Niacin determination

Microbiological methods are common in niacin determination, but they are time consuming and laborious. Instead, HPLC with RP column enables a better separation and identification of compounds. 

Diaz-Pollan, C., and Vidal-Valverde, C., Niacin determination in legumes by capillary electrophoresis (CE). Comparison with high performance liquid chromatography (HPLC), J. High Resolut. 

Niacin determinations have similarly been performed by Lieck (1954) on samples of liver tissue, heart, and skclct il muscle obtained from calves and from adult cattle the analyses showed essentially ctiual niacin concentrations for the immature and the mature animals. In contrast to this, analyses made by Denton et al. (1947) on liver and muscular tissue specimens from chickens between 6 and 18 weeks of age revealed a definite decrease in the niacin levels of these tissues with age. 

Table 19.2 contains the results of niacin determinations performed in MRM mode for some grain-based food materials, including appropriate reference materials, and compares them to expected levels. For the commercial food materials, expected values are as listed on the packaging. The US National Institute of Standards and Technology (NIST) does not provide a reference value for niacin for RM 8437 however, there have been determinations of its niacin value reported in the literature (LaCroix et al. 1999 Tanner et al. 1988). The expected value for RM25C, an in-house reference material used by an analytical testing and consulting laboratory, was provided by the producer. 

Table 19.2 Results of niacin determinations for food samples. Niacin determinations by LC-IDMS are compared to expected values for six grain-derived food materials. Expected levels for the commercial flour and cereal samples (Brands A, B, C, and D) are according to the package labelling, although it should be noted that actual vitamin levels of vitamin fortified foods are often higher than the stated amounts. The determined niacin levels for these samples, listed in the third column with their 95% confidence limits, are from 30% to 70% higher than the claimed levels. Determined niacin levels for the two reference materials (RM) are in agreement with the expected levels. Data are from Goldschmidt and Wolf (2007), with permission from the publisher.

Table 19.3 contains results of niacin determinations of some milk samples, again in MRM mode, including RM 8435 (whole milk powder) from NIST. These samples are not fortified and contain niacin at considerably lower levels than the samples in Table 19.2. Precision obtained for these samples is in the range 1-5% RSD. An example of an extracted ion chromatogram for commercial milk Brand F is shown in Figure 19.2. The USDA Nutrient Database for Standard Reference, Release 23 (US Department of Agriculture 2010) lists a value of 0.89 ppm niacin for milk, whole, 3.25% milkfat and a value of 0.84ppm niacin for milk, producer, fluid, 3.7% milkfat . We thus assume that expected values for niacin for whole milk samples are near 1 ppm. The levels...

Table 19.3 Results of niacin determinations for milk samples. Niacin determinations by liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) are compared to expected values for four milk samples. Expected niacin levels for milk are roughly 1 ppm, according to the USDA Nutrient Database for Standard Reference (US Department of Agriculture 2010) and results obtained for two commercial milk samples (Brands F and G) are a little under 1 ppm. The result for sample NFY0409F6 is about 30% lower, but is consistent with results obtained for other milk samples from the same source. In addition, the niaein level for NFY0409F6 was estimated by a standard additions experiment, the result from which is in agreement with the estimate from the normal LC-IDMS procedure. The level obtained for the reference material (RM) RM 8435 whole milk powder, reported on a dry mass basis, is in agreement with the reference value. Data are from Goldschmidt and Wolf (2007), with permission from the publisher.

Figure 19.3 Standard additions curve for milk sample NFY0409F6. Four levels of a standard natural niacin and a fixed amount of D4-niacin were added to milk sample NFY0409F6 in a standard additions experiment. The level of niacin determined for the sample, 0.657 ppm niacin, is in agreement with the level obtained by a normal IDMS determination. The linear relationship observed is consistent with complete recovery of added niacin and with an absence of matrix effects. Data are from Goldschmidt and Wolf (2007), with permission from the publisher.

Both nicotinic acid and nicotinamide have been assayed by chemical and biological methods. Owing to the fact that niacin is found in many different forms in nature, it is important to indicate the specific analyte in question. For example, if biological assay procedures are used, it is necessary to indicate whether the analysis is to determine the quantity of nicotinic acid or if niacin activity is the desired result of the analysis. If nicotinic acid is desired, then a method specific for nicotinic acid should be used. If quantitation of niacin activity is the desired outcome, then all compounds (bound and unbound) which behave like niacin will assay biologically for this substance (1). 

Nicotinic acid, HC6H402N (JCa = 1.4 X 1CT5) is another name for niacin, an important member of the vitamin B group. Determine [H+] in a solution prepared by dissolving 3.0 g of nicotinic acid (MM = 123.11 g/mol), HNic, in enough water to form 245 mL of solution. 

Tchetche, A. G., Quantitative determination of vitamin PP or niacin in Coffea canephora var. robusta by a microbiological method using Lactobacillus arabinosus, Colloq. Sci. Int. Cafe, 8, 147, 1977. (CA92 196459)... 

Niacin requires baseline tests of liver function (alanine aminotransferase), uric acid, and glucose. Repeat tests are appropriate at doses of 1,000 to 1,500 mg/day. Symptoms of myopathy or diabetes should be investigated and may require creatine kinase or glucose determinations. Patients with diabetes may require more frequent monitoring. 

Water-soluble vitamins in formulations have been determined by use of ion-pair chromatography. The vitamins include several B vitamins as well as niacin, folic acid, and ascorbic acid (565). Vitamins D and Da were rapidly separated on reverse phase columns (247) as are vitamins A, D, and E in multivitamin tablets (564). Addition of silver ions to the mobile phase has been shown to increase the flexibility inherent in RPC by complexing with the unsaturated bonds and thereby decreasing the retention factor. This effect is also observed with other unsaturated drug molecules including steroids (247). Vitamin A and related compounds have... 

Selected applications of HPLC for the determination of niacin in food matrices are listed in Table 19.17. 

Determination of niacin in milk and cereal based products... 

Determination of B, Bj, Bj, niacin, Bj, folic acid, B12, and vitamin C in supplemented foods... 

More recently [635], a unique extraction step in supplemented foods, by using hot water and a precipitation solution, following by HPLC-ELD/UV analysis has been performed for the simultaneous determination of pyridoxine, thiamine, riboflavin, niacin, pantothenic acid, folic acid, cyanoco-balamin, and ascorbic acid. The mobile phase consisting of phosphate buffer and methanol has been modified in order to perform ion-liquid chromatography by adding l-octanesulfonic acid sodium salt. Furthermore, triethylamine has been also added to improve peak symmetry. 

This familial disorder, which is associated with increased atherogenesis, is determined chiefly by alleles that dictate increased production of the (a) protein moiety. Niacin reduces levels of Lp(a) in many patients. 

All but one of the seven laboratories that recently participated in a intercomparison of niacin assays chose to use microbiological assays (42). The results from the lone HPLC determi-nation/UV absorbance determination were rejected due to lack of chromatographic resolution. 

Although microbiological methods are widely used for quantitation of total niacin, they tend to be time consuming and labor intensive (100). Reproducibility problems have also been reported (96). The HPLC methods for foods generally determine total niacin rather than the individual vitamers. Table 14 summarizes a recent HPLC method for quantitating total niacin in foods. The simultaneous determination of niacin with one or more other B vitamins is covered later in this chapter in Sec. XI. 

Russell (44) and Ball (45) summarized multivitamin methods for foods that determined various combinations of thiamine, riboflavin, niacin, vitamin B6, folacin, and biotin. 

PM Finglas, RM Faulks. Critical review of HPLC methods for the determination of thiamin, riboflavin and niacin in food. J Micronutr Anal 3 251-283, 1987. 

CM Ward, VC Trenerry, I Pant. The application of capillary electrophoresis to the determination of total niacin in concentrated yeast spreads. Food Chem 58 185-192, 1997. 

Primary increases of VLDL probably reflect a number of genetic determinants and are worsened by factors that increase the rate of VLDL secretion from liver, ie, obesity, alcohol, diabetes, and estrogens. A major indication for treatment is the presence of atherosclerosis in the patient or the patient s family. Treatment includes weight reduction, restriction of all types of dietary fat, and avoidance of alcohol. Fibrates or niacin usually produce further reduction in triglyceride levels if dietary measures are not sufficient. Marine omega fatty acids may also be of value. 

S. P. Sood, D. P. Wittmer, S. A. Ismael, and W. G. Haney, Simultaneous high-performance liquid chromatographic determination of niacin and niacinamide multivitamin preparations reversed-phase, ion-pair approach, J. Pharm. Sci., 66 40 (1977). 

When used in conjunction with niacin or niceritol, Sikorski (4) determined that the benzyl amine cholesteryl ester transfer protein inhibiting agent, (III), was effective in treating atherosclerosis. 

Treatment of tardive dyskinesia is often unsatisfactory, especially in severe cases. A large number of treatments have been proposed (SEDA-20,40), including antiparkinsonian drugs, benzodiazepines, baclofen, hormones, calcium channel blockers, valproate, propranolol, opiates, cyproheptadine, tryptophan, lithium, manganese, niacin, botulinum toxin, ECT, dietary control, and biofeedback training. In an open study, 20 patients (mean age 65 years) with severe unresponsive tardive dyskinesia (mean duration 44 months, mean exposure 52 months) were treated with tetrabenazine (mean dose 58 mg/day) (310). The mean score on the AIMS motor subset, determined from videotapes, improved by 54%. Sedation was the only subjective complaint. 

A number of studies have investigated the equivalence of dietary tryptophan and preformed niacin as precursors of the nicotinamide nucleotides, generally by determining the excretion of -methyl nicotinamide and methyl pyridone carboxamide in response to test doses of the precursors, in subjects maintained on deficient diets. 

Measurement of liver and other tissue concentrations of NAD(P) gives a precise estimate of niacin nutritional status and seems to be the most sensitive indicator in experimental animals. Measurement of the whole blood concentration of NAD (P) may serve the same purpose there is a good correlation between blood and liver concentrations of nicotinamide nucleotides in experimental animals. The sensitivity of the method is such that reproducible determinations can be carried out on finger-prick samples of 200 /xL of blood (Bender etal., 1982). 

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