Liquid Chromatographic Determination of Urea in Water-Soluble Urea-Formaldehyde Fertilizer Products and in Aqueous Urea Solutions: Collaborative Study

Water soluble urea-formaldehyde (UF) fertilizers, manufactured by complex reaction of urea and form-aldehyde, typically contain varying amounts of unreacted urea. A liquid chromatography method for the analysis of urea in these products, and in aqueous urea solutions, was collaboratively studied. An amine chromatography column was used to separate the unreacted urea from numerous UF reaction products present in these liquid fertilizers. Unreacted urea was determined by using external urea standards with UV detection at 195 nm. The standards and test samples were prepared in the mobile phase of 85% (v/v) acetonitrile in water. Ten laboratories analyzed 5 different UF-based commercial products containing unreacted urea in the range of 6 to 17% by weight, and 5 different concentrations of urea in water equivalent to commercial products of that nature. The aqueous urea solutions contained 2–20% urea (w/w). The range of sR values for the 5 UF-based commercial fertilizers was 0.49–1.02 and the %RSDR was 1.94–6.14. The sR range for the 5 urea solutions was 0.10 to 0.79 and the %RSDR range was 2.54 to 4.88. The average recovery of urea from the aqueous urea solutions was 96–103%. Therefore, this method is capable of monitoring urea nitrogen manufacturers' label claims and total nitrogen claims in those cases where urea is the sole source of plant food nitrogen. Based on the collaborative study data, the authors recommend this method be approved for AOAC Official First Action status.

Epidemiology of adolescent substance use in London schools

BACKGROUND

Alcohol and substance use in adolescence can be associated with a range of health, emotional, social, behavioural and legal problems. There has been a change in the recreational drugs available to users in recent years; however, little is known about how this impacts the youngest and most vulnerable population of substance users.

AIM

To investigate the prevalence of substance use among children aged 15-18 years in London schools.

DESIGN

Questionnaire survey.

METHOD

Students aged 15-18 years in three London schools self-completed the questionnaire which collected demographic data (age, gender and ethnicity) and data on frequency of use of alcohol, tobacco and classical recreational drugs and novel psychoactive substances.

RESULTS

Completed surveys were available from 533 students (47.8% of those invited to participate). One hundred thirteen (20.4%) students reported lifetime use of at least one recreational drug, cannabis (96, 18.7%) was commonly reported and only 6 (1.1%) reported use of a novel psychoactive substance. A total of 250 (47.8%) reported using alcohol at least once; those from White and Mixed ethnic groups were more likely to report using alcohol than those in other ethnic groups. A total of 382 (74.2%) students reported using tobacco at least once, and students from ethnic minorities were more likely to smoke than their White counterparts.

CONCLUSION

This study supports previous findings that alcohol and drug use are declining in adolescents in UK. There are different patterns of substance use amongst different ethnic groups; this is important to schools and policymakers planning interventions related to substance use in school-aged children.

Examining HIV/AIDS provider stigma: assessing regional concerns in the islands of the Eastern Caribbean

HIV/AIDS provider stigma has been understudied in the context of prevention, testing, and treatment. Results of a survey of persons associated with HIV/AIDS education, health care, and social service delivery in the Eastern Caribbean are described. Reliable constructs were observed for warmth towards PLHA, comfort in association with them, tendencies to distance from or condemn them, beliefs in viral transmission myths, and perceived capacity to counsel effectively. Most discrimination was directed towards MSM and IDUs. Providers whose roles were likely to involve touch felt less comfortable around PLHA and more likely to distance from and condemn them than providers whose roles were not. Implications for improved measurement and incorporation of mindfulness techniques in stigma intervention are discussed.

Two-layer compression hosiery for patients with venous leg ulceration

Patients may experience a recurrence of leg ulceration if they do not wear prescribed compression hosiery when ulcers have healed. This article examines the use of compression hosiery kits, which can be used for the treatment of active ulceration as well as prevention of recurrence. For some patients, the stockings may be easier to apply than traditional compression hosiery, thereby enabling them to benefit from continued wear.

Liquid chromatographic determination of urea in water-soluble urea-formaldehyde fertilizer products and in aqueous urea solutions: collaborative study

Water soluble urea-formaldehyde (UF) fertilizers, manufactured by complex reaction of urea and formaldehyde, typically contain varying amounts of unreacted urea. A liquid chromatography method for the analysis of urea in these products, and in aqueous urea solutions, was collaboratively studied. An amine chromatography column was used to separate the unreacted urea from numerous UF reaction products present in these liquid fertilizers. Unreacted urea was determined by using external urea standards with UV detection at 195 nm. The standards and test samples were prepared in the mobile phase of 85% (v/v) acetonitrile in water. Ten laboratories analyzed 5 different UF-based commercial products containing unreacted urea in the range of 6 to 17% by weight, and 5 different concentrations of urea in water equivalent to commercial products of that nature. The aqueous urea solutions contained 2-20% urea (w/w). The range of s(R) values for the 5 UF-based commercial fertilizers was 0.49-1.02 and the %RSD(R) was 1.94-6.14. The s(R) range for the 5 urea solutions was 0.10 to 0.79 and the %RSD(R) range was 2.54 to 4.88. The average recovery of urea from the aqueous urea solutions was 96-103%. Therefore, this method is capable of monitoring urea nitrogen manufacturers' label claims and total nitrogen claims in those cases where urea is the sole source of plant food nitrogen. Based on the collaborative study data, the authors recommend this method be approved for AOAC Official First Action status.

Gas-Liquid Chromatographic Determination of Pirimicarb in Formulations: Collaborative Study

A method is described for the determination of pirimicarb (2-(dimethylamino)-5,6-dimethyl-4-pyrimidinyl dimethylcarbamate) in formulated products by gas-liquid chromatography (GLC). Samples are dissolved in a chloroform solution of an internal standard and injected into a gas chromatograph equipped with a flame ionization detector. Quantitative data are obtained by comparing peak areas of the compound and internal standard with those obtained by injecting a standard solution. Eleven collaborators made replicate determinations on 6 samples including a technical product, a granular product, and 4 powder products. The average coefficient of variation was 1.14% for the technical product, 1.82% for the granular product, and 0.73% for the powder products.