mL,对2.0×10-6g/mL富马酸依美斯汀滴眼液平行测定11次,其相对标准偏差为1.3%。该方法已成功应用于滴眼液中富马酸依美斯汀的含量测定。     

Determination of sulphur dioxide by flow injection analysis with amperometric detection

Sulphur dioxide can be determined at a sampling rate of 120 h^?1, with amperometric detection after separation in a diffusion cell with a teflon membrane. At 25°C, the calibration graph shows two linear ranges, between 0.06 and 6 mg l^?1 and 12 and 110 ml l^? sulphur dioxide, with a detection limit of 0.03 mg l^?1. At 50°C, the liner range is 04–5 mg l^?1, with a detection limit of mg of l^?1. The procedure has been applied to the determination of sulphur dioxide in wines.     

Bioluminescent assays with immobilized firefly luciferase based on flow injection analysis

A flow-injection manifold incorporating immobilized firefly luciferase is described. The detector design and reaction conditions are discussed and results are presented for the determination of adenosine-5′-triphosphate over the range 1 × 10^?12?1 × 10^?5 M. Modifications for creatine phoshokinase (10–400 U l^?1) and creatine phosphate (10^?t–10^?1 M), both determined indirectly via ATP, are also described.     

流动注射化学发光法测定盐酸美司坦

在碱性介质中,当把鲁米诺和KMnO4的混合溶液注入到盐酸美司坦溶液中时,会产生很强的化学发光现象。由此结合流动注射技术,建立了测定盐酸美司坦的流动注射化学发光新方法。该法的线性范围为2.0×10^-7-8.0×10^-6g/mL,检出限（3σ）为9×10^-8g/mL,对2.0×10^-6g/mL盐酸美司坦样品连续进行11次平行测定,其RSD为0.74%。已用于盐酸美司坦片剂中盐酸美司坦的测定。     

Determination of fungal α-amylase by flow injection analysis

A manual iodine-starch method is adapted to analyse broths from Aspergillus oryzae fermentations. The method is base on degradation of starch by the enzyme, and measurement of the residual starch/iodine complex at 570 nm. Calibration graphs are linear for the range 0.01–0.1 amylase units ml^?1. Eighty samples per hour can be processed.